With the summer season officially here, the main seed-sowing period is over and you may in fact have more than enough work on your hands without adding to it. However, through lack of time, some seeds that should have been sown in late spring may have been left out and there are plants which should be sown specifically in early summer. Soil can therefore be prepared in the usual way for sowing in the nursery bed.
Again there is little work to be done here, except to ensure a display next winter and spring and, if you do not have any seed compost left over from late spring, make up a new batch and cover it with black plastic sheet until needed.
Planting may also be a case of catching up with late spring or of planting which has been delayed due to bad weather, but in any case, clear the site of weeds and rubbish, scatter a little compound fertilizer on the soil and fork it a few centimetres (inches) deep, about a week before planting.
You can also, with advantage, choose a site for a new lawn and start to prepare it now. Cultivate it by digging or with a rotavator to 23cm (9in) deep or to the depth of the topsoil and leave roughly broken up. You may find grey-brown caterpillars and bright-yellow ‘worms’ in it as you do so, especially if it is old turfland or meadow; these are leather-jackets (daddy-long-legs larvae) and wireworms which should be destroyed, though birds may do this for you as you work.
The ground can then be dressed with rotted organic matter at 2.5kg per sq m (5lb per sq yd), or coarse peat at 3kg per sq m (6lb per sq yd) and left fallow through the summer. This results in weed seeds germinating: these can be hoed off at intervals, each time a fresh infestation appears, until most of the weed-seed population on the site has been destroyed. You can alternatively use a ‘new lawn’ weedkiller at the time of grass germination, but the seedling weeds do provide compost-heap material. After hoeing, rake the soil to an even, smooth surface.
If you are dealing with a heavy soil, it is well worth while mixing in coarse sand as you cultivate, at a rate of 6kg per sq m (14lb per sq yd).
Preparing compost for indoor planting From now until autumn, you should always have a supply of compost ready for potting, as plants permanently in pots may need re-potting and others grown from seed will need potting on at irregular intervals through the summer.
Seeds to sow outside in early summer can be any of the biennials sown last month, though they will flower some weeks later next spring, and also forget-me-nots, but leave these until late in early summer. Primulas, polyanthus and primroses can be sown outdoors in a shady nursery bed.
There are also some herbaceous perennials which will grow easily from seed sown now, in a nursery bed, to be transplanted in early autumn to their permanent places. They include aquilegia, delphinium, hollyhock, lupin, oriental poppy and such rock plants as aubricta and armeria. It is worth trying any seed you have available now from perennials and rock plants, as germination of fresh seed, sown as soon as ripe, is nearly always better than if left until the following spring. Plants from early and midsummer sowings will then be strong enough and large enough to survive the winter weather.
Primula malacoides, sown in late spring, may also be sown now, to flower late in winter and in early spring next year; P. sinensis, P. stellata and P. obconica can be sown now as well. Cineraria is another beautiful greenhouse plant for winter flowering which needs to be sown now, for flowering with the primulas. There are some glorious colours amongst modern cinerarias and you could (ill a greenhouse with these plants alone. The range of colour covers pink, rose, white, purple, light and royal blue, crimson and bi-colours. Calceolarias are also showy flowering pot-plants for early-summer sowing to bloom in early spring; the range of colour is quite different, covering shades of yellow and orange, bronze, scarlet and cerise, often heavily spotted with red or bronze. They provide a complete contrast in form, too, with petals fused to form a pouch, instead of the single rays of the daisy-like cinerarias. Calceolarias are a little more sensitive to low temperatures than cinerarias and should always be free from frosts, with a temperature in winter preferably between 7 and 10°C (45 and 50°F).
It should be perfectly safe by now to plant dahlias outdoors; if night frosts are still about, then the weather is very unseasonable and you will have to keep the plants in frames a little longer or cover them with cloches, if not too tall. Treat bedding plants the same way, provided they have been hardened off.
There will be little pricking out to do in the greenhouse. The cinerarias and Primula malacoides sown last month will probably be ready sometime this month to go into trays or, if you only have a few, into pans. Keep them as cool as possible and move them out into a cold frame, shaded from sun, as soon as they have recovered from pricking out. Cobaea and ipomoea should go into 9cm (3-1/2in) pots unless you have sown them singly in 5cm (2in) peat pots, where they can stay until the roots begin to show through the sides or base.
Potting
Plants to go into their final pots and stand outside are the late-flowering chrysanthemum. Fast-growing or vigorous plants permanently in pots, such as chlorophytum, cissus, jasmine, passion flower and trade-scantia, will need re-potting. Seeds sown in late spring and pricked out at the end of that season may need individual pots in early summer, 5 or 7.5cm (2 or 3in) in diameter, depending on the size of the rootballs. These will be cinerarias and Primula malacoides and they can then go into a shaded cold frame. Cobaea, ipomoea and coleus will also need potting on; the size will depend on the size of the root-ball and this in turn depends on the time of sowing, or, in the case of coleus, on the size of the plant when bought in late spring. Cobaea and ipomoea will both need quite large final pots, about 20cm (8in), while coleus do well in 12.5 or 15cm (5 or 6in) sizes. Fuchsia and pelargonium rooted cuttings will need larger pots, probably their final size.
Any half-hardy annuals and bedding plants, hardy annuals and biennials you sowed in late spring outdoors will all need thinning this month; you will probably have to do two thinnings, one at the beginning and one at the end of early summer, depending on the weather and the time at which you sowed them. All the biennials but mullein will only need thinning once, because they will be transplanted before being put in their permanent positions. Mullein is sown where it is to flower, and will therefore be thinned twice, to a spacing of about 45cm (18in) each way.
Although it is generally thought that wallflowers do best if transplanted, they become much stronger plants if sown where they are to flower and thinned there twice. If this is done, the rows should be about 23cm (9in) apart and the plants thinned to a final spacing of 15cm (6in). Since they are part of the same family (Cruciferae) as the cabbage tribe, they should not be grown in acid soil, nor should they follow plants from that family, such as stocks.
At the end of early summer, the biennials may be ready for transplanting. If wallflowers are to be moved do it when there are three true leaves present, and about the same size is right for the other biennials also. Wallflowers can then be planted 10cm (4in) apart in the rows, with 30cm (12in) between the rows, to make weeding easier. All these little plants need moving and replanting quickly, with as much of the root system intact as possible, from moist soil into moist soil, with a watering-in afterwards. Do the job in the evening, so that they do not have to contend with possibly hot midday summer sun before their roots have absorbed water from the new site.
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