Most garden annuals need a long growing season to reach their full height and flowering, they are often given an early start indoors, or in the greenhouse, hotbed, or cold frame. For indoor growing, don’t plant seeds earlier than six weeks before the average date of the last frost in your area. Too-warm air and lack of light will cause them to grow soft, lanky, and weak before outdoor planting time. In the greenhouse or hotbed the interval can be ten weeks or more if you can give the young vines room and some support to start climbing on. In an unheated cold frame two months before the last frost is about right – again, if there is enough room for climbers, and some support.
Biennial and perennial seeds are planted outdoors, in a nursery bed or frame, from late spring through summer. The earlier the start, the stronger the vine will be when it goes into its first winter. Depending on the tenderness of the vine and the rigors of your climate, either keep the plants in the protected frame until the following spring, or place them permanently in early fall. Seeds of house and greenhouse vines are started indoors at almost any time of year.
Some vine seeds, like the morning glory, have a hard outer skin and germinate slowly unless they are nicked with a sharp knife or soaked in water for ten to twelve hours before planting. Plant any kind of seed as thinly as possible, so the seedlings won’t get so entangled with each other they’re hard to separate. And don’t plant seeds too deep. Twice the diameter of the seed is sufficient for most types; tiny or dust-fine seed should not be covered at all.
Indoors or out, seeds and the medium they are planted in should never be allowed to dry out during the germinating and early growing periods. They should be shaded against sun and shielded against chill drafts. Most need light for germination; if not, package directions will usually say, “Cover and keep dark.” To speed germination, set the bottom of a seed flat or container on a heating coil, warm furnace, or even the top of a mechanical refrigerator.
To insure more perfect germination, there are several types of homemade and ready-made devices and containers that will help keep seeds warm and moist during the critical period. Simplest is a shallow pot set in a saucer kept filled with water. Cover the top of the pot with a piece of plastic or glass until new plants appear; then remove the cover gradually over a period of several days.
The same pot, a shallow wooden box, or a plastic flat with a hole in the center of the bottom can be fitted with a wick – one end spread out inside the bottom of the container, the other dangling down into a bowl of water. This “seed-sitter” will keep seeds and seedlings moist for days at a time. So will a pot-in-pot device for rooting cuttings
Delicate seeds can be started in plastic or glass refrigerator dishes, or in casseroles with transparent covers. The planting medium inside should be moist, not soaking wet, at planting time. If the cover is kept tightly closed until germination begins, it is usually not necessary to add water. After germination the cover is lifted a little or removed completely, and water applied carefully so the small plants are not washed out.
Even more attractive and foolproof are plastic propagating cases that control the moisture, humidity, and steady bottom heat most seeds and seedlings require.
Large seeds, and seeds of vines that resent transplanting can be planted two or three to a three-inch clay or plastic pot. After germination, thin out to leave the one or two strongest seedlings. At transplanting time, remove the soil and root ball with as little disturbance as possible. Even better, plant the seeds in peat or other fiber pots that can be set directly in the soil without removing the plants.
Seeds can be planted in soil, a soil substitute, or almost any propagating mixture. Sift soil through a fairly fine screen, to remove pebbles and other unwanted material, then sterilize it (and this is important) to kill insects and fungi. You can bake a small quantity of moist soil in a tightly covered container at low heat (250 degrees) until it is thoroughly heated through the center.
The most devastating enemy of seedlings is a fast-spreading disease, “damp-off,” that circles the stem at or near the soil line and literally strangles it, so water and food can’t reach the leaves. Soil sterilization is one preventive; commercial fungicides are another. So is any practice that promotes good air circulation, like thinning out seedlings to avoid overcrowding.
When you see a number of adjacent seedlings falling over and lying flat on the soil, remove any remaining upright specimens in a hurry to safer, sterile quarters. Supply more fresh air, if possible. The disease spreads fast in a close, humid atmosphere.
Soil substitutes like Perlite, sphagnum, and vermiculite are sterile, but they do not contain nutritive elements. Seedlings in any sterile medium are fed weekly with a weak (one-fourth recommended strength) solution of complete fertilizer until the young plants are transplanted into soil or a mixture containing at least one-third soil.
Give indoor-growing seedlings all possible light. Turn windowsill containers frequently, so stems won’t stretch out and over to one side. Indoors or in the greenhouse, transplant seedlings to individual pots, peat pots, or well-spaced rows in flats as soon as they are large and strong enough to be handled – usually when they have grown good-sized true or typical leaves. After transplanting, harden off seedlings gradually. Remove shading and protection for a slightly longer time every day until the plants have recovered from transplanting shock and are strong enough to be moved.
Starting Seeds Outdoors
In areas with long outdoor growing seasons, vine seeds are planted directly in the garden beds where they are to grow. Soil is kept moist until the seedlings are well up and on their way to maturity. It is often wise to plant two or three seeds in each location and thin out later to leave the strongest plant or two.
Seeds started in hotbeds or cold frames benefit by the same care outlined for indoors. Soil should be fine, light, and free of debris. Treat it with a commercial sterilant, if possible. Plant seeds of varieties that resent transplanting in peat or fiber pots. Keep all soil moist. And when the seedlings have come up, use commercial bait against slugs that chew juicy young leaves.