Vegetable transplants are commonly grown in New England in greenhouses for field setting or as part of the spring sales mix for resale at farm market stands. Many vegetable crops are grown from transplants in New England due to the late spring, short growing season and desire to obtain mature, harvestable crops as soon as possible.
Transplant production is a specialized part of vegetable production that requires a protected environment such as a greenhouse and careful attention to detail. Although vegetable bedding plants may only be in the greenhouse for a short period of time, it is important to produce a high quality pest-free transplant. Scheduling, plant nutrition, greenhouse management, and pest management influence the quality of transplants. Some growers choose to purchase transplants from specialized growers while others grow their own.
Unvented Heaters in Greenhouses. One of the most critical features in greenhouses is a source of heat to provide appropriate temperatures. A frequent question by growers is the use of supplemental heaters in the spring. Do not use unvented heaters when growing transplants in the greenhouse or high tunnel. An unvented heater is one that is designed without a flue connection so that the heat and products of combustion are exhausted into the greenhouse. Unvented heaters can be fired with natural gas, propane or kerosene which all contain traces of sulfur. During combustion sulfur in the fuel is combined with oxygen to form sulfur dioxide. Levels as low as 0.5 part per million (ppm) can cause injury to some plants. Once the sulfur dioxide enters the plant through the stomates, it reacts with water to produce sulfuric acid that causes leaf burn, flecking and general chlorosis. Tomatoes and white petunias are very sensitive and will show damage in as little as one hour. Ethylene gas is another pollutant formed during combustion. Ethylene levels as low as 0.01 ppm can cause symptoms such as malformed leaves and flowers, stunted growth, bud abscission, epinasty (downward bending of leaves) and flower senescence.
Most recent version, New England Greenhouse Floriculture Guide: A Management Guide for Insects, Diseases, Weeds and Growth Regulators, available from: www.negreenhouse.org/index.html
Schnelle R. and J. Barrett. 2009. Sumagic and Tomato Transplants. Greenhouse Product News 9(11).
New England Greenhouse Update http://www.negreenhouseupdate.info/ This website consists of both greenhouse updates and photo gallery. The photo gallery provides photos and descriptions of hundreds of plant problems caused by insects, mites, diseases, nutritional disorders and cultural procedures.
University of Massachusetts Extension Greenhouse Crops and Floriculture Program: https://ag.umass.edu/greenhouse-floriculture
University of Conn Extension Greenhouse IPM Program: http://ipm.uconn.edu/pa_greenhouse/
Biernbaum, John. 2006. Greenhouse Organic Transplant Production. Michigan State University http://www.hrt.msu.edu/uploads/535/78622/Organic-Transplants-2013-13pgs.pdf
Maynard D.N. and G.J. Hochmuth. 2007. Knott’s Handbook for Vegetable Growers. Fifth edition
Organic Greenhouse Vegetable Production, Potting Mixes for Certified Organic Production, Organic Greenhouse Tomato Production, Plug and Transplant Production for Organic Systems. (ATTRA) - National Sustainable Agriculture Information Service http://www.attra.org/horticultural.html#Greenhouse
The National Organic Program Guidelines http://www.ams.usda.gov/nop/indexIE.htm
Helpful Information on Greenhouse Management/Engineering
Energy Conservation for Commercial Greenhouses: PALS Publishing (Formerly NRAES), http://palspublishing.cals.cornell.edu/nra_index.taf
Greenhouses for Homeowners and Gardeners: PALS Publishing (Formerly NRAES), http://palspublishing.cals.cornell.edu/nra_index.taf