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A Northumberland Alpine Gardener's Diary

This entry: 10 September 2006 by John Richards

Northumberland Diary. Entry 4

Avoiding extremes!

Northumberland Diary 4. September 10th 2006.

The longer I grow alpines, the more I am convinced that the secret of success is to avoid extremes. Many species are fussy about both high temperatures, and low temperatures. Equally, they loath drought, but also overwatering (and especially overwatering after drought!). If you can make sure that your plants inhabit a temperate climate with a steady but modest supply of water, then you have solved most of your problems. Of course, there are pests and diseases, not to mention competitors (otherwise known as weeds) to contend with, but the happier the plant is with its environment, the better it will be able to fight unwanted adversaries.

Not every plant is the same; far from it. The real trick is to know the limits of the environmental comfort zone for any one plant, and then try to keep within it. On the whole, the trickier the plant, the more constrained its comfort zone. We have lots of tricks with which we try to ameliorate climatic extremes. We shade glasshouses, run fans, plunge pots, cover plants in winter with frame lights, or bring them under glass, put warmth-loving plants against a south wall, or find the coldest spot in the garden for high alpines. If the plants live in pots, we can try to keep within the comfort zone by moving them about; full light in winter, under the bench, or plunged outside in summer; a cool spot in summer, but with a modicum of frost protection in winter.

Most of us try these tricks to some extent, but when it comes to plants in the garden we find that we have much less room to manoeuvre. There are still techniques we can use of course, portable frame lights or mini-cloches, but the options are more limited. Many of us have favourite plants, for which we are prepared to make an extra effort. I adore the group of Himalayan primulas known collectively as ?the petiolarids? (section Petiolares). I confess I tend to think of them as ?my pets?, at least to myself. Petiolarids seem to have an even narrower comfort zone than many plants. In particular they abominate hot sunlight and dry air, and seem to be happiest when cool and humid. Experiments with a porometer have shown that this group is incapable of closing their stomata (the leaf pores through which they ?breath?), so that the leaves rapidly dessicate in dry air or sunlight. Nevertheless, if you overwater them when they are too hot, they rot! Also, some are not very hardy in a cold winter. Real problem plants!, but exquisitely beautiful in flower and well worth any trouble. You would think the secret would be to grow them in a pot, but they don?t seem to like root restriction much either!

I would never dare say that I have cracked the secret of any tricky plant, let alone petiolarids, but I have been having more success over the last three years, since I started to grow them in fishboxes. I think that fishboxes do have some beneficial properties, for instance thermal inertia, so they tend to stay cool when it is hot, and warm when it is cold. However the real boon is that they are so light that you can move them around, almost like pots. In the summer the boxes live right under a dense Parrotia, in total shade, cool conditions and constant high humidity. In the spring and autumn I keep them in dappled shade. In mid winter the sun never reaches my garden, and I find the plants do best exposed to the maximum light I can find at that time of year. Even fishboxes are not that light, when well watered, and to save my back I move them on a sack trolley. I moved them from under the Parrotia to dappled shade two weeks ago, and thought I would show one of the boxes en route. The shrub in the box is Epacris alpina.

Colchicums and immortality
Since I last wrote, colchicums have been popping up all over the garden. C. bivonae was joined first by the hybrid C. ?agrippinum?, and then by what I think must be ?Lilac Wonder?. This emerges almost white, and then shows paler outer segments than the inner. After two days or so, the whole flower turns a uniform lilac. Then it has become the turn of ?The Giant?, perhaps my favourite of all. I owe these, and several others yet to flower, to one of the most generous and kind gardeners, the late and much missed Paddy Ryan, who brought me quantities of a wide selection of colchicum bulbs shortly after we moved to the present house some 17 years ago. Every autumn when they flower, I think of Paddy. A gift of plants bestows a kind of immortality.

Colchicum ?agrippinum?

Colchicum 'Lilac Wonder'

Daphne 'Beauworth'
I try to grow as many of the wonderful Daphne hybrids raised by Robin White as I can. I think my favourite of all is D. ?Beauworth?, a cross between  two wonderful dwarf species, D. petraea and D. jasminea. Like the latter it has a long flowering period, and is often at its best in autumn. I grow it in a pot planted amongst some of my artificial tufa, which might well form the topic of the next diary entry.

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