Growing plants from seed is fun, a great deal cheaper than buying plants, and in most cases quite easy. We will come to sowing seeds outdoors later. The principal reason for sowing many plants under glass or indoors is to have mature specimens ready for planting out in our temperate climate as soon as the frosts have ended.
Sowing seed indoors
A relatively inexpensive way to greatly improve your chance of success with many types of seed is to invest a modest sum in an electrically heated propagator that will warm up the soil to aid germination but excellent results can be achieved indoors with non-heated propagators and even margarine pots covered with a plastic bag!
One early note of caution about propagating from seed: the biggest problem you may run into is having far too many seedlings (and subsequently plants) for the space available! Unless you can bring yourself to throw some seedlings away you may find yourself supplying most of your family and friends or with every window sill in the house covered with plants until the weather permits them being moved outside. One full seed tray (or better still two half trays or more small trays) of seed can produce a considerable number of plants. If you prick every one of these out and subsequently put them on you may be dealing with hundreds of plants.
Successful germination of Seeds
Successful germination depends on moisture and warmth but also air and light. Some seeds need to be kept out of the light for germination and most young seedlings although needing light for healthy growth cannot cope with full sunlight streaming through a window or the glass of a greenhouse. As a rule of thumb, seeds are usually sown at a depth equal to their thickness but peas and beans that are fleshy should be sown approx. 50 mm (2 in) deep because of the way they move towards the surface of the soil as they germinate. Small seeds need the lightest dusting with very fine soil and ultrafine seeds should not be covered other than with a sheet of glass and some brown paper.
This article cannot incorporate specific advice for every type of seed but the best brands of seeds have all the information you need for the specific type on the packet. Sweet peas, for example, are best germinated in a non-heated propagator or covered tray that is initially shaded from the light. Notoriously tricky germinators, like trailing varieties of Lobelia for planting in baskets, require a little extra care than the basic techniques. It is important with the ultrafine seeds of Lobelia to moisten the compost in the seed tray from below rather than by water from above and the seeds should merely be pressed against the surface of the compost without covering. Lobelia is one of those annuals that benefits from the kickstart of bottom heat.
Check when the seeds can be sown and, if you intend sowing them indoors in trays, check that the seed packet does not suggest this is a type of plant that does not take kindly to any transplanting. This will usually be made clear by any absence of reference to sowing under cover and will include only phrases such as “sow directly in the flowering position.”
A few tips for success growing Seed
The main general recipe for success when sowing seed indoors (or under glass) is to thoroughly sift the compost/ growing medium so there are no clods and to then firm the compost down. Most gardeners who grow plants from seed all the time have a board the right size for seed trays with which they can firm the soil. A general-purpose compost is perfectly acceptable but many people go to the trouble of using a special compost for seedlings or mix their own.
More seedlings and young plants are killed by over-watering than ever fail through neglect. Seeds need moisture to germinate and then to grow but few will thrive if they are sodden. The principal reason for the use of propagators (or polythene bags) when sowing seed is to retain moisture but it is also important that there is ventilation. Most purpose-built propagators also have vents that can be opened.
Generally, seed trays are best kept moist with a mist-type sprayer or by placing the seed tray on a capillary mat that introduces moisture from below rather than from above – until the seedlings become stronger.
Perhaps the biggest mystique surrounding growing plants from seed (and perhaps even in dealing with ready-grown plants) is recognizing the type of plant. Reasons are given for “lack of success” by more than a few “failed” gardeners sometimes reveal a complete misunderstanding about the life cycles of different plants. (click the next button to preview the next page)