JOHN INNES COMPOSTS: 17 March 2003
RW (who gardens on two allotments with a total area of about 570 square metres, and operates a three-year, crop-rotation plan) e-mails: "I understand that John Innes potting compost numbers 1, 2 and 3 relate to the amount of nutrients each has, but am a little confused as to which compost number various plantlets should be potted on to. For instance, in 'R J Harris's Moon Gardening' [see the link at the foot of the page. Ed] you pot on lettuce straight into John Innes No 2 and not No 1. Is there a general rule, or is it a matter of experience?
Mr Harris replies: "All of the vegetable and flower seeds germinated in pots or containers in the walled kitchen garden at Tresillian are sown in John Innes No 1.
"There is no exception to this.
"The manual explains what the No 1 compost is made of, but there is no benefit in trying to make it yourself, because it can be bought in any good garden centre in a very useful range of quantities. In any event, securing sterilised loam -- an essential ingredient in the John Innes composts -- is well nigh impossible for most amateur gardeners. And even if you could secure a supply, you would have terrible trouble ascertaining its nutritional value and then correctly balancing the other ingredients to take account of that value -- which, always, is a unique value.
"See the manual for a detailed explanation of all of this."
The seedlings Mr Harris raises in the No 1 compost are transplanted into John Innes No 2, to grow on to the plantlet stage. See the manual for a description of the No 2.
"This is how the lettuce is treated prior to the lettuce plantlets being transferred to the open garden," says the head gardener.
"The No 3 John Innes -- and, indeed, the No 4 -- is used for the plants that spend all their life in a container of one kind or another. This is whether the plant is a shrub or a tree.
"Note that, as a fixed rule, the higher the number of the John Innes, the greater is its nutritional value."
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