How to Make Mini-Greenhouses

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Barbara Hardesty puts recycled material to good use in her organic garden. Here she explains how to make mini-greenhouses.

Large peanut butter jars, translucent plastic milk containers, and one-gallon glass jugs can all be recycled into mini-greenhouses that will give your garden a big jump on spring.

The peanut butter jars, of course, are the easiest to use: just take off their lids, wash the containers, and turn them upside down over whatever in your vegetable patch needs this kind of protection. Last year, for instance, the mulched soil In which I seeded my first planting of pole lima beans was so cold that the beans began to rot instead of germinate. So I replanted the crop with an upended peanut butter jar over every bean. Presto! The extra heat that collected under each cloche brought the limas right up and quickly forced me to remove the individual greenhouses altogether (to keep the new growth inside from being scalded during the increasingly warm and sunny days).

Translucent plastic milk jugs work even better as garden plant protectors (since you can regulate their internal temperatures by removing and replacing their lids). Just cut the bottoms right out of these containers and set the jugs — upright, this time! — down over your early transplants. I find that these particular recycled containers work extremely well with dwarf dahlias (started from seed in a hot frame) when I’m ready to transplant the flowers to the garden. The translucent plastic keeps the dahlias warm and sheltered from the wind … yet protected from the direct rays of the sun. So protected, the somewhat finicky dahlias dig right in and grow vigorously.

My all-time favorite mini-greenhouses, though, are still the ones I make from one-gallon glass jugs. They’re simply ideal covers for my Green Comet broccoli transplants (four broccoli plants per jug!) and other vegetables that I want to set out in the garden well before the danger of spring’s last hard frosts has passed.

You do, of course, have to work a little harder to transform these glass jugs into cloches. I begin by hoarding vinegar, cider, etc., containers all year in an old shed behind the house. Then, once a year, I carry the cache to the picnic table in the back yard and “have at it.”

 Tools you’ll need are a pint jar inverted over gasoline-soaked string, kitchen matches, jug, bucket of cold water, hammer, scissors, glass cutter, and more (sill unsoaked) twine.

  • Step one: I use the glass cutter to scribe what I hope will be a fairly straight line around the bottom of the jog and approximately one inch above the container’s base.
  • Step two: A length of gasoline-soaked twine is next wrapped right over the scribed line and tied. The jog in then balanced upside down, and the string is set ablaze.
  • Step three: As soon as the twine burns down, the base of the container is immediately plunged into the bucket of cold water (before the jog has a chance to cool.)
  • Step four: The bottom of the jug usually falls into the bucket at this point. If it doesn’t, a tap or two with the hammer just below the scribed line finishes the job.

Yes, an assortment of recycled jugs and upended jars running down each row will give your early garden a rather bizarre appearance. But the results will more than justify the Idea. Try it!

Another Way to Make One-Gallon Greenhouses

There’s another way to make mini-greenhouses from gallon jugs that, perhaps, has two advantages over Barbara’s method: It’s easier, and it allows you to pop only the flat bottom from the container while leaving the curved lower edge of the jug for extra strength.

Remove the cap from one of the jugs and set the container in a shallow pan. Then pour one-quarter inch of boiling water into the pan and lot the jug sit in the water for two or three minutes until its bottom is heated all the way through. At that point, pick the glass container up by Its neck and Immediately set it down in another pan that contains ice water.

Result: The bottom of the jug should neatly drop out all by itself in one almost perfectly round flat slab.