Cultural Practices

Preventing Plant Stretch

Cooler night temperatures combined with the warm sunny days often result in plant stretch. The greater the difference between day and night greenhouse temperatures, the more stretch you will see on your crops. Some growers may be only reducing the night temperatures, to save on energy costs, with the daytime temperatures increasing due to the bright sunny days.

Many growers successfully use an early morning temperature DIP to reduce plant stretch. They reduce the temperature 30 to 60 minutes before dawn and maintain this lower temperature for the first few hours of the day.

Premature Budding of Garden Mums

Garden mum cuttings sometimes form crown buds, however, these plants usually perform satisfactorily if given a pinch and kept actively growing. These cuttings should be given a hard pinch 4 to 6 days after planting, when the plants are fully turgid. Remove at least ½" of new growth when pinching. This will force out lower breaks, which tend to be more vegetative. It is also important to keep them well watered and fertilized. Cuttings that have initiated lateral buds down the stem will not always perform well.


Liverworts (Marchantia polymorpha) are branching, ribbon-like plants lacking distinct roots, stems and leaves. They reproduce by spores and vegetatively. Stalked, umbrella-like structures release spores. Small, bud-like branches produced in cup-like structures on the surface of the plant also help spread liverworts from pot to pot by water droplets during irrigation. Liverworts thrive in conditions of high fertility, moisture and humidity.

Growing Herbs Organically

Growers have expressed interest in growing herbs organically. The US Department of Agriculture has developed a set of standards that food and plants labeled "organic" must meet. To become organically certified, a government approved certifer inspects the farm to make sure the farmer is following all the rules necessary to meet USDA organic standards. The USDA National Organic Program web site provides a listing of certifying agencies.

Here are a few general guidelines to consider:

Preseason Cleanup

Greenhouse sanitation and disinfecting are steps that growers can take now to prepare for the spring growing season. Clean as early as possible to eliminate over-wintering sites for pests to reduce their populations prior to the growing season. Greenhouse pests will over-winter in weeds and protected areas in unheated greenhouses and especially this year with unseasonably warm temperatures. Remember that pests are much easier to prevent than to cure.


Symptoms of edema appear as bumps or blisters initially on the undersides of lower or older leaves on a plant. On ivy geraniums the injury resembles spider mite or thrips damage. Be sure to rule out the possibility that the damage is a result of spider mites or thrips feeding on the plant tissue. The management strategies for solving edema are far different from those used to control insects and mites. Use a handlens and check carefully on the undersides of leaves along midveins for spider mites and in growing points for thrips.

Field Trials Midsummer Ratings

Plant trials are important tools. Pack trials provide you with a snapshot of how new plants perform in the greenhouse. That's valuable information for your production process. Field trials, on the other hand, offer a view of how plants perform in the field. That's valuable information too, because it provides an assessment of how your customers see plants.


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