Plants can be increased in a number of ways. For
example, they can be reproduced from seeds, from
cuttings, by division of the roots, by separation
and replanting of bulb and corm offsets, and by
Many of these techniques are quite simple
and more often than not successful. The more difficult
ones – such as grafting and budding –
are more of a technical challenge, and are not
dealt with here.
Growing plants from seeds is perhaps the most
interesting and satisfying way of increasing your
stock, but for the best results the conditions
must be correct. Moisture, oxygen and a suitable
temperature are essentials, and while most seeds
germinate in the dark, some prefer the light.
The sowing instructions on the seed packet will
usually list the plant’s requirements, but
generally speaking it is the fine seeds, such
as those of begonias,
which need light.
GERMINATION UNDER GLASS.
Before you start, thoroughly clean containers
and propagators with a proprietary garden disinfectant.
Treat wooden seed boxes with a wood preserve.
The compost must be free of pests, diseases and
weed seeds, so use a proprietary brand of a soil-based
John Innes seed compost, or a soil-less compost
containing peat or pulverised bark with possibly
vermiculite, perlite or sand.
Sow the seeds of acid-loving plants, such as heathers,
in an ericaceous, or acid, seed compost.
Some seeds need special treatment before they
Those from trees, shrubs and some alpine
plants need stratifying – exposing to low
temperatures – before they will germinate.
Whatever the size of the eventual plant, most
seeds from these plant groups should be sown in
trays in autumn, and the trays overwintered outside
or in a mouse-proof cold frame.
Some small alpine seeds can be stratified in a
Mix the seeds with a little moist peat
and sand (50/50 by volume) in a plastic bag and
place in a cool drawer of a fridge for 4-8 weeks.
This will break the dormancy, so that the seeds
will germinate once they are placed in the warmth.
Sow the lot – seeds, peat and sand.
Soak hard-coated seeds such as sweet
and lupins for
about 24 hours in water, or between layers of
damp tissue, until they swell. Any that don’t
can be encouraged by removing a small amount of
seed coat on the opposite side to the eye.
Some fine seeds are best sown immediately after
harvesting, for example, primulas,
none of which should be covered with soil. Protect
all seeds placed outside from vermin and birds
with small-mesh wire netting or gauze.
DEALING WITH HALF-HARDIES.
Sow half-hardy annuals and half-hardy perennials
between midwinter and early spring, under cover,
in temperatures of 13-24°C (55-75°F),
preferably in a heated propagator.
Start with those that take a long time to germinate
and to develop flowers, like Begonia
semperflorens and lobelias,
followed by mid-term plants like French
marigolds and ageratum,
and finishing with later-flowering plants like
Choose a container of the correct size –
you can get 100 or more seeds in a seed tray,
and 20-30 in 3 ½ in pots.
Do not sow more
than one variety in each container.
If they germinate
at different times there will be problems when
the time comes to harden off the seedlings –
that is, to acclimatise them to lower temperatures.