The tender young seedlings can be moved to an unheated greenhouse or a cold frame once the danger of severe frost is over, say mid-April. The increased light levels and cooler temperatures will give stronger, less “sappy” growth. Extra protection with bubble wrap is a good idea.
Potting-on of the seedlings may be necessary if you have sown your seeds all together in the same pot. To cut down on “potting-on” of seedlings and save time, disturbance and damage to the seedlings, I favour sowing the seeds more or less separately in individual cells. If it is intended to plant out a group of seedlings together, then sow several seeds in each cell, as shown in the “window sill propagator” photo on the previous page.
Allowing the seedlings to dry out is one of the most common causes of failure following germination of seeds. As they still have tiny roots, they cannot cope with any interruption of moisture supply. The use of capillary matting and a water reservoir, as in the photo, will help to prevent disaster.
Damping off of seedlings or rotting of seeds is usually caused by not enough ventilation, and/or saturated compost. Compost must be able to drain, so that the seedlings are not drowning!
Do not let slugs and snails eat your young seedlings! In a protected location, such as a greenhouse or cold frame, it is alright to use slug pellets. It is virtually impossible to prevent slugs and snails getting into the greenhouse or cold frame, so take precautions.
Protect Bean and Pea seeds and young plants from mice and voles. Mice and voles will find the seeds and seedlings by scent, and then proceed to dig them up and eat them, leaving characteristic little holes in the ground, as shown on the left. Traditionally, peas and bean seeds are dipped in paraffin before being sown, whether in a greenhouse or the open ground. This disguises the smell of the seeds. In addition, try to provide physical protection, by using a lidded box in a greenhouse or cold frame. If sowing the seed directly in the ground, a fine wire mesh will provide protection.
Protect young seedlings from the birds, with some plastic netting, particularly against pigeons. They seem to be particularly fond of the Brassicas, as well as Pea and Bean seedlings.
Do not plant out tender varieties too early. Tropical or Semi-tropical varieties, such as Sweet corn, Courgettes, Squashes, Tomatoes, Peppers absolutely hate it and frequently sulk or even die off if they get chilled by a cold wind at night. The ground is also likely to be rather cold unless you have previously covered the ground with black plastic or cloches for a couple of weeks. You would not like to spend the night outside in April or May!! For details of methods to prevent your seedlings suffering a chill, see the relevant vegetable growing instructions.
There are two well known cold spells that have been given special names in folklore.
“Blackthorn Winter” often occurs just before the middle of April for several days. “Ice Saints” often occurs during the second week in May. For both these periods, make sure that you have fleece or cloches handy to cover any tender seedlings or plants before they get frosted.