Gardening Articles: Health :: Houseplants

The National Gardening Greenhouse (page 3 of 4)

by Charlie Nardozzi


Lettuce grows fast and succulent in our greenhouse.

Salad days
Lettuce is probably the easiest greenhouse crop to grow. 'Ostinata', 'Winter Density', and 'Baby Oak Leaf' transplanted in April were harvested in about 30 to 45 days. I also grew 'Black-Seeded Simpson' successfully in summer, transplanting it in August, but couldn't get it to produce well in winter without supplemental lighting. 'Early Bird' eggplant and 'Ace' pepper transplanted in April grew well, but production was limited by a severe aphid infestation.The aphids also lessened the yields on an experimental crop of mid-winter mustard greens. I direct seeded 'Osaka Purple' mustard greens in late January without supplemental light. The plants grew slowly in low light conditions and battled the aphids, but by early April I harvested a small crop of fresh, tasty greens.

The bed wasn't monopolized by vegetables. 'Super Elfin' impatiens were the best flowering plants in the greenhouse. Plants transplanted into the bed in October provided color and cover for ladybug larvae throughout the winter and well into the spring. Jewel nasturtiums planted in August grew well for two months until their foliage browned and the flowering was reduced by the shorter days.


Here I'm releasing predatory spider mites to reduce the number of plant parasitic mites.

A Haven for Bugs
With heavy traffic through the greenhouse and outdoor flower beds close to the windows, I knew pests would be a major problem. Since many people work in or near the greenhouse, I use only organic insect sprays and insect predators to control pests.

The first culprits were aphids on the eggplant. Insecticidal soap knocked them down, but lured by the potential of an endless dinner, the aphids quickly returned. Pyrethrum was even more effective than the soaps, but again the aphids made a comeback. The most effective method was diligent hand crushing and occasional spraying for the winged adults.

In winter I experimented with releasing ladybugs. They caused quite a stir. The adults were found crawling in the conference room, on windowsills, in offices upstairs--everywhere but on the plants. They seemed more interested in escaping and hibernating than eating aphids, so I was surprised three months later to find ladybug larvae consuming aphids on the mustard greens and impatiens. Once the weather turned warm and the larvae turned to adults, out they went whenever the front door opened.

The second major pest was whiteflies -- especially on tomatoes. The population grew quickly in spite of three yellow sticky traps hung around the plants and weekly soap and pyrethrum sprays. I removed the tomato crops prematurely. The final insect problem was spider mites. I first noticed their webs on the citrus, mint, and banana leaves. At that point they were well on their way to causing substantial damage. However, misting daily and releasing Phytosieuluspe persimilis, a predatory mite, were effective controls. The predatory mite population reproduces faster than the two-spotted spider mite population because of the high humidity in the greenhouse. Two weeks after the release of the predatory mites, there were no signs of the spider mites.

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