3 Use a draw hoe to pull friable soil (from both sides of the row) over the tubers so that it forms a long, continuous mound 10–15 cm (4–6 in) high over the tubers. As the shoots grow, further ‘earthing up’ of the rows will be required.
SOWING PREFERENCES
When sowing seeds in V-shaped drills, there are three main options, depending on the seed and its size:
• Continuous line: Usual way to sow small seeds, such as those of carrots, lettuces, onions, radishes, spinach and turnips. For information about thinning the seedlings, see opposite page.
• Singly spaced: Space individual seeds at intervals along the drill. Used for broad (fava) beans, French beans and runner beans. Garden peas are also treated this way when grown in V-shaped drills.
• In clusters: Sow seeds in clusters (usually formed of three seeds) along the drill. Later, thin the seedlings to just one in each position.
Fluid sowing
Seeds are mixed with a gel, often wallpaper paste, and squeezed out of a small hole made in the corner of a plastic bag into the base of a V-shaped drill. The gel helps to retain moisture around the seeds and encourages even and rapid germination.
Sowing seeds in a greenhouse
What equipment is needed?
You will need a means of providing warmth, usually 16–21°C (61–70°F), in the greenhouse. A strong bench to support sown seed-trays (flats), compost that retains moisture and allows air penetration, a soil presser (to firm the compost uniformly) and a horticultural sieve will also be necessary. Propagation cases or mats to go below trays, which are heated by electricity, are a bonus and will enable the greenhouse’s general temperature to be lowered.
SEEDS TO SOW IN GREENHOUSES
Many plants for the garden and home are raised in gentle warmth in greenhouses. For details of individual plants, see the A–Z of propagating plants (pages 42–78).
• Half-hardy annuals (for later planting into beds and borders): These are sometimes known as summer-flowering bedding plants and include Begonia semperflorens (Wax Begonia), Lobelia erinus (Edging Lobelia) and Lobularia maritima (Sweet Alyssum).
• Indoor flowering pot plants: These are plants for home decoration, including Calceolaria x herbeohybrida (Slipper Plant), Primula malacoides (Fairy Primrose) and Pericallis x hybrida (Florist’s Cineraria).
• Culinary herbs: There is a wide range to choose from, including Ocimum basilicum (Sweet Basil), Origanum majorana (Sweet Marjoram) and Myrrhis odorata (Sweet Cicely). Some herbs can also be sown outdoors.
SOWING SEEDS IN SEED-TRAYS (FLATS) IN A GREENHOUSE
Greenhouses provide assured warmth in which seeds can germinate and young seedlings grow healthily. After germination, transfer the seedlings (‘pricking off’ – see opposite page) to wider spacings in seed-trays (flats). Later, plants for decorating homes need to be moved to individual pots (also see opposite page). Always use pest and disease-free compost. Using clean and dry seed-trays is also essential.
1 Fill a seed-tray (flat) with fresh compost and use your fingers to firm it, especially around the edges. Then refill with compost.
2 Run a straight piece of wood over the top of the tray to remove any excess. Then use a presser to firm the surface to 12 mm (½ in) below the rim.
3 Tip a few seeds onto a piece of stiff, folded paper; tap the end to spread the seeds evenly over the compost surface, but not near the edges.
4 Use a flat-based horticultural sieve to cover the seeds with compost to 3–4 times their thickness. Alternatively, use a culinary sieve, as shown here.
5 To water the compost, stand the seed-tray in a flat-based bowl shallowly filled with water. Remove when the surface is moist. Then cover the tray as described on the opposite page.
PRICKING OFF SEEDLINGS
As soon as the seedlings are large enough to handle, they must be transferred (‘pricked off’) so that each has more space in which to develop, and an increase in light and air. Seedlings left clustered together become weak and etiolated, and more susceptible to diseases than those with a good circulation of air around them. It is better to transfer seedlings when young, rather than leaving them until large, tough and tightly clustered.
1 After germination, remove the cover. Whenever the compost shows signs of drying out, water the seedlings by standing the seed-tray (flat) in a bowl shallowly filled with water (see opposite page).
2 When the seedlings are large enough to handle, water them from below. Then use a small fork to lift a few seedlings and place them on damp newspaper.
3 Fill and firm the compost in another seed-tray. Use a small dibber (dibble) to make holes, keeping the outer row 12 mm (½ in) from the sides of the tray.
4 Hold a seedling by one of its leaves and insert the roots into a hole (to the same depth as before). Gently firm the compost around the seedlings.
5 When the seed-tray is full, gently tap the tray’s edges to level any loose compost. Water carefully from above to settle the compost around the roots, Then proceed as described below.
COVERING THE SEED-TRAY (FLAT)
After you have sown the seeds, the tray (flat) needs to be covered to prevent the surface of the compost drying out. There are a couple of ways of doing this:
• The traditional method is to place a piece of glass over the seed-tray (flat). However, because condensation forms on the underside, you must wipe the glass clear each morning, then invert it so that the dry side is facing the compost.