8.
Nertera Granadensis (Bead Plant)
We recently found that this subject requires a well drained compost
which is completely free from fertiliser (e.g. moss peat and sand
in equal parts). Sow by barely covering the seed and place a sheet
of glass over the container, and leave in a temperature of 65-75'F.
Turn the glass daily as excessive condensation can kill the young
seedlings. On germination the seedlings look very thin and spindly
and the glass should be removed almost immediately and the seed
container moved to a well lit but not sunny position. Prick out
as soon as possible into a compost of 50% pure peat and 50% sand.
Keep moist and shaded until established.
9. Cactus and similar
Make very shallow furrows in compost with a plant label and sow
in these. No seed should be completely buried. Water from beneath
and cover with glass and brown paper or black Polythene. Place
in a dark position in a temperature of 70-75F and keep moist.
On germinating move to a light but not sunny windowsill, give
plenty of ventilation and water from beneath. Pot up when they
begin to overcrowd. During the first winter only keep warm and
do not allow to get too dry. If it is not possible to grow warm
then keep them drier. Subsequent years keep relatively dry through
the winter. Can be planted outside, plunged to the rim, all summer
if required.
10. Lilies
Successful germination of seeds of some lilies requires a period
of warmth followed by one of cold.
Method 1. Put seeds in a screw top jar in moist (not wet) peat
and keep at 70-75F for 3-4 months. Inspect regularly, any normal
seedlings (that is having root and seedling leaves) should be
pricked out as they germinate. Any seeds which produce roots but
not seedling leaves, sow in a pan and keep at 32-40'F for 3 months.
Seed leaves and normal growth will follow.
Method 2. Sow in a pan in summer (warm spell); put in a frame
(or outside covered by a piece of glass) for the winter. Seeds
will germinate in spring. Soil Humus rich (peat or leafmould)
lime free and very free drainage (use 1/3 grit). Never overwater,
keep bulbs almost dry from November to March.
11. For more delicate seeds
A method which has proved useful for not only small delicate seeds
but for a wide range of types is the Polythene bag method.
The seeds should be sown on the surface of the moist compost,
covered to their recommended depth if necessary and the container
is then placed inside a Polythene bag after which the end is sealed
with an elastic band. The bag should 'fog-up' with condensation
within 24 hours and if this does not occur place the container
almost up to its rim in moisture until the soil surface glistens,
then replace in the bag and reseal. The bag is not removed and
normally no more watering is required until the seeds germinate.
However, it is wise, if left for a long period to check the compost
occasionally.
The seed container, bag etc. should be placed in a well lit place
with a steady temperature. As soon as a fair number of the seedlings
emerge remove the polythene bag, lower the temperature a few degrees
and provide plenty of light, but not bright sunshine, to ensure
that sturdy seedlings develop. It is also helpful to spray the
seedlings occasionally for the first 14 days.
SPECIAL TREATMENT
12. Hard Seeds-Chipping
Some seeds, e.g. Sweet peas, lpomaea etc., have hard seed coats
which prevent moisture being absorbed by the seed. All that is
needed is for the outer surface to be scratched or abraided to
allow water to pass through. This can be achieved by chipping
the seed with a sharp knife at a part furthest away from the 'eye',
by rubbing lightly with sandpaper or with very small seed pricking
carefully once with a needle etc.
Some of our geranium seeds have already been treated in this way
when you receive them.
13. Hard Seeds-Soaking
Soaking is beneficial in two ways; it can soften a hard seed coat
and also leach out any chemical inhibitors in the seed which may
prevent germination. 24 hours in water which starts off hand hot
is usually sufficient. If soaking for longer the water should
be changed daily. Seeds of some species (e.g. Cytisus, Caragana,
Clianthus) swell up when they are soaked. If some seeds of a batch
do swell within 24 hours they should be planted immediately and
the remainder pricked gently with a pin and returned to soak.
As each seed swells it should be removed and sown before it has
time to dry out.
14. Stratification (cold treatment)
Some seeds need a period of moisture and cold after harvest before
they will germinate-usually this is necessary to either allow
the embryo to mature or to break dormancy. This period can be
artificially stimulated by placing the moistened seed in a refrigerator
for a certain period of time (usually 3- 5 weeks at around 41
F). With tiny seeds it is best to sow them on moistened compost,
seal the container in a Polythene bag and leave everything in
the refrigerator for the recommended period. However, larger seeds
can be mixed with 2-3 times their volume of damp peat, placed
direct into a Polythene bag which is sealed and placed in the
refrigerator. Look at seeds from time to time. The seeds must
be moist whilst being pre-chilled, but it doesn't usually benefit
them to be actually in water or at temperatures below freezing.
Light also seems to be beneficial after prechilling and so pre-chilled
seeds should have only the lightest covering of compost over them,
if any is required, and the seed trays etc. should be in the light
and not covered with brown paper etc.
15. Double Dormancy
Some seeds have a combination of dormancies and each one has to
be broken in turn and in the right sequence before germination
can take place; for example, some Lilies, Tree paeonies, Taxus
need a three month warm period (68-86'F) during which the root
develops and then a three month chilling to break dormancy of
the shoots, before the seedling actually emerges. Trillium needs
a three month chill followed by three months of warmth and then
a further three month chill before it will germinate.
16. Outdoor treatment
The above mentioned methods (12-15) accelerate the germination
process and help to prevent seeds being lost due to external hazards
(mice, disease, etc.) but outdoor sowing is just as effective
albeit longer. The seeds are best sown in containers of free draining
compost and placed in a cold frame or plunged up to their rim
outdoors in a shaded part of the garden, preferably on the north
side of the house avoiding cold drying winds and strong sun.
Recent tests show that much of the beneficial effects of pre-chilling
are lost if the seed is not exposed to light immediately afterwards.
We therefore recommend sowing the seeds very close to the surface
of the soil and covering the container with a sheet of glass.
An alternative method especially with larger seeds, is to sow
the seed in a well prepared ground, cover with a jam jar and press
this down well into the soil so that the seeds are enclosed and
safe from predators, drying out etc.
We would also recommend you consult No. 6 which contains further
practical suggestions regarding the special treatment of seeds.