No, you don’t need a greenhouse

I often hear people say “I need to get a greenhouse” very early on in their gardening lives. They assume that a greenhouse is just one of those big things you need to “garden right,” like a hose and seeds.

Nope.

I owned a greenhouse for four years, and while it had its good points, I am not in a hurry to do it again. Here are my observations, based on my own greenhouse, those of friends, and my stint working on a commercial organic farm – you make your own decision.

Particulars of my greenhouse

  • 8×12′ “barn-shaped” twin wall polycarbonate greenhouse – NOT very air-tight
  • No irrigation system (beyond dragging a hose in the door and watering)
  • Automatic vent openers failed again and again, so venting was manual (roof, gable end, and door). Rigged window screen and a low fence in the door to keep critters out when the door was open
  • Oriented on east/west axis (so the long sides faced north and south)
  • Very exposed site
  • Insulated with straw bales around base each winter
  • Southern Michigan, zone 5, min temp -30

Basic physics and maintenance

  • A greenhouse this size (or smaller) doesn’t have the thermal mass to avoid big temperature swings. There was a huge danger of freezing/cooking crops…perhaps in the same day.
  • In the winter, it was generally 5-10 degrees warmer than outside.
  • By May, it was regularly too hot for any cool-weather crops, even with the vents open.
  • Summer temps (with all vents/door open) were generally around 100 degrees.
  • Greenhouses are NOT good places for starting seeds, due to temp swings and pests. Much better to start indoors under good lights.
  • I could not water it enough in the summer months to allow warm-weather crops to thrive. And, because it wasn’t movable, it never really recharged the soil moisture over the winter.
  • Pests LOVE greenhouses. Aphids, hornworms, voles, chipmunks all flock in there because you’ve protected them from the elements and predators.
  • In short, you have to be much more hands-on in a greenhouse and provide for more of its needs than in an open-air garden.

Good points

  • Somewhat extended growing season.
    • Peas in greenhouse bore fruit 6 weeks before those outside (keep in mind, they were planted 11 weeks earlier than those outside).
    • Kale overwintered reliably and resprouted in spring, resulting in huge harvests in April and May.
  • Amazing to have a warm place to sit in the sun on sunny winter days.
  • Friends who have somewhat larger, better-sealed hoop houses (often with chickens/rabbits in the mix) have had much better luck with extended harvests.

If I did it again…

  • I’d make it bigger.
  • I’d use a solid, insulated north wall and add thermal mass in any way possible.
  • I’d have some kind of irrigation on a timer. Knowing myself, I can’t be bothered to water every day, and timed irrigation is the only way I’d keep the soil hydrated.

My conclusion

For me, home-sized greenhouses aren’t worth it. I will gladly buy produce from farms with commercial-sized hoop houses for the early spring months. I will start seeds indoors under lights. I will grow a few greens in a southern window of my house in February. But I’d save the money and hassle of another big thing to maintain and not buy another greenhouse.

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1 Comment

  1. August 23, 2017 at 2:19 pm

    […] No, you don’t need a greenhouse […]


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