Asian Potted Herbs
Answered by: Conrad Richter
Question from: Specchierla
Posted on: November 6, 2000

I agree, your site is the source for info on commercial herb growing. So now a question from a novice herb grower weighing some options. Currently we grow organic tomatoes and bell peppers off season in greenhouses located in Chico, CA. Additionally we have started selling organic heirloom tomato starts and organic fertilizer through Smith & Hawken. We have an opportunity to sell an Asian herb pack also, Vietnamese coriander (Rao Ram), lemon basil, Queen of Siam Basil, garlic chives, and lemon grass. They would like to market this as a summer product. What would be the challenges in bringing this product to market (i.e. temperature variances -- it gets hot by end of June 100F), and what are suggested cooling methods that don’t compromise health. Can these varieties share a common environment? We would like to grow from seed and sell in 4" pots.

Most of the herbs you mention thrive in heat, although persistent exposure to 100 degrees Fahrenheit will stunt growth. Probably the ideal daytime temperature is about 80 to 85 degrees, with garlic chives probably preferring somewhat cooler temperatures about five degrees less. I say "probably" because there have not been any controlled trials to compare growth of these herbs at high temperatures that we are aware of.

Keeping temperatures down is a challenge in the summer. If the ambient outside temperature is 100 degrees, it is impossible to keep greenhouse temperatures lower without expensive cooling systems. Fans, vents and shade cloth are the obvious things to start with, then perhaps try some short bursts of fine mist (while ventilating) to take away some of the heat as the water evaporates. It is not likely to be economic to install cooling systems to grow these crops.

You should note that Vietnamese coriander cannot be grown from seed. And the lemon grass variety that best suits this pack is the West Indian variety which is the one most used for culinary use in the Orient, and that variety of lemongrass cannot be grown from seed either. These varieties are available from Richters as plugs.

I like your theory on beneficial insects and the goal of pest extinction. White flies, thrips, and spider mites seem to be the major culprits. Would enjoy some more detailed description of your beneficial insect policy.

In a closed environment such as a greenhouse with adequate insect screening and controlled entry of personnel and plant material, it is theoretically possible to drive pest populations down to zero if pressure from predators is strong enough. The theory does not appear to be well understood by advocates of beneficial insects in the closed greenhouse environment; they say the only realistic goal is to push pest populations to levels at which pest damage is tolerable commercially. Their recommendated rates of introduction of beneficials are based on achieving these tolerance levels, not on achieving complete extinction. The trouble is that a single pest on a potted herb that is taken home and placed on the windowsill will develop into a serious infestation. This is because when the plant is taken out of the greenhouse environment where conditions and the presence of predators on nearby plants are enough to keep pests below tolerance levels, the conditions suddenly change and there is no longer any migration of predators from nearby plants.

What is needed is research to determine what introduction rates result in extinction in an closed greenhouse system. Such rates of introduction will necessarily be heavier than typical recommended rates, but how much heavier is required needs to be determined in controlled trials.

Once a pest is pushed to extinction then it should be possible to discontinue the beneficials application as long as no new pests migrate into the greenhouse. Extinction force applications will be very expensive at first, but cost analyses need to take into account the savings that will accrue when extinction is achieved.

Recently, I spoke with a greenhouse tomato grower who managed to virtually eradicate whiteflies from his greenhouses. He said that he applies 150% of the recommended rate every week whether he has whiteflies or not. Over the past year he found only 5 whiteflies in more than an acre of greenhouses. Perhaps this is the extinction theory at work.

Will be looking more closely at your catalog when it arrives.

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