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is a sunflower a weed

How A Sunflower Gene Crossed The Line From Weed To Crop

Sunflowers in Birmingham, Ala. Michelle Campbell/Birmingham News /Landov hide caption

Sunflowers in Birmingham, Ala.

Michelle Campbell/Birmingham News /Landov

I’m rounding out The Salt’s impromptu Pest Resistance Week (which started with stories about weeds and corn rootworms) with a little-known tale that may scramble your mental categories.

You’ve heard about herbicide-resistant weeds (which farmers hate) and herbicide-resistant crops like Roundup Ready soybeans or corn (which farmers like). But here’s a case — the only one I know of — in which a weed helped create a herbicide-resistant crop.

The story begins in 1996, in a soybean field in Kansas. The soybeans in this field were able to tolerate a class of weedkillers known as “ALS inhibitors.” This line of soybeans had been created through “mutation breeding.”

This technique involves exposing thousands of seeds to chemicals that cause genetic mutations. One of those mutations allowed the resulting soybean plant to withstand the herbicides. (Similar kinds of herbicide-tolerant wheat, rice, and other crops have been created using the same method.)

Among the soybeans in this Kansas field, however, a few weeds also survived after the farmers sprayed their herbicide. The weeds were native sunflowers, wild relatives of the sunflowers that farmers grow as a crop. (As I reported a few months ago, sunflowers are one of a very small handful of crops that originated in our part of the world.)

The farmer contacted Kassim Al-Khatib, who was then a weed expert at Kansas State University. Al-Khatib collected some of the surviving weeds from this field, did some tests on them, and confirmed that these sunflowers were indeed resistant to ALS inhibitor herbicides.

A few months later, through a chance encounter at a scientific meeting, word of this discovery reached Jerry Miller, a sunflower breeder at the U.S. Department of Agriculture’s Sunflower Research Unit in Fargo, N.D. “I couldn’t believe it. I called Kassim right away,” recalls Miller. He saw the possibility of a herbicide-tolerant commercial sunflower created through traditional breeding, avoiding controversies over genetic engineering.

Miller did manage to create such a sunflower — although it took some heroic efforts to get the wild and cultivated sunflowers to exchange pollen and produce viable offspring.

When Miller finally had some herbicide-tolerant offspring in hand, he broke the news to a big meeting of sunflower growers. He told the farmers that, very soon, they might be able to spray ALS inhibiting herbicides right over their sunflowers, killing a host of problematic weeds without harming their crop. “The room got completely quiet,” he recalls.

Today, commercial sunflowers from North Dakota to Turkey contain this genetic trait, and many sunflower growers rely heavily on ALS inhibitors to control their weeds.

What’s the lesson from this tale?

For one thing, that it doesn’t take genetic engineering to create resistance to a herbicide — whether in a weed or a crop. Probably more important, it’s a reminder that our food crops are descended from plants that once grew wild, and the line that separates a despised weed from a valuable crop is sometimes a very fuzzy one. It’s a boundary porous enough for genes to find their way through.

All of our food crops are descended from plants that once grew wild. But the line that separates a despised weed from a valuable crop is sometimes a very fuzzy one.

Weeds And Sunflowers: Do Sunflowers Limit Weeds In The Garden

There is no denying that sunflowers are a summertime favorite. Excellent for beginner growers, sunflowers are loved by children and adults alike. Homegrown sunflowers are a veritable haven for pollinators in search of rich nectar. While some gardeners may cut the blooms for use in a vase, others who let the plants mature are rewarded with an abundance of seeds.

Regardless of the rationale behind growing these beautiful plants, there is no doubt that planting sunflowers is an asset to many gardeners. However, there is one thing that many do not know – sunflower weed control can be used in the garden. But how can sunflowers stop weeds from sprouting? Let’s find out.

Do Sunflowers Limit Weeds?

While sunflowers are commonplace in the garden, one interesting and frequently overlooked aspect of these plants is that they are allelopathic. Weeds and sunflowers, as with any other plant in the garden, are always in competition. In order to gain the growing advantage, sunflowers contain chemical compounds that inhibit the germination and growth of other seedlings in the growing area.

These toxins are present in all parts of the sunflower,including the roots, leaves, and seed hulls. The chemicals create a small area in which weeds and other plants have difficulty growing. While this may seem detrimental in the garden, allelopathy (the inhibition of germination) actually has many beneficial aspects. Allelopathic sunflowers can actually help suppress weed growth.

Sunflower Weed Control

With strategic planning, growers are able to use this attribute to reduce weeds within the garden. While the growth of many plants has been proven to be diminished by the presence of sunflowers nearby, other plants show a distinctive resistance.

Ornamental flowering plants such as roses and lemon balm are just a few examples of plants able to withstand and thrive when planted near sunflowers, making them excellent companion plants.

Though there are some exceptions, many garden plants may struggle to grow in the vicinity of sunflowers. While delayed germination may lead to reduced yields, other crops may be more drastically impacted. Potatoes, for example, may have particular difficulty when grown near sunflowers.

When left in the garden, residue and debris from sunflowers can allow the chemical compounds to stay within the garden soil for a longer period of time. To avoid this, remove old sunflower stalks, flowers, and seeds from the growing area at the end of each season. Frequent crop rotation will also help to avoid the buildup of these allelopathic compounds.

There is no doubt that planting sunflowers is an asset to many gardeners. However, there is one thing that many do not know – sunflower weed control can be used in the garden. But how can sunflowers stop weeds from sprouting? Click here to find out.