Transplanting seedlings outside will mean changes in the temperature, water levels, fertility and even depth, all of which could prove fatal if not handled properly. Several steps, such as allowing plants to grow sufficiently sturdy for the move, encouraging greater strength, hardening off, protecting the plant during transfer and making the new soil as hospitable as possible for the fledgling plant, will ensure a shock-free transition to the great outdoors.
Let Them Grow Enough
The first set of leaves that break out of most seeds were generally already formed within the shell. There is no proof that the sprouts are thriving until at least that second set of leaves, known as the "true leaves," forms. So long as the roots don't run out of room in their container, there is generally no harm in letting plants grow for six to eight weeks indoors before transplanting.
Out in the open air, gentle breezes encourage stems to stiffen and strengthen. You can do the same thing by lightly brushing them with your hand a few times each week.
One of the biggest shocks the transplants will experience is the drop in temperature outside. If the shift is gradual enough, plants can insulate themselves against the cold by thickening their cell walls with carbohydrates. Take them outside in a sheltered location, at first for just a couple of hours. Over a couple of weeks, gradually increase the time and exposure until they can stay out overnight. Some gardeners decrease watering to further condition the plants. This gradual process of transplanting is known as "hardening off."
Too many gardeners successfully raise their seedlings into thriving plants, only to snap the fragile stem or tear the roots during the transplanting process outside. Take care to loosen the sides of the container from the dirt and root ball inside. With thumb and forefinger holding the base of the plant, not the stem, turn the container upside-down and tap or shake gently to release the contents. Some plants, like tomatoes, gain by deeper planting, but strawberries do not, so take care that the transplant goes into the right depth in the outdoor plot. If the plant is root-bound, carefully tug on the roots to untwist them from each other.
Give Them a Warm Welcome
It should go without saying that the beds outside must be fertile, with loose, moist soil, but this is especially true when the plants are adjusting to their new digs. After transplant, secure the soil around the plants and water well. A mild, liquid-based fertilizer that young roots can take in right away would be a good idea, but take care not to "burn" them with too much of a good thing. Keep them hydrated until they become established.
Plants don't like surprises. If the transition from windowsill to garden plot is smooth, the plant will continue uninterrupted growth into maturity and good yield.