This weekend will see the major start of transplanting in our community gardens. Here are some of the things I think are most important for successful transplanting:
1) HARDEN OFF THE PLANTS This means increase sunlight and wind over a few days before the plants go in the garden. Too much sun all at once will sunburn the plants and the leaves will turn white or get white spots. Often it's a good idea to reduce watering to a minimum too. The garden is a harsher environment, and you want your plants ready to take in as much water as possible, not panting because they've had plenty and haven't had to grow new little rootlets. It's very important to harden off your plants, even if means delaying your transplanting a few days.
2) COOL, CALM, AND CLOUDY are the ideal conditions for transplanting. The middle of the day on a breezy, sunny, Saturday is not. The idea is to shock the plants as little as possible, and help them adjust before they have to face the sun and the wind. I usually transplant in the evening as well, which gives the plants an overnight to settle in.
3) PLANT DEEPER. This isn't a universal, but lots of plants are eager to send out new roots along the stem. Planting deeper also puts the original root ball further from the hot dry surface in our sandy garden, and as the plant grows it will be protected somewhat from fluctuations in moisture. Plants that root along the stem include all of the tomato family (tomatoes, peppers, eggplants), coles (broccoli, cabbage, cauliflower etc), and the squash family (including cucumbers and melons). Although lots of people plant their tomatoes quite a bit deeper, I prefer to have a longer distance between the ground and the bottom stems, to help prevent disease. (see 3 entries earlier) That's not necessary if you're mulching. If the stems are spindly then planting deeper also protects the stem from whipping about in the wind.
4) REMOVE THE BOTTOM LEAVES! This is one of the easiest steps to helping your transplants adjust. Preserve the growing tip and a couple of leaves below it, but otherwise you really don't need the lower leaves on most of your vegetable transplants. They are likely to yellow and drop off later anyway - or as with lettuce, you'd be removing them to eat. At the first sign of wilting you can remove the lower leaves even if you don't do it at transplant time. Your first task with transplants is to help the roots get established. I routinely remove the bottom leaves from tomatoes, peppers, cabbage, and broccoli. (I usually start the squash family in place and don't transplant).
5) IN SANDY SOILS TRANSPLANT INTO BOWLS, NOT HILLS. Our soil in the community gardens is so sandy that anything we can do to help the soil around the plant retain water is a big help. I plant most of my transplants into a recess, rather than a hill. This makes watering easier all through the summer. (The advice to plant in hills is to encourage the soil to warm up faster, and to ensure the soil will drain. Not a problem for us).
6) ADD A CUTWORM COLLAR Cutworms are 1/2 to 1 inch grey caterpillars that curl around stems at ground level during the night and eat right through the stem. In the morning you'll find the plant lying on the ground, and it looks like it was cut off with scissors. If you dig around the stem in the early morning you'll find the cutworm near the stem. But as the sun rises and warms the soil the cutworm will travel lower and wait to get an adjacent plant the next time it feeds. To prevent this, put a collar around the stem that extends an inch and a half below and above ground. Wrapping with a few layers of a strip of newspaper is the most practical, and in time it will disintegrate. JP uses toil paper tubes cut in half. On plants I really care about I use a strip of aluminum foil, since the cutworms never climb over that, but it needs to be removed about the 3rd week in June, which is a bit of a nuisance. On tiny plants that would get swallowed by a collar, or plants with a short stem such as cabbage, you can try putting 3 toothpicks vertically around the stem, so the cutworm won't feel the soft stem when it wraps around. not clear if this works. This year I'm going to try putting some oysters shell pieces (intended to protect fall bulbs from moles) around these stems and see if that works. I've already lost a few peas to cutworms. Update: Paul from the community gardens reminded me this morning that he's used paper or stryrofoam cups with the bottom cut out, as a collar. And he and I have both learned the hard way to make sure the large end is down, so you don't pull soil up when you pull the collar off later on.
7). GIVE SOME TRANSPLANT SOLUTION. Once you've settled the plants in, water them well and add a cup or so of very diluted fertilizer (such as miracle grow or fish emulsion), and/or some sea weed extract. (see a couple of entries earlier). This helps the root system start to expand, and in the case of the sea weed it boosts the immune system and helps the plant respond to the shock of transplanting.
8) WAIT TO TRANSPLANT YOUR PEPPERS, and probably your eggplants, too. One year I transplanted about half my peppers into the garden about the same time I transplanted the tomtoes. The temperature seemed warm enough, and the plants got established nicely. But the remaining half that stayed in the house under lights really flourished, and by the time I got them transplanted they were much bigger and sturdier than the earlier ones. Peppers are very sensitive to temperature. Peppers that spend the night in the low 40's will stop growing for a week, even though they won't show any damage from low temperatures. So if you've got your peppers, transplant into larger pots if you can (9 oz cold drink paper cups are fine) and wait til the first of June to transplant. Leave them outside during the day, and bring into the house at night.