Cover Crops: Sweet Clover

Table of Contents

  1. Description: Family
  2. Growth Habits
  3. Sensitivity to Herbicides
  4. Weed Control
  5. Benefits and Cautions
  6. Getting Started
  7. Related Links



Figure 1. Sweet Clover in flower.

Figure 1. Sweet Clover in flower.

Figure 2. Sweet Clover by roadside.

Figure 2. Sweet Clover by roadside.


  • Leguminosae;species Melilotus spp

Growth Habits


  • White sweetclover have hard shells and need to be scarified prior to germination
  • Require the same strain of rhizobial bacteria as alfalfa for inoculation

Top Growth

  • Yellow sweet clover: 30-280 cm
  • White sweet clover: 100-200 cm., annual or perennial, grows as a 1 m stem
  • Flowers May-September; seeds in mid-to late fall

Root System

  • Strong taproot system – can penetrate up to 2 m
  • Can penetrate compacted silty and clayey soils


  • Seldom winterkills

Site Suitability

  • pH tolerance 6.5 to 7.5;
  • Average annual temperature range between 5° and 22° C
  • White sweetclover does well does on a wide range of soil textures
  • Tolerates calcareous conditions;
  • Sweetclovers perform well in moderately well drained conditions

Sensitivity to Herbicides

  • There are no herbicides available that are safe for use on sweet clover and control these broadleaf weeds.
  • Sweet clover is also sensitive to the soil residues of atrazine and some Group 2 herbicides.

Weed Control

  • Sweet clover is frequently underseeded into a cereal crop and any weed control herbicide program must be:
    1. safe to the cereal crop
    2. effective on the weeds
    3. safe to the cover crop
  • Usually the major weed control problems will be with winter annuals in fall seeded crops and with annual broadleaf weeds in spring cereals.

Benefits and Cautions

Nutrient Management

  • Fixes nitrogen and should be credited for N-additions; believed to move P and K to the root zone via its tap root system

Pest Management

  • Attracts beneficial flowering insects

Organic Matter

  • Biennial whites yield 2,200-3,500 lbs/ac (Yr. 1) and 2,200-8,100 lbs/ac (Yr. 2)
  • Yellow sweetclover 4,200-4,500 lbs/ac (Yr. 1) and 5,500-8,500 lbs/ac (Yr. 2)

Erosion Control

  • Strong taproot said to reduce hard pan problems

Soil Moisture

  • Shows intermediate values for water use efficiency

Getting Started


  • Plant in early spring – March-April
  • May need to be scarified
  • Needs to be covered lightly
  • Planting rate: 10-30 lbs/ac, depending upon variety. Most require 8-10 lbs/ac
  • Seeding depth ~ 1.25 cm
  • Can be underseeded into corn

Cost & Availability

  • Inexpensive to moderate cost (US $0.80 to $ 2.50/lb.)
  • Most varieties suitable to Ontario conditions are widely available

Related Links

For more information:
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