Gardening How To

Simply, a cold frame is a wooden frame you set on the ground around your cold-hardy vegetables.  Think of it as a small, 12” high greenhouse with wooden sides, no bottom, and a cover that allows sunlight to penetrate.  During the day, the sun warms the air and ground inside, even on cloudy days.  In fact, often on sunny winter days, it’s often necessary to vent (or open) the cover so the inside doesn’t become too hot.  The first year I tried this, a 50 degree sunny January day successfully fried my lettuce by 11am.  The temperature in my tiny hoop house nearby registered 90 degrees!

Have you ever grown so many carrots, lettuce, spinach, onions, or beets that you can’t eat them all by the time cold weather arrives?  Don’t want to freeze, can, or pickle?  Or maybe you haven’t had enough of your fresh, home-grown produce …. Well, a cold frame might be an answer to consider.  A cold frame is a low-tech alternative to a greenhouse, with a lower profile (in case an HOA is watching) and smaller footprint.  While not without some effort, making and using a cold frame can harness the benefits of solar energy to keep mature (or almost mature) vegetables alive, in a semi-dormant state, until you decide to harvest them.  Baby plants will not grow – or not grow very much – but mature plants will go into their own type of hibernation until you’re ready to use them.

In the afternoon, shortly before the sun goes down, put the glass back on so that the inside of the box stays warm during the night from heat retained by the ground.  The cold frame creates a micro-climate in which the plants can survive cold nights or extreme cold spells.

To take advantage of daily solar gain, make the north end of the cold frame taller than the south end.  The east & west sides will slope from north to south.  If you’re not the handy type or don’t know someone handy with a saw, then skip the sloping – a wooden box with glass or clear plastic on top will work just fine.  Maybe not ideal, but in future years you can make enhancements.  The important thing is that the box doesn’t let air in unless you vent it, so things need to fit together well.  

The cover can be an old glass storm window, well anchored plastic sheeting, or other more rigid clear plastic.  The first year I tried this I made an 18” high hoop from chicken wire, covered it with clear plastic, and clothes-pinned the plastic to the chicken wire.  During really cold spells, I threw a blanket on top.  All was well till that fateful, sunny January day mentioned above.

There are many resources on the Internet that describe how to make a simple cold frame.  VCE Publication 426-381 describes how to construct a cold frame and suggests other ways to extend the growing season.  (Another benefit of cold frames is they are a great way to get an early start on your plants in the spring).  Other resources are available at our local libraries.  Often these resources recommend orienting the cold frame in one direction or another (north-south, east-west).  In my opinion, you need to make it work for your garden, regardless of what the experts say.  In our case, our beds are long from north to south and narrow from east to west and so my cold frames are oriented to work within this constraint — much easier than trying to re-orient the entire garden.  However, I refer you to these resources because they can describe the construction details for cold frames in far more detail than can be addressed here. 

In my second year of cold frames, as an experiment, we used a cold frame to prevent the ground from freezing around the several hundred carrots we had in October.   We quickly cobbled together one cold frame using stacking, hinged wood boxes from a local recycler, lined them with Styrofoam, and covered them with two old aluminum storm windows.  We enjoyed carrots much of the winter and harvested the last ones in mid-January 2014.  This was a vast improvement over the prior winter, when we had no cold frame, and beginning in mid-December had to literally use a chisel to get the carrots out of the frozen ground!  Surprisingly, they tasted fine – until we had a thaw and re-freeze.  Then they were mush and went directly into the compost pile.

During our fourth year of winter gardening, we expanded our cold frame efforts.  We had six cold frames – built from “culled” wood and lined with Styrofoam insulation because culled wood doesn’t fit together tightly (a design flaw on our part). We covered our cold frames with rigid plastic.  Most years we hope to harvest spinach, lettuce, carrots, beets, and leeks – throughout the winter.  Sure, we’ll have to remember to vent them most mornings and cover them most evenings but we’ll also have fresh, home-grown veggies all winter. 

Tomatoes – they’re a genuine American pastime.  Growing them, eating them.  You could say I have a crush on tomatoes!  What’s better than a home-grown tomato?  I can’t think of anything and many fellow gardeners agree.  At least one survey says that nine out of ten gardeners will try growing tomatoes.

Here are twelve tips for success:

1. Select healthy, disease-resistant plants. Some plants are labelled VFN, indicating resistance to Verticillium wilt, Fusarium wilt, and nematodes.  There are also new varieties that are resistant to early and late blight.
2. Keep in mind our growing season and check the plant label for days to maturity. Many gardeners select indeterminate varieties, which develop flowers and fruit until frost; others prefer determinate tomatoes, which have a compact growing period.
3. Harden tomato plants before planting, if necessary. Tomatoes grown in greenhouse conditions until purchase can suffer from shock if planted immediately after purchase.  Hardening gradually accustoms them to the outdoors by putting them outside in full sun (and wind) for a few hours a day, increasing the time they stay out at night too, weather permitting.  Ask your local retailer if the plants you’re buying are already hardened off.
4. Select a location with a minimum of 8 hours of sunlight.
5. Amend your soil with organic matter, and loosen an area larger than you need.
6. Space tomato plants at least 3 feet apart. Many diseases affecting tomatoes spread from lack of air circulation or touching leaves. Using stakes, cages, or trellis will help control disease.
7. Before planting, remove any blossoms that have developed in the greenhouse. This may seem counter-intuitive, but it eliminates competition for crucial energy and nutrients during root development.
8. Gently separate the roots to encourage the root system to generate new roots that will spread away from the plant.
9. Plant the tomato with as much of the stem covered as you can, removing the lowest leaves. Roots will form along the entire length of the buried stem, resulting in a more vigorous and health plant.  Add a narrow band of aluminum foil to the stem to protect from tomato cutworm.
10. Mulching will reduce weeds and help retain moisture. Organic mulches should be at least 2” deep. Or, you can use several layers of newspaper or UV-resistant black plastic at least 6ml thick as mulch.  Whichever you select, be sure it doesn’t touch the plant.  Use copper or other metal rings to discourage slugs and other insects that may be in the mulch from getting to the plant.
11. Provide consistent, even moisture to reduce blossom end rot. One to three inches of water weekly is critical to getting water deep enough (5 – 6”) to promote vigorous growth.  When watering, take rain into account.  Water should be applied at one time if possible, so use drip irrigation, a soaker hose, or flooding since overhead watering can spread disease. Morning is the best time to water because any foliage that does get wet will have time to dry out.
12. Apply a starter fertilizer when you first plant and then establish a sound fertilizer program to keep plants vigorous and productive.

Even if you plant a little late, your tomatoes will catch-up.  With the right weather conditions and a little luck, these tips will help you grow a great tomato crop.