How to Build a Garden on Top of an Asphalt Driveway

Asphalt gardening, an urban trend resulting in more green space, adds beauty and functionality to an unused driveway. Whether you choose to grow flowers or food, you will find gardening a way to strengthen your relationship with nature, reduce stress, and perhaps even get better acquainted with your neighbors. This version of an asphalt garden uses straw bales as a growing medium, which may be one of the easiest ways to create a growing space on top of pavement.

Things You'll Need

• Sheet of black plastic
• Straw bales (number needed depends on size of garden desired)
• Agricultural limestone
• Ammonium nitrate
• Spatula
• Seedlings of your choice

Instructions

1. Lay black plastic on the asphalt to help prevent water from seeping out of the bales and chemicals from the asphalt from seeping in. Set rows of wheat or barley straw bales, positioned on their side (so the twines are parallel to the asphalt), on top of the plastic.

2. Soak the bales with water. Sprinkle about three fourths of a pound of limestone per bale on top and fork it into the bales.

3. Add fertilizer to encourage the bales to begin composting. Fertilize with six ounces of ammonium nitrate per bale.

4. Keep the bales moist. Check the internal temperature of the bales after three days. If they are not over 100 degrees Fahrenheit, add more fertilizer.

5. Six days after the initial application, apply an additional three ounces of ammonium nitrate per bale.

6. Approximately two weeks after the bales began composting, you should be ready to plant. Check the bales to make sure the heat generated from composting has diminished. If it has, then you may plant your seedlings by inserting them into the bales. You may use a spatula to create a space in the bale.

7. Keep the bales well watered and enjoy gardening on top of asphalt.

   The straw bales should be good for spring and fall planting, but will probably have to be composted after one year's growing, according to Mississippi State University Extension.

Tips & Warnings

• You may plant just about any vegetable or perennial in the bales as long as it will not get too tall and top heavy. Corn and sunflowers, for example, are not a good choice.

• Some recommended planting rates are two tomato or squash plants per bale or four cucumber, lettuce, or pepper plants per bale.

References

• Mississippi State University Extension: Growing in the Bale
• Pioneer Thinking: Straw Bale Culture Technique

Resources

• Carolina Country: How to Grow a Straw Bale Garden
• The Root: When Fresh Food is a Luxury