Home Gardener's Propagation (UK Only). David Squire
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Storing seeds
If you are storing seeds gathered from your garden, it is essential first to remove pieces of debris from them; if left, they tend to rot and encourage decay in the seeds. Always collect seeds as soon as they are ripe (see opposite page).
Both home-gathered and bought seeds (that may have been left over from the previous year) can be stored in a dry, dark, airy place with a temperature of 1–5ºC (34–41ºF). For many gardeners, storing seeds in paper bags in sealed glass or polythene containers in a cool refrigerator is the best solution.
Stratifying seeds
This is a way to encourage seeds to germinate by softening seedcoats and allowing water to enter. It involves soaking the seeds, then chilling them for several weeks to simulate their natural period of dormancy. It is used mainly for large, hard-coated seeds of shrubs and trees, including those of Amelanchier, Cotoneaster, Euonymus and some viburnums. Traditionally, the seeds were put between layers of sharp sand and left outdoors during winter, hence the name ‘stratification’.
F1 hybrids
In recent decades, seed companies have offered an increasing number of vegetables and flowers as F1 hybrids. This means that they are a first filial generation, the result of a cross between two pure-bred parents. Their progeny are large, strong and uniform. However, seeds saved from them will not produce replicas of the parents.
Plants to increase from seeds
Do all plants produce seeds?
The majority of wild flowering plants, from those seen in meadows to grasses, increase themselves by means of seeds. They do this naturally and successfully, although not all of the seeds will germinate. Many cultivated plants, however, can be given a more assured start if you take cuttings and root them, or divide established plants. Grafting and budding methods provide plants with roots that have a known vigour and influence on growth.
CHANGING LIFE CYCLES
When raised for growing in gardens or as plants for home decoration, many seed-raised plants grown in temperate climates have a different growth pattern or life cycle from their natural one. For example, Lobelia erinus (Edging Lobelia) is a half-hardy perennial usually grown as a half-hardy annual; Mirabilis jalapa (Marvel of Peru) is a perennial grown as a half-hardy annual; and Impatiens walleriana (Busy Lizzie) is a greenhouse perennial invariably grown as a half-hardy annual. Bellis perennis (Daisy) and Dianthus barbatus (Sweet William) are perennials grown as biennials. The purpose of changing the cycle of growth of such plants is to produce many plants at the same time, in the easiest way possible.
WHEN TO SOW
The life cycle of plants, from hardy annuals to half-hardy annuals, biennials and hardy herbaceous perennials, influences when and how you should sow them:
Hardy annuals
Sow mainly during mid- and late spring (see pages 12–13). Their range is wide and you can easily create medleys, including a yellow border fronted by yellow annual lupins and backed by tall sunflowers.
Agrostemma githago ‘Milas’
Half-hardy annuals
Sow mainly in late winter and spring in greenhouses in gentle warmth (see pages 18–19). A traditional medley is Begonia semperflorens (Wax Begonia), Lobelia erinus (Edging Lobelia) and Lobularia maritima (Sweet Alyssum).
Petunia x hybrida
Hardy biennials
Sow in a nursery bed in spring and early summer (see pages 14–15). For extra colour, combine spring-flowering bulbs such as tulips with the popular biennials Bellis perennis (Common Daisy) and Myosotis sylvatica (Forget-me-not).
Dianthus barbatus
Hardy herbaceous perennials
Sow in nursery beds in spring and early summer (see pages 14–15). Seed catalogues abound with herbaceous perennials that can be raised from seeds, including Achillea (Yarrow), Dictamnus albus (Burning Bush) and Echinacea purpurea (Purple Cone Flower).
Coreopsis verticillata
Shrubs and trees
Sow seeds of shrubs and trees at any time of year. As their seeds usually have tough coats, they need to be stratified (see page 9). Alternatively, chip or sandpaper them to improve their chances of germination.
Cistus x dansereaui
Climbers
Lathyrus odoratus (Sweet Pea)
Many climbers are increased from cuttings or layered stems, but a few can be raised from seeds, including Lathyrus latifolius (Everlasting Sweet Pea), Lathyrus odoratus (Sweet Pea) and Tropaeolum peregrinum (Canary Creeper).
Vegetables
Lettuce ‘Buttercrunch’
Most vegetables are grown from seeds (see pages 16–17). Many, such as peas, lettuces, beetroot and spring onions (scallions), should be sown where they will germinate and grow until harvested. Others, including Brussels sprouts and cabbages, should be sown in seed beds; later, the young plants should be transferred to their growing positions.
Culinary herbs
Petroselinum crispum (Parsley)
A few culinary herbs, such as Allium sativum (Garlic) and Allium schoenoprasum (Chives), are bulbous and are easily increased by division. Others, such as Anethum graveolens (Dill), Anthriscus cerefolium (Chervil), Carum carvi (Caraway), Ocimum basilicum (Sweet Basil), Origanum majorana (Sweet Marjoram), Petroselinum crispum (Parsley) and