Difference between revisions of "Grow Tomatoes in a Greenhouse"

Tomatoes are the most popular greenhouse crop on the planet. With good temperature control and plenty of light, greenhouse growers in most areas of the world can get two tomato crops per year.<ref name="rf1">http://aces.nmsu.edu/pubs/_circulars/circ556.html</ref> Indoor conditions do require more careful handling to prevent disease and successfully pollinate the flowers.

#Check temperature. Tomatoes grow best at daytime temperatures of 70 to 80ºF (21–27ºC), and nighttime temperatures of 60–65ºF (16–18ºC).<ref name="rf2">http://www.uky.edu/Ag/CDBREC/anderson/gh_tom.htm</ref><ref name="rf3">http://www.lsuagcenter.com/NR/rdonlyres/5794BBA0-4628-4B79-869A-EA529E647A51/10421/pub1808greenhousetomatoes1.pdf</ref> Make sure you can maintain these temperatures in your greenhouse for the next several months before you plant.

#*The letters VFNT and A after the name mean the variety is resistant to disease.<ref name="rf4">http://www.ext.nodak.edu/extnews/hortiscope/fruitveg/tomato.htm</ref>

#*Perlite bags or rock wool slabs are the cheapest options in many areas.<ref name="rf2" />

#*Some growers prefer a 1:1 mix of sphagnum peat moss and vermiculite.<ref name="rf5">http://www.greenhouse.cornell.edu/crops/factsheets/peatlite.pdf</ref>

#[[Install-a-Drip-Irrigation-System|Install an irrigation system (recommended)]]. Most growers install drip tubing to deliver water to each plant. A fertilizer injector attached to the tubing can automate fertilizing as well.<ref name="rf6">http://edis.ifas.ufl.edu/cv255</ref>

#Plant each seed in its own cup. Poke a ¼ inch (6mm) hole into each compartment of the starting tray. Drop a single seed into each hole. Cover lightly with the potting mix.<ref name="rf3" />

#Moisten with water or dilute nutrient solution. Use plain water for soil, or seedling nutrient solution for soil-less mixes. Either way, water until the mixture is just damp enough to press into a clump, with only a few drops squeezed out.<ref name="rf7">http://edis.ifas.ufl.edu/cv266</ref> Water regularly to keep the mix damp.<ref name="rf3" />

#Keep the tray on a warm windowsill. Do not bring the seeds into the greenhouse until they've sprouted, so you can check for disease and pests. Provide plenty of sunlight and keep the temperature at 75–80ºF (24–27ºC) during the day.<ref name="rf7" />

#*To keep temperatures under control, you may want to start the tray in partial sun. Move to full sun once all seedlings have sprouted.<ref name="rf3" /> This usually takes 5 to 12 days.

#Transplant to larger containers. Transplant the seedlings to small pots in the greenhouse about two weeks after they emerge.<ref name="rf2" /> After six to eight weeks, or once seedlings are 4 to 6 inches (10–15 cm) tall, transplant them to larger pots or bags. A typical plant needs roughly ½ to 1 cubic foot of potting material (3.7–7.5 gallons, or 14–28 liters).<ref name="rf2" /> Even smaller varieties may produce less fruit if grown in smaller pots.<ref name="rf8">http://www.tomatodirt.com/tomatoes-in-pots.html</ref>

#*Give each plant about 4 square feet (0.37 m²) of floor space.<ref name="rf2" /> Planting too close together can reduce air flow and encourage disease.

#Adjust pH and calcium levels. Before the final transplant, you may want to [[Test-Soil-pH|check soil pH]], which ideally falls between 5.8 and 6.8.<ref name="rf3" /> If your soil is too acidic, add about 1 tsp (5 mL) hydrated lime for each gallon (3.8 L) of potting mix. Besides raising the pH, this adds calcium that can prevent blossom rot later on.<ref name="rf9">http://www.jasons-indoor-guide-to-organic-and-hydroponics-gardening.com/how-to-grow-tomatoes.html</ref>

#*If your pH is fine, mix in gypsum or calcium sulfate instead to add calcium without changing the pH.<ref name="rf3" /> Alternatively, just choose a fertilizer that contains calcium and apply every week or two.

#*In a hydroponics setup, you can supply calcium by injecting calcium nitrate into the irrigation feed. This requires a second injector, as calcium nitrate cannot be stored with your main fertilizer.<ref name="rf10">https://ag.umass.edu/fact-sheets/greenhouse-tomatoes-fertilizing-plants-growing-in-soilless-media</ref>

#Fertilize regularly. Start fertilizing the day you transplant the tomatoes into their final pot. Use a complete fertilizer high in nitrogen (N) and potassium (K), such as a 15-5-15 or 5-2-5.<ref name="rf2" /> Dilute and apply the fertilizer according to label instructions.

#*Reduce fertilizer as the final fruits ripen. Do not fertilize in late autumn or winter, unless using artificial grow lights and reliable heaters.<ref name="rf11">http://vric.ucdavis.edu/pdf/greenhouse_yearroundgardening.pdf</ref>

#Remove suckers weekly. Once a week, pinch off "suckers," or side shoots that emerge where a leaf meets the main stem. Leave only the main bud at the top of the steam, plus the highest sucker below it. This trains the plant to grow upward instead of wide.<ref name="rf3" />

#*Commercial operations save on materials by stringing a wire over each row, with a support post every 20 ft (6m). Wrap the twine around each plant and fasten to the overhead wire.<ref name="rf7" />

#Pollinate the flowers. Unlike many plants, a tomato can pollinate itself — but it needs some help. The pollen in a tomato flower is trapped inside a tube, and must be released through vibration. Since most greenhouses lack bees or high wind, you'll need to act as the pollinator once flowers are fully open:<ref name="rf12">http://aggie-horticulture.tamu.edu/greenhouse/hydroponics/tomato.html</ref>

#*Once fruit starts to grow, thin each cluster down to four or five fruits, removing the smallest or most misshapen. Very large fruits or winter conditions may require going down to three per cluster. Varieties with small fruits may not need any thinning.<ref name="rf7" />

#*As the fruit matures, snap off older leaves from the lower clusters. This helps improve air circulation.<ref name="rf3" />

#Harvest as late as possible. The longer the tomatoes stay on the vine, the fuller and redder they become.<ref name="rf12" /> Commercial growers typically pick a little early, when the fruit is 60–90% red, to allow for time in shipping.<ref name="rf3" />

*While you can harvest seeds to plant next year, they may not belong to the parent variety. The next generation may look or taste different, or even fail to ripen in your climate. They can also carry diseases that affected the parent.<ref name="rf4" />

*Unless you're planting in winter, the tomatoes should get plenty of sun in the greenhouse. Artificial grow lights can speed up growth by extending the "day" to 16 hours, but this is expensive. If you are a commercial grower, using HID lights may be worth it to grow a winter crop, but only if customers in your area are willing to pay extra for winter tomatoes.<ref name="rf2" /> Hobbyists typically choose cheaper fluorescent grow lights if additional light is necessary.<ref name="rf13">http://www.tomatodirt.com/tomato-grow-lights.html</ref>

*Be careful when removing suckers. If you accidentally remove the main stem instead, fruit yields could drop by half.<ref name="rf2" />