LED plant lights, tap water for houseplants and ice-melting products
Q: In looking for LED lights to start seedlings, I notice some types give off bluish-red light, while others give off white light. Which is better for seedlings? — Bob M., Casselton, N.D.
A: Seedlings grow well under both LED and standard fluorescent lights, with LED being more economical to run, although the initial cost of bulbs is usually greater.
Science classes taught us that natural sunlight is a combination of many colored wavelengths, and together they appear white. Green leaves reflect and derive little energy from yellow and green light wavelengths, while red and blue wavelengths are the most important energy source for plants. Plant lights emitting red and blue light are attempting to provide more of what plants need.
Here at our North Dakota State University Extension office in Cass County, we’re doing a homeowner-type test of both white and red/blue colored lights for growing seedlings. So far, the results are about the same, but reports indicate that some plant types will prefer the red/blue.
From a practical standpoint, though, the purple-colored lighting produced by the red/blue bulbs is very difficult in which to work. I much prefer working with seedlings under a white-toned light. As a compromise, if a fixture holds two tubes, select a warm white and a cool white for a broader light spectrum.
Q: Should we be using something other than tap water to water our houseplants? — Mae Tinguely, Fargo.
A: Whether to use one's tap water depends on the source of the water. For example, if a rural home's plumbing uses water from a well, it might contain minerals that could build up in potting soil, depending on the analysis of the well water. Or if municipal water contains fluorine and chlorine, the tips of some susceptible plants often burn.
If water is purified primarily by ozone instead of chlorine, like Fargo’s water, then there isn't the problem of chlorine salts accumulating, although the fluoride added to most drinking water still can contribute to leaf tip burn. If water is chlorinated and fluorinated, allowing it to sit overnight might help somewhat, although the actual benefit has been debated.
Rainwater and melted snow are great sources of naturally "soft" water. One type of water to absolutely avoid is water that has been softened through a water-softening unit. The salts added during the softening process quickly accumulate dangerously in potted plants.
Occasional "leaching" or flushing of the soil by repeated watering can help remove harmful chemical buildups in potting soil, as does repotting more frequently if one's water source is less than ideal. If one has a small quantity of plants, or a plant of special value, distilled and reverse-osmosis water are good choices also.
Q: When pellets used for melting ice dams run off your roof, do they damage plants if used in normal levels? —Tim Flakoll, Fargo.
A: Great question, as our roofs have plenty of snow and ice again this year. Whether snow and ice melting products damage plants depends greatly on the ingredients of the product used.
Products containing sodium chloride are quite damaging to plants, and are responsible for many patches of dead grass along sidewalks and boulevards. When investigating products used to melt ice dams on roofs, I’ve found many contain calcium chloride as the melting agent. University of Minnesota, Purdue University and many others indicate that calcium chloride is much less damaging to plants than sodium chloride, making it a safer choice. In some ice dam melting systems, the calcium chloride is located in a “sock,” which helps minimize product runoff.
Any of these chloride-based chemicals can adversely affect plants, but look at the ingredients and select calcium chloride instead of sodium chloride when possible, to lessen the chance of plant damage. If you can, guide runoff away from landscapes and plant material.
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at firstname.lastname@example.org or call 701-241-5707. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.