Hardy palms

Images: Tobias W Spanner and Martin Gibbons, and provided by The Palm Centre who supply a wide range of palms

Palms have become more and more popular in UK gardens - mainly as a result of milder winters.

Most palms need tropical or sub-tropical temperatures but there are some suitable for outdoor planting in the British Isles; those that thrive in favoured areas include Trachycarpus fortunei, T. wagnerianus, Chamaerops humilis, Butia capitata and Jubaea chilensis. Where varying degrees of protection can be provided during winter, species of borderline hardiness can be grown - including Washingtonia filifera and Phoenix canariensis. Several species are extremely cold-resistant but require summer heat to grow well; they include Sabal minor and Brahea armata.

Hardy palms are invaluable as structural plants in ‘tropical’ style gardens in temperate areas. Many are best grown as individual specimens, whereas others look good in groups of a single species. They associate well with phormiums, cordylines, yuccas and bamboos together with hardy bananas, cannas and tree ferns.

Cultivation

Palms can be grown in containers of loam-based John Innes No 3 compost. Hardy palms for planting out in the garden should be grown initially in containers and brought under cover for the winter until well established in at least 5-litre pots. Plant out well-rooted plants in mid-spring to allow time to establish before the winter. Choose a sheltered position with well-drained soil as few palms tolerate windswept locations.

On heavier clay soils prone to winter waterlogging thoroughly cultivate a wide area. If adding organic matter spread it over the surface of the prepared soil and fork in. Then throw the soil up into a low mound. Planting into the centre of this will keep at least some of the roots above saturated soil in winter. Do not place grit or gravel in the bottom of a hole dug in clay - this will merely create a sump where water collects in winter.

Palms grow slowly but need adequate space as they do not compete well with surrounding plants and most are not tolerant of shading. Unsightly dead lower fronds can be removed but do not cut them back too close to the trunk. Apply an annual feed of a general-purpose fertiliser each spring and keep well watered in dry weather.

Winter protection

As the palm's stems thicken with age, the plants become more tolerant of lower temperatures, although smaller plants should always be protected in cold spells. Prolonged winter frosts and cold winds damage the leaves and may kill the central growing point. Where cold winters occur, prepare plants by tying the leaves together to protect the growing point. Wrap the whole plant loosely with a breathable material such as hessian, loft insulation, carpet underlay or similar material. A protective covering of polythene supported over the plant will keep the worst of the winter wet or snow off but do not wrap with polythene as this will encourage rot.

In areas with mild winters plants can be left unprotected except for very cold spells. If posts are hammered in place in the autumn it is then a relatively simply task to place protection around the plant if a very cold spell is forecast. A 10cm (4in) mulch of coarse bark or similar material over the soil will help protect roots. For colder areas more substantial protection can be provided using a timber framework with a double layer of polythene stapled to the inside and outside of the structure.

Palms grown in containers should also be protected or brought under cover for the winter. Where containers are left outdoors ensure the pot is also wrapped to prevent frost damage to the roots.

Selections

Horticulturally palms can be divided into two broad groups: fan palms with palmate leaves and feather palms with longer pinnate leaves.

Most of the palms discussed here are sufficiently cold hardy to survive winter temperatures in much of lowland Britain. However, plants wet at the roots or exposed to hard frosts following wet weather will be more liable to winter damage. So the temperatures quoted should be regarded as a guide to relative hardiness. Temperature hardiness refers to mature specimens - young plants will be more liable to cold damage.

Brahea armata (Mexican blue palm)

Native to Mexico and California. Attractive slow-growing fan palm with stiff pale blue leaves. Hardy to about -10C (14F) in a well-drained, sheltered sunny spot. Brahea edulis (Guadalupe palm) has large fan-shaped leaves. It is probably not as hardy and needs protection from winter wet.

Butia capitata (jelly palm)

Native to Brazil and Uruguay. Relatively slow growing with attractive arching green-blue leaves. One of the hardiest feather palms, it can be grown outdoors in sheltered gardens where it may tolerate -10C (14F). It is also suitable for heavier clay soils. Butia yatay has lighter coloured leaves.