This time of year, gardeners are often a bit itchy to get going! One way to partially alleviate that itch is to inventory your tools and review your gardening practices. So, let’s look at seed-starting and review the basics of indoor lighting.
The light plants need
Plants use almost the entire spectrum of the sun’s light, so once they germinate, seedlings are much affected by the kind of light they receive. Most important are the ultraviolet range at the low end of the spectrum and the infrared portion at the upper end. The blue part of the spectrum encourages leafy growth, while the red seems to affect stem growth, budding, or flowering. In other words, blue light serves as the seedlings’ nitrogen, and red as their phosphorus, affecting the development of flower and fruit production of the adult plant.
Fluorescent light bulbs, unlike traditional incandescent bulbs, provide red and blue light without producing much heat. Fluorescent “grow lamps” provide an even better balance of light at both ends of the spectrum.
Remember that fluorescent bulbs also produce some heat, so you need to adjust their height above the plants. You can establish the best distance by holding your hand above the plants and adjusting the bulb’s distance to a “just right” feel.
Another thing to keep in mind: long fluorescent bulbs produce more light at their center than closer to the ends. If plants are to remain under lights for any length of time, switch them around to even out their exposure so they don’t get “leggy.” Consider more expensive LED lights if you intend to grow plants indoors long-term.
Another cause of sickly seedlings is “damping off,” a fungal disease that will rot the lower stem and/or roots. Reduce the risk of disease by using fresh or sterilized potting soil, decontaminating pots and flats with a bleach solution, and careful watering. As with adult plants, when you water, don’t just sprinkle those plants, water thoroughly and then let the soil dry out a bit before watering again.
Article written by Glenn Palmer, Extension Master Gardener Volunteer.