Legume Seed

Willamette Valley Legume Seed Production

The Willamette Valley of western Oregon is a premier seed production region, especially for clovers and cool-season grasses. In 2010, 26 million pounds of legume seed was produced on 20,800 acres in the Willamette Valley. Farm gate sales accounted for nearly $24 million . The clover seeds grown in Oregon are primarily red, crimson, arrowleaf, and white or Ladino. Red, crimson, and arrowleaf clover seed is grown mostly in the north valley (Washington, Yamhill, and Polk counties). White clover seed is grown in the south valley (Linn County). About 1,500 acres of red, crimson, and arrowleaf clovers for seed are grown under irrigation in other areas of Oregon. Small acreages of legumes including alalfa, common vetch and hairy vetch are also grown in the Willamette Valley.

Red Clover

Red Clover Seed Field & Red Clover Flowers


Red clover is a perennial. In the Willamette Valley, it is commonly planted in the spring, but may also be planted in August or September, especially if the grower can irrigate. In late May the plants start to bloom, but growers cut the fields for forage around this time. The purpose is to delay the bloom so that all the flowers come at the same time. Most growers sell the forage as green chop to dairies. Even if a grower does not sell the forage, he will clip the field, because a uniform bloom is important for seed production. Seed is harvested in August and September.





White Clover

White Clover Seed Field & White Clover Flower


White clover seed in the south Willamette Valley is grown primarily for the soil quality benefit it provides to the grass seed crop following it. White clover is a perennial that spreads by stolons. Seed growers plant in rows up to 20 inches wide to allow room for stolons to grow. They deliberately stress the plants by grazing them heavily with sheep after harvest in the fall and again for about a month in the spring. Achieving the right amount of stress on the plants is a matter of trial and error. Each year is different, and each variety is different. For this reason, white clover is notorious for variable seed yields. Seed is harvested in August.



Crimson Clover 

 Crimson Clover Seed Field & Crimson Clover Flowers

The hills of the north Willamette Valley are beautiful in mid-May, when the crimson clover fields bloom scarlet red. Crimson clover is an annual, planted in late September or early October.

Crimson clover is harvested in late June and early July. As with the other clovers, it is swathed at night, when dew is on the plants, to reduce seed shatter. It's allowed to dry in the swath for about a week, then harvested with a combine using a belt pick-up header.


Arrowleaf Clover

Arrowleaf Clover Seed Field & Arrowleaf Leaf & Arrowleaf Flower


Arrowleaf clover is an annual, similar to crimson clover in it's requirements. Like crimson, it's planted in the fall, but harvested later, in August and early September. Also like crimson, the flowers bloom from bottom to top, and the flower head will continue to grow taller and produce more seed as long as growing conditions are good.

For more information on clover produced in Oregon or the Willamette Valley:

Seed Production Research Reports

Oregon Clover Commission

Legume Seed Nutrient Management

Nutrient Management in Legume Seed Crops

Little, if any, fertilizer nitrogen is needed by legume seed crops. Measure soil pH, phosphorus, potassium, and boron with a soil test to determine need. Red Clover requires a soil pH above 6.0.  Annually apply sulfur before mid-March with other nutrients, if they are needed.


Click on the following links to view related OSU Extension Publications:

Soil Acidity in Oregon: Understanding and Using Concepts for Crop Production, EM 9061

Applying Lime to Raise Soil pH for Crop Production (Western Oregon), EM 9057

Red Clover Western Oregon Fertilizer Guide

Crimson Clover, Vetch, Field Peas Western Oregon Fertilizer Guide

Soil Test Interpretation Guide

Monitoring Soil Nutrients Using a Management Unit Approach

Legume Seed Weed Management


The OSU Weed Science Group conducts greenhouse, laboratory and small plot herbicide evaluation trials in support of the development of weed management activities in the diverse cropping systems of Western Oregon.  Labeled and experimental herbicides are evaluated for crop safety and weed control efficacy in the following crops:  Winter and Spring Wheat, Cool-season grasses grown for seed, native cool-season grasses and forbs grown for seed, canola, meadowfoam, camelina, clovers and peppermint among others.

Small broomrape (Orobanche minor Sm.) is a parasitic weed that recently has become troublesome in red clover seed production in Oregon. It was identified in a single red clover seed production field in 1998, and the number of infestations increased to 15 by 2000 and 22 by 2001. A small broomrape infestation can cause severe crop destruction, yield loss, and seed contamination. Small broomrape is a federally prohibited noxious weed and is restricted from export as a seed contaminant. Please see the following OSU Extension Publication for biology and management information for small broomrape - click here.

Italian Ryegrass

Annual Bluegrass

Small Broomrape



Prickly Lettuce

Common Groundsel

Wild Carrot

Catchweed Bedstraw


Weed Science Related Links:

Weeds of the West

Weeds of California and Other Western States 

PNW Weed Management Handbook 

PNW Weed Management Extension Publications Series

Oregon Society of Weed Science

Western Society of Weed Science


Weed Identification Resources:

Weed Science Society of America

Center for Invasive Plant Management

USDA Plants Database


Herbicide Labels:

CDMS Database

Legume Seed Disease/Insect Management

Legume Disease


Northern Anthracnose

Black Stem

Powdery Mildew

Stem Nematode


Legume Insects


Clover Root Borer

Clover Aphid

Clover Seed Weevil

Lesser Clover Weevil

Garden Symphylan

Crane Fly


Grey Garden Slug

Lygus Bug