Greenhouse Growing 101

If you're a control freak, and can't stand the uncertainty of growing outdoors with the whims of Mother Nature at the helm, greenhouse gardening may be the growing method you've been searching for. It's relatively easy and cost-effective and once you've got the environmental controls down, it can provide a lot of fun and rewards.

A greenhouse is the perfect place to germinate seeds and allows you to extend the natural growing season. So if you want to grow vegetables year-round, it may be a reality if you're willing to put in the work and if greenhouse growing is practical given your geographical location. But with such control, comes a lot of responsibility and work, which we'll get to later.

There's nothing new about greenhouse gardening. The concept of using an environmentally-controlled apparatus to grow year-round has been around since Roman times when cucumber-like vegetables were planted in wheeled carts, which were put in the sun during the day, and taken inside at night to stay warm. Roman emperor Tiberius had an affinity for these vegetables so they were provided at his table every day and grown using artificial methods.

Technology continued to evolve but for the most part, was reserved for the rich and elite. The playing field is more level today, as most home growers can afford a plastic or glass greenhouse.

Today's gardeners have a few more advantages over those growing using greenhouse concepts thousands of years ago in that factors such as temperature, humidity, soil aeration, soil moisture and drainage, fertility levels and light are mostly within one's control. But before embarking on a greenhouse growing adventure, there are a few tips to be mindful of, especially if you're just starting out.

The main greenhouse gardening factors are light, temperature, ventilation and watering. But that's just touching the surface; the more you get into this style of growing the more you recognize virtually everything is within arm's reach, from the lighting to pollination. But first things first: if you're not up to speed on the basics, the whole thing can wither away and die before your eyes.

Keep in mind you don't need a bunch of fancy equipment to grow in a greenhouse. In fact, simplicity can be your friend here. Then, once you've got a grip on the greenhouse, explore more. For now, let's focus on getting those plants growing.

What You Need to Start a Greenhouse

Seeds or starters

Seeds can easily be propagated easily inside a greenhouse. They are the cheapest way to go and provide the greatest sense of pride for the grower. If you don't have the patience or time for seeds, starters are almost always available at your local nursery.

Whatever you're planting, however, be sure that you're growing sturdy, productive, disease- and pest-resistant plants. The last thing you want is a species prone to aphids regardless of ideal growing conditions, or plants that need constant feeding and attention. Next, you'll want to find soil, containers, and fertilizer.

Soil

First of all, do not use unsterilized soil. Going cheap and easy doesn't pay off, and may end up causing more problems in the long run. Unsterilized soil often contains parasites, but if you insist on using dirt that's straight from the ground or otherwise previously used, do yourself a big favor and sterilize it.

Bake it, if you will, by placing in the oven for an hour at 250°F, being sure to thoroughly moisten it first. And be prepared to leave the kitchen while this is going on, as the scent isn't terribly pleasing.

Once baked, add about one tablespoon of fertilizer to each gallon of soil, and blend. You can always make your own soil mixture, but if you want to save yourself some time and messiness, just skip it all and throw down some money on soil. Save yourself from the hassle and get into the best part of it all, the actual growing.

Containers

Just as your soil should be either fresh from the store or sterilized, so should the containers you'll be using. Keep in mind that plants should only be transplanted once due to the shock to the plant, so go big, but be realistic. Be sure that the container is deep enough for the plant's root system, as root-bound plants aren't healthy plants.

If sterilizing a container, use a bleach mix of one part bleach to 10 parts water, or half water and half vinegar. Then submerge the container in the solution for 30 to 45 minutes, being sure to remove caked-on dirt and debris with a scouring sponge. Rinse thoroughly afterward with warm water and allow to completely dry before putting more life back into them.

Fertilizer

Most plants like food, but can be hurt if the grower feeds it too much. Keep in mind that most commercial soil already has nutrients to sustain plants for about three weeks. So introduce fertilizer gradually, being sure to start with a diluted solution and slowly increase the dosage. Starting off with a high dose can burn a plant and damage its roots. Be slow, be mindful and be aware that adding fertilizer changes the pH of the soil, making it more acidic.

Factors Affecting Growth in a Greenhouse

Humidity

While rainforests are ideal environments for some plants, such a climate can actually hinder plant growth if humidity levels get too high. Levels should be between 70 to 85% during high-growth periods, and levels between 90 and 95% should be avoided if possible. Too much humidity can weaken plants and encourage early bolting and fungal diseases, making otherwise sturdy, healthy plants limp and prone to problems that will only compound and leave you with a mess to clean.

Humidity levels can be lowered through venting, exhausting humid air and watering only when needed. If you need to increase such levels, spraying water on the floor can help. Moisture levels can also be upped by placing containers of water in the greenhouse, allowing it to evaporate to maintain humidity levels.

Watering

This is a no-brainer, but it's usually the overabundance of water or lack thereof, that can kill. So be mindful-water is necessary, but the amount and frequency depend on temperature, length of day, plant size and growing medium. Many recommend thoroughly soaking the plants once a day, but too much water can be harmful as well. It's a balancing act.

Use well-draining soil and be sure the pots are equipped to allow excess water to drain away from the plant's roots. An abundance of moisture can lead to root rot, killing the plants. If you can only water once a day, do so, but if your schedule permits watering in smaller amounts twice daily, take the time.

And with the exception of the hot summer months, many crops can be watered every other day. Also, remember to kill the chlorine. Allow the water to stand for 24 hours in an open container, which will not only help to evaporate the chlorine but will also bring it to room temperature, allowing you to avoid the shock that your plants receive when given cold water.

If there's too much chlorine in your water, you may want to invest in some anti-chlorine drops at your local pet or fish store.

Ventilation

Just like people, greenhouse plants require fresh air often. It's arguably the most important part of a successful greenhouse, as it helps regulate temperature, provides plenty of fresh air for photosynthesis, prevents pest infestations and disease, and encourages pollination.

Stagnant air can provide breeding grounds for unwelcome pests, fungi, mildew and diseases that take advantage of such an atmosphere, so make sure the greenhouse is well-ventilated by opening some windows or getting a fan.

Use rooftop air vents to allow moisture and heat to expel naturally, or invest in fans, air circulators, screens and other equipment to manually control the greenhouse environment.

Light

Full sun on your greenhouse is best, and can cut down on the need for additional heat during the winter. Remember that you can always provide more shade to limit the sunlight, but you can't bring in additional sun once it's been blocked by the shade. But when natural lighting isn't cutting it, artificial means are the next best thing.

Depending on your plants' needs and the time of year, they will require between six and 12 hours of light daily. There are a myriad of types of artificial lighting, which require entire articles of its own. So choose according to plant needs, and don't skimp on this investment.