Home Gardener's Annuals. Miranda Smith

      If you want to try growing seedlings without using artificial lighting, your best bet is a south-facing window covered with sheer curtains (to keep the heat from becoming too intense) or a bright, unshaded east or west window. Turn the flats every day to keep the stems growing straight.

      Water. Seeds and young seedlings need to be watered carefully so that the seeds aren’t washed out of the soil and the delicate new roots aren’t disturbed. The best approach is to water from below, setting the flats or pots in lukewarm water in a sink or special watering tray. Watering from below allows you to evenly and thoroughly moisten the soil without dislodging seeds or tiny seedlings, as can happen with a stream of water from overhead. Set flats or pots in a container of water an inch or so deep until the soil surface feels moist, or use a specially made flat and wicking mat. This method gives you the most control over the amount of water your plants receive. Another technique is to mist the soil surface with a plant mister until the soil is thoroughly moistened. If you use this method, be sure to keep an eye on the soil. Make sure your seedlings don’t dry out; water stress can set back young plants permanently, so you will need to be attentive until the plants are well established. But don’t overwater either. Constantly soggy soil encourages root rot and damping-off. Water your seedlings when the soil is somewhat dry—early enough so that leaves can dry by dark.

       Fluorescent lights provide a very even light to plants. For best results, use a timer to keep the light on the plants for 16 hours each day.

       Feeding seedlings

      Because the soilless mixes for seed-starting contain almost no nutrients, you’ll have to supply some as soon as seedlings develop their first true leaves (the second set they form). But don’t go overboard; overfertilizing seedlings can result in weak, floppy plants more prone to problems. Young seedlings can’t handle full-strength fertilizer. Dilute liquid fertilizers to one-quarter the recommended strength (or if you use fish emulsion, half strength). Use the diluted fertilizer once a week for the first three or four weeks. After that, gradually work up to using a normal dilution.

      If you’ve added compost to the seed-starting mix, you can probably wait to feed your seedlings until they are four or five weeks old. But check their color every day; at the first sign or yellowing or purpling, begin feeding once a week with a half-strength dilution of liquid fertilizer.

       TRANSPLANTING PLANTS IN PEAT POTS

      Seedlings in peat pots need special treatment at transplanting time; peat pots can be so rigid that roots have difficulty breaking through them. Set the pots in a water-filled tray for 30 minutes to an hour before transplanting. When you plant, tear through the sides of each pot, and place the seedling so that the pot rim is below the soil surface, left. You may need to tear off the top ½ inch or so; if the rim sticks out of the soil, it can dry and act as a wick, drawing moisture out of the soil and evaporating it into the air. On a sunny, breezy day this wicking action can cause serious water stress for young plants.

      Harden off seedlings in a cold frame by opening the lid for a gradually increasing length of time over several days, finally leaving it open all night, middle.

      Thin seedlings by snipping them off with sharp scissors instead of pulling them up to avoid disturbing nearby roots, right.

       THINNING AND TRANSPLANTING SEEDLINGS

      When the seedlings develop their first true leaves—the second set of leaves to grow but the first that have the plant’s characteristic shape—it’s time to thin. You can thin by pulling up unwanted seedlings individually, snipping off the stems at soil level with nail scissors, or carefully lifting and transplanting the young plants to other containers.

      Spacing for seedlings in flats or pots depends on the size of their leaves, but 3 inches is considered a good average spacing distance. Crowding seedlings together increases root competition, encourages the spread of damping-off and other diseases, and causes plants to shade each other, which makes them spindly. To avoid problems, keep seedlings far enough apart so their leaves don’t touch. When the leaves threaten to touch each other, the plants are probably big enough to go into individual pots or, if weather conditions are appropriate, outdoors into the garden. (See “Transplanting Outdoors,” right.)

      If you’ve grown seedlings in an unsegmented flat, cut the soil into blocks a few days before transplanting. The cut roots will heal before the plants are transplanted.

       HARDENING OFF

      Seedlings started indoors need to adjust gradually to the harsher environment outdoors. Leaves, like skin that’s been indoors all winter, can easily get sunburned. Before you move your indoor seedlings out to the garden, harden them off. Over a two-week period, cut back on watering slightly while also increasing their exposure to colder temperatures. Begin by setting seedlings outdoors in a sheltered spot for an hour or two; then bring them back inside. Move them outside for a longer time each day, eventually leaving them out overnight. By the end of the second week the plants should be ready to move into the garden.

      Another method that works well is to place the plants in a cold frame. Plants can be hardened off in a cold frame if you open the lid a bit farther each day, removing it entirely for the last two or three days.

       TRANSPLANTING OUTDOORS

      Transplanting to the garden is largely governed by weather conditions. The best time to transplant is on a cloudy, calm day, ideally in mid to late afternoon. Bright sun and wind can dry out transplants.

      Dig the planting hole before you remove a plant from its pot or flat, even on a cloudy, humid day. This advance preparation should protect the roots from drying out. Planting holes must be big enough to comfortably accommodate all the roots and deep enough to allow the plant to sit at the same depth as it did in its growing container. If the garden soil is dry, pour some water into the hole before planting. Set the plant in the hole, and fill in around its roots with soil. Firm the soil gently; don’t compact it. Then water the plant.

      Protect your transplants from wind and bright light for the first few days. Floating row covers, made from lightweight spun polyester fabric, are convenient to use and effective for shading. Glass or plastic cloches, plastic gallon jugs with their bottoms cut out, and floating row covers all give wind protection.

       SELF-SOWERS

      Some annuals plant themselves. If you don’t deadhead, or remove the faded flowers, their seeds drop on the ground and produce a new generation of plants the next year. If you like serendipity, let a few plants go to seed and allow the volunteer seedlings to grow where they will. If you want more control, transplant the volunteers in spring. And if you don’t want to have volunteers, deadhead before plants have a chance to form seeds.

      Many self-sown seedlings don’t produce plants identical to the parents. The flowers are often smaller and the colors different. Petunias, for example, tend to revert to the magenta-purple color of the original species form of the plant. Such variation can wreak havoc with a carefully planned color scheme, but it can be fun to see what you get from one year to the next.

      The following annuals are likely to self-sow in your garden:

      • Bachelor’s button (Centaurea cyanus)

      • Candytuft, annual (Iberis umbellata)