How would you like to harvest a crop of vegetables without weeding, watering, spraying, or dusting? Or grow off-season crops such as head lettuce in August or carrots ready to harvest by Christmas?
The modern miracle-mulch which has made this a reality in tidewater Virginia is aluminum foil.
Aluminum foil is aluminum rolled very thin, .005” inch to .00035” inch thick. It comes in various widths, from a very narrow width to as much as 3’ feet, and can be fitted to any size row. The most suitable foil for garden mulch is from .001” inch to .0015” inch gauge.
Advantages Of Aluminum Foil Mulch
Research at the Virginia Truck Experiment Station during the past two years shows that aluminum foil has many advantages. However, its cost now limits it to crops of high value per acre or to the average garden, where costs are less important than the job of weeding.
Like other mulching materials, aluminum foil controls the growth of weeds but does a better job because it is not porous. It completely shields the soil it covers.
An Insulating Material
This foil is an ideal insulating material. Because it reflects the sunlight, it has a cooling effect on the soil.
A temperature record of soil under aluminum foil shows that on bright, sunny days, the covered soil may be as much as 20° degrees Fahrenheit cooler than soil exposed to the sun’s rays. This is good for potatoes and root crops; lower temperatures cause starches to accumulate.
On cold nights when temperatures approach freezing, the soil under the foil will remain as much as 8° degrees Fahrenheit warmer than the exposed soil. Here the foil acts as a blanket which prevents the heat from escaping.
This benefits plant growth by keeping the surface soil sufficiently warm so that the roots remain active longer.
The evenness of soil temperature tends to promote more consistent growth, reflected in higher yields and much-improved quality.
Moisture-Retainer
The moisture content in soil under aluminum foil is always at least 8% percent higher than in exposed soil. This is because the aluminum foil is usually cool.
Water vapor coming to the soil’s surface is condensed on the foil and drips back into the soil. Thus the surface-feeding roots benefit.
Even during the hottest days, if aluminum foil is lifted, beads of moisture will be found on the underside.
The soil is covered with the foil except where the plants come through a 2” inch open strip along each row. Any rainwater that hits the aluminum must run down this small crack or runoff as it is. It cannot soak through the aluminum.
Because the foil protects the soil from beating rain, the surface never bakes tinder the foil. After two years, the soil under the aluminum foil tested at the Experiment Station was as mellow as when the foil was put down.
Disease And Insect Control
Aluminum foil also has a controlling effect on disease and insect damage. Mildew and other plant diseases require a moist environment in which to develop. Plants mulched with aluminum foil show mildew less readily.
This may be because the moisture from the soil does not come in contact with the foliage. The foil acts as a perfect seal, preventing the water vapor from moistening the air around the foliage.
Using aluminum foil prevented damage to beans from Mexican bean beetles and to cantaloupes and cucumbers from pickle worms.
Our foil-mulched beans were unharmed, while the leaves were completely eaten on the unmulched plots. The same thing was true in the case of the pickle worms.
This may be due, at least in part, to the glare from the shiny aluminum foil, which might discourage adult insects from descending on the leaves.
Use of Aluminum Foil
Experiments using aluminum foil as a mulch for garden plants were made in coastal Virginia, where maximum summer temperatures do not exceed 94° and green crops may be grown mostly during winter.
Garden plants tested, all of which showed a phenomenal increase in yield, included:
- Beets
- Broccoli
- Cantaloupe
- Carrots
- Celery
- Chicory
- Cucumbers
- Endive
- Head lettuce
- Leaf lettuce
- Parsley
- Snap beans
- Sweet corn
- Sweet peppers
- Sweet potatoes
- White peppers
- Tomatoes
Laying Aluminum Foil
Before the crop is planted, fertilizer should be broadcast. Later, if necessary, the plants can be fed by pouring a fertilizer solution along the row between the edges of the foil or in the openings around the plants.
When you are ready to lay the foil, try to have the soil free of large clods and as smooth as possible. Any small lumps will disintegrate as soon as the moisture under the aluminum foil soaks up the soil.
The foil is laid in strips, with a row of seed or young plants along one edge. Then another strip is laid, with the edges pressed in and covered with soil.
Using aluminum foil makes it possible to grow plants closer together since there is no weeding, and moisture under the foil seems adequate. Head lettuce may be set 9” inches apart; leaf lettuce, carrots, and beets may be sown in rows 9” inches apart.
In some cases, where beds are used as nurseries, the entire bed may be covered with foil, and plants set through holes punched in the foil. This works well for propagating azaleas, as these plants remain in the beds for two years.
Gladiolus should be planted in rows 4’ feet apart. Bulblets planted under foil show emerging shoots one to two weeks earlier than unmulched cormels.
Of the 1,001 new garden aids, there is probably nothing with more potential all year round than aluminum foil. It does everything for the gardener except plant the seed and harvests the crop.
44659 by Dr. V. A. Tiedjens