Growing the Desert Garden

Welcome to the Desert Garden, with garden coach Tyler Storey, where we talk about everything having to do with gardening and landscaping in the Desert Southwest. From composting to Cercidium and agaves to arugula — we'll cover everything you want to know to grow your own beautiful Desert Garden.

Saturday, May 10, 2008

Back at the Ranch: Sweet Corn

Corn tassel © Tyler StoreyNext to tomatoes, sweet corn may be the vegetable that home gardeners are most eager to grow. For me, sweet corn comes first on the list; while I have occasionally eaten a purchased tomato that had all the best qualities of home-grown, I've never had corn that came even close.

This year at the Ranch, I'm growing a small plot of an heirloom sweet corn called Golden Bantam, grown from seeds purchased from Victory Seeds ( and sown directly into the garden. Golden Bantam is an open-pollinated "normal sugary" variety introduced at the beginning of the twentieth century, and it set the standard for sweet corn for most of the century. The hybrid "sugary-enhanced" and "supersweets" were developed for the market, with sugars that last longer; they're what you buy at the grocery. To my palate, they don't taste quite right.

Irrelevant Side Note: I recently read in an organic gardening book that the "monotony of the common yellow cobs" may be relieved by planting white or white-and-yellow varieties. There are white and mixed varieties that are excellent and I encourage you to try them on their own merits, but anyone who finds "monotony" in home-grown corn of whatever color is deeply and possible irredeemably jaded.

My block of Golden Bantam corn is about my height now, and the tassels are emerging from the top. I can see the ears beginning to form along the stalks, and very soon the silks will emerge, ready for the pollen to fall on them from the tassels and start the kernels forming. I put the corn in a little late this year, so we'll pray the weather stays cool enough that the pollen isn't sterilized.

One pest you will almost inevitably have to confront if you grow sweet corn is the Corn Earworm, the larval form of a moth called Helicoverpa zea. The female moth lays solitary, though multiple, small white eggs on the corn silk. Once they hatch, the larvae head down into the ear, eating the silks and kernels and making an unappetizing and inedible mess out of your corn.

Helicoverpa zea © Tyler StoreyNote the picture above, taken yesterday morning. It's a view from above of the tassels emerging. Note the small brown area at the base of the tassel, and now look at the enlargement of that area to the left. Yup, you guessed it: that's Mrs. Helicoverpa, here making an advance check on the facilities at her maternity ward of choice. You can squish her on sight, but she has friends to take her place.

Foliar sprays will not keep her young in check, because they move into the protected area enclosed by the husk immediately upon hatching. Here's how you control them:

Four to six days after silk growth starts, at which time the silks should be mature, mix up a batch of BT (Bacillus thuringiensis) with ordinary corn oil. Using a narrow-aperture oil can, a syringe, or something similar, carefully apply 0.5 ml, or about 1/8th of a teaspoon, of the oil/BT mixture directly into the hollow at the center of the silks where they emerge from the husk, or slightly into the silk channel. The timing is important with this method: too early and it interferes with pollination; too late and control is poor.

Using oil to smother the developing larvae was first used by farmers in the early 1940's using mineral oil; adding BT increases the effectiveness of the treatment, and corn oil is as effective as mineral oil while being exempt from pesticide labeling and tolerance requirements. It is the only control method available to the home gardener or farmer who doesn't wish to use synthetic insecticides, and it is highly effective. In field trials it has had a control rate nearing and reaching 100%.


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