Last June I had the extraordinary opportunity to visit the “Lost Gardens of Heligan” in Cornwall, United Kingdom.

Last June I had the extraordinary opportunity to visit the “Lost Gardens of Heligan” in Cornwall, United Kingdom.

I was impressed by this garden which had been in existence since the 1800s. Having been told by a local that we must visit this garden, it was truly a stroke of luck that we happen to visit the garden.

By my standards this lovely garden rivaled even Kew Gardens in London. Though, by the end of the trip, I was homesick for the woodlands of the Ozarks.

“But why does he mention this garden?” you are probably asking yourself. “How can such a garden in the United Kingdom have an impact on Rolla gardeners?”
I present to you the cover photo of this week’s column: “consider the cold frame.”

To tell you the truth, despite the century-old amazing jungle like rhododendron forests at this garden, I was truly blown away by the perfectly restored Victorian style vegetable and fruit gardens, greenhouses, manure heated hotbed, and the topic of this article, the wonderful and useful cold frame.

What is a cold frame?

A cold frame is a small 3-foot-by-6-foot greenhouse without a heat source.   Typically these paned glass covered wooden boxes are built over a garden bed to extend the growing season or are used to harden off seedlings in the spring.

Gardeners have been using cold frames for centuries. They are usually made of a three-sided wooden frame but bricks or concrete can be used.  The roof is made of framed glass or clear polyethylene called “sash,” is slanted at a rate of one inch per foot and is set up to face a south-southwestern direction.

These frames protect plants form the harsh conditions of the outdoors preventing rain, wind and cold air from damaging the crop.  Typically the conditions within a cold frame can be 5-10 degrees warmer than air temperature around the outside the structure.

Many times, cold frames are placed on the south side of buildings to provide a northern windbreak.  To provide more insulation, the cold frames are usually buried slightly below ground. Cold frames are hinged to allow for the proper ventilation on warm sunny spring days.

If constructing a cold frame yourself, try using cedar wood to increase the longevity of the structure. It is important to note that when constructing a cold frame, that the bed be well drained and level.

If you are interested in constructing a cold frame, the University of Missouri Extension has a guide, No. G6965 available through our website

When starting seeds indoors, cold frames can play a critical roll in the process of hardening off seedlings.  Hardening off is the process of allowing seedlings to be gradually introduced to the outdoors elements before being directly planted outside.

Seedlings grown indoors have become accustomed to the filtered sunlight of a greenhouse or window and are not used to the fluctuating temperatures of spring nights in Missouri.  This process of carrying flats of plants back and forth from a greenhouse or home to the outdoors can be time consuming, yet is an important process.

Before placing seedling transplants directly into the garden, cold frames can be used to prevent wind burn and sun scald before plants become adjusted to the elements without the hassle of back-and-forth transport.

Limiting changing temperature shock and sun scald of seedlings can be accomplished by gradually increasing the ventilation gap in the roof.

Getting a jump start on the planting season is another benefit of building cold frames.

Cool season vegetable crops and flowers can be started outdoors in early spring before being transplanted directly into your garden.  

In planning your own vegetable garden at home, consider making this old world tradition an important part of your modern vegetable garden.