Perennials & Biennials Seeds
Covering the majority of wild flowers seeds. Do not sow straight into the garden soil. Treat them the same as herbaceous border perennial plants and they should be propagated in clean seed compost before transplanting into final outdoor positions.
Some wild flower species are strictly spring germinators whilst others will germinate in autumn or spring.
Those which germinate exclusively in spring may require a prior exposure to prolonged moist cold weather. This is called ‘stratification‘ or ‘vernalisation‘ and occurs naturally over winter with head seed in autumn. Where sowing in spring or summer species needing stratification we recommend mixing seed with silver sand and keeping moist in the refrigerator for around 6 weeks or longer prior to sowing in trays, pots or modules of clean seed compost. Moving the seed into and out of the refrigerator to give alternating cold and warmer conditions will promote this artificial stratification process.
A few species have a hard seed coat which prevents water uptake and hence germination. Again this serves as natures method of ensuring that not all the seed shed germinates immediately, but over an extended period improving survival of the species.
In order to break down the seed coat or achieve ‘scarification’ we suggest rubbing the seeds between two sheets of abrasive paper. The seed coat of large seeds such as Cranesbill, Vetch and Sweet Pea can be broken one at a time with coarse sand paper or a junior hacksaw blade or soaking in water
General recommendations for sowing perennials and biennials
From late June to September with prior ‘scarification’ if recommended, sow seed shallowly into trays/pots/modules of clean seed compost. Place outside (against north side of wall or fence so that the trays are shaded and can be kept watered with minimum effort when sun strength increases in spring)
A wooden framework around the trays covered with fine-mesh wire will exclude small mammals which might find seeds and young seedlings appetising. Many species will germinate almost immediately and can be pricked out into pots prior to transplanting into their flowering positions in late autumn or the following spring.
Species not germinating should be held outside over winter and retained until mid-May. Take care that the boxes are not allowed to dry out. Watering should only be necessary to any degree in early autumn and late spring. Most species needing cold exposure will germinate late March/April. Species definitely known to require stratification i.e. spring germinators can with advantage be sown outside up to the end of January whilst a spell of cold weather can still be expected.
Seed received in spring should again be sown outside from April onwards. Any cold treatments required can be carried out in the refrigerator prior to sowing and scarification where indicated. Most species will grow readily, but if some species have been spring sown without their necessary cold exposure they may be held over to the following spring. Seedlings from spring or summer sowings are potted-on before being planted out into their flowering positions when soil conditions allow.
Seeds requiring ‘Scarification’
Cranesbills, Dyer’s Greenweed, Meadow Pea, Restharrows, Vetches
Seeds requiring ‘Stratification’
Agrimony, Angelica, Bellflowers, Bittersweet, Bluebell, Bryony, Cuckoo Pint, Dropwort, Garlic Mustard, Globe Flower, Hay (Yellow) Rattle, Hemp Agrimony, Iris, Marsh Marigold, Meadowsweet, Monkshood, Primula species. Ramsons, Sweet Cicely, Violets, Wood Sage, Yellow Archangel
Should it be necessary to hold the plants in pots or containers we suggest they are potted-on into a John Innes Potting Compost, where the soil component will retain more moisture and is heavier (tall plants will fall over in light-weight composts)
Cornfield and other Annuals
Annuals can be sown direct into a well prepared seedbed outside. The preparation should be well before any intended sowing date to allow for a flush of weeds which can be removed prior to sowing into an otherwise dirty seedbed.
Seed sowing of annuals is best undertaken from mid-August to mid-October allowing good establishment of the plants ready to provide a wonderful display the following spring/summer. Spring sown annuals tend to be smaller by comparison and flower later – but no less colourfully.
Alternatively, the annual seeds may be sown into clean compost in pots or modules. Fine seeds such as poppies should be sown on the surface of the compost and given only a trace of compost covering.. This method avoids the root disturbance that annuals resent when they are transplanted out into the garden 15-22cm apart. This should be done in the autumn or spring when the plants have a reasonable rootball. This method also gives some control over colour.
Grasses may be sown in spring or autumn and anytime between if adequate moisture levels can be maintained. Normally grasses would be sown into well prepared soil, but for seeds sown for study we recommend sowing into clean seed compost in trays/pots/modules. Finer seeds such as bent grasses should be sown on the surface of the compost with a trace of covering compost whilst others may be sown with 4-6mm of covering compost. Moisten the compost from below to avoid disturbing the seed. The best results are with sowings taking place from mid-August until mid-October, producing sturdy plants ready for planting out into a grass border the following spring.
Should it be necessary to hold the grass plants in pots or containers we suggest they are potted-on into a John Innes Potting Compost, where the soil component will retain more moisture and is heavier (tall grass plants will fall over in light-weight composts)
A sample seed packet contains a few seeds (approx 10 or more). They are a low cost option suited to growing on and then saving your own seed from the resulting flowering plants
- Sow directly into flowering position into disturbed soil. Sow August-October/March-May.
- Sowings for autumn will produce much bigger plants.
- Alternatively sow into sectioned trays (modules) or pots and then transplant into final flowering position. Do not attempt to separate clumps of plants when transplanting.
- Sow into modules using seed compost from April – September, leave outdoors. Also sow in March- October, under cold glass.
- When seedlings are large enough to handle, transplant into small pots using potting compost. Leave to grow on before planting in final flowering position
- Sow seeds in autumn, into modules or seed compost and place outside
- Cover sowings with fine wire mesh to exclude mice, birds, place in shaded spot. make sure the sowings don’t dry out, germination will occur around April depending on spring conditions. If you receive seed when a prolonged cold period is not expected, mix seed with sand in a plastic bag and place in a refrigerator for 6 weeks before removing and sowing as above