How To Plant Your Garden Seeds
Almost any plant that produces seeds can be grown from seed, even though the requirements for some of them, a few of them, are extraordinary. Germination time of two years is required for certain tree seeds; long cold spells necessary for a dormancy that has to precede germination for some seeds can cause failure if ommitted. A few seeds, such as maple seeds for instance, must never be allowed to get dry or they will not be viable; and a few must have light to germinate. In general, however, good soil, enough warmth, some moisture, and a careful patting of the soil around the seeds will mean that they will come up and start new plants for you. As soon as they are up, they have to be protected from the fungus disease, "damping off," especially if grown indoors or in a greenhouse. And though it is moisture which causes this fungus to thrive, plus lack of air circulation, the young plant must never be allowed to dry out.
There is an interdependence of closely placed young plants, throughout through a sharing of water and through through mutual benefits from root exudates, so avoid isolating them. Neverheless they must not be crowed for long. If the soil is very loose and partly dry, it is possible to pull up the weaker plants in a row or in a flat or peat pot. But the best advice is not to do it. It is better to take a small pair of sharp scissors and snip off the weak and crowding plant at soil level. The remaining little plants will stay strong and grow stronger, especially if they continue their interdependence.
Most seed packages tell you what distances you should thin your plants. At first the distance always looks too great. When faced with two or three-inch plants, it seems almost wasteful to thin them to eight inches apart. But do what the packet says. They will need that space when they mature; and the resources of soil nutrients available to the young plants in an uncrowded space mean that they will grow all that much better.
Indoor Seed Planting
There are two absolute necessities for growing good little plants indoors to set out in your garden later – or sometimes route through a cold frame first and then set our in the garden. The first is to get good seeds from a good reliable seedsman (or use the very best of your own home-grown seeds). The second is to have a set-up which will provide the right warmth, moisture, air and light for little plants.
Most of the seeds you will grow for garden flowers or other ornamentals will be more or less fresh seeds, but the point is for them to be viable, or capable of germinating. Some you gather yourself you can keep for several years. The seeds of asters will keep a year or up to 13 years, depending on the variety. Bee balm seeds will remain viable for four to seven years; nasturtiums for five to eight years. If you save the seeds of azaleas, birches, deutzia, hydrangeas, mock orange, potentillas and rhododendrons, for example, you do not need to put them through a cold period, but other plants do need a cold dormancy: maple seeds should get three months of cold, either outdoors or in the refrigerator; barberry seeds need two or three months, bittersweet seeds need three months, as do flowering dogwood, ash, beech, sweetgum, tupelo and most of the members of the Prunas group, including cherries. Pine seeds need two months; spruce one to three months and apples one to three months as well.