My comparative compost test seems to be producing a definitive result more quickly than I'd expected. I was over by the greenhouse, heading for the pot shed and not even thinking about the plants on the concrete particularly, when I noticed out of the corner of my eye how well the repotted Verbascum chaixii var. album were doing. From being sad, stunted things whose few leaves were rapidly dying back, they are transformed to big, lush specimens with foliage covering the compost and glowing with health. I paused, and looked more carefully at the other plants I'd potted on.
Four Salvia lavandulifolia, going nicely in six inch pots. Lysimachia atropurpurea 'Beaujolais', much bushier than it was, pretty much doubled in size and a far healthier shade of green. Linaria purpurea 'Canon Went' likewise much taller and bushier, and leaves a nice shade of glaucous green. Echium vulgare, which had like the Verbascum started to die back to miserable little central rosettes of dormant leaves pending a change in their fortune, leafy once again and a match for those planted in the open ground (which I noticed when I went up to put sugar on the bees).
One Linaria had come out purple instead of pink, as 'Canon Went' should be. I went to write a label for the pot so that I'd know it was a rogue colour, and as I leant over to push the label into the pot it struck me that the purple plant wasn't looking nearly so good as the others, and nor were the others in the same row. They were shorter than their neighbours, far less bushy, and a pale, sad colour. Indeed, some stems had already started to die back as if they had given up for the season. Then I noticed a similar stunted short row of Verbascum, whose leaves were not nearly covering the compost, and a pallid trio of undersized Lysimachia.
I guessed the answer before checking the label in each pot and seeing that all had PF written next to the plant name, standing for peat free. Those of you who read my earlier post on the compost test will know that I bought a small bag of B&Q peat free compost when I was buying my usual large bales of their regular compost. I'd go peat free if I could, for the sake of the environment, but I would like some reassurance that the peat free alternative works as well as the normal compost. Or at least works acceptably well. You may remember that after some thought I decided to group the peat free pots of each variety, in case they needed watering more or less often than the other. That made the trial less perfectly random than it would have been if I'd mixed them in, but fairer in as far as each type of compost could get the treatment that suited it. One of the difficulties with watering at the plant centre where much of the stock was bought in from a variety of suppliers was coping with the fact that pots of compost that hung on to water like a sponge ended up mixed with pots of compost that appeared to have no water retaining abilities whatsoever.
When I put the peat free pots in separate rows from the rest of that variety I wasn't thinking about how I'd judge the results of the test, but it turned out to make a visual assessment brutally easy. The B&Q own brand peat free compost did not support plant growth nearly so well as their regular compost. Or at least, not the top growth. I haven't knocked any of the subjects out of their pots to look at their roots, but as far as leaf growth goes the peat based compost won by a mile. In fact I'm surprised by how quickly the repotted plants have responded. I checked just now, and I only potted them on 12 August, three weeks ago and a day.
I hope B&Q can produce a good peat free compost, I really do. I'd buy it if they did. But if you are going to go to all the expense and trouble of buying and sowing seed and taking cuttings you want to use compost that produces decent results. Bad compost is a terrible waste of money and enthusiasm. At its worst it can produce stunningly bad results, though the gardener may never know the reason for their run of duds. A few years ago I bought a root of Anemone rivularis from the normally reliable Avon Bulbs, and around the same time a colleague gave me a small rooted cutting from her grandmother's Hoya. I potted both up and neither did anything. The Anemone sent up about two leaves and lingered on in its pot in the greenhouse, never looking strong enough to plant out into the garden while refusing to absolutely die. Eventually in despair I planted the Anemone out anyway, and repotted the Hoya, whose failure to grow had been a mystery to its donor who insisted they were normally pretty vigorous. Both sprang into life, the Hoya making feet of new stems and quickly graduating to a thirty centimetre pot, and the Anemone making a normal sized plant the following year. I could only conclude I'd had a bag of particularly bad compost.
Back to the compost trial, it does go to show how if you've bought a plant and aren't able to get it into the ground as quickly as you'd hoped, it may be very grateful for a bigger pot with some extra space to root into and fresh nutrients, even if it's only for a month.
Addendum I'm afraid the above is an untidy mixture of imperial and metric measurements, but so is my mind (along with many people my age) and much of UK commerce. And when did you ever hear somebody mutter the warning 'give him a centimetre and he'll take a kilometre'? Inches, yards and miles are still deeply embedded in the English psyche, even if we do manage to measure our flowerpots in centimetres on occasion.
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