NEWBERG, Oregon—My greenhouse is alive. Shifting a pot to a new location, I surprised a small nest of sow bugs, which scurried for new cover. And when the skies darken and the first heavy drops fall on the greenhouse plastic, a chorus of croaking frogs begins.
Last summer, the garden was overrun by 5- to 6-inch-long praying mantises. I had no idea whether they could winter over outside, and so my children coaxed me into bringing five of them into the warmth of the greenhouse. They were a delight; all were soon hand-fed pets. Then suddenly, they all disappeared. A few days later, my six-year-old son found a pair hidden among the leaves “fighting”. Actually, they were courting. After watching the four-hour mating ritual, I can state confidently that the female does not always eat the head off the male at the end.
The next day, the female deposited an egg case on the stem of a Salvia madrensis. Since the apparent demise of all my adult mantises, I have uncovered four more egg cases scattered around the greenhouse, so now I am vigilantly awaiting the birth of hundreds of young as the weather warms.
I certainly don’t look forward to finding whiteflies on the scented-geranium stock plants—usually on the oldest leaves, near the bottom of the plant—or aphids on the new growth. Because aphids and whiteflies are particularly attracted to yellow, I place yellow sticky cards just above the foliage of the scented geraniums to monitor their numbers. On the other hand, just picking out affected parts and getting them out of the greenhouse can help forestall a bad infestation.
Even with good ventilation, the rise in relative humidity with warmer weather increases the likelihood of powdery mildew in the greenhouse. Fine-foliaged rosemaries such as Rosmarinus officinalis ‘Majorca Pink’ and ‘Benenden Blue’ and purple and Tricolor sages are indicator plants. If I find any infected specimens, I get them out of the greenhouse quickly before they spread the disease throughout. I’ve found that a weekly application of a kelp-based organic fertilizer helps prevent both powdery mildew and damping-off of young seedlings, especially basil. If a seed lot is infected with the damping-off fungus, watering may splash its spores onto previously uninfected areas, so I maintain good sanitation and get rid of any infected seed lots immediately.
A well groomed, fertilized, and watered plant stands a far better chance of avoiding insect or disease damage than one that is under stress. Lemon verbena is susceptible to spider mites, yet stock plants that are free of mites stand side by side with infested ones. While outside temperatures are still low, a good spray of insecticidal soap or horticultural spray oil knocks down any overwintering mites. Predator mites have been very effective, and I am able to order them for three different temperature and humidity regimes. The trick is to release them in the greenhouse before there is a spider mite problem.
Now that I realize that I’m not alone in the greenhouse, I monitor my plants and pests daily. That can be difficult because as soon as I enter my greenhouse, my glasses steam up. I wonder whether it’s the warmth and humidity or the heat of passion among the bugs.