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Archive for July, 2014

Palm Growing At Home

Everybody recognises palm trees, they are the universal symbol for the tropics but many are hardy enough for our temperate climate gardens. Until recently New Zealand gardeners have had only a very limited range of palms to choose from. In the last five years the range has grown enormously as nurseries have been encouraged by gardeners eager to experiment.

Nevertheless, palms are, on the whole, slightly tender plants. Those that will tolerate regular frosts of -6°C. or more are few in number. If your minimum temperature does not drop below -2°C or if you are in a frost free area the range of suitable plants increases considerably.

There are two main styles of palms; the fan and the feather. The names refer to the layout of the fronds. Fan palms have the leaflets of the frond arranged just like a hand operated fan. The most widely grown fan palm is Trachycarpus fortunei, the Chinese Fan Palm. Feather palms have the leaflets of their fronds arranged along a rigid midrib like a bird’s feather. The most commonly grown feather palm is Phoenix canariensis, the Canary Island Date Palm.

Palms are extremely important plants to the world’s economy. The true date palm or commerce, Phoenix dactylifera, is rarely seen in New Zealand but is the most common commercially grown palm. The coconut, Cocos nucifera, is not far behind. Possibly more significant than fruit crops is the use of palms for shelter. Virtually every tropical third world village relies on palms as a roofing material.

Siting

Although palms are associated with sun and sand most species appreciate light shade when young. Shelter from wind is important if the fronds are to look their best but as the plants eventually become quite large they will eventually have to tolerate exposure to sun and wind.

When siting a palm remember to take into account the spread of the crown. This is not so significant with a mature plant as the crown is usually well above most obstructions. The problem is adolescent plants, which tend to have much the same spread as adults without the height. They take up a considerable area until the trunk begins to develop.

Soil conditions

Palms generally do best in a rich, moist well-drained soil. They have fairly strong roots that anchor them firmly. The roots of many palms can withstand a considerable amount of abuse, which enables the trees to be safely transplanted at almost any size.

Climate adaptability

Many palms are frost tender but there are quite a few that tolerate reasonably tough frosts. The best known are Phoenix canariensis and Trachycarpus fortunei but you should also consider Jubaea chilensis, Chamaerops humilis, Butia capitata, Washingtonia robusta and Brahea armata.
Palms often grow well in coastal conditions but benefit from occasional wash downs to remove any salt spray deposits.

Container growing

Palms often make superb container plants, both indoors and outdoors. Many are undemanding and tolerant of neglect. In cold areas it’s often best to keep young palms in containers until well established. That way they can be moved under cover for winter. Once they have a spread of over 1.5 m or so they should be hardy enough to plant out but if it’s not inconvenient it’s better to wait as long as possible.

Propagation

Palms are nearly always propagated by seed. They usually have only one growing point so vegetative propagation is not practical. Occasionally suckers form at the base of established plants and may be carefully removed for growing on but this is not a reliable method of propagation.

Palm seed varies greatly in its ease of germination. The most common problem is very hard seed coats. No amount of scarification or soaking will soften the toughest of them. Sometimes acid treatment is resorted to but patience is the usual method. Some, such as Butia capitata, may take upwards of a year in the soil before germination but eventually with the right combination of moisture, temperature and time they sprout.

Pests and diseases

Palms are not prone to any unusual pests or diseases. Frost damage is far more likely to the biggest problem.

Palm selection

Do not expect to find all of the species at your local garden centre; many of these palms are only available as seed. Unless otherwise stated all of these palms have panicles of small yellow flowers.

Archontophoenix

The King Palm (Archontophoenix alexandrae) is a prominent feature in many tropical and sub-tropical areas but it is too tender for all but the very far north. Archontophoenix cunninghamiana is a better bet but it still requires a near frost free climate with warm summers. It is a feather palm with long arching frond. It can reach 20 m high but rarely exceeds 7 m in New Zealand gardens. The flowers are followed by masses of small red berry-like fruit. Archontophoenix cunninghamiana may be grown indoors but it needs high light and humidity levels. The seeds germinate easily.

Arenga

Two species of this genera are suitable for growing outdoors in mild areas. Both are feather palms with broad leaves that have silvery undersides. Arenga pinnata requires near frost free conditions but Arenga engleri from Taiwan will tolerate infrequent light frosts. Both species have interesting flowering habits and fruit. Arenga pinnata is monocarpic; it dies after flowering although it takes at least ten years to reach maturity. Arenga engleri survives to flower again but the leaf stem beside the flower stalk dies. Both species have fruit with extremely caustic pulp. Both species are unlikely to exceed 3.5 m high under New Zealand conditions but Arenga pinnata may reach 18 m high in its native South East Asian region. Arenga pinnata seed germinates quickly and easily but Arenga engleri is erratic and may take several months to sprout. Not usually grown indoors.

Brahea

These fan palms are becoming more common in New Zealand gardens. Both of the common species Mexican Blue Palm (Brahea armata) and Guadeloupe Palm (Brahea edulis), are reasonably hardy and adaptable plants. B. armata has beautiful, finely divided glaucous fronds. It is the hardier of the two and will withstand -8°C once established. It has a stocky trunk for many years but may eventually reach 12 m high. Brahea edulis is tender when young but withstands -6°C once the trunk is over 10-15 cm diameter. It grows slowly to about 15 m high. Both species are tolerant of drought and low humidity. Brahea armata has 12 mm diameter brown fruit, while Brahea edulis has edible 18 mm diameter blackish fruit. Grow in full sun. The germination of Brahea armata seed is very erratic and may take up to year. Brahea edulis is less tricky but still not very reliable. High light requirements make Brahea unsuitable for indoor cultivation.

Butia

The Yatay, Pindo Palm or Jelly Palm (Butia capitata) from Brazil is a hardy feather palm with long drooping olive to bluish green fronds. It will withstand -10°C once established and deserves to be more extensively grown. It grows to about 7 m high. The flowers are followed by yellow to red 25 mm diameter pulpy fruit. Grow in full sun. Seed germination is highly variable, it is unlikely to take less than two months and may be a year or more. High light requirements mean this palm is not very suitable for growing indoors.

Caryota

The Fishtail Palm (Caryota mitis) is often grown as a house plant and is unlikely to grow well outdoors except in the very far north. Caryota urens has slightly lower heat requirements but will not tolerate any frost. It has very dark green, slightly arching fronds. All Caryota palms have intricately cut bipinnate feather fronds. Most species grow to large sizes (over 18 m high) in the tropics but are unlikely to exceed 8 m high under New Zealand conditions. They have fruit with caustic pulp that should not be handled with bare hands. The seed germinates easily. Caryota palms grow well indoors but prefer warmth and high humidity.

Chamaerops

The Mediterranean Fan Palm (Chamaerops humilis) is a bushy fan palm that is usually multi-trunked and will not exceed 6 m high. The trunks take many years to form and are seldom seen in gardens. Most plants grow to about 1.5 m high x 5 m wide. The fronds are tipped with sharp spines. It is a very hardy palm that tolerates -15°C. Tolerant of low humidity and drought. Grow in full sun. The seed germinate well and takes about six weeks to sprout. High light requirements and sharp spines make it unsuitable for indoor use.
Chilean wine palm-see Jubaea

Cocos

The Coconut Palm (Cocos nucifera) is one the most important commercial crops. It is essentially a tropical palm but will grow outdoors in frost free areas of the far north. It is a large feather palm that often develops a leaning trunk. It may grow to 30 m high in the tropics but rarely exceeds 8 m in gardens. The fruit seldom will not develop to its normal size in our climate but becomes large enough to be a conversation piece. Coconuts germinate well but take at least three months to sprout. They need consistent warmth and the whole nut must be planted, do not strip away the husk. May be grown indoors but resents cold draughts.
Date palm-see Phoenix

Euterpe

Although primarily a tropical plant the Assai Palm (Euterpe edulis) will grow outdoors in frost free areas with warm summers. It is a feather palm with arching fronds and graceful drooping leaflets. The trunk is improbably slim fro the size of the foliage head and may grow to 25 m high although it is unlikely to exceed 10 m high under New Zealand conditions. The fruit is black and about 12 mm diameter. The seeds germinate easily. May be grown indoors when young.

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