The 5 Biggest Mistakes Made by Beginning Greenhouse Gardeners

by Jason Stuck of Growing Spaces

As an enthusiast gardener wanting to extend your growing season, the right greenhouse can provide a safe, protected space for your dream garden. Greenhouse gardening allows you to enjoy fresh produce, herbs, flowers and even trees whenever your outside garden isn’t viable. Imagine having a warm, vibrant oasis teeming with life right in your backyard while it snows outside!

A reliable greenhouse that will last you many seasons can be a significant investment in money, time and focus. Unfortunately, many beginning greenhouse gardeners make common mistakes that end up turning their investment into a barren extra storage space. Don’t let this happen to you.

With a little bit of planning and insider knowledge, you can set yourself up for success and enjoy a beautiful lush greenhouse full of thriving food and plants.

Mistake #1 — Choosing the Wrong Greenhouse

Not all greenhouses are created equal. There are many factors that determine which one is best for you. In a sea of confusing options, it can be hard for a newbie to know what matters, and what doesn’t.

The lowest cost greenhouses — such as hoop houses, and other DIY models — are easy to construct. You can grow a lot of food in them and they are relatively inexpensive in the spectrum of greenhouses. This can be a tempting place to start for a new greenhouse gardener. However, while you invest less money and time upfront with these types of greenhouses, they will not last as long as other types. They’re likely to be damaged by heavy snow and high wind. Also, they may not extend your growing season as long as you would like. They cost a lot to heat and cool, and the covering needs to be replaced frequently. Thus, while your upfront costs will be lower, operating, maintenance and repair/replacement costs will be higher. Nonetheless, if you are unsure whether greenhouse gardening is right for you, it may make sense to experiment with one of these types of greenhouses first to get your feet wet.

However, if you are certain you want the benefits of a year-round garden, then a higher-quality, more robust type of greenhouse — such as a growing dome — is a wiser investment. While quality greenhouses cost more up front, they are significantly stronger and will last much longer. And if you choose to grow food, your return on investment can be offset in just a few years from your savings on fresh produce.

To help you decide which type of greenhouse is right for you, consider these questions:

  • How much space do you have outdoors that can be dedicated to the greenhouse?
  • How many people do you want to feed?
  • What kind of plants do you want to grow?
  • What’s your budget and how much are you willing to invest in heating and cooling?
  • Do you want to extend your growing season a few months on either end of your frost-free days, or do you want to grow all year round?
  • What kind of climate, and microclimate, do you live in?
  • Do you want to use your greenhouse for non-gardening activities such as yoga, meditation, reading, etc.?
  • Do you want to experiment with as little investment as possible to see if greenhouse gardening is for you? Or are you ‘all in’ and want to avoid future hassles and expenses by building a long-lasting greenhouse so you can just start planting?

Your answers will determine the type of greenhouse that will best suit your situation. Consider your gardening goals and make sure you end up with the greenhouse that matches your needs and your lifestyle.

Mistake #2 — Choosing the Wrong Location

Once you’ve identified the perfect greenhouse for you, where are you going to put it? On the north slope of the forested hill out back where the view is best? You’d be shocked how often new greenhouse gardeners choose the worst possible spot.

Since most greenhouse gardeners start their gardening lives outside, they pride themselves on their outdoor garden plots. They take great pains marking the ground, preparing the soil and fencing out critters. Detailed analysis goes into picking just the right spot with the perfect amount of sunlight. Because sunlight is critical for your garden, right?

Yet many of those same accomplished outdoor gardeners fail to factor in sunlight when they move their gardening indoors. Just like your outside garden plot, you want to have sufficient sunlight coming through to your plants in your greenhouse. Pay close attention to the angle of the sun on your chosen location. Make sure you get enough sun exposure. Also, consider objects that will block the sun such as trees, buildings or your neighbor’s house. Ideally, you want to know the path of the sun throughout the time of day, and throughout the seasons, for your chosen greenhouse location.

Just as important as ensuring enough sunlight, you need to consider that, by design, greenhouses get hot. So if you’re not careful, they can get too hot and cook your plants in the summer. Depending on the type of greenhouse you decide to grow in, one way of dealing with this is to place your greenhouse in the shade of a deciduous tree. In the summer, the foliage will block some of the sunlight from reaching your greenhouse, and in the winter, the tree will have dropped its leaves and allow more sunlight in. It could be risky. It’s difficult to judge how much light and heat a tree will block out in the summer, and how much it will obstruct in the winter — but when you find a sweet spot, it can help regulate temperature. Fortunately, there are other ways to regulate temperature that we’ll get to later.

Mistake #3 — Planting in Unhealthy Soil

Imagine investing in a greenhouse, putting it up, loading it with plants and … crickets. Or whiteflies and aphids. After all the planning, research, and hard work, having a greenhouse garden that won’t produce is heartbreaking. Beginning greenhouse gardeners often make this frustrating mistake. Not ensuring healthy soil before planting wastes effort, money and time.

When it’s all said and done, your greenhouse should provide an ideal container for plant growth by giving plants what they need… good soil. Not dirt, but living nutrient and mineral-rich soil. There is a direct correlation between the health of your soil, the health of your plants (and the health of your body, but that’s another article).

To avoid frustration and wasted investment of resources, invest in quality soil from the beginning. Plan it into your budget. It makes zero sense to invest in the safe haven of a greenhouse and fill it with dead lifeless dirt. Invest in the best soil you can find. It will be a worthwhile investment in your health, well-being and gardening happiness.

Mistake #4 — Planting Too Much

After you have the right greenhouse situated in the sweet spot on the landscape, filled full of rich soil, you will want to fill it brimming with plants. That was the whole point, after all… right?! You want to fill up every spot of soil with seeds and transplants. Lettuce and chard everywhere. Churn out your bumper crop from the first season on. But wise greenhouse gardeners will tell you, “Resist this temptation.”

While greenhouse growing gives you untold advantages, it is not a magic pill without challenges. By moving your growing inside you lose certain beneficial qualities of growing outside that you may not realize. For example, in a greenhouse there is no natural gentle breeze. You must create air circulation with open doors, window, fans or other design elements. With limited air circulation, plant density becomes critical.

Optimal spacing between plants is always important whether indoors or outdoors. But in a greenhouse, it’s important to pay careful attention to the density of growth. Leaving plants densely growing together can spell disaster. Therefore, be sure to keep plenty of air circulation by not overplanting.

Mistake #5 — Watering Too Much or Too Often

Watering your greenhouse garden might become your new meditation practice. There is something so deeply fulfilling about caring for and tending a garden. Watering gets you moving, gently observing and activates your senses. You smell the richness of soil, the green growth of plants and the fragrance of blossoms in the air. Watering your garden instantly lulls you into a peaceful mind with a caretaker’s attitude.

And it can kill your greenhouse garden if you’re not careful! The interplay of humidity, temperature and water retention of the soil is unique in a greenhouse. It’s easy to saturate your soil and drown your plants. Over watering quickly leads to mold growth, weakens plants and invites all sorts of pests, bugs and diseases.

To ensure you don’t over water, use a moisture meter to keep yourself in check. They are cheap and effective, will save your plants as well as decrease your water bills, and it will help you keep your gardening peace of mind.

Always test your soil with your moisture meter before watering. Of course, different plants have different moisture needs so check each one. With a little research, and a bit of diligence, you can keep your soil at ideal moisture levels to optimize growth of all your plants.

Bonus Tips for Success —

Greenhouse Temperature Control

Some of the higher-quality types of greenhouses, such as a Growing Dome, offer numerous built-in features that make temperature control worry-free. For example, with a Growing Dome you can have automatic opening window vents, solar-powered air circulation and a built in passive solar heat sink that helps regulate temperatures.

However, if the greenhouse you choose doesn’t provide these benefits, a shade cloth is an excellent way to cut down on light and heat during the summer months. You can find them relatively inexpensive, and depending on your greenhouse structure, they can be easy to install in the summer and take down in the fall. A properly placed shade cloth can reduce light penetration up to 50 percent without depriving the plants of too much light.

Another excellent way to help keep your greenhouse cool in the summer, aside from fans and shade cloths, is to harness the natural power of your plants and the magic of transpiration. In the summer your garden beds get hot. If you have exposed soil, it heats up and acts as a thermal heat sink and radiates heat throughout your greenhouse. Therefore, you need to keep your beds shaded in the summer.

A great way to do this is to plant large foliage plants that will provide interior shade in the summer. One of my favorites is fig trees (because… well, figs!). But they also grow great in a greenhouse and produce large leaves that shade the beds during the hot months. Of course, they’re deciduous and drop their leaves in the winter when you want the most heat and light you can get. If you’re using a year-round, or four-season greenhouse, fig trees can be a great addition to your garden.

By keeping your greenhouse cool in the summer using large foliage plants, you will also get the benefit of transpiration. Plants, and especially trees, move a lot of water. They pull moisture up from the soil and pump it out through their stems, leaves and flowers. They’re like giant misting systems adding moisture and coolness to the air. So that future fig tree of yours is not only deciduously delicious, but also shades the soil and helps keep your greenhouse cool.

In conclusion, greenhouse gardening can be a very rewarding experience. You can extend your growing season, and depending on the type of greenhouse you choose, even grow all year long. It’s incredibly fulfilling to have a warm, green safe haven where you know you can grow regardless of what’s happening outside. And by avoiding these five common mistakes you can enjoy your own fresh produce and a peaceful oasis all year long.

Happy gardening!

Photos courtesy of Growing Spaces

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