Seed stratification information

Many species are dioecious in nature, meaning that male and female flowers occur on different plants, and fruits form only on female plants. Growing these species from seed is an ideal way of ensuring that a mixture of male and female plants is obtained; if possible, grow on at least 4 or 5 plants to give yourself a good chance of having at least one male. Excess male plants can always be weeded out once it becomes clear what sex the plants are.

Details given for seeds in the tables below have a code for the recommended seed treatment prior to sowing:

Recommended seed treatments

Stratification of seeds involves mixing the seed with a moist medium and keeping warm and/or cold for a certain time before sowing. We recommend mixing seeds with moist (not wet) silver sand, using 4 parts or more sand to one of seeds; the mix should be placed in a plastic bag which can be sealed and re-opened. Label the bag well! Warm stratification means keeping the seed/sand mix at about room temperature, 60-70°F or 15-21°C; cold means keeping the mix at about 40°F (5°C) – a domestic fridge is ideal for small quantities. When cold stratifying over winter, seed/sand mixes can be placed outside in a rodent/bird-proof container (eg. a plastic dustbin). Whenever stratifying seed, check every week or two to see if germination is starting. When it does you will see white roots start to emerge from seeds, and if this happens then the seeds should be sown immediately. If this isn’t possible, keep the mix at a temperature just above freezing until you can sow.

Scarification of seeds involves softening the hard seed coat in some way to allow water to be imbibed into the seed. The simplest way of achieving this is to give the seeds a hot water soak, putting them into water at about 190°F (88°C) and allowing them to stand for several hours while the water cools. Alternatively, the seeds can be physically rubbed, eg. between two sheets of fine sandpaper – take care not to rub too much.

Dewaxing – some seeds are covered in a layer of wax (notably Myrica species) which stops the seeds imbibing water and germinating. This must be removed before stratification or sowing – the best way to do this is to rub the seeds between two sheets of coarse sandpaper (do it for periods of a few seconds at a time, then check the seeds – you only want to get rid of the wax and not damage the seeds!)

Seeds which take a long time to germinate are best sown in seed trays or pots, and covered with sand rather than compost. Very small seeds should be sown on the surface of the compost and the tray/pot kept moist by enclosing it in a plastic bag. Finally, don’t give up if seeds don’t germinate, or only a few germinate, in the first year – many seeds spread out their germination over more than one year. If the seeds are large enough, you can check their viability by cutting one in half – the seed embryo inside should be white and solid, and not soft or watery.

After the description of each species, codes are given for the recommended treatment to promote good germination. (Note that using these treatments does not guarantee germination. Seed lots vary in their requirements and these are a general guide only.) The codes used are:

  • ND Not dormant, sow in spring.
  • SI Not dormant, but must be sown immediately.
  • SC Scarify and sow in spring.
  • CS Cold stratify. Followed by a number of weeks, eg CS 13 = cold stratify 13 weeks (3 months).
  • WS Warm stratify. Followed by a number of weeks, eg WS 6 = warm stratify 6 weeks.

Warm stratification can sometimes be followed by cold stratification, eg. WS 13 + CS 13 means 13 weeks warm first then 13 weeks cold stratification.

Example: Assuming an intended sowing date of April 1st, then 4 weeks of stratification should start on 4th March, 6 weeks on 17th February, 8 weeks on 3rd February, 13 weeks on 1st January, 16 weeks on 10th December, 20 weeks on 12th November, 26 weeks on 1st October, etc. If you have trouble counting the weeks backwards there is a handy date calculator at http://www.timeanddate.com/date/dateadd.html

Species

Stratification details

Abies amabilis

CS4

Abies balsamea

CS4

Abies grandis

CS4

Abies nobilis

CS4

Acanthopanax senticosus

CS26+WS13

Acanthus mollis

ND

Acca sellowiana

ND

Acer saccharum

CS13

Achillea millefolium

ND

Actinidia arguta

CS13

Actinidia chinensis

CS4

Actinidia kolomikta

WS13+CS13

Agastache foeniculum

ND

Agastache rugosa

ND

Akebia quinata

CS4

Alchemilla mollis

CS4

Akebia trifoliata

CS4

Alliaria petiolata

ND

Allium babingtonii

ND

Allium moly

WS4+CS4

Allium neapolitanum

ND

Allium carinatum pulchellum

ND

Allium schoenoprasum

ND

Allium tuberosum

ND

Allium senescens

ND

Allium sphaerocephalum

ND

Allium ramosum

ND

Allium fistulosum

ND

Allium ursinum

CS13-17

Alnus cordata

CS8

Alnus glutinosa

CS8

Alnus incana

CS8

Alnus rubra

CS8

Alnus sinuata

CS8

Alnus viridis

CS8

Althaea officinalis

ND

Amelanchier alnifolia

WS4+CS16

Amelanchier canadensis

CS20

Amelanchier lamarckii

WS4+CS16

Amorpha fruticosa

CS2

Angelica dahurica

ND

Angelica archangelica

WS4+CS4

Anthriscus sylvestris

ND

Anthyllis vulneraria

SC+CS8

Aquilegia vulgaris

CS13

Aralia chinensis

CS13

Arbutus unedo

ND

Arctostaphylos uva-ursi

SC

Aronia melanocarpa

CS13

Artemisia dracunculus

ND

Artemisia vulgaris

ND

Asclepias syriaca

ND

Asclepias speciosa

ND

Asclepias tuberosa

ND

Asimina triloba

CS13

Asperula odorata

CS13

Astragalus glycyphyllos

SC

Astragalus mongholicus

 

Atriplex canescens

ND

Atriplex halimus

ND

Barbarea vulgaris

CS8

Berberis buxifolia

CS20

Berberis darwinii

CS17

Berberis lycium

CS8

Berberis vulgaris

CS8

Berberis wilsonii

CS8

Beta vulgaris maritima

ND

Betula lenta

CS4

Betula papyrifera

CS4

Broussonetia papyrifera

ND

Betula pendula

CS4

Betula pubescens

CS4

Calendula officinalis

ND

Calluna vulgaris

CS20

Caltha palustris

WS4+CS6

Bunias orientalis

ND

Buxus sempervirens

CS26

Calamintha nepeta

ND

Camassia quamash

ND

Calycanthus floridus

CS13

Campanula latifolia

ND

Campanula rapunculoides

ND

Campanula rapunculus

ND

Capsicum pubescens Hidalgo

ND

Caragana arborescens

SC

Ceanothus sanguineus

SC

Cedrus atlantica

CS4

Celtis australis

CS13

Centranthus ruber

ND

Cephalotaxus fortunei

CS13

Cephalotaxus harr.drup.

CS13

Ceratonia siliqua

SC

Cercidiphyllum japonicum

ND

Cercis canadensis

SC+CS8

Cercis occidentalis

ND

Cercis siliquastrum

SC+CS8

Chaenomeles cathayensis

CS13

Chaenomeles japonica

CS13

Chamaemelum nobile

ND

Cichorium intybus var.intybus

ND

Clematis vitalba

CS12

Chenopodium bonus-henricus

ND

Chimonanthus praecox

WS13+CS13

Cladrastis lutea

SC

Claytonia sibirica

ND

Colutea arborescens

SC

Cornus canadensis

WS13+CS13

Cornus capitata

CS8

Cornus kousa chinensis

CS14

Cornus mas

CS23

Cornus officinalis

CS23

Coronilla emerus

SC

Coronilla varia

SC

Crambe cordifolia

ND

Crataegus arnoldiana

CS13

Crataegus durobrivensis

CS13

Crataegus ellwangeriana

CS13

Crataegus mollis

CS13

Crataegus monogyna

WS13+CS26

Crataegus oxycantha

WS13+CS26

Crataegus tanacetifolia

CS13

Cryptotaenia japonica f.viridis

ND

Cupressus macrocarpa

CS4

Cynara cardunculus

ND

Cynara scolymus

ND

Cytisus scoparius

SC

Decaisnea fargesii

CS16

Diospyros kaki

ND

Diospyros lotus

CS4

Diospyros virginiana

CS13

Diplotaxis tenuifolia

ND

Drimys winterii

ND

Duchesnea indica

ND

Echinacea purpurea

ND

Elaeagnus angustifolia

ND

Elaeagnus multiflora

CS8

Elaeagnus umbellata

WS4+CS10

Ephedra nevadensis

ND

Eupatorium perforatum

ND

Filipendula ulmaria

CS13

Foeniculum vulgare

ND

Fragaria vesca

CS4

Galium album

CS8

Galega officinalis

ND

Galium verum

ND

Eryngium campestre

ND

Gaultheria shallon

CS17

Genista tinctoria

SC

Gentiana lutea

WS4+CS4

Gleditsia triacanthos

SC

Glycyrrhiza echinata

SC

Glycyrrhiza glabra

SC

Halesia carolina

CS13

Hamamelis virginiana

CS34

Herniaria glabra

ND

Helianthus maximiliani

ND

Hemerocallis minor

ND

Hemerocallis lilioasphodelus

ND

Hippophae rhamnoides

CS17

Hosta sieboldiana elegans

ND

Hippophae salicifolia

CS4-8

Hovenia dulcis

SC

Hypericum androsaemum

ND

Ilex aquifolium

WS12+CS40+WS12

Hypericum perforatum

ND

Juncus inflexus

ND

Hyssopus officinalis

ND

Hypericum calycinum

CS4

Juniperus communis

WS13+CS13

Juniperus virginiana

CS8

Koelreuteria paniculata

WS13+CS26

Larix decidua

CS4

Laburnum anagyroides

SC

Lamium purpureum

WS4+CS6

Lespedeza bicolor

SC

Lathyrus maritimus

SC

Lathyrus pratensis

SC

Lavandula angustifolia

ND

Lavandula latifolia

ND

Levisticum officinale

ND

Leonurus cardiaca

ND

Lindera benzoin

CS14

Liquidambar styraciflua

CS4

Liriodendron tulipifera

CS26

Lotus corniculatus

SC

Lotus pedunculatus

SC

Lupinus arboreus

SC

Lupinus albus Dieta

ND

Lupinus perennis

SC

Lycium barbarum

ND

Maackia amurensis

SC

Maclura pomifera

CS4

Mahonia aquifolium

CS17

Mahonia nervosa

CS17

Malva alcea

ND

Malva moschata

ND

Malva verticillata Crispa

ND

Malva sylvestris

ND

Marrubium vulgare

ND

Medicago lupulina

ND

Melilotus officinalis

ND

Mahonia repens

CS17

Mentha aquatica

ND

Melissa officinalis

ND

Mentha longifolia

ND

Mentha suaveolens

ND

Mentha pulegium

ND

Morus alba

CS16

Metasequoia glyptostroboides

CS4

Mentha piperita

ND

Mentha spicata

ND

Micromeria thymifolia

ND

Monarda citriodora

ND

Monarda didyma

ND

Monarda fistulosa

ND

Morus alba tatarica

CS13

Morus nigra

CS16

Myrica californica

dewax+CS4

Myrica cerifera

dewax+CS8

Myrica pensylvanica

dewax+CS13

Myrrhis Odorata

CS20

Myrtus communis

ND

Nasturtium officinale

ND

Origanum vulgare

ND

Oenothera biennis

ND

Origanum majorana

ND

Oxyria digyna

ND

Onobrychis viciifolia

SC

Parthenocissus quinquefolia

CS12

Passiflora caerulea

CS4

Paulownia tomentosa

ND

Phellodendron amurense

CS4

Ostrya carpinifolia

WS13+CS13

Parthenocissus tricuspidata

CS12

Parthenium integrifolium

ND

Passiflora edulis

ND

Phormium colensoi

ND

Phormium tenax

ND

Phragmites australis

ND

Physalis alkekengi

ND

Phytolacca americana

ND

Pimpinella saxifaga

ND

Pinus armandii

CS13

Pinus cembra

WS13+CS13

Pinus nigra austriaca

CS4

Pinus nigra corsicana

CS4

Pinus pinaster

CS4

Pinus pumila

CS18

Pinus radiata

CS4

Pinus sylvestris

CS4

Plantago coronopus Minutina

ND

Plantago lanceolata

ND

Pinus koraiensis

CS13

Pinus pinea

CS0-4

Platanus acerifolia

CS4

Polemonium caeruleum

ND

Polemonium reptans

ND

Polygonatum multiflorum

WS4+CS6

Polygonatum odoratum

ND

Poncirus trifoliata

ND

Prunella vulgaris

ND

Prunus cerasifera

WS4+CS20

Prunus mahaleb

WS3+CS26

Prunus lusitanica

CS20

Prunus serotina

WS3+CS26

Pseudotsuga menziesii

CS4

Pyrus communis

CS16

Pulmonaria officinale

CS8

Pycnanthemum pilosum

ND

Rheum officinale

ND

Rheum australe

ND

Rheum palmatum

ND

Rhus glabra

WS13+CS13

Rhus typhina

WS2+CS13

Robinia pseudoacacia

SC

Rosa rubiginosa

WS13+CS26

Rosa rugosa

CS17

Salvia officinalis

ND

Rosmarinus officinalis

ND

Rumex acetosa Large leaved

ND

Rumex sangineus var.sanguineus

ND

Ruta graveolens

ND

Ruscus aculeatus

CS8

Sambucus nigra

WS13+CS26

Sanguinaria canadensis

CS8

Sanicula europaea

CS8

Sanguisorba minor

ND

Sanguisorba officinalis

ND

Scirpus lacustris

ND

Secale montanum x

ND

Sambucus racemosa

WS13+CS26

Saponaria officinalis

WS4+CS4

Sassafras albidum

CS16

Schisandra chinensis

CS13

Sedum telephium

ND

Sedum rupestre

ND

Sequioa sempervirens

CS4

Sequioadendron giganteum

CS4

Sedum kamtschaticum

ND

Shepherdia argentea

CS13

Silene vulgaris

ND

Smilacina racemosa

WS8+CS8

Shepherdia canadensis

WS4+CS12

Smyrnium olusatrum

ND

Solanum abutiloides

 

Sophora japonica

SC

Solidago virgaurea

CS13

Sorbus aria

CS16

Sorbus aucuparia

CS16

Sorbus domestica

CS17

Sorbus intermedia

CS16

Sorbus torminalis

CS17

Spartium junceum

SC

Staphylea pinnata

WS22+CS13

Symphytum officinale

ND

Tanacetum vulgare

ND

Tanacetum parthenium

ND

Taxus baccata

WS20+CS50

Taxodium distichum

CS4

Thuja occidentalis

CS4

Thuja plicata

CS4

Thymus serpyllum

ND

Tilia cordata

WS13+CS26

Thymus vulgaris

ND

Tilia platyphyllos

WS26+CS26

Tilia tomentosa

WS26+CS26

Toona sinensis

CS8

Trifolium dubium

ND

Trifolium hybridum

ND

Trifolium pratense

ND

Trifolium repens

ND

Ulex europaeus

SC

Tsuga heterophylla

CS4

Ulmus pumila

ND

Ulmus glabra

ND

Vaccinium myrtillus

CS16

Valeriana officinalis

ND

Viburnum opulus

WS17+CS9

Viburnum trilobum

WS17+CS13

Viola odorata

ND

Vicia sativa spp nigra

ND

Vitex agnus-castus

ND

Vicia sylvatica

ND

Viola tricolor

ND

Wisteria sinensis

SC

Yucca baccata

SC

Zanthoxylum alatum

CS17

Zanthoxylum schinifolium

CS13

Zizyphus jujube

Snip down central suture with secateurs+ND

 

 

 

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