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Shrubs and Trees - Seeds - 3) Planting Seeds

Introduction

This is final part of our three-part How to collect, store and plant woody tree and shrub seeds.

1) Collecting Seeds.

2) Storing Seeds.

3) Planting Seeds.


Planting seeds in spring

What do I need and how do I begin?

You are not growing annuals, herbaceous plants or vegetable seeds which will germinate very quickly in a week or two so a slightly different approach is needed.

Smaller seeds are best grown in plastic seed trays or, better still, more old fashioned wooden seed trays.

Old fashioned wooden seed trays click for larger image
Old fashioned wooden seed trays
or plastic seed trays click for larger image
or plastic seed trays
2 Old fashioned wooden seed trays click for larger image
Old fashioned wooden seed trays
3 Old fashioned wooden seed trays click for larger image
Old fashioned wooden seed trays

Larger seeds are best grown in deeper pots either individually or with three to five larger seeds per pot.

2 seeds in deeper pots   click for larger image
Seeds in deeper pots
1 seeds in deeper pots   click for larger image
Seeds in deeper pots
Styrax seeds in pot  click for larger image
Styrax seeds in pot

Standard size compost (purchased from any garden centre) is fine but not ideal on its own – you can do better.

The best seed mixture for ericaceous (woody trees and shrubs) is finely sieved good quality TOPSOIL mixed with some sand or grit and peat if you prefer but say 60-70% pure (natural) topsoil. Some seed composts may well already contain grit.

1 compost with gritclick for larger image
Compost with grit
2 compost with gritclick for larger image
Compost with grit
3 compost with gritclick for larger image
Compost with grit

While it may be advisable to grow seeds of annuals sown early with a heat pod underneath the seed tray this is not needed or even advisable for these sorts of seeds which may take far longer to germinate.

What is needed is plenty of warmth and daylight (ie the kitchen windowsill is not ideal) together with the moisture and humidity of the greenhouse.

Warmth and daylight neededclick for larger image
Warmth and daylight needed

The plants you are trying to grow germinate in the wild (often in China) in moist leaf litter on the forest floor. Those are the conditions you are trying to recreate and improve on to germinate your seeds.

A solid base of slate or wood will help dissipate warmth up into the seed tray or box.

Solid base to dissipate heat
Solid base to dissipate heat
Solid base to dissipate heatclick for larger image
Solid base to dissipate heat

Covering your trays and boxes with sheets of glass will also warm the soil and generate warm humidity over the seeds.

Covering trays with glassclick for larger image
Covering trays with glass

More importantly still this will prevent mice or shrews digging up your seeds or eating your emerging seedlings.

The exact spacings between seeds of varying sizes and, more importantly, the depth to which they should be planted in the seed trays or pots requires common sense.

Basically tiny seeds should be sown on the surface and bigger seeds more deeply.

Various examples (with pictures) of how to plant different types of seeds are shown below.

One more thing before you start

If you have plenty of seeds of anyone variety take secateurs, a sharp knife or razor blade and cut one in half.

If it is green the seed is alive, has overwintered well, and should germinate properly.

If, even in the tiniest seed, there is no sign of life but rather a shrivelled void or perhaps a rotten ‘mush’ then you are wasting your time planting them as they are already unviable and dead.

Different techniques for sowing different types of seed.

Magnolias

Magnolia seeds had a thick orange outer coating when gathered. This outer coating which, by now, may well be brown and growing a hairy down needs to be removed or squeezed off between finger and thumb before sowing. If you do not do this germination will be poor or non-existent. In the wild this coating would be digested by the rodent or bird which ate the seed before it was secreted.

Cleaning magnolia seedsclick for larger image
Cleaning magnolia seeds
2 Washing magnolia seedsclick for larger image
Washing magnolia seeds
3 Washing magnolia seedsclick for larger image
Washing magnolia seeds

Seed spacing needs to be about 1 inch. So you would plant 40 magnolia seeds in one standard tray.

Seed spacingclick for larger image
Seed spacing

The seed holes can be made with a pencil about an inch or less deep and the seeds then individually inserted and firmed in.

Seed spacingclick for larger image
Seed hole & firm in
Seed spacingclick for larger image
Seed hole & firm in
Seed spacingclick for larger image
Seed hole & firm in

Water the seeds in and cover with a pane of glass until the first 'juvenile' leaves appear say six to ten weeks.

Seeds under glassclick for larger image
Seeds under glass

The seed tray needs to stay moist but not too soggy and wet or the seeds will rot.

After germination remove the glass but cover the tray with mesh to keep the mice out. Mice love the smell of magnolia and relish the challenge. Slugs too are a threat and need to be deterred and squashed when seen.

Mesh to keep mice outclick for larger image
Mesh to keep mice out
2 Mesh to keep mice outclick for larger image
Mesh to keep mice out

The young seedlings need protection from direct sunlight on hot days for several weeks. Old newspaper can be used between mid-morning and the early evenings.

Protect with newspaper
Protect with newspaper

The seedlings can stay and grow on in the same tray for a whole year before they need to be potted on the next spring just before growth recommences.

Seedlings in trayclick for larger image
Seedlings in tray
2 Seedlings in trayclick for larger image
Seedlings in tray
3 Seedlings in trayclick for larger image
Seedlings in tray
5 Seedlings in trayclick for larger image
Seedlings in tray
6 Seedlings in trayclick for larger image
Seedlings in tray

Usually, after a good first growing season, they can go straight into a 2 or 3 litre pot.

Seedling large enough to pot onclick for larger image
Seedling large enough to pot on
Moving onto 2 / 3 litre potsclick for larger image
Moving onto 2 / 3 litre pots
2 Moving onto 2 / 3 litre potsclick for larger image
Moving onto 2 / 3 litre pots
3 Moving onto 2 / 3 litre potsclick for larger image
Moving onto 2 / 3 litre pots

Rhododendrons

Here the problem and solutions are different.

The seeds are so numerous and tiny that a sneeze or a puff of wind can blow them away. They need to be sown on the surface of the seed tray and gently smoothed in rather than buried.

Sewing seeds on the surfaceclick for larger image
Tiny seeds easily blown away
Rhododendron sowing seedsclick for larger image
Rhododendron sowing seeds
Rhododendron sowing seedsclick for larger image
Rhododendron sowing seeds
Chopping mossclick for larger image
Chopping moss
Moss covered seedsclick for larger image
Moss covered seeds

So the old fashioned way of ensuring a high rate of germination is to collect some moss, dry it off a little, and cut it up with scissors.

Seeds in mossclick for larger image
Collect moss and add compost to tray
2 Seeds in mossclick for larger image
Cut up moss
3 Seeds in mossclick for larger image
Place moss over compost

Then spread it lightly over the top of the seed tray and sow the seeds from the palm of your hand (or a salt cellar with the seed mixed with sand). Make sure the soil level is well below the top of the tray so that the glass covering does not touch the soil and, indeed, is well below it.

Water in the seeds and moss with a hand held water sprayer. A watering can or any other method of watering in will mean the seeds all float to one end of the tray. Standing the seed box in a tray will allow self-watering from below but this must not be excessive or the seeds will rot in a waterlogged seed mix.

Self-watering seed boxclick for larger image
Hand water seed box

The moss will start to grow quickly and the rhododendron seedlings will germinate in four to six weeks in and around the moss. These are EXACTLY the moist, shady and humid conditions in which rhododendron seeds would and do naturally germinate in the wild on Chinese mountains or, less readily, but occasionally, in English gardens.

Moss with rhodo seedlingsclick for larger image
Moss with rhodo seedlings

The greatest risk to emerging rhododendron seedlings is direct sunlight which can readily scorch and kill them. So your see tray needs not only a glass covering until germination is well underway, but also a newspaper covering (or similar). Shading on the greenhouse itself is often not enough on its own.

Shading in greenhouseclick for larger image
Shading in greenhouse

Germination of more rhododendron seedlings in the tray may well take place right through the summer months. You should therefore ‘prick out’ the first larger seedlings from the tray and transfer them to grow on in small 7cm pots or something similar to give the others room to develop. These transplants will also be vulnerable to scorching on hot days and will continue to need protection from direct sunlight.

Rhododendron seedlingsclick for larger image
Rhododendron seedlings
2 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
3 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron seedlingsclick for larger image
Rhododendron seedlings

If there are tiny seedlings still in abundance in the seed tray by September spread the risk and leave what is left overwinter. Try pricking out and potting on more in the following May or June when they have put on another set of new growth. Do not overwater over winter but just keep moist while the seedlings are dormant. Provide frost protection if need be on occasion with a fleece covering if your greenhouse is unheated.

Rhododendron seedlingsclick for larger image
Rhododendron seedlings
2 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
3 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron seedlingsclick for larger image
Rhododendron seedlings
4 Rhododendron lindleyi seedlingsclick for larger image
Rhododendron lindleyi

Camellias

These are easier to deal with although germination rates can vary hugely from year to year.

Camellias are top rooted plants (one central dominant root) and camellia seedlings are the same.

Plant three to five seeds only in a deep 2 or 3 litre pot with the same soil/compost mix as for all these woody plants.

Planting camellia seedsclick for larger image
Planting camellia seeds
Camellia Mary Williamsclick for larger image
Camellia Mary Williams

Cover the pots with glass until germination occurs after six to eight weeks. Again germination may well not all occur at once but remove the glass soon after the first sign of germination.

If the pots are large enough there is no need to prick out or transplant seedlings until the next spring when they should easily be big enough to pot on in March or April.

Other plants

All woody plants take different times to germinate.

Some rarities or difficult plants may only germinate in the second spring after planting. Davidias, rehderodendrons and oaks with larger acorns fall into this category. So just plant them in big pots (preferably clay), keep the mice out and forget about them for a year hoping for a big surprise.

Acer capillipes seedlingsclick for larger image
Acer capillipes seedlings
Acer capillipes seedlingsclick for larger image
Acer capillipes seedlings
Berberis hookeri seedlingsclick for larger image
Berberis hookeri seedlings
Cupressus tortulosa seedlingsclick for larger image
Cupressus tortulosa seedlings
Enkianthus 'Wallaby'  seedlingclick for larger image
Enkianthus 'Wallaby' seedling
Puya chilensis seedlingclick for larger image
Puya chilensis seedling
Rehderodendrons macrocarpum seedlingsclick for larger image
Rehderodendrons macrocarpum
Rehderodendrons seedlingsclick for larger image
Rehderodendrons seedlings
2 Rehderodendrons seedlingsclick for larger image
Rehderodendrons seedlings
Staphylea seedlingsclick for larger image
Staphylea seedlings
Stewartia rostrata seedlingsclick for larger image
Stewartia rostrata seedlings
Styrax hookeri seedlingclick for larger image
Styrax hookeri seedling

Within the boundaries of what is set out above treat all woody trees and shrubs in the same manner. Plant bigger seeds in pots and smaller ones in trays.

If you fail with a particular type of seed one year try again next autumn as rarer plants can be fickle and germination rates can vary hugely for individual plants from season to season.
 


Good Luck!

Luck can however be improved by following these instructions.

Please call the nursery or email us if you have any specific queries or problems growing particular plants. If we have tried them ourselves we may know the answers some of the time!


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