Herbs and Vegetables in the Winter Greenhouse

Herbs and Vegetables in the Winter Greenhouse

Herbs and Vegetables in the Winter Greenhouse

Herbs and Vegetables in the Winter Greenhouse

By Tom Eckert, Dillsburg, PA
It is possible for the hobby greenhouse grower to enjoy many types of vegetables in the winter greenhouse, however a favorite, the tomato and pepper are usually not one of them. The shortened photoperiod and cool temperatures combine to discourage tomato and pepper from setting flowers or ripening their fruit. Natural pollinators -bees- are absent; and the pests – white fly and aphids – can be abundant if not controlled. And then levels of carbon dioxide needed for photosynthesis are low in the un-ventilated hobby greenhouse. Disease can thrive in the high humidity of the greenhouse.
Join the Hobby Greenhouse Association

Join the Hobby Greenhouse Association

Do not be discouraged, with choosing the right varieties of herbs and vegetable to grow, fresh vegetables can be enjoyed from fall till spring when the outside garden is idled.
You can extend the tomato season by digging up your tomato plants from the garden, potting them up and moving them inside. However, this in not too practical for most tomato varieties in the gardens grow into vary large plants usually 6 foot tall and about that wide.
There are a few tomato varieties bred to be grown in pots or 5-gallon buckets. These tomatoes are many times referred to as patio or bush tomato. The “better bush” is one example that produces 3 to 4-inch red fruits on a bush of some 4-foot tall and about 3- foot wide. The tomatoes are sweet and very tasty.
By bringing the plants inside the greenhouse you can extend their growing season by month or until the green fruit on them ripens. If the plant does produce more blooms you can always try the pollinate them yourself with an artist brush going bloom to bloom like bees would do. The pepper plants can also be dug and moved inside. Plants brought
into the greenhouse should be inspected for insects and disease. You do not want to introduce these problems into the greenhouse.
Most retail green houses, markets and the box stores pull their seed packs in August if not before making room for fall plants. If you have waited you may have to purchase seed from all those seed catalogs you have been receiving. Shipping charges can add greatly to your order, for that reason it is generally better to purchase from only one seed catalog company.
Growing winter herbs provides a good variety of plants available usually in 4-inch pots or from seed. Locally we have one greenhouse, Ashcombes Farm and Greenhouse, that have a very large variety of potted herbs available almost all winter. In general, leafy greens and root crops (herbs, lettuce, greens, beets, carrots, and radishes) do better than those grown for their fruit (tomato, peppers, and cucumbers). Varieties bred specifically for the short days and cool temperatures of winter perform better under these conditions.
One of the biggest growing problems in the winter months is the soil. Use soil containing plenty of perlite which will provide good drainage for the plant’s root system. Compacted soil will hold too much water and root systems may rot. The use of manure and other compost should be well-aged to minimize disease and salt toxicity.
Leaf compost from the local township piles is not a recommendation from me. Leaves and even grass cuttings dropped off at township sites usually contain a variety of chemicals sprayed on lawns. In late fall with the first snows the collected leaves contain road salts used to melt snow and ice. Township compost can be good for the outside gardens when worked into the soil but not necessarily for potted plants. Your winter grown vegetables and herbs will need some light fertilizing. Do not overdo it on the mixture. Half strength should be tried first and if needed increase the strength of the mix. Water soluble fertilizers are readily available to the plant and easy to regulate. Fish emulsion and liquid seaweed are excellent for winter vegetables. You can use a complete fertilizer like 15-15-15 of one that it tailored to your specific crop. In the dark short days of winter, the plants will not require as much fertilizing, or none if prolonged cloudy days persist.
Ventilation and good air circulation within the greenhouse are vital to minimize disease and insect problems and to maintain a constant supply of carbon dioxide necessary for plant growth. On good sunny days when the greenhouse temperature climbs open some vents or the door to allow fresh air to enter. Just remember to close them in the evening. For this reason, electric temperature controlled intake vents or the use of solar controllers on intake vents works quite well for exchanging air within the greenhouse.
Speaking of solar vents, if the greenhouse is closed in the winter months disconnect the opening rod from the controller cylinder or the adjusting thumb nut from the
controller itself. This is important if the vent is locked in position on its frame. On sunny days the controller will try to push open the vent and may damage the vent or may cause the cylinder to blow its seal rendering the opener somewhat useless. New cylinders are however available from the manufacture just for this reason.
Vegetables can be grown in raised or inground beds, in containers, there is no ending to what they can be grown in. Just remember that inground beds are the best since they will help keep the roots warmer. Pots on benches will have soil temperature equal to the surrounding air temperature in the greenhouse. Several thermometers positioned around the greenhouse are essential for knowing the temperature. Winter grown vegetables usually do not have the root masses those grown outside in the summer garden.
Root Crops
Beets, carrots, radish, and turnips tolerate a cool greenhouse and require only about 6 to 8 inches of soil. Research your seed catalogs for short varieties. Broccoli, Brussel Sprouts and Cauliflower need more depth because of their long tap roots, usually some 10 to 12 inches deep. There are apparently miniature varieties available on the market. Do not be afraid to experiment in the greenhouse. Seeds are pretty cheap and down to fifty cents a pack some in stores in the fall months. Keep your seed stored in dry average room temperatures. Most seed do not like freezing temperatures and moisture. And remember that the garage and basement are generally the worst places to store seed.
Tom Eckert is the Director of Publication
and Editor for the HGA.



Greenhouse Growing – The Good, The Bad and The Bugly

Greenhouse Growing – The Good, The Bad and The Bugly

Greenhouse Growing

Diseases, pests and good bugs in the greenhouse

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I love to spend time in my greenhouse. It is like my personal oasis. I turn off my phone and go in and get lost in the comfort of my plants. Unfortunately there are some diseases and bugs that may desire this warm, friendly atmosphere as well. If you are diligent in your efforts to monitor for this and keep your greenhouse environment clean, you may never have an issue at all. A healthy environment is critical for your greenhouse production, be it for pleasure or profit.

The Good – Do these to prevent diseases

Keeping it clean – The best way to fight disease in the greenhouse is to keep everything clean. If you are reusing your soil it should be sterilized. If you are purchasing new soil or soilless mix you should be certain that they are pathogen free.

Always keep your tools, bench surfaces and floors clean. Clear all debris from previous crops out of the greenhouse. Many of the diseases will go dormant in these dead leaves, etc just waiting for the proper conditions to reappear.

Bugs such as thrips, whiteflies, and aphids may find a home in weeds that have been let grow in the greenhouse.

Circulating Fans – This is an often overlooked greenhouse accessory. They provide many beneficial features to your greenhouse. They should be running 24 /7 in the spring, winter and fall. These fans provide a slow, steady air flow to the greenhouse. They will help to avoid any hot or cold spots in corner, etc. They help to keep condensation down, therefore curbing back on disease. They mimic a gentle, blowing breeze which will increase the strength of your plant stems, giving a stronger, healthier plant.

Greenhouse Circulating Fan

Greenhouse Circulating Fan

Bumble Bees or Honey Bees – These are both excellent pollinators. Bumble bees are least aggressive and require smaller colonies. Also, if you use honey bees you have the added task of taking care of the honey that is produced.

Yellow Sticky Traps – These are used as early detection for adult whiteflies, thrips, adult leafminer flies, fungus gnats and aphids. Early detection is critical for elimination of these pest. Hang these in your greenhouse around your active crops.

The Bad – Diseases of the greenhouse

Botrytis – Botrytis is a fungus that can affect any plant in a greenhouse. It presents as a gray, fuzzy  mold. It usually appears as a Spring or Fall issue, as it grows best in temperatures of 55 – 75 degrees F. Excess humidity can cause Botrytis to appear. To avoid this, keep the greenhouse clean and remove any plants which appear to be affected. Make sure that your plants are not overcrowded. You need good air circulation. This is where your circulating fans come into play. Water only in the morning. Avoid placing plants where water is dripping from the roof.

Tobacco Mosaic Virus – This may affect petunias, tomatoes and tobacco plants among others. It may affect up to 350 species of plants. Some plants are carriers but show no sign of the disease. This virus can stay active for long periods of time in plant debris and even on surfaces such as greenhouse floor or benches. You can spray the affected plants with a 20% nonfat dry milk mix. This will coat the virus and inactivate it. This presents as a mosaic pattern of light and dark green on the leaves. There is no chemical cure for this virus. Discard infected plants.

Bacterial Blight – This is incurable, so the best way to handle this is with prevention. The most obvious sign of this is wilting of the leaves. The root may appear rotted, but not always. If you over fertilize you may see similar symptoms. Make sure to differentiate.  Be sure to sanitize all tools and surfaces. Affected plants must be destroyed and removed. The soil should not be reused.

The Bugly – Good bugs and bad bugs

Biological control – To me this is a fancy way of saying good bugs. There are some bugs that will naturally prey on other bugs. This is a whole lot better than using chemicals. The most important step, once you have found you have an issue, is proper identification. You must pair up the proper predator with your pest.

  • Parasitic wasps will control aphids. Aphidius wasp.
  • Ladybugs are good for spider mites and aphids.
  • If you have a mite issue there are predatory mites.
  • Parasitic wasps will control whitefly. Encarsia formosa.
  • Parasitic nematodes are for controlling larvae or grubs of some beetles and weevils

The early detection is very important. Once a pest has been established it is harder for the beneficials to completely eradicate the problem. This is because the beneficial bugs have a hard time reproducing as fast as the bugs already in residence.

Well, just as there are good bugs for the greenhouse, there are bad bugs as well. They can cause a whole lot of damage in a greenhouse. The best way to keep this under control is to monitor your plants for signs of bugs on a regular basis. Also, the yellow sticky tape mentioned earlier will help you to monitor your bug situation.

Caterpillars – The easiest way to keep these out of the greenhouse is to keep butterflies and moths out of the greenhouse. They will chew holes in leaves. You should be able to spot these with regular monitoring. They can be manually disposed of.

Thrips – Thrips are small slender insects. They have wings, but do not fly well. They may affect plants such as onions, beans, carrots and squash. They feed by cutting the leaf and drinking the sap. They spread tomato spotted wilt virus. The leaves will have stippling and discolored flecking. Insecticidal soap can be used to rid your plants of these pests.

Aphids – There are many different types of Aphids. They are relatively small and may or may not have wings. They prey on the plants by sucking the juices out. Their population will increase exponentially. You can manually remove the infected leaves to help curb these bugs. Ladybugs and lacewings are natural predators.

Whiteflies – These pests are appropriately named for the color of their wings. They are small and moth like in appearance. They lay their eggs on the bottoms of plant leaves and suck the sap out of the plant leaves. Immature stages are more difficult to see and locate. The Whiteflies can transmit several viral  diseases.  Yellow sticky cards will help to monitor this situation, but they are not really effective as a control measure. Ladybugs and lacewings are natural predators.


The best way to keep a healthy greenhouse is to keep a clean greenhouse. If you are unfortunate enough to run up against one of these issues make sure to properly identify first so you can take the appropriate measures.


Greenhouse Heaters – Our Top Pick

Natural Gas or Propane Greenhouse Heater

Vented Natural Gas or Propane Greenhouse Heater

Getting ready to heat your greenhouse? Well, now is the time to either check your existing heater or to purchase a new one. Our top pick, the Southern Burner natural gas or propane greenhouse heater is going to have a price increase (the first time since 2008) on November 20th. So you want to be sure to order prior to that date. This is a super greenhouse heater that will fit under a bench and not take up any valuable floor space. It requires no electricity. The heater is all aluminum and stainless steel. They will keep the temperature at the top of the greenhouse within about 5 to 7 degrees of the floor heat. There is a vented and a non vented model available. The vented model is 25,000 BTu’s and will be adequate to heat most small hobby greenhouses. If you have a larger greenhouse you would simply add a heater or two. There is a formula to calculate how many BTu’s will be required to heat your greenhouse based on the size of your hothouse, the glazing type, the indoor and outdoor temperatures. Please be sure to follow this formula, or your heater may be too small to get your greenhouse to the desired indoor temperature. Plan ahead. Winter is headed our way. Don’t be left out in the cold this year!


What Tools Do You Need in Your Greenhouse?

Acadian Lean to Greenhouse

Plants Growing in A Lean To Greenhouse

If you are in the process of designing or purchasing a greenhouse you probably have questions about what accessories you should purchase with the greenhouse. I get asked this a lot. Some people want to completely ignore the accessories, while others have read every article and believe they should buy everything that you can put in a greenhouse. My recommendation is to start with the ventilation package. Yes, you will need it even if you are only overwintering plants and even if you are in a cold location. I have seen sunny winter days when it was 60 degrees outside and my fan and shutters were operating. And, I keep my ventilation system set at 90 degrees. On the other hand, I hate to see people load up on a lot of items that they will never use. A heater is a good idea, if it is close to the time of year you will need it, or if any modifications to the structure are needed to accommodate for vents, etc. I think the rest of the items should be added as needed.

Here is a nice article from our friends at Garden and Greenhouse which talks about some small hand tools and re purposed items. These are things probably most of us would never think about, but will be used over and over again.

Inexpensive Tools and Materials Every Small Greenhouse Grower Should Have

If you already have or are thinking about getting a greenhouse you should consider purchasing several inexpensive tools and related products. Although the items are not very expensive they can make a difference in how much you enjoy greenhouse gardening and how efficient you are at doing it.


The Key To Optimal Growth in Your Greenhouse

Growing Healthy Plants in Greenhouse

Greenhouse and Indoor Garden Growing

This is an excellent article from our friends at Garden and Greenhouse magazine regarding the need for consistency in your greenhouse environment. In order to have the best, consistent growth it is important to have the best, consistent climate. Although I must say that I find this a little bit more on the advanced end of greenhouse growing. I do not suggest that someone jump in with every known greenhouse accessory when initially purchasing their greenhouse. I recommend getting a ventilation system, as it is an integral part of the building. You can retrofit them, but it is easier to install them when you are putting up your structure. A heater is also a good accessory to order with your greenhouse. As far as some of the other systems are involved, I suggest experimenting and finding out what  you need rather than outlaying a bunch of money for accessories that your climate or plants may not need. Unless  you are an experienced orchid grower, for example,  you will know what humidity, etc your plants will need. Then it would be a wise decision to get your greenhouse set up with these systems at the beginning.

The Importance of Consistency in Greenhouses and Indoor Gardens

Consistency is the key to unlocking the maximum potential of an indoor garden or greenhouse. Plants thrive on consistency. Plants respond best to light energy, atmospheric conditions, and nutrients when they are kept as consistent as possible. Like people, plants burn sugars to provide energy for growth. In contrast to people, plants have the unique ability to create those sugars from sunlight. The creation and consumption of these sugars are actually part of a chemical equation. In other words, there are countless chemical reactions occurring at all times within and around the plant that contribute to healthy development.

When atmospheric conditions, lighting and nutrient levels are at optimal levels, the plant has everything it needs to make those chemical reactions happen without interruption. When the chemical reactions can occur without interruption, the plant’s growth rate is maximized. Maximizing the potential of a particular crop is the goal of just about every indoor horticulturist or greenhouse hobbyist. In order to maximize the potential of an indoor garden or hobby greenhouse, a horticulturist should closely monitor the consistency of the garden’s temperature, humidity, lighting and nutrient solution. Each of these factors has a significant effect on the chemical reactions that contribute to plant growth.


Double Polyfilm Greenhouse

Greenhouse With Inflated Double Polyfilm Glazing

Double Polyfilm Greenhouse

There are many benefits to polyfilm greenhouses. One thing is that some municipalities will consider this a temporary structure and will not require permits, wind and snow load ratings, etc. They are also less expensive than a rigid polycarbonate covered greenhouse. One disadvantage to this is that most of the greenhouse polyfilm found today has a 4 year UV protection, so you will have to figure on replacing the covering every so often. Double polyfilm greenhouses consist of 2 layers of polyfilm with an air inflation system for greenhouse film blowing air between the 2 layers. This will give you a much better R rating than just a single layer of film. Manufacturers claim that it can save you up to 40% of your energy costs. That is quite a considerable savings. I find that the inflated film is more rigid and less susceptible to damage than a single layer of film. This all happens without lowering the light transmission properties of the polyfilm. This is an excellent choice that has been used by many commercial growers through the years and is totally acceptable for a backyard greenhouse operation. Be sure to use greenhouse polyfilm that is UV protected and has an anti condensate coating on it. If the film is not UV protected you should not expect to get any more than one years use out of it, sometimes even less. The anti condensate coating keeps droplets from forming on the film. This will contribute to the overall health of your plants. Any condensation that does form on the roof will come off in sheets rather than in droplets. If you have water dripping on your plants you will have damage to your leaves, fruits, flowers and overall less healthy plants. So, when considering your first or next greenhouse, take a look at a double polyfilm greenhouse and see what benefits it will give you.