Sowing and Aftercare - Species
For sowing individual species we give a guide as to the number of seeds contained in each gram of seed. We generally advise sowing two or more times the number of seeds as you require plants, as seed dormancy and erratic germination mean that only a proportion of the seeds are likely to germinate in any one flush. Furthermore having germinated, not all seedlings will successfully grow to an established plant.
Establishment rates are likely to be higher in a protected and nurtured seed tray than in open ground. A standard seed tray will have sufficient space to produce 200-500 seedlings for potting on.
Sowing Under Cover
Autumn and spring are good times to sow under glass, in a polythene tunnel, or in a conservatory, although seeds requiring vernalisation are best sown in the autumn.
Fill a seed tray to ¾ deep with peat-free seed sowing compost, firm and water well. Sprinkle seeds on the surface at 100-500 seeds per tray and add a light covering of horticultural grit. Do not bury the seeds. Cover the tray with a sheet of glass and place in an unheated position, out of direct sunlight. Remove the glass at the first sign of germination. From an autumn sowing this will normally be in February or March. Place the tray on a bench, watering as required. Prick out the seedlings into potting compost as soon as they can be handled, holding only by the cotyledon. Grow on under glass, harden off outside, and plant out as soon as the conditions are suitable.
Spring and autumn are the best times to sow outside. Prepare a weed free seed bed with a medium/fine firm tilth. Sow the seeds on the surface in patches (1000-4000 seeds/m2), or in rows (100-500 seeds/m). Firm the surface to give good seed/soil contact, but do not cover the seeds. Germination will occur over a period of time depending on the species, conditions and sowing date.