Species details

The following section contains details on seed collection, storage, pre-sowing treatment and sowing for different species of native trees and shrubs.

Note the following points, on which further details are given as indicated:

Trees do not produce good seed every year, so you may wish to store seeds from good years. Storage for several years is possible for small seeds, but large seeds including acorns, chestnuts and beech nuts must not be allowed to dry out, and must be sown by the following spring.
All seeds are vulnerable to being eaten by birds, mice and other animals. For storage, use airtight containers for small, dry seed. Hang large seeds up in hessian bags, suspended where mice cannot reach them.
Fleshy seeds need maceration (soaking) after collection, to separate seed from flesh.
Stratification is a method of breaking dormancy by storing seeds outside where they are subjected to a period of chilling.
Controlled temperature treatment is a method of breaking dormancy by storing seeds in warm (20˚c) and/or cold (2-5˚c) conditions. Seeds are treated either ‘naked’, or mixed with compost or other medium.
The pretreatment details given below are for a sowing date of 1 March, unless otherwise indicated.

Trees

Alder (Alnus glutinosa)

Good seed crops every 2-3 years
Pick ripe cones from September onwards, when the cones start opening. cones may be gathered until spring.
If cones are not open, they can be dried in a warm room. Then shake the cones in a bag to release the seeds. separate the seed from the cones using a sieve. Store the seed in a cool dry place in a hessian bag. Don’t store seed in a plastic bag.
Sow in spring.
OR use ‘shallow dormancy’ method.

Ash (Fraxinus excelsior)

Good seed crops every 3-5 years.
Pick from August to January. If picked green in august, seeds can be sown immediately. some will germinate straightaway, with sporadic germination the next spring. If picked from October onwards when fully ripe, stratification or temperature treatment will be needed.
Do not remove seed from wing.
Store fully ripe seeds by stratifying in sand for 16-18 months.
OR mix in a medium, and store warm for 8-12 weeks, then chill for 8-12 weeks.
Sow temperature-treated seed in the following March/April, or stratified seed in March/April of the second year after collection.
Sow singly in pots, or spaced in trays for pricking out. Lightly cover with com- post and keep moist.
OR sow outdoors in a prepared seedbed.

Aspen (Populus tremula)

Propagate by suckers, or by softwood cuttings, taken in June/July. Choose vigorous shoot tips about 13cm (5”) long, and inser t into pots of compost of equal par ts peat, coarse sand and sterilised loam. Keep in poly bags until rooted.

Beech (Fagus sylvatica)

Good seed crops every 3-5 years.
Collect seeds in September or November. Check for fertility by putting them into water. infer tile seeds will float to the top.
Can be sown immediately in pots, trays or well-drained outdoor beds.
OR store by stratifying outdoors, protected from predators.
OR chill naked for 12-16 weeks. Spray regularly.
Sow in March, in pots or trays, or outdoors in a seedbed.

Birch (Betulus pendula)

Good seed crops every 1-3 years.
Pick the catkins from August onwards, when they are dry and about to disintegrate. The catkins will fall apart releasing the seeds and scales. store the seeds and scales in a hessian sack hung up in a cool air y room, and shake regularly to encourage air circulation.
OR sow immediately in pots, trays or outdoor seedbeds. Sprinkle seed thinly on surface. Cover with a very thin layer of sand to help keep the surface moist, but not so much that light is excluded. Keep moist during germination and for 2 weeks after wards.
OR stratify outdoors for 6 months or until spring.
OR store and then chill naked for 4 weeks before sowing.
OR use ‘shallow dormancy’ method.

Cherry, wild (Prunus avium)

Small quantities can be propagated by removing suckers from existing trees.
Good seed crops every 1-3 years, on groups of trees which have been cross-pollinated. single trees or groups suckered from one tree are self-sterile.
Pick berries in July/August, just before the birds get them. in good years, cherry stones can be gathered from beneath the tree in August.
Store unripe fruit in plastic bags until soft or partly rotten, and then wash to remove the pulp. Ripe flesh can be easily removed.
Sow immediately in pots, trays or outdoor beds, protected from mice and birds.
OR store in a sealed container in a cool place until October. Then stratify outdoors for 4 months, before sowing in spring.
OR store in a sealed container in a cool place until October. Then mix with a medium and keep warm for 2 weeks, and then chill for 18 weeks, before sowing in spring.

Cherry, bird (Prunus padus)

Note locations of trees when in flower in may, as the tree is not conspicuous at other times of year. Produces small, bitter black fruits which ripen in July.
Propagate as for wild cherry.

Crab apple (Malus sylvestris)

Good seed crops every 1-2 years.
Pick fruits in October.
Extract seed immediately and stratify outdoors until February.
OR warm for 2 weeks, and then chill for 14 weeks.
OR store fruit in a cool place until January and then cut open to extract seed and sow immediately.
Sow in pots, trays or outdoor beds. Lightly cover seed with sand or compost.

Elm, English (Ulmus procera)

Seeds are sterile. Propagate from suckers.

Elm, wych (Ulmus glabra)

Good seed crops every 1-2 years.
Collect seeds in May/early June.
Sow immediately in pots, trays or outdoor beds, lightly covered with com- post and kept moist. Germination is very quick, and seedlings should make significant growth in the first year.

Holly (Ilex aquifolium)

Good seed crops every 2-3 years.
Collect berries between November and February.
Stratify outdoors for 16 months.
OR mix with medium and store in warmth for 40 weeks then chill for 24 weeks before sowing.
Sow in pots, or in trays for pricking out into pots. Holly resents root disturbance – avoid transplanting after the first year.

Hornbeam (Carpinus betulus)

Good seed crops every 2-4 years.
Collect in November, while wing is still slightly green, for immediate sowing.
OR collect from November-spring, when wing is brown and seed coat is hard. Seed can then be stored as necessary.
To break dormancy, stratify outdoors for 18 months, protected from mice and birds.
OR mix with medium and store in warmth for 4 weeks, then chill for 12-24 weeks.
Sow in pots, trays or outdoor seedbeds.

Lime, small-leaved (Tilia cordata)

Good seed crops every 2-3 years.
Collect seeds in October.
Stratify outdoors for 18 months.
OR mix with medium, and store in warmth for 4-8 weeks, and then chill for 16 weeks.
Sow in pots, trays or outdoor beds.

Lime, large-leaved (Tilia platyphyllos)

Propagate as for small-leaved lime.

Maple, field (Acer campestre)

Good seed crops every year.
Collect the winged seeds in September/October, when they are still a yellow to light brown colour, before they form a hard seed coat.
Sow seed immediately.
OR mix with medium and store in warmth for 4-8 weeks, then chill for 12-24 weeks.
Sow in pots, trays or outdoor beds.

Oak, pedunculate (Quercus robur)

Good seed crops every 2-4 years.
Collect from September to November. The first acorns to fall are usually infer tile. normally the morning after the first frost there will be a large fall of acorns.
Preferably sow straight away in pots, trays or outdoor seedbeds, as stored seed loses viability. Protect from predators with extra layer of soil or netting.
OR store in hessian bags hung up in a cool place. Shake gently every few days to prevent the acorns heating up. Gently spray with cool water at intervals from January until sowing time, to prevent the acorns shrivelling and to keep them plump and viable.
Sow in pots or outdoor beds.

Oak, sessile (Quercus petraea)

As for pedunculate oak.

Rowan (Sorbus aucuparia)

Good seed crops ever y 2-3 years.
Collect fully ripe seed, macerate and sow immediately, for germination the following march.

Service tree (Sorbus torminalis)

Seeds most years.
Pick berries in September, when brown and ripe.
Store in poly bags until partly rotten.
Wash to remove pulp and sow immediately in pots, trays or outdoor beds.
OR stratify cleaned seeds outdoors, and sow in late winter.

Scots pine (Pinus sylvestris)

Good seed crops every 2-3 years.
Collect cones from November to February, before they open. Dry in a warm room until they open and the seeds drop out.
Store seed in a sealed container in the fridge.
Four weeks before you wish to sow, mix the seeds with a medium and return to the fridge to chill.
OR use ‘shallow dormancy’ method.
Sow in pots, trays or outdoor beds, covering the seeds lightly. Keep moist.

Sweet chestnut (Castanea sativa)

Seeds every 1-4 years, with best seed after a warm summer.
Gather fallen nuts from the ground or pick from the trees as soon as the outer cases begin to break open, in October/November.
Sow immediately in free-draining soils, protected from birds and animals.
OR spread the nuts out to surface dry for about a week in a protected, shaded, ventilated place, then store in hessian sacks, hung up in a cool, dry place.
Spray weekly to keep moist. Sow in spring.

Whitebeam (Sorbus aria)

As for rowan.

Yew (Taxus baccata)

Crops most years.
Collect from September to November. The seed and red flesh are poisonous.
Soak to remove flesh.
Stratify outdoors for 16 months.
OR mix with medium, keep in warmth for 40 weeks, then chill for 20-24 weeks.
Sow in pots, trays or outdoor beds.

Shrubs

Blackthorn (Prunus spinosa)

Seeds every 1-2 years.
Pick when fruit is blue-black, in October.
Soak to extract seed from pulp.
Keep in warmth for 2 weeks, then chill for 18 weeks.
Sow in trays or outdoor beds.

Broom (Cytisus scoparius)

Seeds every year.
Pick pods when black, in August.
Pop pods to extract seeds.
Store seed in a sealed container until spring.
Sow in pots, as plants resent root disturbance.

Buckthorn, alder (Frangula alnus)

Propagate as for purging buckthorn.
Keep seedlings and young plants moist.

Buckthorn, purging (Rhamnus catharticus)

Seeds most years, on female plants in mixed groups.
Gather fruits when fully black in autumn.
Stratify outdoors.
OR store and then chill for 8 weeks.
Sow in February, in pots, trays or outdoor beds.

Dogwood (Cornus sanguinea)

Seeds every year.
Pick berries as soon as they change from green to black in late summer, before birds get them. sow immediately.
OR soak to soften flesh.
Then stratify outdoors until spring.
OR warm for 10 weeks and then chill for 10 weeks.
Sow in pots, trays or outdoor beds.
Can also be propagated from cuttings, suckers or layers.

Elder (Sambucus nigra)

Gather ripe berries and keep in poly bags until partly rotten, or crush in a blender, and then wash out the seeds.
Stratify outdoors.
Sow in pots, trays or outdoor beds in late winter.
OR propagate from hardwood cuttings taken with a heel in October/November.

Gorse (Ulex europaeus)

As for broom.

Guelder rose (Viburnum opulus)

Good seed crops most years.
Gather fruits in August/September before they are fully ripe.
Store fruit in poly bags until partly rotten.
Separate seed from flesh by washing. Sow immediately.
OR keep in warmth for 8 weeks, and then chill for 8 weeks. Even after this treatment, germination may be erratic.
Sow in trays or beds and cover with 2cm (1”) of soil.

Hawthorn (Crataegus monogyna)

Good seed crops every 1-2 years.
Collect haws in September/October, when fully ripe.
Soak to remove pulp from seeds.
Stratify outdoors for 18 months.
OR mix with medium and store in warmth for 4-8 weeks, then chill for 12-16 weeks.
Sow in pots, trays or outdoor beds.

Hazel (Corylus avellana)

Good seed crops ever y 2-3 years.
First nuts that fall are usually sterile. Pick from the tree in August/September just as nuts begin to turn brown. Fully ripe nuts will fall to the ground, but they must be gathered promptly as birds or squirrels will take them.
Place nuts in water and discard sterile ones which float to the surface.
Sow immediately in pots or trays.
OR stratify outdoors for 6 months.
OR store for up to 4 weeks in a hessian bag hung up in a cool, air y place and then chill for 16 weeks before sowing.
When sowing in pots or trays, use a dibber or similar to make a hole so that the top of the nut is just covered. For outdoor beds, broadcast the nuts and then cover with a layer of soil or compost. protect from mice and birds.

Juniper (Juniperus communis)

Propagate from cuttings, taken with a heel in late summer from that season’s growth.
OR gather berries in October.
Seeds have ‘double dormancy’ (both hard coat and embryo) and require either 18 months’ stratification or accelerated cold-warm-cold treatment.

Spindle (Euonymus europaeus)

Seeds most years.
Collect in September. Remove bright pink cases which enclose the orange seeds. note that all par ts of the seed are toxic.
Dry in a warm room until seed covering can be removed by beating the seeds in a bag.
Store in warmth for 10 weeks and then chill for 12 weeks.
Sow in pots, trays or outdoor seedbeds, covered with a thin layer of coarse sand.
Germination is erratic, so leave until at least the second spring.

Wayfaring tree (Viburnum lantana)

Seeds most years.
Gather in August as soon as at least a few berries in each cluster turn from red to black.
Macerate until flesh can be removed.
Sow immediately.
OR stratify outdoors until spring.
OR store in warmth for 8 weeks and then chill for 8 weeks.
Sow into pots or trays and germinate in a greenhouse or cold frame.