Greenhouse & Indoor Gardening

How to Avoid 5 Common Greenhouse Growing Problems

My family bought a greenhouse a little over 2 years ago to extend the growing season both before spring started and after summer ended. Our greenhouse is designed for a homeowner and has been working out well. From the fresh smell in the air once the doors are opened to the colors, to the warmth you feel as if you are really succeeding in not only creating something from scratch but also teaching your family the value of rewards of doing something on your own.

As exciting and pretty as the greenhouse is in our yard there are challenges when growing in a greenhouse and solutions to make for a much better experience. Over the past two seasons I have come up with a few suggestions to help make greenhouse gardening much more enjoyable.

Temperature Control

Hotter is not always better. Each variety has its own optimum temperature preference, and sometimes these desires change with the stages of plant development. However, in general, the air temperature of a greenhouse should not rise above 90 degrees. Temperatures higher than this may cause pollination problems with your tomatoes and cucumbers. There are ways to control these temperatures through fans and greenhouse shades.

The problem with temperature is that it can rise quickly. On more than one occasion I left the house in the morning and the greenhouse temperature was around 70 degrees to return an hour later o find the temperature over 100 degrees. Leaving the door open is insufficient on especially warm or sunny days, for without cross ventilation the air hangs heavy, still, and hot.

To aid with the cross ventilation many greenhouses come standard with automatic roof vents that are controlled by temperature in the greenhouse. When the temperature rises the fluid in the piston that opens the vent expands and pushes the vent open. Then when it cools down the vent closes. The addition of a fan on a timer (set for the times when the greenhouse gets the warmest) will also help get air circulating both in and out of the greenhouse. You do not want to use an air conditioning system, as this will pull much needed moisture out of the air.


Long term high humidity and dampness can be cause permanent damage to your plants. There have been several studies over the years that have found that if it is too damp the plants cannot pass the oxygen and water they produce back out into the atmosphere and growth can be stunted. Most experts feel that humidity levels between 25 to 80 percent will not adversely affect most plant growth. At a consistently higher rate of humidity most plants will develop problems with being able to absorb moisture and develop diseases associated with moist environments such as funguses. So, the same high humidity that stresses your plants provides the perfect conditions for disease growth–two reasons for keeping it under control.

Watering only when necessary, helps, as will making sure you don’t leave pools of water lying around when you drag the hose back out the door. The same venting that reduces temperatures will also reduce humidity.

Air Circulation

When the air is stagnant, humidity builds up, diseases thrive, and plant stems don’t become as strong as they do when air movement is more vigorous. Fans and venting will help maintain a healthy circulation.

Using Trellises for sprawling plants and trimming back some leaves will also encourage circulation. You do not want to pull at these overgrown plants as you disturb the roots of other plants that have entwined themselves with the chosen sacrifice. Going through this cycle 2 times I have learned that what looks to be an empty greenhouse in March or April turns into a Jungle buy July or August so make sure you have a chance to plan out the greenhouse and leave enough space for all your plants.

Pest Control

Since this is a closed ecosystem there are even greater chances for bugs to get into the greenhouse and spread very quickly. Spot-check flowers, buds, the undersides of leaves, and the places where stems and stalks intersect. At the first sign of aphids, remove the plant and use a wash to clean the plant. I prefer using the organic version since what I spray today, I will be eating in a few weeks. There is also no better way to protect your plants that by using natural defenders. Ladybugs are great. You can buy them online and just open the package of live ladybugs and watch them go to work. Since this is an eco system there needs to be balance. Ladybugs will eat the aphids as well as start families in the dirt, which will lead to a nice productive life cycle. I have found that periodic additions of ladybugs are needed as well. If a plant looks to have caught a disease, I am ruthless about culling. I first try cutting off just the affected parts, but if the spots, splotches, or rot continues I decapitate at root level.


It sounds funny but a clean greenhouse makes for a clean plant and growing environment. Managing the surroundings will help ensure a great harvest as well as hours of enjoyment.

It sounds like a lot of work, but it really is not. Once you get into a routine you will find that gardening with a greenhouse is truly delightful and the diligence you applied in the beginning will pay off.

Samantha Michaels works for a company that offers environmentally friendly “green” products.

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