Seed germination requirements

Get some general guidelines and tips to help you when sowing your RHS seeds, along with specific detailed requirements for each type of plant

General guidelines

Begin your seed growing journey with some quick tips and tricks to sowing and growing:

Getting ready
Before sowing the seed prepare all the pots. Use pots and modules for larger seeds or seed trays for smaller ones – why not try making recyled pots? See our guide to going plastic-free. A peat free seed-sowing compost usually provides excellent results. Mix up the compost to break up large lumps and to aerate it.

Overfill the pot, tap the base on a surface to settle the compost, score off any excess and then lightly firm to make a smooth level surface. Leave a gap from the top of the pot depending on the size of the seed. For very small seed leave a small gap of about 2mm. For larger seed leave a larger gap of between 5–10mm. Once all the pots are filled, soak them with an upturned fine rose attached to a watering can and allow excess water to drain away.

Find out more about how to sow seeds indoors >
Sowing seed
Fine seed

Mix seed with a small quantity of fine dry sand and put in the palm of your hand. Holding your hand above the pot, gently tap your hand so the seed trickles out of your hand and is distributed evenly over the compost.

Medium seed

You can sow seed directly from the packet, from a piece of folded paper or put some seed in the palm of your hand, pick up a pinch of seed and sprinkle the seed evenly over the compost.

Large seed

Place each seed on the compost, sowing up to five seeds in a 9cm pot depending on seed size.

The exception is seed which doesn’t like root disturbance (where indicated in the germination table). You should sow these into individual pots or modules and not transplant them at the seedling stage.
 
Sow seed thinly and evenly to give each seed the air, light and moisture it needs and to minimise the risk of disease.

Covering seed
Fine seed

There is no need to cover very small fine seed, or seed that requires light for germination.

Seed germinating within 30 days

Spring is the best time of year for most seed that germinates within 30 days. Cover seed with a layer of compost to the lip of the pot. Cover to a depth of between 2–5mm depending on seed size.

Seed germinating in 60 days or longer

Seed should be covered with a 6mm layer using coarse grit.

Aftercare
Place pots in good light. A greenhouse or a cold frame is ideal and using a heated propagator in a greenhouse will speed up germination.
Overcoming dormacy

Some seeds have factors that delay germination (see germination table for details). The main barriers delaying germination are: hard or watertight seed coats; chemical inhibitors; immature embryos and cold temperature requirements.

Some seeds have more than one barrier to germination that have to be overcome in a certain order. For example the hard seed coat must be penetrated to allow water to enter the seed, releasing inhibitory chemicals. This then initiates the seed to respond to a period of chilling.

Delayed germination

Some seed may take over a year to germinate because they need more than one chilling period or treatment to break the dormancy or barriers preventing germination.

Cold moist stratification

Sow seed and place outside in an open cold frame or place into damp compost and store in the fridge for up to 12 weeks.

Chipping or softening seed coats

Hard seed coats may be softened by soaking in hot or cold water, or ‘chipped’ (nicked) with a sharp knife.

Warm stratification

This may be necessary either to break down the hard seed coat or to mature the embryo. If sowing in spring, this will happen naturally as the temperature rises. Alternatively, put the seed in damp compost and place in the airing cupboard for up to 12 weeks before sowing.

Pricking out
Germinated seedlings need good quality light to avoid becoming weak and spindly. To thin out the seedlings prick them out when the first true leaves have emerged. Prepare pots using a general peat-free potting compost, creating an even, firm surface as before.

Handle seedlings gently by the leaves. Use a pencil or dibber to tease out the seedlings and to make a hole in the newly prepared pot to put the seedling roots into. Fully moisten the compost carefully using an upturned fine rose on a watering can. Place the pots in good quality light.

See our video guide to sowing and pricking out seedlings >

Looking for specific requirements?

To ensure successful germination of your RHS seeds, find the seeds you’ve selected and how to grow them:

Annuals and biennials | Bulbs, corms and tubers | Grasses | Herbaceous perennials | Trees and shrubs

Annuals and biennials

Genus How to sow Height Sunlight
Agrostemma Sow directly where they are to flower, and lightly cover with soil. Germination takes 30–90 days at 13–16°c 0.5–1m Full sun
Alcea Sow in spring. Lightly cover with a thin layer of soil. Germination can take up to 90 days at 16–21°c 1.5–2.5m Full sun
Amaranthus Sow in spring. Don’t cover them with compost, as the seeds need light to germinate. Germination can take up to 90 days at 21–24ºc 1–2.5m Full sun
Ammi Can be sown in spring or autumn into well-drained compost. Germination can be slow or erratic, taking up to 21 days at 16–21°c 0.5–1m Full sun and semi-shade
Atriplex Sow in spring, lightly covering seeds. Can be direct sown outdoors onto prepared soil. Germination in 30 days at 15°c 1–1.5m Full sun
Calendula Can be direct sown in spring or autumn. Germination within 30 days at 15°c 0.1–0.5m Full sun and semi-shade
Carum Germination can take up to 90 days at 16–18°c. Transplant seedlings when small to avoid bolting 0.1–0.5m Full sun
Centaurea Direct sow where they are to grow from early spring in any well-drained soil. Sow seeds thinly over the soil, lightly covering. Germination in 30 days at 10–15°c 0.5–1m Full sun
Cleome Surface sow seeds. Germination seems to improve with warm days and cooler nights. Germination can take up to 30 days at 18–24°c 1–1.5m Full sun
Coreopsis Direct sow where they are to grow from early spring in any well-drained soil. Sow seeds thinly over the soil, lightly covering. Germination in 30 days at 15–20°c 0.5–1m Full sun
Cosmos Sow in spring, lightly covering with compost. Germination within 30 days at 15–20°c 0.1–2.5m Full sun
Daucus Direct sow where they are to grow from early spring in any well-drained soil. Protect early sowings from frost. Sow seeds thinly over the soil, lightly covering. Germination in 30 days at 10–15°c 0.5–1m Full sun
Digitalis Surface sow seeds in late spring as they need light to germinate. Germination in 30–90 days at 15°c 1.5–2.5m Full sun and semi-shade
Dipsacus Best direct sown in spring. Lightly cover seeds. Germination in 30 days at 20°c 1.5–2.5m Full sun, semi-shade
Eccremocarpus Sow in early spring, lightly covering seeds. Germination can be erratic. Germination within 90 days at 13–16°c 2.5–4m Full sun
Echium Sow seeds directly in situ in early spring. Germination within 30 days at 15–18°c 0.5–1m Full sun
Eryngium Moisten seed and place on a piece of kitchen roll and then place in a sealed plastic bag. Seed will germinate in 30 days at 15°c 0.5–1m Full sun
Fibigia Sow in summer, covering seeds with 3mm of compost. Germination may be slow and erratic and seeds may need a period of cold, moist stratification. Germination in 90 days at 15–20°c 0.5–1m Full sun
Glebionis Can be sown indoors in spring, or directly outdoors slightly later. Germination in 10–14 days at 16–21°c 0.5–1m Full sun
Lunaria Sow in summer, covering seeds with 3mm of compost. Germination may be slow and erratic and seeds may need a period of cold, moist stratification. Germination in 90 days at 15–20°c 0.5–1m full sun and semi-shade
Nicandra Sow in spring, indoors or in situ, lightly covering seeds. Germination within 90 days at 15–24°c 1–1.5m Full sun and semi-shade
Nicotiana Leave seeds uncovered when sown as requires light to germinate. Germination can take up to 90 days at 18–20°c 1–1.5m Full sun and semi-shade
Nigella Sow in situ in mid-spring or autumn, lightly covering seeds. Autumn-sown seeds may need winter protection. Germination within 90 days at 13–18°c 0.1–0.5m Full sun and semi-shade
Papaver Best sown direct in spring, lightly cover seeds. Germination in up to 90 days at 13–18°c 0.5-1.5m Full sun and semi-shade
Silybum Sow direct at the depth of 3mm in early summer or just after the last frost. Or sow indoors about two months before they are due to be transplanted outdoors. Germination within 3 weeks at 12–15°c 1–1.5m Full sun
Tagetes Sow in early April, and lightly cover with compost. Germination can take up to 10 days at 21–24°c 0.1–0.5m Full sun
Xerochrysum Sow indoors from March or direct sow outdoors from May. Cover lightly. Germination in 30 days at 18°c 0.5–1m Full sun

Bulbs, corms and tubers

Genus How to sow Height Sunlight
Camassia Lightly cover seeds. Requires a period of cold moist stratification. Germination can take up to 90 days at 10–16°c 1–1.5m Full sun, semi-shade
Cardiocrinum Sow in deep pans with bottom heat. Germination can take more than 90 days at 10–16°c. May take seven years to flower from seed 1.5–2.5m Semi-shade
Crocus Sow in autumn as requires a period of cold moist stratification. Species doesn’t like root disturbance, so sow directly into suitable container. Germination up to one year at 10–15°c 0.1–0.15m Full sun
Cyclamen Sow in autumn, as requires a period of cold moist stratification. Can be beneficial to soak seeds in cold water 10 hours prior to sowing. May need two chilling periods to break dormancy. Germination up to one year at 10–15°c 0.1m Semi-shade
Eucomis Sow in spring to early summer. Lightly cover as some light is needed for germination. Can be slow to germinate. Germination can take up to one year at 18–24°c 0.5–1m Full sun
Fritillaria Sow in autumn, lightly covering seeds. Requires a period of cold moist stratification. Germination can take up to one year at 13–18°c 0.1–0.5m Full sun and semi-shade
Muscari Sow in the autumn. Pre-soak in cold water then lightly cover with grit. As species doesn’t like root disturbance, sow directly into suitable container. Germination up to one year at 10–15°c 0.1–0.5m Full sun, semi-shade
Tigridia Species doesn’t like disturbance, sow directly outdoors or indoors in modules in spring. Germination can take up to one year at 15°c 1–1.5m Full sun
Watsonia Species doesn’t like root disturbance, sow directly outdoors or indoors in modules, covering lightly. Germination can take up to one year at 10–16°c 0.5–1m Full sun

Grasses

Genus How to sow Height Sunlight
Ampelodesmos Sow in pots in a cold frame in spring. Leave seeds uncovered when sown, requires light to germinate. Germination can take 30-90 days at 18–21°c 1.5–2.5m Full sun and semi-shade
Anemanthele Sow in spring or autumn. Cover very lightly with compost. Germination in 30–90 days at 18–21°c 0.5–1m Full sun and semi-shade
Briza Direct sow where they are to grow from early spring in any well-drained soil. Sow seeds thinly over the soil, lightly covering. Germination in 30–90 days at 10–15°c 0.5–1m Full sun
Calamagrostis Surface sow, lightly covering with compost. Germination within 30 days at 20°c 1–1.5m Full sun and semi-shade
Deschampsia Sow in spring, lightly covering with compost. Germination within 30 days at 20°c 1–1.5m Full sun and semi-shade
Elymus Cover seeds lightly. Germination within 30 days at 15–20°c 0.5–1m Full sun and semi-shaed
Eragrostis Surface sow seeds, keeping the compost moist and humidity high. Germination in 30 days at 20–22°c 1–1.5m Full sun
Festuca Sow in spring in well draining compost. Germination within 30 days at 16–21°c 0.1–0.5m Full sun
Lagurus Sow seed 5mm deep in a well-drained compost, or directly in situ, in spring or autumn. Germination within 30 days at approx 12°c 0.1–0.5m Full sun
Miscanthus Surface sow in spring as requires light to germinate. Germination can take up to 90 days at 21–27°c. If germination does not occur, then cold moist stratification may be required for 2–4 weeks 0.5–1m Full sun
Molinia Sow in autumn, lightly covering seeds. Requires a period of cold, moist stratification. Germination within 6 months at 10–15°c 1–1.5m Full sun, semi-shade
Panicum Sow in spring, lightly covering seeds. Germination may take up to 6 month at 16–21°c 0.5–1m Full sun
Pennisetum Sow in spring, in well-draining compost. Germination in up to 30 days at 18–21°c 0.5–1m Full sun
Sesleria Surface sow in spring. Germination can take up to 30 days, keep consistently moist and warm at just under 20°c 0.5–1m Full sun and semi-shade
Sporobolus Sow indoors from autumn to early spring. Germination within 30 days at 15–20°c 0.5–1m Full sun
Stipa
Sow in well-drained compost in spring. Germination in 30–90 days at 18–21°c
 0.5–2.5m Full sun

Herbaceous perennials

Genus How to sow Height Sunlight
Acaena Lightly cover seed and use well-drained compost. Requires warm/cold/warm stratification. Germination may be slow and erratic. Germination can take up to one year at 10–16°c 0.1m Full sun and semi-shade
Adenophora Doesn’t like root disturbance. Sow directly into suitable container. Chilling may improve germination. Germination takes 30–90 days at 10–13°c 1–1.5m Full sun and semi-shade
Agastache Sow in spring. Lightly cover seeds with seed compost. Ideal temp 10ºC–16ºc, germination 30–90 days 1–1.5m Full sun
Althaea Leave seeds uncovered when sown, requires light to germinate. Germination can take up to 90 days at 10–16°c 1.5–2.5m Full sun and semi-shade
Amsonia Can be sown between autumn or spring. Sow on the surface of the soil and gently press in, the seeds need light to germinate. Germination can take up to 90 days at 13–16°c 0.5–1m Full sun, semi-shade
Anemone Sow in spring or autumn. Lightly cover the seeds with compost. Require a period of cold, moist stratification. Germination can take up to one year at 10–15°c 1–1.5m Full sun and semi-shade
Angelica Sow in spring or autumn. Can be direct sown. Lightly cover the seeds with compost, as they require light to germinate. Transplant seedlings while small, large plants resent disturbance. Germination in 30–90 days at 10–15°c 1.5–2.5m Full sun, semi-shade
Armeria Sow in spring or autumn. Pre-soak the seeds in warm water overnight before sowing. Lightly cover the seeds with compost. Germination in 30–90 days at 15–20°c 0.1–0.5m Full sun
Aruncus Sow in autumn. Require a period of cold, moist stratification. Germination can be erratic and may take over one year at 13–18°c 1.5–2.5m Full sun and semi-shade
Asphodeline Sow seeds at any time covering them very thinly with compost, seeds require light to germinate. Can be direct sown. Species resents root disturbance. Germination in 30–90 days at 15–20°c 1–1.5m Full sun
Asphodelus Sow seeds at any time covering them very thinly with compost, seeds require light to germinate. Can be direct sown. Species doesn’t like root disturbance. Germination in 30–90 days at 15–20°c 0.5–1m Full sun
Astrantia Cold stratify for four weeks. Leave seeds uncovered when sown, requires light to germinate. Germination can take up to one year at 13–18°c 0.5–1m Full sun and semi-shade
Baptisia Requires a very free draining soil. Pre-soak seeds in hot water for 12 hours. Germination can be erratic. Germination in 30 days at 20°c 1–1.5m Full sun
Campanula Surface sow in spring, as requires light to germinate. Germination in 90 days at 15–20°c 1–1.5m Full sun and semi-shade
Cenolophium
Sow in the autumn, as needs a period of cold moist stratification. Very lightly cover with compost, as light is needed for germination. Germination can take up to one year at 15–20°c
 1–1.5m Full sun and semi-shade
Centaurea Direct sow where they are to grow from early spring in any well-drained soil. Sow seeds thinly over the soil, lightly covering. Germination in 30 days at 10–15°c 0.5–1m Full sun and semi-shade
Cephalaria Sow in spring, lightly covering seeds. Germination within 90 days at 15°c 1.5–2.5m Full sun and semi-shade
Chelone Sow in spring, lightly covering with compost. Good drainage required. Germination within 90 days at 15°c 0.5–1m Full sun and semi-shade
Cichorium Sow in spring, lightly covering with compost. Germination within 30 days at 10–15°c 1–1.5m Full sun
Cyperus Germination can take 30–90 days at 18–21°c 0.1–0.5m Full sun
Datisca Surface sow, as requires light to germinate. Germination may be slow and erratic. Germination within 30 days at 18°c 1.5–2.5m Full sun and semi-shade
Dianthus
Sow in spring, lightly covering with compost. Needs good drainage. Germination within 90 days at 15–20°c
 0.1–0.5m Full sun
Dierama Sow in spring or autumn. Good drainage required. Cover to twice the seed’s depth with compost. Germination may be slow and erratic and can take up to one year, at 20°c 1–1.5m Full sun
Digitalis Surface sow seeds in late spring, as they need light to germinate. Germination in 30–90 days at 15°c 0.5–1.5m Full sun, semi-shade and full shade
Echinacea Sow seeds in spring or autumn, as they need a period of cold moist stratification. Germination within 90 days at 13°c 1–1.5m Full sun and semi-shade
Eryngium >Moisten seed and place on a piece of kitchen roll and then place in a sealed plastic bag. Seed will germinate in 30 days at 15°c 0.5–1m Full sun
Erysimum Sow late summer for spring flowering, or late winter for autumn flowering. Lightly cover seeds. Germination within 30 days at 16–18°c 0.1–0.5m Full sun
Ferula Sow in the autumn, as requires a period of cold, moist stratification. Very lightly cover with compost as needs light to germinate. Prick out seedlings into deep pots to allow tap root to develop. Germination can take up to one year. After chilling raise temp to 15–20°c 2.5–4m Full sun
Foeniculum It may help to soak seeds for a day before sowing. Sow in late spring. Germination in 30 days at 13–18°c 1.5–2.5m Full sun
Francoa Sow from late winter through to June, lightly covering seeds. Germination in 30 days at 13–16°c 0.5–1m Full sun and semi-shade
Gillenia Sow in autumn, as requires a period of cold, moist stratification. Germination within 30–90 days at 15–18°c 0.5–1m Semi-shade
Glycyrrhiza Pre-soak in cold water for 24 hours before sowing in spring. Germination within 30–90 days at 15–18°c 1–1.5m Semi-shade
Haplocarpha Sow in spring, lightly covering the seeds. Germination within 30–90 days at 18–20°c 0.5m Full sun
Helleborus Sow in autumn, as requires a period of cold, moist stratification. Germination can take up to one year at 16–18°c 0.1–0.5m Full sun and semi-shade
Hesperis Sow in the spring, lightly covering the seeds. Germination in 30 days at 18–21°c 0.5–1m Full sun and semi-shade
Hosta Sow in spring, lightly covering seeds. Germination in 90 days at 10–16°c 0.5–1m Semi-shade
Hydrangea Surface sow seeds in spring. Germination can be erratic, in more than 90 days at 13–16°c 0.1–0.5m Semi-shade
Hyssopus Germination can take up to 90 days at 13–18°c 0.1m–0.5m Full sun and semi-shade
Iris Sow in autumn, as requires a period of cold, moist stratification. Germination up to one year at 13–18°c 1–1.5m Full sun and semi-shade
Kirengeshoma Keep moist and dark. Sow in spring, germination can be erratic. Germination can take up to 30 days at 13–18°c 0.5–1m Full sun and semi-shade
Kniphofia Surface sow, as requires light for germination. Germination can take up to 90 days at 13–18°c 0.1–2m Full sun
Libertia Sow in autumn, lightly covering seeds with compost or grit. Requires a period of cold, moist stratification. Germination within one year at 15–20°c 0.5–1m Full sun
Limonium Lightly cover indoors in early spring, or sow direct in late spring. Germination in up to 20 days at 18–21°c 0.5–1m Full sun
Lobelia Surface sow seeds in late winter, keeping the compost moist. Germination in 90 days at 15–18°c 0.5–1m Full sun and semi-shade
Lunaria Sow in summer, covering seeds with 3mm of compost. Germination may be slow and erratic and seeds may need a period of cold, moist stratification. Germination in 90 days at 15–20°c 0.5–1m Full sun and semi-shade
Luzula Sow in spring or autumn, lightly covering with compost. Germination in 90 days at 15–20°c 0.5–1m Full sun and semi-shade
Lysimachia Sow seeds in the spring or autumn, covering with a thin layer of gravel. Requires a period of cold moist stratification. Germination can be erratic. Germination in 90 days at 13–18°c 0.5–1m Full sun
Lythrum Sow in spring or autumn, lightly covering seeds. Can be direct sown into prepared soil. Germination in 30 days at 15–20°c 1–1.5m Full sun
Maianthemum Sow in late summer, lightly covering seeds with compost. Seeds need a period of warm stratification followed by a period of cold moist stratification. Germination up to one year at 10–15°c 0.5–1m Full shade and semi-shade
Malva Sow in early summer, lightly cover seeds. Germination can take up to 90 days at 16–21°c 0.5–1m Full sun
Papaver Best sown direct, lightly cover seeds. Germination in up to 90 days at 13–18°c 0.1–0.5m Full sun and semi-shade
Phlomis Sow in spring, lightly covering the seeds. Germination may take up to six months at 13–18°c 1–1.5m Full sun
Potentilla Sow in autumn, lightly covering seeds. Requires a period of cold, moist stratification. Germination in 30–90 days at 18-21°c 0.1–0.5m Full sun
Primula Leave seeds uncovered when sown. Requires a period of cold, moist stratification. Germination in up to 90 days, at 13–16°c 0.5–1.5m Full sun and semi-shade
Pulsatilla Lightly cover the seeds. Requires a period of cold, moist stratification. Germination can take up to one year, at 13–16°c 0.1–0.5m Full sun
Rodgersia Sow in spring. Leave seeds uncovered, as requires light to germinate. Chilling may improve germination. Germination can take more than 90 days at 10°c 1–1.5m Full sun and semi-shade
Rudbeckia Sow in spring, lightly covering the seeds. If germination is poor, cold stratify for four weeks. Germination in up to 30 days, at 16–18°c 1.5–2.5m Full sun and semi-shade
Rumex
Propagate by seed sown in situ. Germination can take up to 30 days at 18–21°c
 0.1–0.5m Full sun and semi-shade
Salvia Sow in spring and leave seeds uncovered when sown. Germination in up to 30 days at 18–24°c 0.1–1m Full sun and semi-shade
Sanguisorba Sow in autumn. Doesn’t like root disturbance. Can be direct sown, or indoors preferably in modules, lightly covering seeds with compost. Requires a period of cold moist stratification. Germination in up to three months at 15–20°c 1.5–2.5m Full sun and semi-shade
Scabiosa Sow in autumn, lightly covering seeds. Germination can be erratic, and take up to 90 days at 16–21°c 0.1–1m Full sun
Silene Direct sow in prepared soil in early spring or autumn, lightly covering seeds. Germination in up to 30 days at 16–21°c 0.5–1m Full sun and semi-shade
Sisyrinchium Lightly cover seeds. Germination can be slow and erratic, taking up to one year at 13–18°c 0.5–1m Full sun
Stachys Sow in spring, lightly covering seeds. Germination in 30–90 days at 18–21°c 0.1–0.5m Full sun
Tellima Sow in autumn or spring, lightly covering the seeds. Germination can take more than 90 days at 16–21°c 0.5–1m Full sun, semi-shade and full shade
Teucrium Sow in spring, lightly covering seeds. Germination can take up to 30 days at 16–21°c 0.5–1m Full sun and semi-shade
Thalictrum Lightly cover seeds. Germination can take up to 30 days at 13–18°c 0.5–2.5m Full sun and semi-shade
Trifolium Sow in spring, lightly covering seeds. Germination in 30 days at 18–21°c 0.5–1m Full sun
Valeriana Surface sow in spring. Leave uncovered as requires light to germinate. Germination in 30 days at 15–18°c 1–1.5m Full sun and semi-shade
Verbascum Sow in spring, lightly covering seeds. Germination in up to 30 days at 15–18°c 0.5–2.5m Full sun
Verbena Lightly cover seeds in autumn to early spring. Germination can be slow and erratic. Germination in 90 days at 18–21°c 0.5–2.5m Full sun
Veronica Surface sow seeds. Leave uncovered as requires light to germinate. Germination in 90 days at 13–18°c 1–1.5m Full sun and semi-shade
Veronicastrum Leave seeds uncovered, as requires light to germinate. Germination can take up to 90 days at 16–21°c 1–1.5m Full sun and semi-shade

Trees and shrubs

Genus How to sow Height Sunlight
Akebia Scarify the seeds and soak in water for 24 hours. Sow 1/4 inch deep and a few inches apart in well-drained compost. Keep temperature at 20–24°c. Germination can be slow or erratic 8–12m Full sun and semi-shade
Amorpha Soak in warm water for 24 hours or until seeds swell. Sow at any time of year 2mm deep in moist, free-draining compost. Germination should take place in 30–120 days at 10–15°c 2.5–4m Full sun and semi-shade
Betula Requires period of cold moist stratification. Germination can take up to 90 days at 13–16°c 12m+ Full sun and semi-shade
Bupleurum Germination can take up to 30 days at 13–16°c 1.5–2.5m Full sun
Callistemon Leave seeds uncovered, as requires light to germinate. Germination can take more than 90 days at 16–21°c 2m Full sun
Catalpa Soak seeds for 24 hours before sowing, then surface sow as requires light to germinate. Germination in 30 days at 15°c 12m+ Full sun
Cladrastis Sow in autumn. Soak seeds in hot water, leaving to soak for 24 hours. Needs period of cold moist stratification. Germination can take up to one year at 16–21°c 8–12m Full sun
Cordyline Sow 2mm deep in late spring. Do not overwater as seeds are susceptible to damping off. Germination within 90 days at 20°c 4–8m Full sun and semi-shade
Cupressus Lightly cover seeds. Germination can take more than 90 days at 10–16°c 12m+ Full sun
Decaisnea Use well-drained compost. Sow in autumn. Germination can take more than 90 days at 16–18°c with variable results 4–8m Full sun and semi-shade
Euphorbia Lightly cover seed. Germination can be erratic, but generally takes place in 30 days at 18–24°c 1–1.5m Full sun
Halesia Sow seed indoors in autumn and place at 18–22°c for 2–4 weeks, then move to -4–4°c for 4–6 weeks, then return to warmth for germination. Even under ideal conditions, germination can be erratic, and several cycles of warm/cold/warm stratification may be necessary 4–8m Full sun and semi-shade
Hibiscus Soak seed for several hours in hot water before sowing. Lightly cover seeds with compost. Germination can be erratic. Germination in 90 days at 20°c 2.5–4m Full sun
Hydrangea Surface sow seeds in spring. Germination in more than 90 days at 13–16°c 2.5m–4m Full shade and semi-shade
Hypericum Lightly cover seeds. Germination can take up to 90 days at 10–16°c 1–1.5m Full sun and semi-shade
Kolkwitza Germination can take 30–90 days at 10-13°c. Chilling may improve germination 2.5–4m Full sun and semi-shade
Liriodendron Sow in the autumn, as requires a period of cold moist stratification. Germination in 90 days at 10–15°c 12m+ Full sun and semi-shade
Paulownia Surface sow, as requires light for germination. Sow in autumn or spring, but protect from frost. Germination in up to 90 days at 16–18°c 8–12m Full sun
Rhododendron Surface sow in early spring. Germination within 30 days at 10–24°c 2.5–4m Semi-shade
Staphylea Sow seed in containers in a cold frame in autumn. Cold stratify for six weeks, chilling may improve germination. Germination in up to one year at 13–16°c 4–8m Full sun and semi-shade
Trachycarpus Pre-soak in cold water for a few days. Requires a period of cold, moist stratification. Germination can take up to one year at 25–28°c 12m+ Full sun and semi-shade
Trochodendron Sow in autumn. Requires a period of cold moist stratification. Germination can take more than 90 days at 13–16°c 4–8m Full shade and semi-shade
Viburnum Warm stratify for four weeks, then cold stratify for four weeks. Chilling may improve germination. Germination can take up to one year at 18–21°c 1.5–2.5m Full sun and semi-shade

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RHS Grow app

Keep track of your seeds as they turn into plants

Get in touch

If you are looking to commercialise the genetic material, its products or resources derived from it, please get in touch with the RHS Seed team.
 

Email

[email protected]

Explore more with the RHS

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.