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March Mania

Removing geranium flowers, pesky flies on plants and salty potting soil

Don Kinzler, Growing Together and Fielding Questions columnist. The Forum1 / 2
A reader wonders if it's a good thing that these geraniums are flowering already. Special to The Forum2 / 2

Q: Look what happily greets us under their grow lights in the basement! Is flowering this soon a good thing or bad thing? I cut them back as I've done before and we brought them indoors in mid-October. The lights are 12 inches above the plants, depending on the height of each plant. Do we need to adjust? They are LED lights on fixtures with chains so we can raise or lower as needed. — Beth and Tom Iverson, Moorhead.

A: Your geraniums look like they're off to a great start. I like the way you've cut them back, which encourages fresh, vigorous new sprouts from the base. I would definitely remove the blossoms and flower buds, so the strength can go into producing new shoots and sprouts.

After the plants have fully developed, you can let them bloom in midwinter if you like. Then, on about March 1, pinch the tips of the geranium shoots to remove any spindly growth, and remove all flowers and buds one more time. This produces healthy, stocky plants in time for moving them outdoors in May, and they should be back in strong bloom by mid-May.

The plants are a little distant from the lights. I’ve found that geraniums grow best very close, within at least 4 inches of standard fluorescent or LED tube lights. When the plants are closer to the lights, the new growth is stronger, darker green and better branched. The proper time length for lighting most plants is 16 hours on and eight hours off.

Q: I started some geranium plants inside and now see some little bugs flying around the plants. How can I get rid of them? I tried a spray, but it didn’t work. — Donna Braton, Barnesville, Minn.

A: If the insects are small black flies that flit around, they are probably fungus gnats. The adult flies only live about 10 days, according to Colorado State University, but they lay hundreds of eggs in the soil, which hatch into hundreds of larvae that feed on organic matter and can chew on plant roots. They emerge as adults in another 20 days, and the cycle starts over, meaning nuisance populations can quickly build.

Fungus gnats can be controlled with a product called Mosquito Bits, which might sound strange, but if you look at the label, it's also for fungus gnat control. It contains Bacillus thuringiensis israeliensis, which is a naturally occurring bacterium that specifically kills larvae, breaking the fungus gnats’ life cycle chain. Mosquito Bits is sold at many garden centers and national chain stores. Always follow label instructions for use.

Letting the surface of potting soil dry more completely between waterings also discourages fungus gnat development.

Q: My potted indoor Japanese maple isn’t happy, and the leaf edges keep turning brown. I’ve been soaking it once a week but it acts so thirsty all the time. What can I do to help? — Annette McIntyre, Moorhead.

A: From the photo you sent me, I see a whitish crust on the soil, which is likely salt or mineral buildup. These salts not only result in burning of leaf margins, but also burn the roots. Loss of roots through burning causes the plant to wilt, giving the impression that it is dry, even though the soil might be wet. Adding more water compounds the problem, and can lead to root rot.

Replacing the soil is the most straightforward solution, repotting into a high-quality mix like Miracle-Gro Potting Mix, or one recommended by a locally owned garden center. When you take the plant out of the pot, gently scrape away the top layer of current soil, and some from along the sides and bottom, to reduce the quantity of old, salty soil. A high-quality, well-drained mix is less likely to accumulate salts that cause burning of roots and leaf margins.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at or call 701-241-5707. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.