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Understanding Weed Seed Banks and Germination

County Agent News
Dan Folske
May 7, 2018 

Soil Temperature/ Bowbells: 54F

Understanding Weed Seed Banks and Germination 

Weed seeds have a host of characteristics that assure their survival. They are adapted to many

types of disturbance and many climatic conditions.

One feature which can be used to manage weeds is their germination temperature range. A field which has primarily weeds with cooler germination temperatures will have the weeds growing early and delaying cultivation or spraying of a burn down herbicide prior to seeding may have most of the potential weeds emerged for good control. If a field has primarily warm emerging species of weeds, you may want to plant it early so the crop can get ahead of the weed emergence. Changing from early to late planting or late to early every few years for some fields can be a good management tool.

 

Minimum Germination Temperature for Weeds

Early Emerging

Late Emerging

Min. Soil Temp: 35-40 °F

Min. Soil Temp: 50 °F or higher

Kochia

Wild Mustard

Wild Buckwheat

Russian Thistle

Absinth Wormwood

Canada Thistle

Common Lambsquarters

Quackgrass

Wild Oats

Field Pennycress

Tansy Mustard

Shepherd's Purse

Redroot Pigweed

Wild Sunflower

Volunteer Sunflower

Field Bindweed

Yellow Foxtail

Green Foxtail

Cutleaf Nightshade

Lanceleaf Sage

Cocklebur

Common Ragweed

Weeds have several seed-dispersal mechanisms assuring wide distribution. Their seeds can also last a long time in the soil without rotting. Additionally, seeds can go dormant until favorable conditions come around again.

Survival and germination of weed seeds in the soil depend on the weed species, depth of seed

burial, soil type, and tillage. Seeds at or near the soil surface can easily be eaten by insects,

rodents, or birds. Also, they may rot or germinate.

Buried seeds are more protected from seed eating animals and buffered from extremes of

temperature and moisture. On average, about 4% of broadleaf and 9% of grass weed seeds

present in the soil germinate in a given year.

Results from seed burial experiments demonstrated that seeds of barnyard grass and green

foxtail buried at 10 inches showed germination rates of 34 to 38% when dug up and spread on

the soil surface. In the same study, seed buried at one inch showed only one to five percent germination.

 

In another study, seeds were buried at different depths for a period of three years.

Seed germination was greater with increasing depth of burial. These studies show that

seeds near the surface face lots of hazards to their survival, while those buried deeply by tillage

are more protected. When those deep-buried seed are plowed up to the surface again they

have a good chance of germinating and growing.

 

Some weed species have very long potential dormancy times while others lose their germination ability within a few years under most conditions.

 

Properly identifying the weeds in your fields and noting changes in weed specie populations over time can help you make management decisions that can greatly increase control of those weeds in your fields.

 

Can’t identify the weeds in your fields? Or you find a new one which you haven’t seen before? Bring it in to me or to your local agronomist, or take a picture and text or email to me at 701-339-1133, or email; dan.folske@ndsu.edu

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