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Avoid Over-Crowding the Vegetable Plants

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How & why to avoid a crowded greenhouse

Crowded greenhouses are mixed blessings! In fact, overcrowding a greenhouse¬†— or even in a planting bed — is a sure-fire way to invite pest and disease problems. But it can also be highly productive and desirable. However, if you’re like me and unwilling to spray pesticides and fungicides, then keeping your greenhouse clean and free of unwanted yuck may be difficult.
Crowded greenhouse
I think of this when my greenhouse starts getting impassible: “Oh, here go hell come.” (Calvin Tran).

What can cause a crowded greenhouse?

Gardeners employ greenhouses to maximize their gardens. That’s because greenhouses help plants grow faster, earlier. And they mostly do this by increasing warmth. Plus, they may intensify light. And those are two things most plants need to really thrive. But when plants get too happy in a greenhouse, that space may become overcrowded fast. In fact this is especially true when we have many plants growing together in tight greenhouse growing spaces.

So if you’re growing, say, tomatoes and cucumbers in your late summer or spring greenhouse, you may end up with issues. That’s because these intense heat lovers rapidly crowd each other with overlapping vines and leaves. Then the problems may quickly begin.

Why are crowded plants a problem?

When plants crowd each other a few problems happen. First, when one leaf overlaps another, the bottom leaf gets shaded. And a plant in shade can’t photosynthesize well. So because photosynthesis is how your plants feed themselves, that shaded plant may become weak. Moreover, when plants become weak, they become targets for pest and disease. So this is one reason to not have keep a crowded greenhouse.

How can I reduce crowding & maximize plants in my greenhouse?

There are a few easy things you can do to maximize greenhouse productivity. And it is possible to do this without running into potential problems of a crowded greenhouse.
healthy crowded greenhouse with ventilation

5 Simple tips to grow a healthy greenhouse garden:

  1. Maintain airflow in your greenhouse to keep it healthy. This may mean you open the doors (or dutch doors). As well, you may wish to include vents in your greenhouse plans. Moreover, adding fans can also help ventilate your greenhouse. In fact, ventilation is key in any indoor gardening situation!
  2. Don’t allow plants to shade each other. So for instance, trim tomato suckers regularly and try growing them vertically in a greenhouse.
  3. If you see disease begin, cut it out immediately. Or remove the plants from your greenhouse to stop the spread of disease before it spreads to other plants. So for instance, if you see powdery mildew on your cucumber leaves, get rid of the leaves fast. Or take the plants out of the greenhouse. The reality is, as you plant materials begin to get dense in your greenhouse, moisture may build up. Wet coupled with moisture is a recipe for fungus and mildew problems.
  4. If you see insects on your plants, get them out of the greenhouse right away. Increasing airflow may help, but once unwanted pest insects like aphids or thrips are visible on your greenhouse plants, it may be too late. So, save the other plants, by removing the pest infested right away.
  5. Plan your greenhouse growing season carefully. This means use a calendar to map out what will be growing in your greenhouse month by month. For instance, you may choose to over-winter house plants in your greenhouse. And later you may want to start seeds for spring in there. But you’ll also need a plan for spacing the seed starts once they sprout. And that may mean you’ll need lots of extra space for those plants as they get bigger and bigger. This can get complicated. So, in conclusion, if you need help planning your garden season-by-season, sign up for our online gardening academy to get lots of growing information as well as seasonal gardening guides and planners!

2 comments on “Avoid Over-Crowding the Vegetable Plants

  1. Amy on

    Hi there,

    I found you through Willi’s capture of your greenhouse in her Kitchen Gardens Pinterest board. We just tried our first greenhouse last summer (purchased, on sale, demo floor model) and it wasn’t great…no easy ventilation led to incredible heat inside during the height of our late prairie summer (Western WA, Thurston County). I was afraid to keep any plants in it, for fear they’d burst into flames! It’s not very nice to look at, either. I’d prefer something like yours, but I’m curious…how did it fair in winter? Have you had to deal with much snow load? (We get more than Seattle, normally…last month’s freak storm brought 14″, which was excessive, and in other years we’ve had only 8″ but lows as low as 4 degrees.)


  2. Garden Mentors on

    Amy thanks so much for following Willi and for getting in touch re: our greenhouse. I’ll tell you, I still really love this greenhouse. I’ve had it several years now, and it hasn’t needed any repairs yet. We’re getting a bit of algae build up at the polycarbonate cut points, but it isn’t bad. It tends to dry out and fall off by summer and never creeps up the walls to block light (yet).

    As for snow load. As you know, we don’t get a lot of snow in Seattle, but we did get hit pretty good with snow then heavy ice earlier this winter. And, it was no problem for this greenhouse. The roofline is very steep, so snow doesn’t usually pile up for long on it. Nothing broken at all to date.

    There are several posts and pics of this greenhouse throughout And, you like Pinterest, please follow us at

    Again, thanks!

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