Growing trees from seed

Most tree seeds are contained in some kind of fruit – apple pips and cherry stones are good examples – and they will first need to be extracted and cleaned.

The method you should use depends on the type of fruit or seed you have collected – nuts, fleshy fruits, winged seeds or cones.

Once you have separated your seeds into types, you will know whether they need to be either stratified for the winter, or sown immediately into pots or seedbeds.

You will never get all of your seeds to germinate, but by using the following methods your chances of success can be greatly increased.

Fleshy Fruits

Mix the berries with water and then gently mash them with a potato masher or similar device. Viable seed will sink to the bottom and the residue of the fleshy fruit can be discarded. For rowan and mulberry, put the berries in a sieve and gently squeeze them with your fingers under running water to release the seeds. The seeds of all fleshy fruits need to be stratified.

Cones

Put your ripe cones in a paper bag to dry out naturally for a few days – but not in direct sunlight, or on a radiator, or by a fire. The cones will open up and release their seeds which will then be ready to be sown.

Nuts

For acorns and chestnuts, separate the nuts from their cups or outer casings and drop them into a bucket or bowl of water. Discard the ones that float and collect those that sink for sowing. Beech, walnut and hazel nuts should be stratified and then sown when they have germinated.

Winged seeds

Winged seeds can be planted with the wings left on. Separate the seeds from each other and from their twigs, then stratify. Of the species that we’ve have chosen, the only exception to this method is wych elm, which is collected in summer and should be sown immediately.

Very few tree seeds will germinate (shoot or sprout) without exposure to the cold of at least one winter. Other species take even longer, needing the following summer plus another winter before showing signs of life. This is because of a natural defence mechanism built into the seeds, which ensures that they do not grow during the winter months when the young seedlings might be killed by the cold.

Tree growers have developed a technique called stratification which aims to mimic this natural process. To stratify your seeds, mix them with an equal volume of stratification medium (see caption for recipe) and put them in a pot or bucket which has holes in the bottom for drainage.

The container should then be covered with a fine wire-mesh lid, to keep out birds and rodents, and either buried in the ground, placed against a north-facing wall or kept in a cool outhouse. It is essential to keep the mixture moist but not saturated. It’s moist enough if you can squeeze out a drop of water when you pinch the mixture between your thumb and forefinger.

In the spring, tip out the mixture and remove any seeds that are showing small shoots or roots. These seeds are germinating and are ready for sowing. Any seeds that haven’t germinated should be put back into the stratification mixture. Keep checking the seeds weekly during the spring, sowing any that germinate.

Once the seeds are growing, it is important to sow them quickly, as the new shoots are fragile. If they get too large, they can be damaged during planting. If any seeds haven’t germinated by the end of the spring, don’t be disheartened. It is possible they may need two winters, but check that the seeds haven’t rotted before continuing to stratify.

Stratification is a technique designed to mimic nature by exposing seeds to the cold of at least one winter. Germination is when seeds develop small shoots or roots.

A good recipe for a stratification mixture:

Add one volume of peat free potting compost (fresh or recycled) to an equal volume of a coarse-particle material, such as barkchips, perlite, sand or grit. Then mix an equal volume of seeds and stratification mixture together and put in a pot, bucket or dustbin.

When your seedlings have grown into small trees, they need to be transplanted to their final growing positions. This should be undertaken during the winter planting season, normally November to March.

There are many potential places where a tree can be planted including gardens, communal and public open space, road verges, parks, hedgerows, woodlands and churchyards. However, it is vital that you only plant a tree when you have the landowner’s permission and ensure that there will be enough space for your tree when it reaches maturity. Choose well-drained sites where the ground is not too hard. Test this by seeing whether you can push a trowel or spade into the ground simply by leaning on it.

If rabbits, squirrels, deer or livestock are found in the area, protect your tree from bark damage with a tree guard – essentially a plastic tube that fits round the stem. These guards also help to protect the tree against strimmers or lawnmowers. Guards come in many shapes and sizes, so make sure you buy one of the right size.

For small trees grown in cartons or Rootrainers, use a trowel to dig a hole for the tree. Ensure that the hole is deep enough to take all the soil and roots from the pots. If required, use a little extra compost or fine soil to pack around the tree.

• Rootrainer:

Use essentially the same procedure as when planting from a carton. However, as the soil volume is smaller, these trees can also be planted by using a spade to make a slot in the ground. Widen it by wiggling the spade backwards and forwards and then put the tree and its soil in the centre of the slot. Carefully push the sides of the slot back together using your foot to close the slot and firm the soil around the tree.

• Carton:

Moisten the compost before removing the tree from its carton. When planted, the surface of the soil from the pot should be level with the soil around it.

• Seedbed:

Trees grow at different rates, but are most easily transplanted from a seedbed when they are 15-20 cms tall. Once the tree has reached this size, dig up with a spade as shown in the diagram. Ease the tree from the ground and shake to remove loose soil.

If you do not intend to plant the tree immediately, wrap the roots in plastic to protect them and keep them moist. Don’t dig up more trees than you need! Do not leave any plants, particularly those in bags, exposed to direct sunlight.

Make sure the hole you dig for your tree is big enough to enable you to spread out the roots and, equally important, plant the tree so that the root collar – the point from which the roots grow – is at the soil surface. Fill the hole with soil and firm the roots down.

When your tree has been planted in its permanent position, there are still a range of tasks that need to be undertaken to ensure it survives. Research has shown that 50% of newly planted trees may die in their first five years due to a lack of aftercare.

The Tree Council has therefore developed the TLC campaign to remind you of the three simple tasks that need to be undertaken at least once a year – between March and September – for the first five years, to ensure that your young tree survives and thrives.

TLC for young trees involves:

• Tending the tree, checking its health, watering if necessary, making the tree firm in the ground if it has been rocked by the wind, and removing broken branches.
• Loosening ties – small straps used to secure trees to stakes – to make sure they are not rubbing or chafing the tree, and checking the guard to make sure that it is still effective. (Small trees do not need stakes.)
• Clearing all weeds and grasses from one square metre around the tree’s base, and ensuring that the mulching is still effective.

Young trees often die from lack of water particularly if they have to compete with surrounding grass. Cutting the grass only makes things worse as cut grass grows more vigorously. The solution is to create a one square metre weed-free area around the tree. To keep the area free of weeds, you can cover it with a ‘mulch mat’ or with bark chippings or other composted woody material.

Look at the guard that you have placed around the tree. Check that it is still intact and effectively protecting the tree. If not, replace it. Once the tree has become well established, remove the guard entirely.

Sometimes it is difficult to know whether your tree is alive or dead. To check, look for living buds or scrape a little bark from a twig – a live tree will be green beneath the bark, not brown. Branches that are broken or dead can be removed. Cut the branches off with a cut just away from the main stem.