Another growing season is under way and an outline plan is in place for the main crops but as always it will remain flexible, allowing for the occasional impulse buy, be it seeds or plants.
We should all be organised for the marathon of a gardening year ahead, with the elements that support seed sowing and subsequent potting-up of young plants all to hand. But it is understandable if you’re so confused about which compost to buy that no decision has been made yet.
Acquaintances will often boast of finding a cheap source of growing bag or multi-purpose compost, and perhaps that is every gardener’s dream, but you have to ask how good is it? A particular mix might facilitate the germination of seeds but what follows is the most important bit. Will it have the substance to support a vigorous plant in the first six weeks of its life?
Even the best composts will run out of steam later in the season, when hungry plants such as tomatoes demand more food for developing fruits. That’s when we step in with supplementary feeding, but if there’s a doubt about it taking them to that stage, leave well alone.
The performance of different composts is spread by word of mouth between gardeners who grow for show, and that can be a reasonable pointer for others. However, the most valuable information comes from organisations that specialise in this field through experimentation. In this respect, Gardening Which is streets ahead. They have been testing different composts every year since 1985 and the most recent magazine issue offers an update on their latest trials.
The tests involved buying 22 different composts listed as being multi-purpose, for seeds or for growing-on young plants. They were purchased in different parts of the UK to overcome the fact that quality varies from bag to bag. Each was tested with several criteria in mind: Is the texture fine enough for small seeds? Does it support germination? Do seedlings and plugs perform well in it? Is the quality consistent from bag-to-bag? Several plant species were used to allow for differing germination and growth requirements.
J Arthur Bowers Traditional All Purpose Compost came out top with a score of 81 per cent. This was followed by B&Q’s own brand Verve Sowing and Cutting Compost on 76 per cent, and Verve Grow Your Own Growing Bag 74 per cent. Westland Grow-Sure Seed and Cutting Compost 73 per cent, and Verve Sowing and Cutting Compost 71 per cent, completed the top five.
A few composts that scored below 40 per cent in these trials were given the ‘don’t buy’ tag because at least one of the plant species struggled to grow in them. J Arthur Bowers John Innes No.1 soil-based compost and Verve John Innes No.2 Potting-on Compost came well below expectation.
Unfortunately, the best composts still use peat as the bulking agent, and it is a finite resource. The top three in the Which test had a 100 per cent, 75 per cent and 8o per cent content respectively. But gardeners have relied upon peat for generations and are reluctant to give it up. It would take something comparable to peat, not least in performance, to encourage change and this is the problem. None of the bulking materials, natural or otherwise, used in experimental composts to date, have convinced the gardening public they’d be a worthy substitute.
In explaining why no peat-free composts have been recommended this time, Gardening Which explains that they have never done well in their annual trials, but they see hope in Melcort Sylvagrow Compost (wood bark-based) on sale to the gardening public this spring.