Growing outdoors successfully hinges on how happy your plants are. Giving them a good start from day one makes a big difference, as well as the timing of when you decide to put your plants outside. But when is too early to plant your garden? This depends greatly on your geographic location and sun exposure of your garden location. The general consensus in planting zones north of Central California is to put your plants outside around memorial day weekend or the 1st of June. Warmer zones can plant outside in early to mid May. If planting delicate seedlings or clones outside, wait until mid-end of May. The long cold nights early in the spring will often induce flowering much too early and take away the energy used for vigorous vegetative growth. But many gardeners like to get a head start on the growing season. If you start your plants indoors under artificial plant lighting, it’s a good idea not to move them outside until the days are longer and the nights shorter.
Starting plants indoors for my outdoor garden? Yes, using plant lights to grow your cuttings and seedlings indoors in the late winter or early spring is a great way to insure that your plants get an early jump on the season. If your greenhouse is geared to harvest year round this is something you are already using. But for those seasonal gardeners adding light to promote a longer veg cycle is extremely advantageous. Whether you are in a greenhouse or outdoors, adding light to make longer days can be easily accomplished. If you are a year-round greenhouse grower the use of HID lights is definitely the way to go but for the seasonal grower T5’s, LEDs or compact fluorescents are a cost effective way to maximize vegetative growth time. The sun is by far the main light source for your plants, but supplementing just a small amount of light in the early morning or beginning of the evening will keep the plants awake and keep your crop heading in the direction of a full potential harvest. You’re goal is not to prolong photosynthesis (growth). The goal is to extend the photoperiod (day length and flowering). Commonly affected plants are poinsettias and chrysanthemums. If you do have a greenhouse and are able to hang light fixtures then adding lights is a relatively easy process. Even just hanging the single strip T5 fixtures throughout your greenhouse can trick plants into believing the days are longer. Obviously the more time your plants have to grow under the sun the larger they will be before they begin to bloom and the greater the potential for a bigger, more bountiful harvest come the fall. For folks who do not have a structure or greenhouse to hang lights from, installing a series of posts around your garden and mounting T5 lights vertically or CFLs (compact fluorescents) will provide that extra few hours of light your plants may need.
Especially with clones started inside, you must acclimate your plants to the environment outside. If you have a greenhouse that has regulated temperature and humidity this will be much less of an adjustment process than plants that are being transplanting into full sun. The temperature changes alone will take some getting used to for the garden. On a normal late spring or early summer day the temperature can fluctuate as much as 40 degrees. This is why you must give your crop a week or two to harden off. Hardening off is the process of moving plants outdoors for a portion of the day to gradually introduce them to the direct sunlight and cold nights. Keep in mind how intense the direct sun is when first placing your plants in full sun. Even when plants are started under HID lights, the sun is much brighter and in most cases the crop will not be able to handle it immediately. But there are ways to acclimate your garden to the intensity of the sun. This can be achieved with the use of shade cloth for a week or two or by slowly exposing them to direct sun little by little. The goal here is for your plants to be left in full sun all day without burning or showing signs of stress. This is an important part of the process when growing plants indoors and transplanting outdoors.
Another factor to consider when moving your plants outside is the amount of light your plants were getting before you put them outside. A common trick amongst indoor growers is to vegetate plants under 18+ hours of light per day. Essentially this is like getting one and a half days of growth in a 24 hour period. But if the plants are coming from a 18-24 hour light cycle and then are placed outside, the plants could easily go into shock. Even in late May when the days are relatively long your indoor plants will need an adjustment period. Just another reason why supplemental lighting outdoors to extend the photoperiod is so helpful. The lights, even if relatively minimal, will keep your plants photocycle steady until they are acclimated properly.
Once the garden has fully adjusted to its new environment you can begin to wean the plants off the supplemental lighting until they no longer need them. Once you remove or turn off your lights completely off, sit back and watch the magic of Mother Nature as you head into the fall.