THINNING AND WEEDING
When the seedlings are about 1 in. high, thin out according to the distances recommended for the varieties being grown. At the same time remove any weeds that have come up. After thinning, firm the soil where it has been disturbed. It is better not to thin autumn-sown seedlings until the following March; where they have come through too thickly (as they may in the warmer southern counties) they should be lightly thinned in October and fully thinned the following March.
HOW TO TELL SEEDLINGS FROM WEEDS
The easiest way to recognize the seedlings of the varieties sown inis to sow a very small quantity of each in a box in the . Label each kind clearly. The seedlings will come up two or three weeks before those sown out-side, thus giving the gardener time to become familiar with the look of the plants. If No-Soil or John Innes compost is used and the box is covered with glass, there will be no competition from weeds.
Stiff-growing, like tagetes and , require no staking and even the taller ones, like cosmos, will stand unaided. Soft plants, like cornflowers and eschscholzias, need support. Provide this by inserting small twiggy sticks at about 6- or 8-in. intervals all over the area once the seedlings have been thinned.
Sowannuals in boxes in the greenhouse in late February or early March. Use No-soil compost, John Innes seed compost or a vermiculite mixture, pressed down and levelled 1/4 in. from the top of the box. Sow the seeds very thinly on the compost, sift some silver sand over just to cover them and firm it down with a wooden presser.
Water each box by immersing it carefully and gradually in water with the chill off until the compost is thoroughly moist up to the level of the seeds, then slowly remove the box and place it on the greenhouse staging.
Cover the box with a sheet of glass and place a sheet of newspaper over the glass to exclude the light. Each day remove the glass to wipe off the moisture, then replace it. Alternatively, place the box in a polythene sheet or bag and cover with paper till germination takes place. The temperature of the greenhouse should be 55 to 60° F. (13 to 16° C.).
When the seedlings are through, remove the glass and paper or polythene and allow the plants to grow naturally. When they are large enough to handle, prick them out into seed trays containing suitable potting compost at 30 to 48 seedlings per tray.
Prick the seedlings out so that the bottom leaves are lying just above the top of the soil. Then water with a watering-can fitted with a fine rose, and put the boxes on a shelf near the greenhouse glass.
Grow the plants on in the greenhouse until they are well established, and then put the boxes into a cold frame to harden off the plants. Gradually increase the amount ofin the frame until by the third week in May the glass light over the plants is taken away.
A week or so later put the plants in the bed where they are to flower, spacing them out as recommended in the following list of plants. Follow the planting instructions in Biennials.
In May, manycan be bought from nurserymen as young plants ready for planting out.
Some annuals are not hardy enough to be grown out-of-doors and should be grown in the greenhouse in pots. Plants treated in this way include Primula malacoides, Primula sinensis, Impatiens (balsam),cristata and Celosia plumose. Sow the seeds as required by the variety, transfer the seedlings to small pots and gradually move into larger pots until the plants are ready. Celosias can, however, be put out as dot plants in bedding schemes during the height of summer.
ANNUALS IN POTS
Several hardy and half-hardy annuals can be sown in September in pots containing John lnnes No. I potting compost, and gradually potted on through the winter to flower in early spring under glass.
Those suitable are clarkia, schizanthus,, mignonette, stocks, marigolds, nemesia and nasturtiums. Do not over-water, and do not feed until the flower buds appear. Stake as and when necessary, because the growth is softer than that of plants grown out-of-doors. .