Preparing the soil for sowing seed outdoors
One of the bigger jobs to do in the spring is producing a lawn from seed. The soil should have been thoroughly dug in autumn or early winter and most of the weeds removed. Now it needs a final cleaning up, about a week before you intend to sow, by forking the top few centimetres (inches) to remove weeds and rubbish, and to break up large lumps of soil. Add a compound fertilizer dressing with an analysis of about 7:7:7 when you do the forking. A week later, on the day you sow, you can rake to make the soil surface really fine and to do some rough levelling, and then make a finished level, using a line, pegs, boards and a spirit level. Once you are sure there are no bumps and hollows, tread the seed-bed to consolidate it lightly, and give a final raking, standing on boards, to produce the right tilth.
Seed-beds for flowering plants can also be prepared now, as in early spring.
If you did not have time to make up compost in late winter or early spring, it should be mixed as soon as possible so that it has a little time, at any rate, to blend together.
Much of the planting in mid-spring is the same as in early spring, with some additions, so you can follow the instructions given in that season, and make sure that any fertilizer added goes on a few days in advance of planting.
As with the seed composts, so potting composts need to be made early in mid-spring and left in the greenhouse to warm up to the same temperature as the one in which the plants are growing.
Grass seed should be sown fairly early in mid-spring; it takes about seven to ten days to germinate and perhaps another ten to fourteen before the first cut can be made. A windless day is best; marking out the area in square metres (yards) with lines will help you to make sowing more even.
Average rate for sowing seed is about 45-60g per sq m (1-1/2oz per sq yd), using the higher rate if birds are likely to be a nuisance or germination conditions a bit problematical. Another way of ensuring evenness of sowing, when doing it by hand, is to sow half the seed in one direction and the remainder at right angles to it. This evenness of sowing is important, otherwise you will start with a patchy lawn, and subsequently you will never be able to produce an evenly thick sward. Large areas can be sown with a fertilizer distributor, to which a metering roller for sowing seeds is attached. Again, two half sowings are advisable.
After sowing, a very light raking, then cross-raking, can be done to give the best results, though if time is short, this can be dispensed with. Finally, bird inhibitors can be put on or, on small areas, black cotton strung above the soil. Seed treated against birds can be bought, but loses its viability quickly, so should be used in the season for which it was intended and not kept for later use.
Hardy annuals can be sown this month with more chance of a good display later on; germination in early spring can be risky due to treacherous weather conditions. You can add to those suggested for early spring: aster, dahlia, layia (tidy tips), nasturtium, nicotiana, salpiglossis, sweet sultan, ursinia, xeranthemum (everlasting flowers) and zinnia. It is not quite too late for sweetpeas but those sown now will not flower until late summer.
If you have a nursery bed, which is really rather in-dispensable for flower as well as vegetable gardening, you can also sow seed now of bulbs such as crocus, lilies and snowdrops and of herbaceous perennials and rock plants, giving the seeds cloche protection if the temperature is down to freezing at night. Sow as thinly as possible, especially the bulbs.
In the greenhouse you can sow the same half-hardy annuals and bedding plants as last month but, unless the weather is very cold, you should be able to do without artificial heat during the day. You can also sow cobaea and ipomoea, and freesia for flowering during autumn and early winter. Cobaea and ipomoea have rather large seeds and grow quickly once they have germinated, so sowing them singly in 5cm (2in) pots, preferably peat pots, makes it easier to deal with their first potting.
Ipomoea in particular does not like its roots being disturbed; if they are, the first two or three true leaves tend to turn yellow and then white, the plant ceases to grow and eventually dies. This yellowing will also appear if the young plants are kept in bright sunlight or if the temperature drops below 16°C (60°F). They do need to be kept really quite warm, both in the compost and air temperature and if you can supply a temperature of nearer 21°C (70°F), so much the better.
Freesias can easily be grown from seed, and if it is sown now in a temperature of 16°C (60°F), the first flowers will start to appear in mid-autumn.
They grow an unusually long taproot, so the deeper the container the better; the depth should be at least 17.5cm (7in). Use a compost containing soil, such as J.I. Potting No. 3, and sow the seeds spaced 2.5cm (1in) apart and at the same depth. A 23cm (9in) pot will take about nine or ten seeds. The leaves and stems tend to be rather long and straggly, especially the stems, so 37.5cm (15in) long split canes with string threaded across them should be provided for support. Place them round the container edge and in the centre, so that the plants grow up through a supporting network. After germination, the temperature can be lowered a little.
As in early spring, you can plant or lift and divide herbaceous plants, but it is advisable to do this as early in the month as possible, as growth will really be getting under way.
This is the best time to plant rock garden plants as well, preferably when they have just finished flowering, though they can be moved or planted successfully while in flower. You must then do it quickly, with as little damage to the roots as possible, water them in and make quite sure they do not want for water while establishing. Cool, moist weather conditions are best.
Violets can be planted now, either bought plants, or crowns from your own plants. Crowns are pieces separated from a parent plant, each with plenty of roots. Violets thrive if planted where they are protected from summer sun at midday and given a moist, humus-rich soil. They must be watered in after planting, unless rain is imminent. If you see any signs of violet midge trouble, pick off the affected leaves.
Gladioli can be planted during mid-spring, at intervals of a week or so to provide a succession of flowers; allium, crinum and montbretia can all be planted at the beginning of the season. Alliums tend to prefer a sunny place and gritty soil and, given these, some species will naturalize so well that they become a nuisance.
Crinum x powellii produces beautiful deep pink, lily-like flowers in late summer and autumn; its large bulbs should be planted 15cm (6in) deep and about 23cm (9in) apart. A well-drained soil, to which plenty of rotted organic matter was added in winter, is required, and a sunny place at the foot of a south or west-facing wall. Once planted, it can be left alone for many years, provided it is mulched each spring. Planted with agapanthus, the blue African lily which likes much the same conditions, the resulting combination of flower colour is very pretty.
The seeds sow n outdoors in early spring will need thinning-some time during the next few weeks. Thinning means removing some of the seedlings which have germinated, to allow the remainder enough space to grow and mature fully. It should be done when they are just large enough to handle, to leave roughly 5cm (2in) between each remaining seedling; thin a second time when they have produced five or six true leaves, so that there is about 10-20cm (4-8in) between the plants, depending on their final height.
The wild white daisy has been bred and selected so that strains of seed will now produce double rose-pink flowers.
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