Palms have always enchanted gardeners with their exotic looks, and are easily recognizable by their large leaves, or fronds, which occur in two general forms, pinnate and palmate. The Palmae are also one of the most fascinating and largest plant families in the world, with about 2,600 species. They can have single or multiple stems, and range in size from less than a meter tall at maturity, to arborescent forms such as the Quindio Wax Palms (Ceroxylon quindiuense), the tallest palms in the world, reaching majestic heights between 57 to 59 meters when mature. Wax palms are found in Colombia and Peru where they form an important element of the cloud forests of the tropical Andes.
Click here to see Google images of the tallest Palms in the world
The Palmae or palm family is concentrated in the humid lowland tropics, but extends outside of the tropics, usually in temperate latitudes, into deserts and regions with a Mediterranean climate. They are an important part of the ecosystems of warmer regions, where their broad fronds and deep leaf axils provide shelter and food for many birds, reptiles, and mammals.
To understand the needs of our garden plants, it’s always good to know where they come from and which conditions they thrive in, and this is especially true for the stately Queen Palm with its tall, single trunk. It is native to South America, from northern Argentina to eastern Brazil, and west into eastern Bolivia; where it can be found growing in native forests and rainforests in lowland areas, particularly along river banks, or on small mountain ranges, and near the coast.
The elegance and majesty of this palm won many hearts and the world fell in love with it; and due to its popularity as an ornamental tree, it was widely introduced in tropical and subtropical areas around the world, even doing well in colder climates. Sadly, in warm climates it thrived and naturalised itself in many places, and in favourable habitats like the Australian state of Queensland, and Florida in the USA, it is considered an invasive species. Read more about its invasive status at the end of this article.
Syagrus romanzoffiana flowers. Picture courtesy mauro halpern from flickrThe Queen Palm also has an identity crisis! It was first named after Nikolay Rumyantsev (1754–1826), Russia's Foreign Minister and Imperial Chancellor, and notable patron of the Russian voyages of exploration, sponsoring the first Russian circumnavigation of the globe from 1803-1806, with two ships, the "Nadezhda" and the "Neva".
In 1822, in Paris, this palm was first scientifically described and published as Cocos romanzoffiana. It also appeared in a folio of illustrations made by the artist Louis Choris, with a description by the French-German poet and botanist Adelbert von Chamisso. Both men were on the boats of the first Russian circumnavigation of the globe. In late 1815, in the hinterland of Santa Catarina, Brazil, they discovered and collected specimens of this beautiful palm tree.
Sometime around 1825, in England, Loddiges Nursery imported seed of a palm from Brazil which they dubbed "Cocos plumosa" in their catalogue. This, however, was not its scientific name, and it has caused confusion amongst gardeners and horticulturalists ever since. For example, in 1830 John Claudius Loudon, a Scottish botanist, garden designer and author, listed this plant with its incorrect name of Cocos among 3 species of the Cocos genus then grown in Britain, even mentioning its possible identification as Cocos comosa 'Karl von Martius'. Karl Friedrich Philipp von Martius, (1794-1868) was a German botanist best known for his work on Brazilian flora.
A single seedling eventually found its way from Loddiges Nursery to Kew Gardens. It was planted to adorn the new Palm Glass House, constructed in 1844 by Richard Turner, and the first to be built on such a large scale. The palm thrived and eventually matured at a height of around 18m. Botanists were certain that this specimen was another of von Martius' species, Cocos coronata. However, when this palm eventually flowered and produced fruit for the first time in 1859, it became clear that its previous identification was incorrect.
The name saga continued, and in 1912 Alwin Berger reduced the taxon Cocos plumosa to a variety of Cocos romanzoffiana, as Cocos romanzoffiana var. plumosa. Odoardo Beccari (1843–1920) an Italian botanist and plant taxonomist (a scientist who finds, identifies, describes, classifies, and names plants) published a review of the genus Cocos in 1916. And, under the subgenus Arecastrum he listed Cocos romanzoffiana as Arecastrum romanzoffianum. He also noted that many of the palms being offered in catalogues under various species names were actually Cocos geriba.
By this time South American imports of palm seed were being sold across Europe under a plethora of names, and the name confusion continued in the horticultural trade, and during the late 1960’s and 70’s most experts began referring to it as Arecastrum romanzoffianum.
Today, the queen palm has been placed in the genus Syagrus, and the species name became romanzoffiana - hopefully its new scientific name Syagrus romanzoffiana will stick! All this name confusion is still evident today, and many plants around the world are still sold as Cocos plumosa, and the common name "Cocos Palm" also seems to be here to stay.
The Queen Palm certainly does live up to its name, and although it is classified as a medium-sized palm, it’s single, smooth grey trunk, that varies from 20 to 38cm in diameter, depending on the seed source and environment, generally reaches regal heights of between 7 to 15m tall. Under optimal growing conditions it grows quickly, producing a graceful, drooping canopy, 4.5 to 7.5m wide, of glossy, bright green, pinnate leaves, which on mature trees can be 3 to 5m long.
In summer, drooping panicles of creamy white flowers appear in groups of three; one of the flowering stems is female, and the other two produce male flowers. The complete flower head (inflorescence) including stems, stalks, bracts, and flowers can reach up to 2m in length, and is initially enclosed by two very attractive, pointed woody bracts.
The fruits (dates) are produced in abundance on large hanging bunches, ripening later in summer and into the winter months. They consist of a hard round nut surrounded with a thin layer of fibrous flesh that is orange and sticky when ripe. They are sought after by both birds and mammals; and in their native habitat they are eaten by the Pampas Fox and the Crab-eating Fox.
Fruit drop is a major concern for queen palms because fruit clusters can weigh over 45kg and contain over a thousand seeds. These accumulate on the ground beneath the canopy, where some will sprout into unwanted seedlings
Syagrus romanzoffiana fruit. Picture courtesy mauro halpern from flickrUses:
The fruit of the queen palm is edible, and the sweet fruits are described as a mixture of plum and banana, and in its countries of origin the queen palm has long been a source of food for indigenous South American peoples. It is also widely utilised for other resources, and both the leaves and inflorescences are used as cattle fodder, especially for milking cows.
The flesh of the fruit is fragrant and can be used to create a variety of jams, jellies, and baked products. It can also be consumed fresh, either on its own or as a garnish for salads and other meals. The fruit contains fibre as well as vitamins and minerals like vitamin C, potassium, and magnesium. It is also rich in antioxidants, which can help safeguard the body from free radical damage.
The hard kernel inside the fruit is used in a variety of traditional medicines to treat fever, inflammation, and digestive problems. The seed is also used in a traditional snake injury remedy.
The kernels are also used for many traditional crafts, as the smooth surface of the seeds makes them ideal for carving and etching, and they are frequently used to create small ornamental items like rings and necklaces.
In the Garden:
The Queen palm remains very popular as an ornamental tree in South Africa, and because it also tolerates cold and frost, is especially popular inland to add some tropical flair to gardens.
It is often recommended for both large and small gardens but it is not really suitable for very small gardens as this palm can be extremely messy. When small, it’s easy to prune off the dead leaves, but once it matures it’s almost impossible to prune this palm with normal gardening equipment.
In small gardens plant it in large pots, which are easy to maintain, while still providing that lush, tropical ambiance we all love in a garden. And thanks to its reasonable drought resistance and durability to heat, it can thrive in harsh urban conditions. The queen palm can also add flair to indoor spaces if it has a large pot and is placed in a warm and sunny room.
Because all palms have fibrous root systems that are not invasive, the queen palm is often recommended to plant around swimming pools, but bear in mind the mess it creates and its eventual size, and use it in the background of the pool garden, or in pots.
The queen palm is used extensively in commercial landscapes, and is most effective in large parks and gardens, or planted in rows to line long driveways or walkways, or for shading parking lots. In these larger landscapes regular pruning and maintenance is carried out, not only to keep the trees neat and less messy, but also to keep the walkways etc. underneath them safe for people, animals, and cars to park, because the sheer weight of the branches or fruit clusters when they come crashing down, can really hurt someone.
No matter where you plant this palm, make sure it’s easily accessible to prune and maintain.
Syagrus romanzoffiana Picture courtesy K M from flickrCultivation:
The queen palm is grown throughout South Africa but it really thrives in our hot and humid sub-tropical regions with good rainfall. It has a moderate tolerance of salt spray, making it great in coastal gardens, and once established it is also one of the hardiest of the tropical-looking palms, tolerating frost and temperatures as low as -5°C. In cold winter regions, plant it in a sheltered part of the garden and cover for the first few seasons with a frost protector cloth. Although this palm can grow quite large in the tropics and subtropics, in cooler and drier regions it will remain much smaller.
In most areas, one should plant this palm in full sun; but in extremely hot and dry inland gardens some semi-shade would be best for small plants. Water young plants regularly, until they are established, and because the queen palm is only moderately drought tolerant once established, in dry regions, or during long and dry summer spells, it will require regular watering to look its best in the garden.
To plant a queen palm, dig a square hole that is wider and deeper than the root ball of the plant. Once the hole has been prepared, remove the plant from its container, place in the hole and backfill with soil, ensuring that the tree is planted at the same depth it was growing in its original container. Avoid planting palms too deeply, as oxygen needed for potassium uptake decreases with soil depth. Larger plants may need to be staked but be very careful that the stake or the ties do not hurt the stem. To help the roots establish after planting, it’s essential to water regularly.
Soil pH
Although the queen palm will adapt to most fertile and well drained garden soils, to grow magnificent healthy specimens the soil pH must be right. This palm shows most nutritional deficiencies in its leaves, and these deficiencies are usually the result of incorrect soil pH levels which limit the uptake of available nutrients. If planted in soil with the correct pH, combined with regular fertilisation, your queen palm should thrive.
Soils are acidic, alkaline or neutral, and the pH level of the soil is determined by its composition, such as sand-based or loam-based, and is also affected by fertilisers and rainfall. Neutral soils have a pH of 7, acidic soils are below 7, and alkaline soils are above 7. The best growth for the queen palm occurs in sandy, slightly acidic soils with a pH between 6.0 and 6.5.
It is important to remember that the pH of the soil cannot be determined by guesswork, and before you even consider planting queen palms, it would be worthwhile to purchase a soil pH tester kit at your garden shop. Alternatively, if you are planning to purchase many palms to use as specimens, you may prefer to send soil samples to be tested professionally first.
Alkaline Soils:
The queen palm will suffer from many problems if it is grown in alkaline soils, and if your garden soil is very alkaline I would not recommend planting this palm, as amending the soil and keeping the pH correct is a lot of work. Queen palms grow poorly on alkaline soils because the availability of micronutrients such as Manganese, Boron, or Iron to the plants decreases sharply with increasing soil pH levels.
If you already have this palm in the garden or your soil is only slightly alkaline and you want to amend it, you may have heard or read a statement like "add sulphur to your soil to acidify it." This is generally true but determining what form of sulphur product to use, and how much to use, can be a bit challenging. For gardeners Ammonium Sulphate is a safe and easy chemical option to lower your soil's pH, either to prepare your soil for planting, or to maintain a lower pH in naturally alkaline or neutral soils. It has been produced since the 19th century as a horticultural fertiliser and soil treatment, and should be available at your garden centre, or they can order it for you. Aluminium Sulphate is also a granular fertiliser which will instantly acidify the soil while adding nitrogen. Apply it to the soil, according to package directions.
Acidic Soils:
Very acidic soils are also no good for the queen palm and pH levels lower than 6.0 can cause calcium, potassium and magnesium deficiencies. However, when supplementing by feeding with calcium and magnesium, avoid over-fertilisation, as calcium and magnesium ions compete with potassium ions for binding sites on soil particles, and potassium is also vital for healthy palm growth.
Agricultural lime increases pH levels, and if added to acidic soils it helps to improve potassium intake, although it can take up to a month for it to neutralize the soil, and applications may have to be repeated. Wood ashes also increase pH levels but is only applied on the surface of the soil, as ashes can damage roots if they are worked in.
Fertilising:
Considering all of the above, it makes sense to feed your queen palm trees on a regular basis. They need a good quality fertiliser that meets all their essential needs. Choose a balanced NPK fertilizer (N for Nitrogen, P for Phosphate, and K for Potassium), and using a fertiliser that contains micronutrients, like iron, boron and manganese would be best. Generally a ratio of 3:1:3 is recommended for palm trees, but because this is not readily available for gardeners in South Africa, good alternatives would be 5:1:5 or 3:1:5, as these fertilisers are high in nitrogen and potassium.
If your soil pH is correct, applying a fertiliser that contains micronutrients twice a year, or every four months, should keep your palm trees healthy, and the amount you apply will depend on the size of your tree. Spread granular fertilisers to the soil surface in a band, starting a short distance from the trunk and extending out to the drip line of the leaves. Liquid soil drenches should also extend out to the drip line.
Working compost into the soil before planting will help to correct both high and low pH levels and applying well-rotted compost to the soil around your palms at least once a year will also help a lot in keeping them healthy.
How to Trim Queen Palms:
Queen palm trees grow vertically, with new leaves sprouting from above as the trees get taller. When the old leaves die, the leaf base becomes part of the tree's trunk, which is what causes the scarred pattern that's typical of palm trunks. However, unlike other types of palms, queen palms don't shed their dead leaves efficiently, which can lead to a build-up of dead leaves and leaf stems, so to keep your tree looking neat and tidy as it grows, you'll need to give it an occasional trim.
Removing dead fronds is important for safety reasons, as falling fronds can seriously hurt someone, they can also be problematic during storms, and a fire hazard. Removing large fruit clusters is also recommended as they are very heavy and messy.
Because palms cannot repair wood tissue, they are more susceptible to diseases when their trunks are damaged, or they are pruned too severely. It is vital that you do not damage the trunk of your queen palm when trimming, even nailing something to the trunk is not beneficial.
When the trees are still small, trimming can easily be done at home with loppers or a saw, but once the palms mature, reaching the canopy will be impossible for the average gardener to achieve, and the services of a specialist palm pruner will be essential. If they are allowed to remain on the tree, the fruits and dead fronds are persistent and can remain on the tree for several months before they fall off naturally, looking very untidy.
Understanding when and how to trim a queen palms trunk can help ensure that you don't damage your tree, as it is very susceptible to decay. Technically, you can trim your palm tree any time or season of the year. However, if you want your tree to enjoy the best health, you should trim in late spring or early summer. Trimming is usually necessary once or twice a year, but do not take out too many fronds at one time, as this can cause the decline of the plant. In mid-summer try to keep trimming to a minimum, or not at all, as it may be more challenging for the tree to recover and thrive.
Take your safety into account when you're trimming a queen palm or any other type of plant. Safety gear, like gardening gloves and goggles, can be helpful in protecting your hands and eyes. You must also protect the safety of your tree by sanitizing the blades of your cutting tools to help prevent the spread of disease. You can do this by thoroughly cleaning your lopper or pruning saw, then dipping or wiping their blades with rubbing alcohol, which doesn't need to be rinsed off prior to use.
Select fronds that are hanging downward and are clearly dead and brown all the way to their bases. Cut the frond parallel to the queen palm's trunk, and to prevent damage, keep it about 5 to 8cm from the trunk. Remember that evenly spaced leaf scars are a natural feature of a queen palm and can't be trimmed away without harming your tree.
Because damage to the trunk can be fatal, also remember to keep lawn mowers and weed-eaters well away from queen palms, and especially from those growing in lawns.
Propagation:
If you want to propagate the Queen palm from seeds, they should be half to fully ripe with the fruit pulp removed. Soaking the cleaned seeds in water for two days improves germination. Sow in a well-drained but uniformly moist potting soil. The seeds can germinate slowly and erratically, taking from six weeks to six months. As with most palm species, high temperatures around 32 to 35°C are required for seed germination.
Problems:
Most problems with the queen palm are related to soil pH and fertilisation (see under Cultivation)
Iron (Fe)
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The queen palm may exhibit uniformly yellow (chlorotic) new leaves, which is common on alkaline soils, and typically caused by Iron (Fe) deficiency. Using a liquid or granular fertiliser which contains trace elements will help to correct deficiencies.
DynaGro is a ready-to-use, liquid fertiliser, suitable for all kinds of plants, and contains all the required trace elements.
Volcanic Basalt Rock Dust is an organic amendment designed to enhance the quality of your garden soil. This dust is derived from finely ground basalt rock, which is rich in nutrients, minerals and trace elements essential for plant growth.
Trelmix is a trace element solution which promotes growth and corrects chlorosis (yellowing), blotching and stunting where these are due to trace element deficiencies. It is not a whole fertiliser and should be used in addition to other basic fertilisers. Trelmix can be applied as a foliar feed, which is easy for treating small palm trees, or as a soil drench, which is best for mature palm trees, but could work out very expensive.
Boron (B)
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Various leaf distortions on otherwise dark green new leaves are caused by Boron (B) deficiency. Boron deficiency can cause puckering, crumpling, truncation, incomplete opening, twisting, or stunting of the new leaves, or it may cause the palm to branch or grow sideways, or even downwards.
The malformed new growth is caused by the lack of just a tiny amount of an element called boron, a micronutrient. Boron is associated with cell division and cell production in buds and root tips. Because this element is water soluble, it appears to leach faster than the palm roots can pick it up, especially in sandy soils, and during particularly rainy periods, or if over-irrigated.
Normal growth may resume once the heavy watering events cease, but in some situations additional boron may need to be supplied or the palm will die. The “feather” frond palm group is more prone to boron sensitivity than the fan (palmate) shaped frond group. The problem is common with Queen and Royal palms.
Some symptoms of Boron deficiency could be confused with those of manganese (Mn) deficiency. However, boron deficiency symptoms tend to be worse at the leaf tips, while manganese deficiency symptoms are more severe towards the base of the frond. Boron deficient leaves are also usually not chlorotic (yellowed) as manganese and iron deficient new leaves are.
Because there is a fine line between correction and overdose (death) with Boron, treatment must be approached with caution, and a specialist may be required.
Using a liquid or granular fertiliser which contains trace elements will help to correct deficiencies.
DynaGro is a ready-to-use, liquid fertiliser, suitable for all kinds of plants, and contains all the required trace elements.
Volcanic Basalt Rock Dust is an organic amendment designed to enhance the quality of your garden soil. This dust is derived from finely ground basalt rock, which is rich in nutrients, minerals and trace elements essential for plant growth.
Trelmix is a trace element solution which promotes growth and corrects chlorosis (yellowing), blotching and stunting where these are due to trace element deficiencies. It is not a whole fertiliser and should be used in addition to other basic fertilisers. Trelmix can be applied as a foliar feed, which is easy for treating small palm trees, or as a soil drench, which is best for mature palm trees, but could work out very expensive.
Manganese (Mn)
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Manganese deficiency can be fatal to palms. This is a common problem in high pH soils above 6.5, because manganese is insoluble at high pH levels. Additional causes can be high water tables or poor drainage, and excessive amounts of soil phosphorus which tie up certain micronutrients, particularly manganese.
Early symptoms of manganese deficiency are interveinal chlorosis (yellowing between the veins) and upon closer examination you will see longitudinal necrotic streaking on the chlorotic (yellowing) leaflets. If the deficiency is advanced, frizzling of the leaflets at the base of the youngest leaves is apparent.
To know if it’s a Potassium or Manganese deficiency, you need to observe if the frizzling occurs on the base of the leaves, or on the tips. From a distance they may appear identical, and it’s not unusual to see both manganese and potassium deficiencies on the same palm or even on the same leaf.
Advanced symptoms of manganese deficiency also include a reduced canopy size and smaller trunk diameter, also known as "pencil-pointing". This condition can be corrected by spreading Manganese Sulphate on the soil beneath the palm, and watering it in well. The amount you use will depend on the size of the tree, and for mature specimens between 450g to 1kg of manganese sulphate can be spread out as far out as the canopy reaches.
Using a liquid or granular fertiliser which contains trace elements will help to correct deficiencies.
DynaGro is a ready-to-use, liquid fertiliser, suitable for all kinds of plants, and contains all the required trace elements.
Volcanic Basalt Rock Dust is an organic amendment designed to enhance the quality of your garden soil. This dust is derived from finely ground basalt rock, which is rich in nutrients, minerals and trace elements essential for plant growth.
Trelmix is a trace element solution which promotes growth and corrects chlorosis (yellowing), blotching and stunting where these are due to trace element deficiencies. It is not a whole fertiliser and should be used in addition to other basic fertilisers. Trelmix can be applied as a foliar feed, which is easy for treating small palm trees, or as a soil drench, which is best for mature palm trees, but could work out very expensive.
Magnesium (Mg)
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Magnesium deficiency in the soil is sometimes observed in the leaves of palm trees, as magnesium is readily leached from sandy soils and other soils having little cation exchange capacity. Cation exchange capacity (CEC) is a measure of the total negative charges within the soil that adsorb plant nutrient cations such as calcium, magnesium, and potassium. As such, the CEC is a property of a soil that describes its capacity to supply nutrient cations to the soil solution for plant uptake.
Although magnesium deficiency is never fatal in palms, it is the central element of the chlorophyll molecule necessary for perfect plant health. Symptoms of this deficiency appears on the oldest leaves of palms as broad chlorotic (yellow) bands along their margins with the central portion of the leaves remaining distinctly green.
Frequently, magnesium and potassium deficiencies coexist on the same palm, the oldest leaves will show typical potassium deficiency symptoms, while magnesium deficiency symptoms will be visible on mid-canopy.
Although some slow-release fertilisers contain micronutrients, and products like Trelmix provide all the micronutrients a plant requires, a quick treatment with Epsom salt for a yellowing palm tree will certainly help because it is water soluble and will work quickly.
Combined with regular fertilising, Epson salt can be beneficial for palms, but using too much will cause potassium problems. High levels of nitrogen, potassium or calcium in the soil can also induce or exacerbate magnesium deficiency, so feed your palm correctly, and in the right quantities.
The amount of Epson salt you use will depend on the size of your palm tree, and for fairly mature trees you will need to sprinkle 1 to 1.5kg under the tree’s canopy, then water it in well.
Potassium (K)
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Potassium (K) is one of the key elements necessary for palm health and is required in relatively large amounts. There are two primary symptoms of this deficiency: Light-coloured or brown necrotic speckling of the leaves; and scorching of the leaf tips or margins can occur. The extent of the speckling and scorching depends on the severity of the potassium deficiency. Some species of palms may develop translucent orange and yellow spots, while others develop necrotic spots or yellowing of the leaves.
A deficiency of potassium also results in a condition called "frizzle top" which causes leaves to look frayed and torn. And when the frizzling of the leaflets is at the ends of the oldest leaves, this is indicative of Potassium (K) deficiency.
Potassium tends to leach rapidly from sandy soils, and it is in these soils that potassium deficiency is more apt to occur. In heavier clay soils, the rate of potassium leaching is reduced. Potassium deficiency can be prevented and/or treated with correct fertilisation.
Palms in lawns may become potassium deficient as many turf grass fertilisers are high in nitrogen but low in potassium. Palms need fertilisers that contain potassium as high as, or higher than the nitrogen content. Fertilise palms growing in lawn separately from the turf.
Nitrogen (N)
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Nitrogen deficiency shows first with a yellowing of older leaves. If the deficiency is not corrected, the entire canopy of the queen palm will yellow and the palm's growth will slow. Correct fertilisation should remedy nitrogen deficiencies.
Pests & Diseases:
Queen Palm trees, like all vegetation, are vulnerable to pests and diseases, and spider mites, mealybugs, and scale insects are some of the most common pests that can harm queen palms. These pests can cause major harm to the plant and even kill it if left unchecked.
To handle insect infestations on small trees is as simple as spraying with an appropriate pesticide for the problem, however tall, mature trees are not that easy, and will require specialist equipment to ensure a full cover spray; or alternatively, systemic pesticides can be applied around the roots.
Spraying with organic insecticidal soaps like Biogrow: Neudosan is effective against many soft-bodied insects, including scale, aphids, mealy bugs, and mites. Biogrow: Bioneem is another powerful insecticide; and Biogrow: Pyrol has naturally occurring plant oils as its active ingredients and kills all stages of insects, as does Margaret Roberts Organic Insecticide.
You will need to apply the remedies as a full cover spray, and repeat applications will be required if infestations are severe. Adding G49 wetter/sticker assists in breaking down the protective shell of some scale insects and helps the remedy stick better to the leaves and trunk of the tree.
Systemic solutions are applied to the roots of plants and are quickly absorbed by the plant to control various insect pests. Koinor is a systemic, contact, suspension concentrate insecticide for the control of various pests; and Insecticide Granules Plus is a ready-to-use systemic insecticide in granular form, which is effective against most sucking insects, and provides long term control, between 4 to 8 weeks.
Fusarium Wilt
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A fungus, (Fusarium oxysporum f. sp. palmarum) can infect Canary Island Date Palms (Phoenix canariensis) and Queen Palms (Syagrus romanzoffiana). Occurrence of Fusarium wilt is most common in mature palms, but it has also been observed in juvenile palms. The pathogen reproduces by means of short-lived spores (micro- and macro-conidia) and long-lived chlamydospores that apparently can live in the soil or in infected plant tissue for years. The fungus obstructs water conducting xylem tissue, which causes leaf wilt, leading to the decline and death of infected palms.
Symptoms occur first in lower, mature leaves, which develop yellowing, browning and wilting of leaflets on one side of the rachis, while leaflets on other side of the leaf may initially remain green. Reddish-brown or dark-brown streaks develop on the petiole and rachis on the symptomatic side of the leaf. Eventually, the entire leaf dies, but the leaves do not droop or hang down around the trunk.
As the disease develops, it progresses towards the top of the tree rapidly, and infected palms decline and die quickly, within 2 to 3 months after the onset of leaf symptoms, with the entire canopy becoming desiccated and necrotic.
The disease is spread by contaminated pruning tools and by air-borne spores. Laboratory diagnosis using molecular techniques is required to confirm the identity of the disease. There is also no known cure for infected palms. Disease management options are limited to limiting further spread of the disease by prompt removal and sanitary disposal of infected trees and leaves, and disinfection of pruning tools.
Pink Rot
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Pink rot is considered a secondary disease that attacks weak or stressed palm trees. Because palms cannot repair wood tissue, they are more susceptible to diseases like pink rot when their trunks are damaged, or they are pruned too severely. It is important to avoid wounding a palm trunk, so even nailing something to the trunk is not beneficial.
Pink rot can attack any portion of the palm, including the trunk, but it most often affects new growth, causing leaf spots, and stunted or deformed growth. A tell-tale symptom is visible pink spore masses which may also produce brown, syrup-like ooze. There are a number of palm trees that are susceptible to pink rot, but it is mostly seen on the Washington Fan Palm, and the King and Queen Palms.
Because there is almost always an underlying cultural problem that encourages pink rot to develop, if possible, you should try to determine the cause and correct the problem. The underlying problem could be the wrong soil pH, planting incorrectly, watering improperly, poor drainage, poor nutrition, or even just the wrong palm for the site.
If the disease has not progressed too far, you can treat it for pink rot, and treatments should begin as soon as possible. Contracting an arborist would be a great advantage to help you create the most effective management plan for pink rot, which will include a systemic treatment applied to the soil, and regular fertilisation with a palm specific fertiliser.
Ganoderma Butt Rot
Click here to see Google images of Conk or fungal fruiting body of Ganoderma on Queen Palms
The fungal genus Ganoderma is a group of wood-decaying fungi that are found throughout the world on all types of wood—gymnosperms, woody dicots, and palms, and there are many different species of this fungus. Ganoderma butt rot is fatal for Queen Palms, so prevention is vital, and the palms seldom show more than a slow decline with stunted growth and discoloured, wilting leaves, until the disease reaches its final stages.
This soil-borne, white-rot fungus causes an internal discoloration and decay of the trunk, which is generally confined to the bottom 90cm to 1.2m of the trunk, destroying the palm’s lignins and cellulose, and eventually disrupting the nutrient-transporting xylem tissue. Once about 85% of the cross sectional area of the trunk has been destroyed by the fungus, the canopy may show signs of wilting or other water stress symptoms, followed by fairly rapid loss of the lower leaves, and eventually the death of the palm.
Fungal fruiting bodies called “conks” may emerge from the lower portion of the trunk prior to the death of the palm. Initially they look like hard marshmallows, but eventually they become woody, shelf-like structures with a brown top and white bottom. These conks can produce billions of reddish-brown dust-like spores that will blow everywhere, spreading the disease. Thus, while there is no control for this disease, removing conks in the early stages of their development can reduce the spread of this disease.
Be sure to remove or grind the stump after cutting down any palm to prevent Ganoderma conks from growing and reproducing on the stump. Some palms, however, never develop conks, and the only way to diagnose Ganoderma accurately is to cut down a declining palm and examine the trunk.
Thielaviopsis Trunk Rot
Click here to see Google images of Thielaviopsis Trunk Rot on Queen Palms
A fungus, Thielaviopsis paradoxa, causes a trunk rot of Queen Palms, but is largely confined to the softer upper parts of the trunk, often just below the crown. This fungus requires a wound in the trunk to become established, so good maintenance methods are essential when growing queen palms. Wounds are often caused by rough handling of these palms during transplanting or pruning, including pulling off dead leaves or leaf bases that are still firmly attached to the trunk.
Once established, this disease causes a soft rot of the trunk that may be visible from the outside as a water-soaked, often bleeding, or soft sunken area on the trunk. Once a majority of the trunk cross-sectional area has been rotted, the palm canopy may still appear to be healthy, and then quickly it may wilt or just suddenly topple over with no warning. There is no control for this disease, but it can easily be prevented by avoiding wounding the trunk.
Caution:
Sadly, Syagrus romanzoffiana can be invasive in many parts of the world; and especially in hot and moist tropical and subtropical regions. In Queensland Australia, and Florida USA, this palm is being monitored for its invasiveness and in certain places is already classified as invasive.
This species has been included by The University of Georgia Center for Invasive Species and Ecosystem Health as an invasive species in California, Florida and Hawaii. The Florida Exotic Pest Plant Council lists this species as a Category II invasive: Exotic plants that show signs of increasing in abundance, but that have not yet altered native plant communities.
In Australia the queen palm was traditionally grown in many Queensland gardens, but it is invading riparian areas and dry eucalypt forest. It is most widespread and common in South East Queensland, and also recorded as naturalised in tropical North Queensland. Flying foxes, bats and other animals eat the fruit and spread the seed, and this palm has caused injuries and death too many flying foxes who are attracted to the fruit, but their wings can get caught in the flower sheaths or leaves. The seeds can also cause severe constipation resulting in dehydration and death in younger flying-foxes.
I am concerned that this palm tree could also become invasive in South Africa, and especially in our subtropical regions. Therefore I urge caution when planting these trees, and would not be surprised if, in the near future, they are also classified as invasive here.
If they become invasive, small seedlings can be hand pulled, or spot sprayed. Larger specimens can be controlled manually by cutting the trunk anywhere below the lowest leaf. The trunks do not need to be treated with herbicides as they will not re-grow. After cutting the trunk remove all fallen fruit from the area to reduce the number of new seedlings, and dispose of appropriately to stop further spreading.
Warning:
The fruits may be poisonous to dogs but no specific toxins have been found. Symptoms reported include: vomiting, diarrhoea, constipation, lethargy, weight loss, blindness and muscle tremors.