Anyone who gardens on the coast or on a wind swept hillside will understand the shelter belt catch-22 – how can I establish a shelter belt when the plants need a shelter belt to get established? The obvious answer is to protect the plants with a physical wind break, which is feasible if the prevailing wind is from one direction but more of a problem when your position is so exposed that the wind comes from all points and can be in excess of 70mph at times. The problem is compounded on coastal sites where plants have to be able to withstand salt laden air and light sandy soil usually with a high pH.
This was the subject of one of my first posts and it has taken us 5 years to solve this particular garden dilemma – what to plant and how to get it to survive. It has been largely trial and error, hard work, a little application of science but hardly Vorsprung durch Technik, and some damage to the bank balance.
The key element was the discover that Olearia traversii, the Chatham Island akeake or tree daisy, would tolerate our climate and soil conditions. Chatham Islands is an archipelago in the Pacific about 680 kilometers southeast of New Zealand. The climate is cold, wet and windy with average high temperatures between 5°C (41°F) and 10°C (50°F) in July, the southern hemisphere winter, very similar to the Outer Hebrides. It tolerates the wind and the salt and seems to thrive in our poor sandy soil, growing over 30cm (12 inches) a year.
As the soil is very light, we have discovered that planting at high density provides adjacent plants with support and helps prevent the plants from being torn out of the ground. However, even if the plants start to rock or develop a list to starboard, provided that the ground around the base of the trunk is heeled in, or in severe cases eroded soil is replaced, the plants will continue to grow.
This winter we have also increased the width the of the shelter belt beds. Ultimately the increased depth of the planting should increase the effectiveness of wind filtering and even if the outer plants are damaged the core of the “hedge” will be protected. The original plants are now over 1.5m (5 feet) tall and in theory could reach 3m or more, but I suspect that wind pruning will limit their height.
Oleariia traversii is attractive shrub, even though the flowers are insignificant and it bears no fruit. The leaves are a rich glossy green with a silvery underside so when the wind ripples the foliage the whole hedge shimmers and shimmys like a green and silver ribbon. It is also a wonderful refuge for the garden life – ever seen a flock of 60 House Sparrows disappear in a twinkling!