When raising seedlings indoors, perhaps the single most important item to consider is lighting. Without adequate light, seedlings grow spindly and weak, unable to support themselves. The plant's internal food production rate is lowered, so plant development is retarded. Also plants that are grown in too dim a light will not be able to adapt to the sun's strong rays once they are set outside, which makes for a disappointing end product.

Some gardening books, especially older ones, have recommended that you grow your seedlings in a "sunny, south-facing window". These authors must live in southern climes, where the spring sun is always bright! Certainly in our corner of the world seedlings simply cannot get adequate light in a window sill.

Fortunately you don't need to spend a small fortune to remedy the situation. An inexpensive shoplight fixture is ideal for this use. Mount it directly over your growing area, at a height where the bulbs will be within a few inches of the plants. Since shoplights are supported on chains, they are easy to raise up as the plants grow. I like to have two of the two-bulb shop fixtures over each 16x48-inch growing shelf.

There is a fair bit of debate regarding what types of bulbs to use. All other things being equal, try to get bulbs with the highest lumen output. While plants only use certain parts of the visible light spectrum, there seems to be very little difference between the common types of bulbs in terms of the overall spectrum they produce - other than some narrow phosphor "spikes" that are used for different lighting effects. Plant bulbs do make a difference, but they cost more. I used to achieve acceptable results just using old-style 40W shoplight tubes. Now in each fixture I combine a 40W plant/aquarium tube with a 40W residential tube, and feel the results are worth spending the extra money. If you decide to mix and match tubes in a single fixture, be sure the fixture is rated to handle the bulbs, and do not combine different wattage bulbs!

It's also a good idea to purchase a timer. While the length of your "on" and "off" cycles doesn't matter to most vegetables, allowing the simulated daylength to change from day to day can cause problems. It is also important to remember which vegetables are photoperiodic. Included in this group are most mustard greens, spinach, and all alliums (onions). If you set your timer for too long a daylength you risk having these plants bolt to seed while they are still young. When I'm not growing these particular plants inside, I like to provide around a 17 hour "on" cycle. By the way, when purchasing a timer be sure to get one that accepts three-pronged plugs; many lamp timers do not.


All contents © Travis Saling
This page was last updated November 18, 2013