Greenhouse Vegetables

Speedier Veggies With Black Plastic Mulch

Gardeners in cooler climates are faced with the same dilemma almost every spring. The nights remain cool and the soil in the vegetable bed just refuses to warm up. Yes, they can sow some of the cool-season vegetables while the ground hasn’t yet warmed up (spinach, beets, radishes, peas, lettuce, etc.), but warm-season vegetables like things decidedly hotter: tomatoes, peppers, melons, sweet potatoes, etc. So, you wait, and wait, and wait. 

Or you heat up the soil.

That’s where black plastic mulches come in. Sold in garden centers and online, they’re designed for a lot of things: to keep weeds down, to reduce evaporation, etc., but they’re also marvelous at raising the soil temperatures in spring.

Tomatoes planted out early using black plastic mulch. Photo: Nick Warren,

The soil under black mulch will warm up quickly, in about 4 to 10 days, depending on local conditions. Then you simply punch holes through the mulch at the desired spacing and plant your tender vegetables in the holes. Dig! Drop! Done!

Well, sometimes.

Often, although the soil is now warm enough, the night air temperatures are still too cool for your plants. Consider 55˚F (12˚C) to be a minimum, while 65˚C (18˚C) is much, much more to their liking.

A mini-greenhouse will keep your plants even warmer. Photo:

So, add a step. Cover the plants with mini-greenhouse of some sort: a cloche, a transparent tunnel, a “tomato tipi” or just a sheet of transparent plastic raised on stakes. A mini-greenhouse combined with black mulch will keep plants nice and warm even on nights of light frost!

However, you’ll have to open or remove your mini-greenhouse on hot days and remove it entirely when summer settles in; otherwise the poor plants may cook in the heat!

What gardeners won’t do to get the earliest possible tomatoes and melons!

Garden writer and blogger, author of more than 60 gardening books, the laidback gardener, Larry Hodgson, lives and gardens in Quebec City, Canada. The Laidback Gardener blog offers more than 2,500 articles to passionate home gardeners, always with the goal of demystifying gardening and making it easier for even novice gardeners. If you have a gardening question, enter it in Search: the answer is probably already there!

1 comment on “Speedier Veggies With Black Plastic Mulch

  1. Goodness; that is too much work for vegetables that should grow like weeds. Well, if it is any consolation, we don’t grow peas, and can only grow cabbage, broccoli and cauliflower through winter.

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