Magazine article The Spectator

The Case for White

Magazine article The Spectator

The Case for White

Article excerpt

Gardens

Nothing about horticulture irritates and soothes, so much as its deep conservatism. Gardeners and nurserymen, aided and abetted by manufacturers and gardening commentators (like me), still pursue some gardening practices more suited to Gosford Park in its heyday than modern, modestly sized and modestly funded gardens. Take just one example: terracotta-- coloured, round, plastic plant pots are widely used, for no better reason than that they 'resemble' the clay pots they finally replaced (which being hand-thrown had to be round); yet this prevents the efficient use of precious space in tens of thousands of small greenhouses and cold frames. Square pots are easier to line out, stack and pack, yet not every commercial grower uses them even now. And, whilst on the subject of pots, why are they not white, rather than terracotta or black?

It has been known for 20 years (though not by me, I confess) that white pots have two distinct advantages over black ones for cultivating any vigorous plant which stays more than a few months in a pot before being sold, such as many perennials, shrubs and, most especially, trees. Black absorbs heat whilst white reflects it, so roots in white pots are less likely to be scorched and damaged in hot weather. Moreover, roots naturally (by the forces of negative phototropism and geotropism, for those who have found it impossible to forget their school botany, however hard they have tried) grow away from light, and obey the pull of gravity. In white pots, which allow a small amount of light through, roots grow straight downwards and do not impede each other; in black pots they grow to the edge and race round, like motorbikes on the Wall of Death. This is especially serious for trees if they stay in the same-sized pot for more than a year, as 'secondary thickening' occurs to roots just as it does to trunks and stems.

This Easter, if you carried home from the garden centre a six-foot-tall ornamental 'standard' tree, you may have discovered, as you planted it, that it had 'girdled' roots. Even if you took care to pull the roots apart, there is a chance that, when you take away the tree's supporting stake a couple of years hence, it will blow over. After planting, the knots of roots only very slowly and imperfectly push outwards into the surrounding soil and may never recover enough to anchor the tree sufficiently. …

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