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Gourds for Purple Martins

Sometime after harvesting last year's crop of my martin gourds, a small, still voice spoke to me. Knowing this to be the voice of reason and common sense, I put off listening to it for as long as I could. Eventually, all that whispering about a long-forgotten file full of stuff from the Purple Martin Conservation Association commanded my attention. Opening the file drawer located about 15 inches from my right elbow, I went to the effort of looking for the jacket cunningly labeled "Purple Martin Stuff." Would that I had done so in April instead of October, but such is the story of my life.

Here is what I discovered in my search for better gourd-growing information:

The best martin gourds are from the plant Lagenaria siceraria, commonly called "birdhouse" or "bottle" gourds.

Plant your gourd seeds the same time as sweet corn -- after the frost is out of the ground and the soil is warm to the touch. Plant them at least three inches deep, in small hills, placing two or three seeds per hill, with the hills six feet apart.

The best growing spots have full sun, in well-drained soil that you can water at least once a week.

A trellis, fence, or pole will give the vines a supportive structure for climbing.

Bottle gourds require a growing season of 140 to 165 days. In areas of North America where an outdoor growing season of this length doesn't exist, starting the plants indoors is the only option. This will enable the fruits to reach maturity before the first frosts kill the vine. To avoid having your seedlings grow too large for their containers, do not start the seeds any earlier than four weeks prior to the date of the typical last frost.

After planting the seeds or seedlings, fertilization is unnecessary, although a potash supplement is helpful for thickening the gourds' skin. I dosed this year's batch with Miracle-Gro via a hose-end sprayer and the vines took off. The result felt like the Venus's-flytrap in "Little Shop of Horrors." The gourd vines took over the entire back corner of my yard and it looked like an alien species had established its beachhead, vanquished the defenders, and was using telepathy to bring in the rest of the gang.

Late-season fertilization is counter-productive, as it delays gourd maturity. I lucked out on this, as I quit fertilizing when the vines started reaching out for the transformer box at the top of the telephone pole.

Prune your vines when they are 8 feet long so that the vines will branch, making more space for gourds.

Harvest time for the gourds comes when vine stems are brown and shriveled, even though gourd growth will usually continue until the first frost. Cut the gourds from the vines, leaving two inches or more of the stem on the top of the gourd. Then wash the gourd with a mild bleach solution and dry it thoroughly. Allow the gourds to cure indoors, on shelves or in individual net bags, in a dry, well-ventilated area. If mildew appears, brush it off by hand, or with steel wool, which can be used after the gourds are fully hardened. It is very important that you WAIT three to six months before doing anything else with the gourds. At that point you can discard the wrinkled or soft gourds. For the best martin houses, choose only gourds that are at least eight inches high and eight inches in diameter (measured at the equator of the gourd).

When completely cured, the gourds will be light in weight, mottled tan, and the seeds will rattle inside.

Clean the outer surface of the gourds by dipping them in hot water for a few minutes, then scraping off the outer film.

Using a 2-1/8-inch-hole saw, drill the entrance hole into the side of the gourd, three to five inches up from the inside floor (on the equator of the gourd). Make the hole on the gourd so that it neither points upward nor downward when the gourd is hanging.

Remove the pith and seeds, and sand off any remaining black mold.

Using a 1/4-inch bit, drill six drainage holes in the lowest spots of the floor. About two inches down from the top of the neck, using a 5/16-inch bit, drill two sets of hanging holes on opposite sides of the neck, so that a hanger wire can be strung through both sides.

Preserve the gourds by soaking them for 15 minutes in a solution of one-pound copper sulfate (from a garden supply store) to five gallons warm water. Repeat this process every two or three years to maintain the durability of the gourds indefinitely.

After soaking, use a primer on the gourds, and then paint the outside with an oil-based exterior white paint.

Hang the gourds at least 10 feet above ground, away from trees and near a water source, if possible. Some feeder owners use a length of barbed wire, suspended horizontally to prevent slippage. From this they suspend the individual gourds with 15-inch lengths of thin-gauge insulated electrical wire, threaded through hanging holes drilled near the top of the gourd.

It is very important that you take the gourds down and store them in a dry place during the off-season. Before storing, be sure to clean all old nests out of the gourds or these will cause the gourds to rot.