Young seedlings are the adolescents of the plant world. While they look like smaller versions of their full-grown predecessors, they lack the hardiness and strength to survive on their own. Use the following tips to take your seedlings from tender to thriving.
Soil temperature is the single most important factor to consider when deciding on a date for transplanting. If overall temperatures have been low, the soil will not be warm enough for your plants to thrive. Lettuce, spinach and other greens can be safely transplanted or sown directly when the soil is a mere 50°, while zucchini and other summer squash prefer dirt that has warmed to around 70°. Tomatoes, peppers and other heat-loving crops can tolerate cool soils, but will not grow much until underground temperatures reach about 80°. To speed soil warming, mulch with black plastic or use small wall-of-water greenhouses to warm each individual plant. You can order an inexpensive soil thermometer or just use a finger to estimate soil warmth.
About 10 days prior to transplanting, begin setting your plants outdoors in a shady spot for increasing amounts of time each day. Start with just one hour and add an hour each day until the plants are spending most the day outside, but still being brought in each night. This process, known as hardening off, helps seedlings gradually adjust to the harsher outdoor elements and can help them avoid going into shock when they are planted in the garden.
Be sure to plant in the later afternoon or during a cloudy time to help avoid plant dehydration and shock. Use your hand to support the stem of each seedling as you gently tip the container on its side and squeeze the root area to loosen the plant. Next, gently rough up the root ball to loosen roots that have begun to grow in a circular shape.
Take care to water each new plant daily for the first few days. After that, you can use a finger to test the soil moisture and only apply additional water when the soil begins to feel dry 3-4 inches below the surface. Roughening up roots and spacing out water applications encourages the roots to reach deep into the soil, lending stronger more resilient plants.