Many seed packets state that heat is required for germination and by that I mean artificial heat as used in large commercial production. However, from my experience I have found that most seeds will germinate in a cold greenhouse or tunnel, and even on a sunny windowsill if the below method is applied. Though germination may be slower and sometimes erratic this should not cause despondency; for domestic production a mere handful of seedlings is usually sufficient. Sow small seed such as fennel and chives in a seed tray in compost that specifies seed sowing as well as potting. This is important as it may be minus the element of phosphate which is essential for healthy seed germination and formation. I usually use half trays and three different varieties may be sown alongside each other.
Do not over sow; in crammed conditions seeds will stifle and disease may strike. A maximum of ten seeds per variety is adequate and allows for a sensible failure rate which can occur for various reasons listed below.
Cover trays with glass and place newspaper on top. This creates a snug micro-environment. Daily inspection is vital; turn the glass to dispense of condensation, to prevent the fungal disease – damping off which causes seedlings to shrivel up and die. Always replace the newspaper to retain moisture in the compost and prevent sun scorch.
This is a very important exercise which requires consistency and diligence. The crucial point is the removal of both glass and newspaper the minute one observes the slightest emergence of green shoots. If this is done too late the resulting seedlings will grow weak and spindly in a frantic effort to reach day light.
Water these seedlings gently at all stages with a fine spray and cover initially by night with newspaper of garden fleece particularly if temperatures fall below 10 degrees. If growing on windowsills rotate the containers each day to aid a balanced access to light otherwise the seedlings will grow askew resulting in a distorted plant,
Seedlings will require transplanting into pots or cell trays when they have developed their second pair of leaves called true leaves. This development varies slightly depending on the variety and temperature but usually it takes about 10 to 20 days. Handle delicately; lifting by the seed leaves (first set of leaves) not the stems.