Gardening > Sowing and Thinning

Sowing and Thinning

Seedling © Wellfordt & Dreamstime
With the exception of large species like bean, pea and cucumber, it is very difficult to sow just the right number of seeds. Inevitably this leads to overcrowded seedlings which need to be thinned out. If their numbers are not reduced the seedlings have to compete for light and food producing weak, spindly specimens which never fully recover from their poor start.

In order to be thinned the seedlings must be large enough to handle. The day before attempting to thin out seedlings, water them, and firm the soil around those which are to be left in place. The next day carefully remove the excess seedlings which are either to be discarded or replanted, with correct spacing, in another row.

The thinnings of root vegetables such as parsnip and carrot can not be replanted as this will cause them to "fork". Thin out carrots when they are just big enough to eat to reduce waste. If you have to dispose of any thinnings do not leave them on the ground as the smell of the bruised stems and leaves will attract slugs, snails and other pests.

Most leafy vegetables do not mind being transplanted. These can be thinned out in their rows leaving some seedlings to mature and the thinnings can be replanted elsewhere in the garden. Alternatively they can be sown in a seed bed in part of the vegetable plot and then all transplanted to a permanent home. When they are transplanted they should be put in with the correct spacing between plants. Water the soil where the seedlings are to be transplanted the day before and use a dibber to make  suitable holes. Plant at the same depth as in the seed bed, water in, and firm the soil. Do not transplant seedlings if the soil is particularly cold or wet.

Tomatoes, aubergines, peppers and runner beans are usually started off under glass in seed trays or individual pots where they grow until being planted outside. Lettuce is best left to mature where it is sown. Always check whether a vegetable can be transplanted or whether it must be thinned and then left to grow in its original seed bed.

It is possible to start off just about any plant indoors in individual  peat pots and then plant them out (pot as well) in the garden when they reach the required size. This is very labour intensive, seedlings need to be hardened off and there are natural limits of space and time to the number of plants that can be raised like this. For large, continuous crops, sowing outside and thinning are necessary options.

Some Vegetables which can be transplanted as thinnings or from the seed bed:

Leek, onion, kohl rabi, celeriac, kale, brussels sprouts

Some vegetables which must be thinned and left to mature (the thinnings cannot be replanted):

radish, carrot, salsify, scorzonera, swede, beetroot, turnip.