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.


Growing Asparagus


Growing asparagus plants

Growing Asparagus

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Growing Asparagus

Like most things in my life, I like my asparagus prepared simply. I love to just steam it lightly. Then I take some extra virgin olive oil, a few drops of lemon juice, a touch of salt and some freshly shredded parmesan. I toss everything together and that is it. I am getting hungry just thinking about it. Unfortunately, the harvesting season for asparagus is for such a short period it is hard to enjoy it all year long. But, the good news is that if fresh asparagus is blanched and frozen, it will preserve well.

Asparagus Facts

Asparagus is typically thought of as being green. But, there are purple hybrid varieties as well. Don’t get too excited about this. If you cook the purple asparagus it will revert back to the green color. That is not the case for white asparagus. It is most desired because it is considered less bitter and more tender. The white color is obtained by keeping the asparagus covered with dirt while it is growing. There is no exposure to the sun so there is no photosynthesis which produces chlorophyll. The chlorophyll is what causes the green color.

  • This plant is a perennial, which means that it lives more than 2 years. Actually it will last a lot longer than that. A well maintained asparagus bed may live up to 15 – 20 years.
  • The plants grow 39″ to 84″ tall.
  • Asparagus is approximately 93% water.
  • Plants are either male or female. Female plants produce a red berry which is poisonous. They will appear after the fern like leaves are already open.
  • There are some hybrid varieties available that only produce male plants. These hybrids are also resistant to some of the more common diseases that plague asparagus such as Fusarium or crown rot.
  • Asparagus does not like to compete with weeds. Be sure to keep your bed weed free.

Planting Asparagus

Asparagus will only grow in zones 4 – 8. You can plant this from seeds, but it will add an additional year onto the time to harvest. Most people will  plant crowns. These are 1 year old dormant plants that can be purchased from seed companies. Yes, they are more expensive than the seeds, but considering the lifetime of the plants, I would opt for getting to harvest a year sooner. This is a plant that does extremely well in a raised bed growing situation.

Crowns should be planted in sunny, well drained, loose soil in the Spring and in the Fall in some warmer climates. In the Spring you should plant outside 4 – 6 weeks before the last frost date. It prefers a pH of 6.5 to 7.5. You should test your soil first and amend before planting if needed.  To plant dig a trench that is 12″ to 15″ wide and 6″ to 8″ deep. If you are planting multiple rows they should be 3′ apart. Soak your crowns in water for 15 – 30 minutes before planting to be sure they are hydrated . Place a small mound of dirt in the bottom of the trench. Place your crown on this. Be sure to fan out your roots around the crown. Fill in you trench . Water immediately after planting. Cover your bed with mulch to help control weeds and maintain moisture levels. Do not use straw as it may contain seeds.

Growing Asparagus

  • Asparagus grows best in temperatures of 65 to 85 degrees F.
  • Production is inhibited at temperatures of 50 degrees F or lower.
  • Keep your beds weed free.
  • Do not over water as this plant does not like wet roots.
  • Keep any mulch off of the plants as it may cause rot.
  • Fertilize before the spring growth and right after harvest
  • Use a fertilizer high in Nitrogen (N) and Potassium (K) and lower in Phosphorus (P)
  • cut back stalks to the ground in fall


During the first year you should maintain the plants per their requirements. But, you will not harvest during the first year. During the second year you can harvest lightly. The third year is when the bed starts to come into full production.

Plants should be harvested when they are 6″ to 8″ tall. You should not harvest plants that are under 1/4″ in diameter. With ideal growing conditions this plant will grow rapidly. You should check for plants to harvest daily during the short 8 week harvest period. You should cut the plants at the soil level using an asparagus knife.

Preparing Asparagus

Asparagus can be steamed, boiled or blanched, roasted, stir fried or it can be eaten raw. Asparagus can also be preserved by freezing or pickling. It is simple to prepare. The woody ends must be removed. To find where this is you would simply hold each end of the spear and flex it. The best way to do this is to just break it while you are bending it. You can however pile up the whole batch and use a knife to cut off the bottoms. Asparagus should be thoroughly rinsed under water before cooking or eating.


This plant is high in many vitamins, but it has very few calories. It is a good source of antioxidants and has been known to help lower blood pressure. Plus, it is simple to prepare and oh yeah, tasty. Go out and plant some asparagus today!

7 Top Ways to Cool A Greenhouse Without Electricity

Cooling a Greenhouse without Electricity

7 Top Ways to Cool A Greenhouse without Electricity

7 Top Ways to Cool A Greenhouse Without Electricity

You want a greenhouse. You know it will build up a lot of heat during the day. Even on sunny days in the middle of the winter. You want to put it by your garden in a remote corner of your lot. Or maybe, on some land that you own that is undeveloped. What do you do? Fortunately, there are multiple options for cooling your greenhouse even when you don’t have electricity. Let’s take a look at the options.

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1) Shade cloth –

Greenhouse Shade Cloth

Reflective Shade Cloth

This one is a no brainer. Just install a shade cloth over the top of your greenhouse. It has much the same effect as standing under a shade tree in the summer. The shaded area will be cooler. Shade cloths are available in a woven, knitted or reflective material. The woven material will ravel when cut and it is necessary to put tape  on the edges. Knitted shade cloth has more give than the woven and does not require taping, although we prefer to do this as you can then put grommets in the tape. You can run a bungee or cord through the grommets to attach the cover to your greenhouse. There is also a reflective cloth available which is much more efficient. They result in lower greenhouse temperatures and a more consistent environment. Shade percentages run from 50% to 70% for greenhouse use, maybe lower for plants will low light requirements.

2) Roof vents –

Greenhouse with open roof vent

Greenhouse with open roof vent

Chances are if you are purchasing a greenhouse kit, it will have roof vents. There are very few kits out there without roof vents, and if you are building your own greenhouse, this is a highly desirable feature. We all learned in high school that warm air rises. Have an opening such as the roof vent in the top of your greenhouse, and the hot air will exit. Manual roof vents are available, but the best way to take advantage of this feature is to have a solar powered opener on it. That way if you are not at the greenhouse every day, you will know that the vents are opening and closing at appropriate times. These solar powered openers are basically wax cylinders. They work on the principle of contraction and expansion. When they get warm they expand, pushing the vents open. When they get cool they contract, pulling the vents shut. These can be adjusted to a certain degree to open and shut at desired temperatures.

roof vent with solar opener in polyfilm greenhouse

There are also roof vents available that will go directly into a polyfilm greenhouse without additional framing. They have the solar powered openers. These vents can be retrofitted onsite to fit in a polycarbonate greenhouse.


3) Side vents in conjunction with roof vents –

Greenhouse with side vent

Greenhouse with side vent

If you place a side vent with a solar powered opener below your roof vents you will get even better ventilation in your greenhouse. We like to place these approximately 6″ from the bottom of the greenhouse. This will give you a chimney type effect drawing the air from the bottom to the top of the greenhouse. We also use the wax cylinders on these to keep things simple.

4) Roll up side curtains –

greenhouse roll up side curtains

greenhouse roll up side curtains

If you have a greenhouse with straight side walls you can install roll up curtains. Using these you can roll the greenhouse sides up during the hottest times of the year. These systems operate with a hand crank or can be automated. These come with a heavy duty 12 mil coated weave fabric. It is recommended to use a kneewall with these systems. That way your plants will have protection from the wind when the curtains are open. Also, if you are in a heavy snow area, this will keep the snow from laying up against your curtain.

5) Solar Powered Ventilation Package –

solar powered exhaust fan

solar powered exhaust fan

These operate on the same principle as a wired ventilation package. But, they are powered by a solar panel. The exhaust fan goes up high in the backwall of the greenhouse. The intake shutter(s) go down low on the opposite wall. The exhaust fans are wired to a thermostat. The manual intake shutters will open to allow fresh air into the greenhouse. The exhaust fan will draw this air through the greenhouse, cooling the air. No electricity is required, you are creating your own power.

6) Solar powered circulating fans –

12 inch solar powered greenhouse circulating fan

12 inch solar powered circulating fan for greenhouse

Circulation fans are essential to the healthy greenhouse. They will increase CO2 availability, an essential for plant growth. They help to reduce excessive moisture creating an environment which reduces disease and pests caused by humid environments. They also help strengthen the plant stems with the same motion as a mild breeze when the plants are grown outside. These are fans that run low and slow.

7) Misting Systems –

Misting systems may be used if you have water to your location. They will help to lower the heat in a greenhouse. These can be set up on a battery operated timer, so no electricity required. These cause a cooling effect by tiny water droplets evaporating.

In Conclusion

I have been fighting an uphill battle at times throughout the years. New greenhouse owners just do not understand the heat that will build up in a greenhouse during sunny days, even in the middle of winter. I have seen my ventilation package come on during a sunny 60 degree February day. And, I keep my thermostat set at 90 degrees. Quite a difference that you really would not expect unless you have experienced it. Proper ventilation is an essential item for your greenhouse. It will keep your plants healthy and happy. No more baked tomatoes on the vine. You will have to pick them and put them under the broiler in the kitchen  for that! These options discussed above provide you with the opportunity to supply adequate ventilation to your greenhouse even when they are in an area with no power available. So, no more excuses. Get out there and build yourself a greenhouse today. I will also be discussing heating your greenhouse without electricity when the season dictates. Good Growing!

Advance Greenhouses Turns 15 on August 14, 2017

Greenhouse with Polycoolite glazing in the snow

Advance Greenhouses Personal Greenhouse

Yep, That is Tom and my greenhouse. We really do practice what we preach. We think everyone in America should own a greenhouse! This was a rare snow storm in SE Louisiana. I don’t think the neighbors could even believe that we were outside in this mess. Today I just wanted to take a minute to reflect on the beginning and growth of Advance Greenhouses. Fifteen years ago Tom and I were studying how to get on the internet. We knew the product we were interested in, as we had been selling and installing greenhouses for a while. Our first adventure with polycarbonate was in 1993. We got a book about 4 inches thick on how to set up a website and dove into it. What in the world language were those people using? Something I had never heard of before. I am sure we fought and cussed our way through it and came up with what was an absolutely horrible website. But, people started to find us. We also did a lot of local garden shows to put the word out. Fifteen years later, here we are. Through the years we have had the pleasure of speaking and working with many like minded people. We love flowers, but we also love fresh food that we have grown for ourselves. Our greenhouse has been multi faceted. We have stored my cherished hibiscus plants, started seeds for the garden, started annuals and perennials for the flower gardens and even grown some food hydroponically in our greenhouse. As I tell people, it is a learning curve to figure out exactly what will work in your greenhouse. There are some hard, fast rules, but we are all growing different plants under different circumstances. We all have to do a little bit of experimenting to figure out what works exactly for us. In closing, we are running some sales this month as a customer appreciation (also an appreciation for what we have thanks to all of you). Visit our website to see the specials. Our business is very personal and very rewarding for both of us. Thank You! Tammy and Tom