Seed Germination Database
The following data is provided by Thompson &
Morgan Successful Seed Raising Guide. This guide is out of print.
A seed is an embryo plant and contains within itself
virtually all the materials and energy to start off a new plant. To get the
most from one's seeds it is needful to understand a little about their needs,
so that just the right conditions can be given for successful growth.
One of the most usual causes of failures with seed is
sowing too deeply; a seed has only enough food within itself for a limited
period of growth and a tiny seed sown too deeply soon expends that energy and
dies before it can reach the surface. Our seed guide therefore states the
optimum depth at which each type of seed should be sown. Another common cause
is watering. Seeds need a supply of moisture and air in the soil around them.
Keeping the soil too wet drives out the air and the seed quickly rots, whereas
insufficient water causes the tender seedling to dry out and die. We can
thoroughly recommend the Polythene bag method (No. 11) which helps to overcome
this problem. Watering of containers of very small seeds should always be done
from below, allowing the water to creep up until the surface glistens.
Most seeds will of course only germinate between certain
temperatures. Too low and the seed takes up water but cannot germinate and
therefore rots, too high and growth within the seed is prevented. Fortunately
most seeds are tolerant of a wide range of temperatures but it is wise to try
to maintain a steady, not fluctuating temperature, at around the figure we have
recommended in our guide. Once several of the seeds start to germinate the
temperatures can be reduced by about 5'F and ventilation and light should be
Some perennials and tree and shrub seeds can be very slow and
erratic in germination. This may sometimes be due to seed dormancy, a condition
which prevents the seed from germinating even when it is perfectly healthy and
all conditions for germination are at optimum. The natural method is to sow the
seeds out of doors somewhere where they will be sheltered from extremes of
climate, predators, etc. and leave them until they emerge, which may be two or
three seasons later. Dormancy, however, can be broken artificially and our
section Nos. 12-16 deals with this.
HINTS ON SEED RAISING
1. Strelitzia and similar
Do not chip or mark the seedcoat at all but merely remove the
orange tuft and soak for up to 2 hours, or even overnight. Sow the seeds in
moist sand, pressing them into the sand until only a small part of the black
seed is visible and grow in a temperature of 75'F in the dark and ensure that
the sand always remains moist. From 7 days onwards inspect the container once a
week and as soon as any bulges, roots or shoots are seen remove the germinated
seed and pot up in a compost of half peat and half sand. We find that
Strelitzias often produce a root without a shoot and we have also found that
the young shoots and roots are susceptible to fungal attack. Therefore as soon
as possible pot up and provide light and fresh air. Germination can start
within 7 days and carry on for 6 months or more.
2. Palms; Banana; Coffee; Mini-Orange; Tea; Cycads and
All these items can take several months to germinate and are
very erratic in germination. Soak for at least 2 hours in warm water before
sowing. (After soaking the parchment shell on the Coffee seeds should be
removed with the fingernail). Sow in Levington or Arthur Bowers compost and
place in the dark in a temperature of 75F, keeping the compost moist at all
times, but not wet. Inspect regularly and occasionally dig around in the
compost with a penknife. We normally sow our seeds just below the surface of
the soilatid we have found that sometimes they make a very vigorous root
without producing a shoot at all. If you find a seed with a root then it should
be excavated and potted up into a 3-4' pot immediately when it will produce a
shoot. Cycads prefer to be potted up into a compost of half sand and half peat.
The Tea requires the above treatment but in a lower temperature of 60-65'F.
3. Clivia and similar
Sow these seeds immediately on receipt in Levington or a peat
based compost, covering with a 112 " compost. Water and place in the dark in a
temperature of 65-70'F. Germination should occur within 3 weeks.
4. Ferns (Garden and Indoor)
The fern spore needs a fine film of moisture over which to
swim in order to complete the process of reproduction, therefore a good peat
compost, such as Levington, ought to be used pressed down very firmly and which
is a lot more moist than one would normally have it in order to provide the
moisture film. The spore (seed) should be sprinkled close together on the
surface of the soil and not covered and the container should be covered with a
piece of glass and placed in diffused light, but not darkness. It is essential
to ensure that the compost remains moist at all times. Germination which
commences with the appearance of a film of green jelly over the soil can take
anything from 1 -5 months.
You may wish to try germinating the fern spore on blotting
paper which is placed in a saucer and kept moist at all times. A transparent
cover is inverted over the saucer and the whole lot placed in a well lit but
not sunny position. You can actually see the fern spores developing and when
you can see small plantlettes appearing along the jelly the blotting paper
should be lifted and placed on the surface of a container of Levington compost
and watered well. It should then be covered with a transparent cover which can
remain there until the plants are quite large.
5. Bromeliads; Cineraria;
Calceolaria; Insect Eaters
(Drosera, Nepenthes, Sarracenias);
Living Stones; Meconopsis;
Plants; Saintpaulia; Streptocarpus;
Tibouchina; Xmas Cactus;
These seeds should be sown on the surface of the compost and
not covered. The compost should be quite moist and we would recommend that you
cover the seed container with a piece of glass or clear plastic and leave in a
temperature of approximately 65'F in a position which receives diffused light.
Once some of the seeds have germinated air should be admitted gradually
otherwise the seedlings may damp off.
Alternatively the seeds can be sown on to moist blotting paper
or kitchen towel placed in a saucer. Cover with a transparent cover and place
on a windowsill which receives plenty of light, but not direct sunlight. Keep
the blotting paper wet at all times and when the tiny seedlings are large
enough to handle prick out into small pots. If the INSECT EATERS are sown using
the first method described the compost requires to be both moist yet free
draining. Use only pure peat with no fertiliser added to which sphagnum moss
should be added if available.
6. Alstroemeria; Bonsai;
Clematis; Hardy Cyclamen;
Eucalyptus; Flower Lawn;
Helleborus; Hosta; Primula;
Sowing OCTOBER-FEBRUARY. Sow the seeds in John Innes seed
compost, covering them with a thin layer of compost. After watering place the
seed container outside against a North wall or in a cold frame, making sure
they are protected against mice, and leave them there until the spring. The
compost should be kept moist but not wet at all times, and if the seed
containers are out in the open then some shelter has to be given against
excessive rain. In the spring bring the seed containers into the greenhouse, or
indoors on to a well lit but not sunny windowsill and keep the compost moist.
This should trigger off germination. If the seeds do not germinate in the
spring keep them in cool moist conditions throughout the summer. As each seed
germinates we would recommend that you transplant it almost immediately into
its own pot.
Sowing MARCH-SEPTEMBER. Sow in John Innes seed compost, or
something similar, and place each container in a polythene bag and put into the
refrigerator (not the freezer compartment) for 2-3 weeks. After this time place
the containers outside in a cold frame or plunge them up to the rims in a shady
part of the garden border and cover with glass or clear plastic. Some of the
seeds may germinate during the spring and summer and these should be
transplanted when large enough to handle. The remainder of the seeds may lay
dormant until next spring.
Germination of some items, particularly Alstroemeria,
Clematis, Hardy Cyclamen and Christmas Rose (Helleborus) may take take 18
months or more.
An alternative method for growing P R I M U LAS is to sow in a
peat based compost which has already been moistened and do not cover the seed.
Cover the container with a piece of glass or plastic and grow in the dark in a
steady temperature of 60F. This is quite adequate and over 65'F germination
will be inhibited. When the seeds start to germinate sprinkle a thin layer of
fine compost over them and when the seed leaves come through this, move the box
to a well lit place with a temperature of 55'F. At no time should the seed box
be in full sun.
Hardy Cyclamen have been found to germinate best in total
darkness at around 55-60'F. We have had good results with the following method.
Place the seeds between two pieces of damp filter paper, Kleenex tissue, etc.,
then put into a polythene bag and place this into an opaque container in order
to exclude all light. Inspect the seeds after a month and remove and prick out
as the seedlings appear, returning the ungerminated seeds to total
Soak the seeds for 24 hours and sow in Levington compost, or
something similar, and place in a temperature of 50-60'F. Germination can
sometimes be slow.
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.
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
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
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
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.
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.
The usual time period in which a particular variety will
germinate given optimum conditions.
Seeds needing light should have no newspaper, brown paper etc.
placed over the trays. Seeds needing dark for germination should be placed in
Slow and irregular germination
This is the column with the "X". Not all seeds will show at
-prick out each seedling as it becomes large enough to handle and
don't discard the container until well over the time suggested.
A steady temperature between these limits is
recommended-fluctuating temperatures can damage a seedling in its critical
Most reputable seed composts will be quite adequate and we
have indicated where a loam based type such as John Innes or a peat based type
such as Levington would be slightly more suitable. On no account should potting
composts, which have additional fertillsers, be used.
If in doubt sow shallowly, but always ensure that the compost
surface is damp.
J.C. =Just cover the seed with compost or sharp
sand. S=Sow on the surface and do not cover at all with compost.
Sowing in situ
Where recommended under the heading of comments, these seeds
can be sown out of doors. Moist soil worked down to a fine tilth is essential.
For hardy annuals and perennials sowing can be carried out from late winter
onwards as soon as the ground is workable and has warriied up and half hardy
annuals after all danger of frost is passed.