Seed Guide 2007 pgs 01/41 - McKenzie Seeds

G R O W I N G I N F O R M A T I O N
Bulb Propagation
Vermiculite can be used for the propagation
of bulbs by the "chip" method.
Place bulb chips in a polythene bag, cover
with Vermiculite, and seal with an elastic
band leaving plenty of air space.
Store in a warm place until the 'chips'
have formed bulbils and pot up into a
mix of 50 / 50 Sow-Lite and potting
compost.
Seedling collapse, or damping-off is a
wide spread problem for gardeners and
commercial growers. As seeds germinate
they may be attacked or the seedling
may be infected in the post emergence
stage. An affected seed tray would have
a bare area of compost, probably near
one end, surrounded by seedlings
growing poorly. Some seedlings might
have collapsed at the base with a watersoaked
appearance. After pricking off,
seedlings may develop brown root tips,
have a weak root system, or collapse at
the stem base and fall over: This is
commonly seen when tomatoes are
pricked off, and the seed leaves turn a
very dark green.
Causes of damping off
Damping-off diseases are caused by
fungi. These microscopic organisms form
colourless threads in soil, compost, or
plant structures. The ones attacking
seedlings are species of Pythium and
Phytophthora, belonging to a group
called the water moulds. The name
highlights the conditions which favour
the spread of these fungi. They flourish
in wet compost and need water to spread
from plant to plant.
When the water is cold they move slowly
and take a long time to come to rest,
whereas at 68F (20C) the spores swim
quickly but soon stop. If they rest on a
root or stem surface a minute thread
emerges and penetrates the plant cells.
These fungi then grow inside the plant
and disrupt the normal cell processes.
There is another soil-borne fungi which
10
Damping Off
Cuttings
Softwood cuttings taken in spring and
summer from Fuchsias, Dahlias,
Chrysanthemums etc., root well in a
mixture of 50% Sow-lite, 50% Seed and
Cutting compost. Make sure that the
compost is thoroughly moist before use
and don't firm down too heavily. Seal
inside a polythene bag until the cuttings
are well rooted.
attacks seedlings, leading to collapse. This
is called Rhizoctonia. Infected plants tend
to develop a dry, reddish-brown stem
called wire-stem, or the seedling roots
may be affected. Seedlings in patches are
unthrifty or pale coloured and die slowly.
If a badly infected seedling is pulled up
an excessive amount of soil may hang
from the shrivelled root indicating the
weft of fungus growth on the root.
Rhizoctonia spreads entirely by threads
which grow through the compost. All
members of the brassica family seem
particularly susceptible to infection.
Susceptible plants
Pythium and Phytophtora
Snapdragon Cucumber
Celery Lobelia
China Aster Marigold
Cineraria Nemesia
Rhizoctonia
Aubrieta Stock
Brassicas Wallflower
Salvia
Preventing attack
Although some plants are especially
prone to damage, it is best to take
sensible precautions against these
diseases whatever seed you plan to sow
as any plant can suffer.
Before you can plan to control any plant
disease, it is important to know where
the fungus comes from and how it is
spread. In the case of the damping-off
diseases they are soil-borne but can