Perennial Oilseeds (Silphium)

A plant in the sunflower family native to the Great Plains and other parts of North America, Silphium integrifolium is an oilseed crop that The Land Institute is domesticating. The goal is for perennial silphium to partially replace annual oilseed crops such as sunflower, canola and soy.

Why Choose Silphium for Crop Domestication?

During the dust bowl years, American botanist John Weaver noted how well silphium survived in Nebraska under extreme drought. Land Institute researchers also noted the plant’s resilience during the hot, dry summers of 2011—2012.

The plant has a taproot that grows several meters deep, which appears to help it exploit a large soil volume for water. While it is still early in the domestication process, silphium has proven to be responsive to selection for seed production and other important crop traits.

Our goal is for silphium varieties — bred by an international network of breeders in different climates, latitudes, and soil types — to displace annual oil and protein crops on hundreds of thousands of acres around the world.

Silphium has the potential to be at least as productive as the oilseed sunflower in favorable environments, but it will be much more resilient to short-term droughts (from weeks to a couple of years) than any annual crop and even some other perennial crops.

Thus, its greatest annual-crop-displacing advantage is likely to be in drought-prone regions with moderate average precipitation but erratic rainfall distribution.

Beyond Food and fuel, Silphium’s Role in Polycultures

Like any perennial, we expect silphium will provide some soil protection and carbon sequestration. In addition, there are published reports showing that silphium provides good habitat for earthworms, hoverflies (pollinators and aphid-eaters), native bees, Monarch butterflies, and honey bees.

We predict that silphium (by itself or in mixtures) will help local populations of pollinators. Combined with other crops, silphium could provide “floral resources” (for pollinators and insects that kill pest insects, such as ladybugs) not provided by monocultures.

At the moment, we speculate that silphium’s long, strong roots might break through soil hardpans, allowing the roots of other species to go deeper. Silphium doesn’t appear to be a competitive plant and thus is a good candidate for intercropping systems.

Timeline for Food and Fuel: Early Interest in a Long-term Plan

Although it is early in the breeding cycle, farmers from the Organic Valley co-op have shown interest in perennial oilseeds.

The co-op members hope to use the oil to fuel their tractors, while the meal or oilcake (the seed leftovers after oil pressing) would be valuable to them as a substitute for certified organic soy meal — currently an expensive source of protein supplement for their dairy cows.

We hope that silphium might be produced on some of their farms by 2021. While there are already small on-farm test plots in Wisconsin and Vermont, they don’t yet produce enough to make pressing the oil realistic.

It may take until 2025 to achieve yields high enough for commercial production of edible vegetable oil. Even then, the crop will be most competitive with annual crops in the gourmet or environmentally labelled markets.

It may also become commercially viable in drought-prone environments that lack access to irrigation water, and in regions outside the range of native silphium pests and diseases (for instance, in parts of Argentina).

The displacement of oilseed sunflower and canola in North America may require another decade or two of intensive plant breeding.

Short-Term Failures Breed Long-term Success

Some people say that failure to plan is like planning to fail. We say that to succeed, we must plan…and we must also plan for some failure each year.

We know we are taking appropriate risks and pushing the breeding program aggressively if we have a good, solid failure every year. So we plan on it and always have several independent experiments happening simultaneously.

If one experiment fails due to weather, weeds, pestilence, or scientist error, others will be likely to survive simply due to their difference in location, age, genetics, or management.

Given that failure is unavoidable, we make sure to take advantage of it. When unseasonable rain one June led to many plants falling over, we selected the plants that stayed upright. When disease and insects kept most plants from producing heads at the normal time, we found 15 plants out of 6,000 that looked almost normal and crossed them together.

So what appeared to be disaster led to success.

On an annual basis we are successful in the silphium breeding program if we:

• Advance at least one of our populations through the breeding cycle. Every cycle is a big chance to bring together genes we need and to break up associations between useful genes and unhelpful ones;
• Identify something important about how this species responds to new situations (new for silphium or new for us); new experiments are usually needed to confirm such observations;
• Learn how to do something that will speed up research in the future: how to germinate seeds more quickly, make stem cuttings, plant in the autumn instead of the spring, or use DNA markers;
• Keep our collaborators supplied with seeds and data so that the work can continue in multiple states and countries, and so that young scientists have a chance to become passionate about domestication and plant breeding.

David talks about perennial oilseeds at the 2019 Prairie Festival.

Learn about other perennial crops under development at The Land Institute.

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