Workshop Notes: Extending Home Vegetable Production Beyond Summer

We attended a workshop last weekend to learn more about fall/winter gardening.  It was put on by the Fayetteville Community Garden Coalition, in conjunction with Ozark Alternatives and The Blackberry Farm Community Garden.

Here are some highlights:

Cold Frames:


Cold frames are semipermanent enclosures that trap solar energy during the day and retain it at night as outside temperatures drop.  This allows the gardening season to be extended late into the fall and begin earlier in the Spring.  On frosty nights, a few hours before sundown, close them allowing heat to become trapped inside.  On very cold days, they can stay closed all day long.  On warm, sunny days the temperature inside can rise too too high.  On these days, open the cold frame to allow the heat to escape.

Straw bale and glass door cold frame

A simple, cheap, and effective cold frame can be built from a recycled glass door, six bales of straw, and a stick.  Simply form a rectangle around the bed with bales of straw to serve as insulated walls of the cold frame.  Elevate the bales on the north side of the frame about 18" to achieve a 35 degree slant towards the south.  Place the glass door on top of the bales of straw to form a transparent roof.  The weight of the door will hold it in place.  The stick is used to prop the roof of the cold frame open when necessary.  During expected freezes, stuff straw into any cracks to seal out cold.  The bales absorb moisture and will decompose over time requiring replacement.  On the bright side, they provide the backyard gardener with a source of compostable material.  Do not use hay in place of straw.  Hay generally contains a lot of weed seeds and you will spend several years battling them.

Total cost of door (free) + straw ($4 a bale) + stick (free) = about $25.00

Wire and plastic cold frame

This cold frame design is built from 2x8" boards, concrete reinforcing wire, and greenhouse grade sheet plastic.  Simply cut one board in half, forming the 4' long ends.  Screw the boards together to form a 4'x8' box.  Make a arching roof out of the wire, making sure that the maximum height of the roof is no more than 2' tall.  Remove any sharp edges on the wire that could snag the plastic sheeting.  Cut two sheets of plastic wide enough to cover about 2/3 of the roof as measured from the ground.  Cut these sheets long enough to leave 4' of plastic on each end.  Tack the long edge of a sheet to the board on one of the long sides of the cold frame.  Repeat this with the other sheet on the other side.  Cut three strips of plastic 2' wide and long enough to go all the way over the arch of the roof.  Leave enough extra length on the ends to provide for tacking it down.  These strips are folded twice lengthwise to give a three sheet thick, 8" strip.  Put these strips over the larger plastic sheets at each end and the middle of the cold frame and tack it down tightly at both ends.  The larger plastic sheets can now be adjusted as needed.

Total cost of three 2"x8"x8' boards ($15) + wire ($15) + plastic ($10) = $40.00

Low tunnel covered with thin, perforated plastic

Framework for a low tunnel

A temporary low tunnel can be built over rows (or beds) to provide frost protection.  It is not well suited to small, backyard gardens because it is somewhat labor intensive to cover a small stretch.  If you have 100' rows to cover, it would be a good option.

Every 4-5' on each side, pound 2' long pieces of reinforcement bar into the soil at an inward angle.  Make a cross support for the tunnel by placing a piece of flexible underground piping over the reinforcement bar.  Stretch the perforated plastic over the framework and secure it by weighting the edges down with 5' pieces of 1/2" reinforcement bar.  The speaker emphasized using 1/2" instead of 3/8" because the increase in weight really helps hold the plastic down in a wind.

Cut up an old piece of garden hose into 3" sections and split them on one side.  Put two of these on each support bar over the plastic and hold them in place with a piece of baling or electric fence wire poked through the plastic.

Cost depends on length of rows.

Tips and Tricks:

• A cold frame should never be higher than 2 feet tall inside or any heat trapped will rise too high to be of any use in warming the plants and soil
• In the northern hemisphere during the winter, the sun travels low in the sky to the south.  When building your cold frame, angle the transparent roof (if possible) to be perpendicular to the sun.  In Northwest Arkansas, the winter sun's angle is about 55 degrees, so build the cold frame such that the roof is tilted towards the south at about 35 degrees when closed.
• Any foliage physically touching the cold frame's exterior plastic or glass during a freeze will turn black and die.
• Wet the soil just before a frost/freeze.  Hydrated plants handle it better and the moisture helps conduct warmth from the subsoil.
• Place dark colored jugs that are filled with water into the cold frame.  They will absorb heat during the day and radiate it back out during the night.  This can make a difference of a few degrees.
• On cold windy nights where it gets into the mid 20's, throw an old blanket over your cold frames to provide extra insulation.
• On nights where it gets into the low 20's or colder, a supplemental heat source will be needed if you wish to continue gardening.  A 100 watt incandescent light bulb, a can of Sterno, or even an electric heater can be used.  Use all caution where fire and electricity are involved.

Vole Trap:

Vole trap

Entrance to the vole trap

Have you ever had a pepper plant wither and die for no apparent reason?  A fruit tree not leaf out in the Spring when it had looked fine going into the fall?  You may have a vole problem.  These small, mouse-like creatures love to eat the roots of pepper plants (and other plants) and during the winter, they will even eat roots and the bark from trees.  One of the speakers showed us this simple, nontoxic vole trap that he claims is very effective.

Construct a wooden box about the size of a shoe box with a removable top.  Cut a small (~1 inch) hole in the side at the very bottom.  Put the box in your garden with a snap-type mouse trap inside.  Bait it with small pieces of cut sweet potato.  That's it.  Pretty simple.  The voles like warm, dry environments like the wooden box and the box will keep your children or dogs from getting caught in the snap trap.

Various Other Notes:

• Green beans will grow in soil that is too cold for it to germinate in.  So, in early Spring, start them inside and plant outdoors after the last killing frost.  A good time to put them into the garden for Northwest Arkansas would be the middle of April.  This will gain us almost a full month of growing season.
• Asparagus, with its 15' deep root system, can withstand high levels of salt once it is established.  Because of this, salt can be used as a weed inhibitor in your asparagus beds.