Gardening: Winners without water

By Meg Liptrot

Subtropicals come out on top in dry summer, writes Meg Liptrot

Musa "Hamoa" bananas thrived in Auckland this summer. Photo / Meg Liptrot
Musa "Hamoa" bananas thrived in Auckland this summer. Photo / Meg Liptrot

When planning a water-savvy garden, think about choosing plants with adaptations for dry weather. You could virtually hear a sigh of relief from plants after the heavy rain last weekend. But although we had some sustained rainfall it wasn't enough to improve the very dry soil beyond the first couple of centimetres.

The subtropicals in our garden are the surprising winners of his long dry spell. The bananas have remained lush, with only occasional watering right through the heat.

I just harvested the best bunch ever from our Musa "Hamoa" bananas. Even our 2-year-old Abysinnian (ornamental) banana looks healthy and vigorous and is at least 3m, filling a corner of the garden with its broad leaves.

Years ago at the Ellerslie Flower Show in Auckland, I bought a couple of Heliconia subdulata for their dramatic lobster-claw flowers. This tropical species has thick rhizomatous roots like ginger, where the plant stores its energy. This root-type helps a plant cope with drought.

The heliconias have flowered beautifully with very little attention, and have colonised themselves in clumps in our food forest, echoing the banana foliage in the sunny margins.

If you look at the adaptations plants have evolved you can see how certain species will cope with dry conditions much better than others. Some retain water in their stems and foliage. Succulents are the most obvious contenders, with their plump juicy innards acting like little water vessels in their natural desert habitat.

Banana plants contain plenty of moisture in their stems and trunks and have done well in the drought.

When planning a water-savvy garden, think about choosing plants with adaptations for dry weather. Many plants fall into this category, so inspiration and design aspirations should not be dampened.

Species with glaucous foliage (silver or grey colours) reflect light, reducing the surface temperature of the plant. Plants with fine fuzzy hairs on the leaves and stems (tomentose) reduce the speed of air flow near the surface of the leaf. This adaptation slows down water loss through tiny holes, called stomata, on the underside of the leaves, and helps keep the air more humid around the foliage.

An example of silvery glaucous foliage is Euphorbia glauca (sand spurge), a threatened species endemic to New Zealand. This plant, found in coastal areas, has soft silver foliage along the length of spreading red stems. This and native iris, Libertia peregrinans, also a vulnerable species, are natural companions. Both are usually available from garden centres or native plant specialists.

Pohutukawa is a perfect example of a tree evolved to cope in harsh conditions. They perch precariously on cliff edges, get buffeted by coastal heat, wind and salt air, yet flower happily year after year. The undersides of leaves, stems and buds are covered in downy tomentose layers that reduce moisture loss. The top surfaces have a hard waxy cuticle layer that guards the leaf from desiccation from salt, and retains moisture and leaf condition like well-buffed and waxed leather shoes.

The feijoa has similar layers. They are both members of the Myrtaceae family, which is easy to see in the flowers, with their clumped red stamens. We have three feijoa "Kakapo" as standards (long trunk, round top) at our place, which haven't been watered but are quite happy.

They are underplanted with a hedge of Hibiscus rosa-sinensis which, without water, has flowered consistently right through summer. Both are mulched in winter.

If you are planning new plantings then get them in the ground in autumn, and water-in well, so they become settled before the onslaught of next summer.

Be prepared for the opposite conditions and a rainy summer next year and put dry-tolerant plants in a spot with good drainage, such as a gentle slope or free-draining soil. Don't plant in an area that is typically wet in an average year. Some of these plants are likely to turn up their toes if they are stuck in waterlogged soil.

Next week: A cutting-edge public garden designed for extreme Australian conditions.

- Herald on Sunday

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