Architectural Plants. Christine Shaw

excess moisture can run away immediately. The planting area should never be allowed to dry out, but boggy conditions would be unsuitable. This is an exceptionally easy fern to grow, providing it has been planted correctly. No annual feeding is needed, and pests and diseases rarely cause problems. The only annual maintenance is removing any older brown fronds. Cut them off as far into the plant as possible with secateurs.

       Dicksonia antarctica

       Tasmanian Tree Fern

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      Dicksonia antarctica is everybody’s favourite tree fern.

      Tree ferns are fabulous plants to own. Few plants are more exotic than this leafy giant. A thick, fibrous chocolate-brown trunk is topped with huge deeply cut fronds 2.2m (7ft) long. Dicksonia antarctica starts to form a trunk after five years, which then grows at only 30cm (1ft) every ten years, so buying a baby plant will need a lot of time and patience to see it develop into something spectacular. A plant this slow would be fine in a container for several years as long as the compost is kept moist at all times. Container-grown specimens look wonderful in a shady conservatory.

      There are lots of mature plants offered for sale at nurseries and garden centres, and many thousands of Dicksonia antarctica are imported from forest clearance sites in Tasmania and Australia. Please buy from a reputable nursery to ensure that these plants are not illegal imports. If there is any doubt at all as to their origin, leave them where they are and buy from somewhere else.

      This fern is extremely fussy in its requirements – it is almost like buying a pet. Shade is essential for the very best results. A sheltered position is also important, not only shelter from the wind but also from anyone brushing past it. Humidity is necessary too – ideally, the trunk should be sprayed twice daily during the hot summer months.

      The best soil is peat, or peat substitute, mixed with leaf mould and silver sand for drainage. This is usually not difficult to organize if the fern is being planted into a container, but it is a little unrealistic for most gardens. It will, in fact, grow in any light soil that holds some moisture without ever being boggy. Enrich it annually with either leaf mould or kitchen waste from the compost heap.

      Watering should be done regularly to keep the soil just about moist. The occasional application of a balanced dilute feed poured into the top of the trunk can have a remarkable effect on how many new fronds are produced – twice the normal number can be expected. Feed weekly from mid-spring until mid-summer.

      The fronds should remain evergreen for several years, but if ideal conditions cannot be met, they are quite likely to go brown. If this happens, cut them off at their base and try to treat next year’s fronds with a little more care. Propagation is difficult and best left to a specialist fern propagator. Pests and diseases are rarely a problem.

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      A bird’s-eye view of a tree fern is an excellent way of appreciating the foliage.

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      In winter, a handful of straw pushed into the crown keeps the frost away from the most delicate part of the plant.

      These plants are reliably hardy only in mild inner city gardens or those near the coast. In colder gardens, some winter protection will be needed. Tucking a handful of straw or fleece into the top of the trunk will be enough to protect next year’s new fronds (see photograph, right). Push the straw down gently into the hollow bit where new fronds emerge. It should stay there without being fastened down.

      The existing year’s fronds can be allowed to frost and turn brown, and then be cut off at their base. A much better plan, however, would be to protect the fronds by wrapping them in horticultural fleece for the winter. Having several years’ worth of fronds on a tree fern makes it even more lush and splendid to look at.

      To wrap Dicksonia antartica for winter, all you need is a ball of hessian string, a roll of horticultural fleece and, unless you are around 2m (6½ft)tall, a stepladder. Instructions for winter wrapping, together with some useful tips, are given on the opposite page.

      1. Scoop the fronds up vertically and tie them together firmly with hessian string.

      2. Tie one end of the roll of horticultural fleece to a leaf stem to act as a starting point.

      3. Wrap the fleece around all the foliage several times.

      4. Once you have wrapped the fern completely, fold some of the fleece over the top of the fern to protect the leaf tips, and secure it in place with string. Tie string around the fern in several more places to secure the rest of the fleece.

      5. This photograph shows the finished ensemble.

       Some points to remember

      • Tie the string firmly but not too tightly to allow for its easy removal during the winter if a warm spell of weather approaches. The fronds would also appreciate a bit of fresh air now and again.

      • Instead of using horticultural fleece, after tying up the fronds with string, stack straw bales around the whole plant instead. This looks more aesthetically pleasing than fleece, although obtaining straw bales isn’t always practical if you live in a large town or city.

      • If you use straw bales, remove them the minute the weather warms up. If they are left on for more than a couple of months at a time, the heat generated by the straw can cook the fronds, turning them into a mushy mess, which rather defeats the whole point of wrapping them up in the first place.

      • If your tree fern is being grown in a container and not in the ground, the roots will need a bit of protection from the frost too. Either move both the plant and its pot into a shady porch or conservatory for the winter, or wrap it all up as described in the steps and, in addition, wrap a large thick blanket around the pot. Rolls of bubble wrap could be used instead, if preferred. This will keep everything – roots, fronds and next year’s new growth – cosy for the winter.

       Dicksonia squarrosa

       New Zealand Tree Fern

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      A beautiful tree fern with chocolate-brown veins across the back of the fronds.

      A sumptuous-looking tree fern from New Zealand that is more delicate in appearance and less well known than the more familiar Dicksonia antarctica described on pages 71–73. The trunk is quite slim and of the very darkest chocolate-brown. The same colour is also found on the underside of each frond, running the length of the leaf veins and, unfortunately, hidden from view for most of the time. The fronds are large and spread out gracefully from the top of the trunk. These can easily be 1.5m (5ft) long.

      Although home-grown tree ferns