compiled by Vern Grubinger, University of Vermont Extension
(802) 257-7967 ext. 13, or


This past December 1,348 people attended the New England Vegetable and Berry Conference and Trade Show.  Based on 231 evaluations, 82% said attending the conference will improve farm profitability and 92% said it will improve pest management. A 357-page conference proceedings with summaries of 99 presentations is available for $16 postage-paid. Send your check to University of Vermont Extension, 11 University Way, Suite 4, Brattleboro VT 05301. Many of the articles are also available on line at:

(adapted from Missouri Extension)

The maintenance and service of gas-fired greenhouse heating systems should be done by you and/or a service technician prior to the growing season. Here is a suggested checklist. For more detailed instructions see:

Fans and Components: 1. Disconnect power source. 2. Check bearings on electric motors. 3. Check and adjust belt tension. 4. Check physical condition of belt. 5. Tighten or replace loose or missing bolts and nuts. 6. Check and adjust fan belt pulley alignment. 7. Check and paint fan blades and/or housing. 8. Clean fan blades/housing with soap/water mixture. 9. Check and service fan-jet distribution system and convection tube.

Heat Exchangers: 1. Check for cracks or corrosion. 2. Check and clean if necessary. 3. Check heat exchanger for overheating.

Gas Burners: 1. Shut off gas supply to the burners. 2. Inspect and clean gas burner(s). 3. Inspect and clean inside burner tubes. 4. Inspect burner for location and alignment.

Gas Controls: 1. Inspect all gas line and pilot tubing connections for tight fits. 2. Inspect main gas burner orifices for cleanliness. 3. Turn on gas, check gas line connections for leakage with soap/water mixture. 4. Check electrical connections to gas valve. 5. Check thermocoupler for cleanliness and tighten connections.

Thermostats: 1. Check thermostat for general cleanliness. 2. Check wiring to and from thermostat. 3. Check thermostat for proper temperature setting. 4. Check thermostat for proper location.

Vent (Exhaust Chimney) Systems: 1. Check  for obstructions. 2. Check all connections for tightness and security. 3. Check vent support system for security. 4. Check joints of vent for signs of leakage. 5. Check vent pipe drip leg and clean-out cap. 6. Check weather cap.

Gas Supply: 1. Check that gas mains are turned on. 2. Check gas line inlet pressure with manometer. 3. Check manifold gas pressure with manometer. 4. Check gas regulator vents for obstructions. 5. Check propane regulators for proper pressure settings and damage. 6. Check propane tanks for size and propane levels. 7. Check heater combustion air inlets for obstructions. 8. Turn on gas, light pilots and observe burner flame. 9. Activate or cycle heater unit to insure proper operation.

Back-Up Heaters and Alarm Systems: 1. Check redundant heater(s) for fuel levels. 2. Check redundant heater(s) for start-up or ignition. 3. Clean, adjust, and recalibrate sensors for temperature alarm system. 4. Run “test” mode on temperature alarm system.

(adapted from:

When making compost for organic potting media, plan at least six months in advance of the time when it will be needed. For spring transplants, compost should be made the previous summer and allowed to age through the fall and winter. Composting is not difficult, but it does require some experience and a variety of clean, organically acceptable components. Animal manures and bedding, farm and garden waste, grass and alfalfa hay, and other materials can be combined to provide a high-quality, reasonably consistent product.

Organic amendments such as greensand and rock phosphate can be added during the composting process to increase nutrient content. Protein-rich sources such as alfalfa and seed meals can also be included if additional nitrogen is needed. While most compost will provide adequate amounts of phosphate, potash, and the necessary micronutrients, nitrogen has proved to be the most variable element and the most important to manage.

Compost is rarely used alone as a potting medium. Most composts are too porous and the soluble salt levels are often high. A range of 20 to 30% compost content is recommended in potting mixes. Growers may use up to 50% in mixes used for larger vegetable transplants.

In many circumstances, compost has been observed to suppress plant disease. Israeli researchers discovered that vegetable and herb seedlings raised in a mix of 40% vermiculite, 30% peat moss, and 30% composted cow manure had faster growth and less incidence of disease than those raised in a 40% vermiculite/60% peat moss mix. To understand how compost suppresses disease, it is helpful to know how plant sub-stances are broken down during the composting process.

Compost goes through three phases. During the first phase, temperatures rise to 104-122?F and materials that degrade easily are broken down. In the second phase, temperatures are between 104 and 149?F, and substances like cellulose are destroyed. Also destroyed in this phase are plant pathogens and weed seeds, and (unfortunately) some beneficial biological-control organisms are also suppressed. The third stage is the curing phase, when temperatures begin to fall. It is during this phase that humus content increases and some beneficial organisms (like Streptomyces, Gliocladium, and Trichoderma, which serve as biocontrol agents) re-colonize the compost. This re-colonization is somewhat random. It has been observed, for example, that composts produced in the open near a forest are more consistently suppressive than those produced in enclosed facilities. The reason is believed to be the abundance of microbial species found in the natural environment. For more information on this topic, call 800-346-9140 and ask for the ATTRA publication Disease Suppressive Potting Mixes, or see:

(adapted from Oklahoma Extension)

Determining the site of a greenhouse operation involves many considerations. A major factor is availability of sunlight, especially when the days are short early or late in the growing season. Select a site that is free of shading at present as well as in the years to come. A rule of thumb is to separate a greenhouse from nearby structures or trees (except those to the north) by at least 2.5 times the height of structure or mature tree. In some cases, removal of the shading object may be a more feasible alternative. Orienting the greenhouse with the ridge going north to south will reduce interior shading on the plants from the greenhouse structure itself.

The greenhouse site should be naturally level to avoid grading costs. If possible, the land should also be large enough to accommodate future greenhouse expansion without excessive grading.
The ideal tract of land has a slight slope, up to five percent, which provides for proper air circulation and excess water runoff. If the soil has a high clay content, a greater slope may be needed. Otherwise, providing adequate drainage may be a costly endeavor. Proper soil drainage is particularly vital when growing plants in ground beds. Without proper drainage a number of problems can develop such as high salts and insufficient soil aeration.

Access to sufficient clean water for irrigation is critical. If town water is not available or desirable, determine if a suitable well can be drilled. Also, look at nearby streams, lakes, etc. Be certain that this water is a reliable source and will not be diverted or diminished in the future. An abundant source of water is particularly critical during summer when frequent watering is necessary. Up to 1/3 gallon of water per square foot per day may be needed in potted plant production. Ideally, a backup system for irrigation should be planned.

Consider utilities carefully. How will you bring in electric lines? Electricity will be needed at the very least for ventilation. What type of heating system are you planning on and where will fuel be stored? Make sure there will be easy access for fuel delivery vehicles, especially during winter weather conditions. An emergency energy source is important to consider for electrical support of heating and ventilation equipment. In addition, an alarm system is imperative to warn of impending freeze damage.

Locating the greenhouse near a major road will help facilitate the movement of materials to and from the site. In planning a retail operation, include ample parking for customers and employees. Provide 18 feet for head-in parking spaces and 30 feet clearance for back-out and turning. Any curves or turns should have a 20 foot inside radius. Check local ordinances on exits, entrances and minimum car stall space. Plan for the greatest exposure possible when retailing to the public.

A common oversight is the possibility of future expansion. By planning for a larger operation in years to come, the need for relocation may be avoided. Many greenhouse operations double in size within a few years and even greater expansion should be anticipated.