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 pot 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.

Recognize the types of plants

The largest group of plants widely grown from seed are annuals that complete their entire life cycle in a single season. These may be hardy, half-hardy or tender, meaning no more than able to withstand life out of doors without protection in the case of hardy, needing some protection from frost in the case of half-hardy, and not safe out of doors until the frosts have finished in the case of the latter. This group of plants provides many of the “bedding” and “pot” plants that are bought each year to fill borders, baskets, and containers. In reality, some of them are actually tender perennials (about which more in a moment) that are grown in our northern European climate as annuals because they keel over with the colder weather. Increasingly with recent winters some of these plants are surviving winter but since they are so easily grown from seed it is best to treat them as annuals.

Annuals plants

Popular annuals to sow include snapdragon (Antirrhinum), pot marigold (Calendula), Convolvulus, Cosmos, Dahlia, sunflower (Helianthus), flax (Linum), Lobelia, morning glory (Ipomoea), nasturtium (Tropaeolum majus), Nemesia, tobacco plant (Nicotiana), love-in-the-mist (Nigella), poppy (Papaver), Petunia, Rudbeckia, scabious (Scabiosa), African and French marigolds (Tagetes), Verbena, and Zinnia.

Biennials Plants

The truly perplexing group of plants for some people are the biennials that are sown one year and complete their life cycle the following year. Perhaps the best known of these are wallflowers and foxgloves. Many of this type of plant can be sown out of doors because they are seeded during summer but there are biennials that are not really biennials but treated as such like polyanthus, pansies, and other types of viola that can be sown as early as March/April. Popular biennials include: Canterbury bell (Campanula medium), wallflower (Cheiranthus allionii and C. cheiri), foxglove (Digitalis), honesty (Lunaria annua (syn. Biennis), stock (Matthiola), forget-me-not (Myosotis alpestris), Iceland poppy (Papaver nudicaule), polyanthus (Primula veris), viola (Viola cornuta), and pansy (Viola tricolour),

Reap the reward of sowing perennials

Although perhaps far more annuals are sown from seed by gardeners than any other type the greatest reward in both enjoyment and cash savings is to be had by sowing seeds of perennials. This group of plants overwinters and comes back if not year after year at least for several seasons in succession. These generally herbaceous plants are invariably the most expensive varieties in the nurseries and garden centers (after shrubs and trees) and a tray or two of perennial seeds that cost next to nothing to sow can be turned into plants that would cost a great deal of money to buy. Of course, after a few successful seasons of sowing perennials, your herbaceous borders will soon be packed but that is no reason to stop sowing perennial seeds.

The late Christopher Lloyd of the famous Great Dixter gardens grew certain perennials as annuals to ensure prime specimens. Lupins tend to have short lives unless they are on a limy soil and are relatively easy to sow from seed (except for the dreaded lupin wilt that can affect spring-sown specimens). Remember though that only a branded type of purchased seed is guaranteed to turn out the color on the packet. If you collect and sow seeds from lupins they will not grow true to type. Avoid the wilt by sowing them in the autumn if you have a greenhouse, cold frame, or conservatory where you can keep the young plants for their first winter.

Incidentally, the term “herbaceous” merely refers to the general habit of this type of plant to die back to a root that remains dormant in the soil through the winter to produce fresh growth in the spring. This is the cause of many other so-called “failures” by inexperienced gardeners who think the plant has died.

Among the more commonly available perennial seeds, you should find on sale are aquilegia or Columbine (Aquilegia), yarrow (Achillea), Bellflower (Campanula), delphinium or larkspur (Delphinium), mullein (Verbascum), and hollyhocks (Althaea rosea). Because hollyhocks are so susceptible to the disease called rust they are best grown annually from seed.

Incidentally, no apology for the small scattering of Latin plant names. The very best way to name a plant accurately so that everyone is entirely certain which plant is being described is to use the scientific name (usually Latin but may also be Greek). The same plant may have a whole host of common names that vary from one part of Britain to another and in these days where websites spread beyond national borders the use of the scientific name is universally recognized. Some scientific names have become common names (e.g. delphinium) and some common names are more widely used in Britain than the scientific name.

Sowing seed out of doors

Many hardy annuals can be sown out of doors during March-April provided the weather and soil conditions are favorable. This can be directly into the intended position in a bed or border or directly into pots and containers. It is a good idea when sowing seed in a bed to make a series of straight drills so that when the seedlings emerge they can be distinguished easily from any surrounding weeds.

Another way to sow annuals is to sow them thinly in containers that also contain perennials. In both this case and with open bed sowings, thin the seedlings out as necessary when they emerge. With annuals sown in pots together with established perennials, it is important to choose varieties that will not be too tall but this does ensure a longer period of interest since many perennials have a shorter period of maximum interest than annuals.

Soil in beds that are used for sowing seed needs to be worked to a fine tilth and any clods should be removed. Where sowing varieties that can be transplanted (see packet for details) use the corner of a hoe or the back of a rake to draw a V-shaped drill alongside a line positioned for guidance. Cover the seeds with fine moist soil and on light dry soil firm the ground by treading lightly.