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HOW TO RAISE SEEDS
SUCCESSFULLY
© Frances Michaels
Raising plants from seeds can be satisfying and fun.
There are hundreds of varieties to choose from, far
more than are available as seedlings. If you are
growing vegetables this also gives you the chance to
go organic from seed to plate, giving you complete
control over what you are eating. There are new
taste sensations just waiting to be discovered.
Don’t be afraid to try seed raising, a bit of time and effort spent getting it right
will reward you with a good germination rate.
When to Sow
Where to Sow
Direct Sowing
Seedbed
Container Sowing
Watering
Seed Storage
Seed Treatment
SEEDS
A seed is a miracle of
life. It is a tiny plant embryo combined with
enough stored energy to bring it to life. The main
requirements are moisture, air and warmth. The
moisture softens the seed coat and allows the seed
to swell. Air or oxygen can then enter and the
seed begins respiration (to breathe), a process
that releases the stored food energy of the seed
and makes it available to the plant embryo. No
fertiliser or light is necessary at this early
stage for most seeds. The plant embryo has limited
food available, it has enough to break through the
soil surface, open its leaves and begin
photosynthesis. It then immediately needs light
and is vulnerable to drying out as it has started
to grow. Fungal diseases may attack it,
particularly if the soil mix is too wet or heavy.
Air is vitally necessary in the root zone for
successful germination and it occupies the spaces
between soil particles. If the growing medium is
too wet all the air spaces are occupied by water
instead; if it is too heavy there is little or no
air space available.
WHEN TO SOW
Always begin by reading the seed packet for
directions.
A. GROWING
SEASON
Timing is very important. Annual seed must
germinate, grow and produce before the onset of
changed weather conditions. Check the plant has
sufficient growing time ahead. Warm season plants
such as eggplants, capsicum and rosellas need 4-5
months frost free in order to produce. Cool season
plants will 'bolt' (i.e. go to seed) in spring due
to higher temperatures if sown too late. Information
on what to plant now can be found in the seasonal
Green Notes
or the
Sow When Poster. Local sources of information
are very useful such as garden clubs or gardening
columns.
B. SOIL
TEMPERATURE
The soil or seed raising mix temperature needs to be
at the correct temperature for the type of seed
being sown. If the soil is too cold or too hot the
seed may not germinate. Many vegetables, including
beans, zucchini, melon, cucumber, tomatoes and
capsicum, need a soil temperature of at least 20°C
to germinate. Tropical and subtropical plants such
as pigeon pea, rosella and winged bean need an even
higher temperature to germinate successfully, over
25°C. Seeds such as carrot and lettuce will fail to
germinate at high temperatures, over 25°C.
In cooler areas you may need to start seed earlier
indoors as otherwise the growing season may simply not be long enough to produce successfully. It is
disappointing to have a plant grow, flower and begin
to fruit and then be cut down by the first frost of
winter. To start seed earlier you will need to use
either a bottom heat propagator or a hothouse. If
this is not available you can try a warm windowsill,
the top of a hot water heater or a
Mini Propagator. Don't worry about the lack of light if your source of
bottom heat is indoors. Seeds don't need light to
germinate; in fact many germinate better in dark
conditions (lettuce is the exception). Just keep a
close eye on them and move them to a well-lit area
as soon as they are germinated. Remember: air
temperature is always warmer than soil temperature.
WHERE TO SOW
Deciding whether to sow
seed directly into the garden, seedbed or into a
container is a choice you need to make.
A. DIRECT
SOWING
An
advantage of direct sowing is it is less hassle;
there is no need for transplanting, the plants
establish easily with no 'transplant shock' and the
seedlings are generally hardier. The disadvantages
of direct sowing are that the soil may be too cool
for the seed to germinate; the soil needs careful
preparation to a fine tilth and this can be hard on
your back; the space may still be occupied by an
earlier crop; or birds, rats and ants may steal the
seed.
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Direct sowing into a seed row in the garden is
used for many vegetables; especially large seeds
such peas, beans, corn and leafy greens such as
rocket or coriander. It is essential for root
vegetables that are difficult to transplant, such
as carrots. To sow seed in a row use a long piece
of bamboo or dowel lightly pressed into the soil.
Use a
marker pen
to mark measurements along your bamboo pole or
dowel, for ease of judging distance between rows
and plants. Check the seed packet directions for
spacing.
-
Seeds of squash, pumpkin or melon are usually
planted in 'hills' instead of rows. This involves
digging a circle 30 cm across and planting 3-5
seeds. Once germinated thin out to the 2 strongest
seedlings.
-
Broadcast sowing, where the seed is evenly
scattered across the growing area and lightly
covered; is used for green manures; covercrops;
lawn seed; wildflower meadow mixes and insectary
mixes such as
Good Bug Mix.
Soil Preparation
To
prepare your soil for direct seeding it is usually
necessary to dig the soil over, breaking up lumps
with a garden fork. Then rake it to a fine tilth. Do
not try to prepare the soil when it is very wet, as
you will just damage the soil structure. Organic
fertiliser or compost can be spread over the area
and forked through as part of the preparation. Lime
should be added several weeks apart from any
fertiliser.
Seed Sowing in Rows
and Seedbeds
As
a general rule sow most seeds to twice their
thickness (diameter). Fine dust-like seeds are
simply pressed into the surface. In cooler
conditions it can help to sow the seed less deep
than recommended, as it is warmer closer to the
surface. If fine seeds like carrots are planted
directly into rows in the garden it can help
germination to cover the rows with folded
shadecloth, cardboard or even an old weatherboard.
Remove the cover as soon as the seed germinates. It
can improve germination of small seeds planted
direct into rows to cover them with sieved material,
coconut fibre or seed raising mix rather than just
soil.
Mulch in Seed Rows or
Seedbeds
Mulch should not cover the seeds, as it will impede
germination. It helps, however, to mulch between the
rows, as weeds will take over very quickly. Tricks
to applying mulch without difficulty include
covering seeds in a small area such as zucchini or
melon with an upturned pot. Then mulch the area and
remove the pot when you are done. This leaves a neat
circle of un-mulched ground around your seeds. For
running vegetables such as melons, cucumbers and
pumpkins you need to mulch heavily as you won't
easily be able to mulch the area once the plants
start to run. Aim for mulch 10 cm (4") deep. Or for
seed in rows, cover the seed row with an old timber
weatherboard or long, 8 cm wide strips of strong
cardboard, mulch the area and then remove the
strips. It helps if the straw or hay mulch is in
fairly fine pieces. Add to the mulch along the rows
once plants are germinated and over 10 cm high, to
at least 8-10 cm deep, to prevent weeds germinating.
It saves heaps of time to beat the weeds with mulch
as trying to weed between young plants is very time
consuming but is crucial to a healthy productive
plant.
B. SEEDBED
A seedbed is a small area of the garden set aside
for seedling production. Pick the sunniest spot with
good soil and drainage. Then dig the soil over
thoroughly. The advantage of using a seedbed is that
you only have to intensively care for a small area.
It is possible to cover a small area during hot
periods with PestGuard fabric or shadecloth on a
frame, for improved germination. In cooler areas try
to cover the seedbed at night with clear plastic or
glass to keep the heat in and protect seedlings from
a late frost. Seeds can be sown in rows in the
seedbed much closer together for later
transplanting.
C. CONTAINER
SOWING
Container sowing should always be used for seeds that are
very fine, expensive, slow to germinate or just to
get a jump on the season. The advantage to
sowing in containers is it gives you greater control
and flexibility. The containers can be placed in a warm
position allowing you to start seeds earlier in
spring. It is possible to control watering and fertilising more
accurately. Pests can more easily be monitored; you
are far less likely to lose a whole batch of
seedlings to a hungry snail. The disadvantage is the
time involved in 'pricking out' the seedlings and the need
for greater attention to watering. It is also more
expensive to buy the trays and seed raising mix. For
gardeners with limited space it is possible to grow many vegetables to maturity in containers.
Larger containers are useful for this such as recycled
styrofoam vegetable boxes or
Super Tubes. An excellent book
Kitchen
Harvest: A Cook’s Guide To Growing Organic
Fruit, Vegetables
and Herbs In Containers
is
available.
Types Of Containers
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Seedling Trays or Punnets
Seedling trays and punnets are shallow so the seed raising
mix stays warm.
Shallow seed trays also a have a better surface/depth
ratio to improve aeration.
Seed can be
sown directly into seedling trays or the seedling
tray used as a tray to hold punnets, jiffy pots,
jiffy starters or 48 cell growing trays.
48 cell
growing trays
are made of a soft
plastic that allows you to squeeze the entire
seedling out without damage to the root ball.
Seedling trays are designed to fit bottom heat
propagators and Mini Propagators. Sowing seed
directly into a seedling tray gives you a good
surface to work from in order to 'prick out' or
just thin your seedlings. Small tree seeds should
first be sown in a seedling tray and later
transplanted at the 4-6-leaf stage, into
individual tree tubes, before planting out into
their final position. This is because pots are too
deep and stay too cold and wet for good
germination. Tree seeds can take 3-6 months
to germinate, depending on factors like soil
temperature so they should be labelled with the
name and date of sowing and left alone in a seed
tray. One day when you have forgotten about them
there may be a tray with hundreds of seedlings!
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Plantable Pots
These include
Jiffy Pots,
Jiffy Plant Starters and
Potmaker
Pots. These allow you to sow individual seeds in
controlled conditions, without the need for
pricking out. A big advantage is they reduce
transplanting shock as the whole container is
planted. The Jiffy Plant Starters are particularly
useful for starting tomatoes, capsicums and
eggplants. The Jiffy Pots are great for starting
larger seeds such as zucchini, corn, melon and
cucumber. A Potmaker is used to make your own
small pots out of newspaper. Jiffy Pots and
handmade Potmaker pots need to be filled with a
seed raising mix, while the Jiffy Plant Starters
are a container and mix combined.
How To Sow Seed in Containers
Choose a good quality seed raising mix, a small expense
that will pay dividends. Look for brands that meet
or exceed the Australian Standard. Seed raising
mixes are designed to allow the right aeration for
the germinating seed.
Seeds need oxygen for respiration or they suffocate
and die, which is why seed raising mixes usually
have quite a bit of sand/vermiculite/perlite to try
and improve aeration.
You can make your own but it is better to become an
experienced seed raiser before attempting this.
Never just use garden soil in a container as it
shrinks and makes watering very difficult and lacks
aeration. Usually potting mix is too coarse to be
used to raise seeds.
First fill the seedling
tray or punnet right to the surface and firm down,
to 1 cm below the rim. A handy tool for firming down
can be made from plywood with a handle glued to the
back, to fit the punnet or seedling tray. Don't
press down too hard; you need to keep air in the
mix. Then water the punnet or tray gently until
water runs out the bottom. Sow seeds evenly, try to
leave space around all seeds. Fine seed can be mixed
with dry, clean sand to help spread it evenly.
Paying attention to spreading the seed out will save
time later and produces a sturdier seedling. It
avoids wasting seed. If you are using a Mini
Propagator keep the ventilator closed until
germination, this allows moisture to condense and be
recycled, keeping the soil evenly moist. Heat is
retained which speeds germination. Place seed trays
in a warm, sheltered position with good light but
not direct sun. Remember to
label
your trays or punnets to avoid later confusion.
How to Raise Seeds in Containers
Seedlings can develop disease, such as damping-off
or to grow too tall and spindly, if they are left
too close together. Pricking out is done at the
4-6-leaf stage, usually 2-4 weeks after germination.
Select the sturdiest seedlings, discard any that are
badly formed, damaged in the pricking out process or
with insufficient root development. Seedlings are
lifted carefully by their leaves (never the stems),
using a dibber to gently loosen the roots and
transplanted into punnets,
Potmaker
pots, recycled yoghurt cups, individual Jiffy Pots
or tree tubes. Certain vegetables like to be
re-planted deeper than they originally germinated.
These include cabbage, broccoli, cauliflower and
tomato. To do this remove the first set of
‘juvenile‘ seed leaves and plant up to the first set
of true leaves. Doing this can increase the root
area of a plant and hasten fruit development. In
general though it is best to replant to the same
depth. Once pricked out water gently, and if using a
Mini Propagator,
open the ventilator to encourage air circulation. At
this stage seedlings need continuous moisture and
nutrients, which can be provided by half-strength
liquid manure,
Seed-Start
or
Natrakelp,
applied every few days. Remove the propagator lid
during the day once the seedlings are growing
vigorously and replace it at night. Once roots reach
the bottom of the growing container, usually after
2-4 weeks, they will be ready to transplant into
their final position.
All seedlings need to be
toughened up to full sun exposure before
transplanting. This is done over a few days by
moving the trays or punnets into steadily more
exposed sun conditions. Keep a close eye on them so
that they don't dry out.
WATERING
Water gently, with a
fine spray, to avoid washing seeds away. Avoid
over-watering, as this will cause 'damping off'.
Damping off pathogens can attack seeds before they
germinate or after seedlings have emerged. Remember
that seeds need to breathe in order to grow and
there is no room for air if all the available spaces
in the soil are constantly filled with water. Seeds
vary in their vulnerability to damping off. Water
when the surface feels dry, once a day may be too
much. Once the green leaves appear it is better to
combine watering with weak liquid feeding as seed
raising mixes contain very few nutrients.
TRANSPLANTING
SEEDLINGS FROM CONTAINERS OR SEEDBEDS
A
bit of planning ahead is needed for successful
transplanting:
-
Give the seedlings
a deep soaking the day before preferably in
diluted seaweed fertiliser. This will strengthen
the seedling and reduce transplant shock.
Transplant shock is best avoided; it means the
seedling may just sit there for many weeks without
making growth or in some cases such as lettuce it
may bolt to seed without producing a head.
-
The very best time
to transplant is on overcast days or even better,
in gentle rain.
-
Prepare the hole,
fill it with water and allow it to drain away
before gently planting the seedling.
-
Handle the
seedling by the leaves if at all possible, if it
is necessary to hold it by the stem use a feather
light touch. Too hard a grip will crush the
channels in the stem needed for the transport of
water and nutrients and the seedling will only
make poor growth.
-
Firm the soil
around the seedling gently, never tramp or pack
the soil down hard around the seedling as you are
damaging the soil structure and reducing the
aeration.
-
Water the seedling
well with a gentle spray as soon as possible after
planting.
-
If hot weather is
expected try to cover the seedlings in the hottest
part of the day with shadecloth.
-
Put snail and slug
protection in place immediately; a lot of
seedlings can be lost the first night. Use either
a small amount of snail pellets around the
seedlings or a circle of
copper barrier tape.
SEED TREATMENT
Some seeds require specific treatments before sowing. The
2 main types of treatment are scarification
and stratification. Scarification is used for
seeds with very hard outer coats and involves either
hot water or rubbing the seed between two sheets of
fine sandpaper. This allows moisture to enter the
seed so that it can swell and begin the process of
germination. Tree lucerne and winged beans need a
treatment like this or germination will be very
slow.
Some seeds such as peas and beans should be soaked overnight until the
seed swells, sown but not watered again until the
seedlings are up.
Stratification
is a cold treatment for plants that evolved in areas
with very cold winters. It involves mixing the seed
with moist sand and placing it in the fridge for 4-8
weeks before sowing. It is unlikely to be necessary
In Australia.
WHY DID MY SEEDS
FAIL?
There are many reasons for poor germination of seed,
just doing the opposite of all the strategies
suggested earlier for starters. When conditions are
right and seed is viable, the plants just seem to
jump out of the ground.
-
If you are trying
to “extend the season” try a few seeds to begin
with and keep a written record.
-
To germinate seed
must be viable, this means capable of germinating.
Seed may not be viable because it is poor quality
to begin with, if you believe this to be the case
you should bring it to your seed suppliers’
attention, many will offer you a replacement.
-
Seed Storage: Seed can lose its
viability if it is stored incorrectly. To store it
correctly use a sealed container and keep it in
your fridge. Seed stored in a hot garden shed or
garage that can reach temperatures greater than 40°
in summer will simply die. Seed stored open to the
air where it can take up moisture will lose
viability. Seed also loses viability with age.
Seed packets are best used within the same year
they are purchased. If you plan to use them the
following year reseal the packets well before
storing.
-
Seeds often fail
because they rot in the ground, this can happen
for several reasons. The soil is kept too wet,
therefore there is not enough air and the seed
suffocates. The soil temperature is too cold for
the particular type of seed. Or the seed is
attacking by fungal ‘damping off’ organisms. There
is a range of these that occur naturally, the best
way to avoid this problem is to use a good quality
seed raising mix.
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If seed fails to
germinate always take a look, especially at bigger
seeds. Carefully dig up a seed and see if it has
rotted. Check that a bird or animal has not eaten
the seed. Also look to see if it has germinated
and then been eaten by an animal or insect, snail
or slug. There may be a row of tiny stems left
behind. Sometimes birds will walk along your row
and yank the entire young seedling up. If this is
the case then you will need to look at better
protection for your seeds.
FURTHER INFORMATION:
Sow When Poster
From
Seeds to Leaves
Seed Production for the Australian Home Vegetable
Garden
Saving your own seed is very worthwhile; good books on
the subject include
The Seed Savers Handbook
and
From
Seeds to Leaves
Suggested Products:
Propagation Supplies
Plant Labels and Tags
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Green Harvest
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