OREGON STATE UNIVERSITY
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Herbaceous, prostrate growing, reseeding, winter annual legume valued as forage in temperate summer moisture deficit areas. Oversown into low quality, low productivity pastures or seeded with perennial ryegrass, orchardgrass, or tall fescue. Provides high quality biomass during late winter and early to mid-spring. Particularly of value to lactating ewes and cows. Unlike most clovers, sub clover is self-pollinated. After self-fertilization, peduncles bend over and florets turn downward. Several sterile, spiny florets emerge at the end of the peduncle, enclosing 2-4 ripening seeds in the dried-out corolla and calyx. These seed burrs become buried in the upper layer of the soil during summer for subsequent germination in autumn.
Inflorescence is composed of three or four white florets. Corolla (petal) is usually white; calyx color varies with cultivar, often with red bands. Buries its seed pods before the onset of summer drought, hence its name.
Stems are pubescent, prostrate runners that do not root at the nodes.
Leaves are palmately trifoliate with heart-shaped, pubescent leaflets borne on long petioles. Cultivar-specific markings vary with seasonal temperatures. Stipules have green or red veining.
Roots are short taproots (~6 in, 15 cm) with lateral roots and nitrogen fixing nodules.
Seeds are oval with a pronounced hilum are about 10 times heavier than white clover seeds (55,000-70,000 per lb, 121,000-154,000 per kg) and vary in color and weight with sub-species and cultivar; subspecies yannicum seeds are cream-colored, subterraneum and brachycalcycinum are black.
Prostrate growth habit, to 6 inches (15 cm) in height. Stems are pubescent, prostrate runners that do not root at the nodes.
Grown extensively in coastal hills and pastures west of the Cascade Mountains in Oregon and California. Sub clover mixtures are used as a cover crop in California almond orchards.
Climate tolerances: Temperature: Suitable for coastal mid-Atlantic and Southeast US in USDA Plant Hardiness zones 7 and greater for forage or as a living or killed mulch. Optimum temperature range is 18-22 C and maximum temperature is 36 C. Precipitation: Early flowering cultivars are suited to low rainfall areas (15 to 20 inches; 375-500 mm); later flowering cultivars suited to higher rainfall (greater than 20 inches (500 mm).
Soil tolerances: pH: Tolerates strongly acid soils to medium alkaline conditions: pH 5.1-8.4. Soil drainage: Best suited to moderately well-drained to well-drained loamy to clay-loamy soils that are moist through late spring. Percent relative yield for the 7 drainage classes 1-7 is: 5, 20, 55, 100, 100, 55, 20, respectively. Salinity: Moderately Sensitive (tolerates 1.5-3 DS/m).
Grows best in moderately to well-drained loamy to clay-loamy soils that are moist through late spring. Tolerates strongly acid soils to medium alkaline soils: pH 5.1-8.4.
Subterranean Clover Suitability Tolerance Values
|
Suitability Class |
Ave Ann Extreme Min (°C/°F)* |
July Mean Max (°C/°F) |
Annual PPT WET (mm/in)** |
Annual PPT DRY (mm/in)** |
Soil pH*** |
Soil Drainage† |
Soil Salinity (dS/m)# |
|
Well-suited |
-12/10.4 |
30/86 |
1524/60 |
650/26 |
5.8-7.5 |
MWD-WD |
<2 |
|
Moderately suited |
-15/5 |
31/88 |
1270/50 |
550/22 |
5.5-8.0 |
SPD-SED |
2-3 |
|
Marginally suited |
-18/-0.4 |
32/90 |
1016/40 |
400/16 |
5.0-8.5 |
SPD-ED |
3-4 |
**Precipitation requirement: Early flowering cultivars are suited to areas with low rainfall (less than 20 inches, 500 mm) while the later flowering cultivars are suited to higher rainfall (greater than 30 inches, 700 mm). The two columns (WET and DRY) represent current use and potential use, respectively.*USDA Plant Hardiness Zones 7-9 for reseeding cool-season fall seeded; 4b-7b as spring-seeded annual.
Rooting: short taproot with many fibrous branching roots; to a depth of 1 foot (30 cm).
*** Soil pH tolerance: NRCS Range and Pasture Handbook, Chapter 3 classification for Sub Clover is strongly acid to moderately alkaline (5.1-8.4).
† Soil drainage: NRCS Range and Pasture Handbook, Chapter 3 classification for Subterranean Clover is PD-WD. Soil drainage class abbreviations: 1=VPD, very poorly drained; 2=PD, poorly drained; 3=SPD, somewhat poorly drained; 4=MWD, moderately well drained, 5=WD, well drained; 6=SED, somewhat excessively drained; 7=ED, excessively drained. Percent relative yield of sub clover for the 7 class values; 1-7: 5, 20, 55, 100, 100, 55, 20, respectively.
Flooding Tolerance: Brief (3-6 days)
# Soil salinity tolerance: NRCS Range and Pasture Handbook, Chapter 3 classification for clovers (alsike, berseem, white, red, strawberry) is Moderately Sensitive (1.5-3 DS/m). No specific listing for sub clover; selected Moderately Sensitive.
Historically, maps have been drawn based on primary use areas, showing broad geographic areas, e.g. Compendium of Common Forages maps within Forages: An Introduction to Grassland Agriculture, 7th ed. (2018), John Wiley & Sons, Inc.
(Subterranean Clover Adaptation & Use Map.)
(SARE Managing Cover Crops Map. Source: Managing Cover Crops Profitably, 3rd Ed., Sustainable Agriculture Research & Education.)
More highly detailed maps, based on quantitative climatic and soil factor tolerances and using GIS spatial grids, provide information on where species are suitable for a variety of intended uses.
The following collection of maps were developed by a group of Oregon State University scientists, using the PRISM-generated collection of climate factor grids and the NRCS soil characteristics database.
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature Wet |
pH Wet |
Climate and Soil Wet |
|
Minimum Temperature Dry |
pH Dry |
Climate and Soil Dry |
|
Maximum Temperature Wet |
Drainage Wet |
All Soil |
|
Precipitation Wet |
Salinity Wet |
All Climate Wet |
|
Precipitation Dry |
Salinity Dry |
All Climate Dry |
Map designations of wet and dry refer to different precipitation requirements for current use areas (40-60 inch rainfall zones, designated wet) and potential use areas (16-26 inch rainfall zones, designated dry).
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature Wet
|
pH Wet
|
Climate and Soil Wet
|
|
Minimum Temperature Dry
|
pH Dry
|
Climate and Soil Dry
|
|
Maximum Temperature Wet
|
Drainage Wet
|
All Soil Wet
|
|
Precipitation Wet
|
Salinity Wet
|
All Climate Wet
|
|
Precipitation Dry
|
Salinity Dry
|
All Climate Dry
|
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature Wet |
pH Wet |
Climate and Soil Wet |
|
Minimum Temperature Dry
|
pH Dry |
Climate and Soil Dry |
|
Maximum Temperature Wet |
Drainage Wet |
All Soil Wet
|
|
Precipitation Wet
|
Salinity Wet |
All Climate Wet |
|
Precipitation Dry
|
Salinity Dry |
All Climate Dry
|
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature Wet |
pH Wet |
Climate and Soil Wet
|
|
Minimum Temperature Dry |
pH Dry |
Climate and Soil Dry |
|
Maximum Temperature Wet |
Drainage Wet |
All Soil Wet |
|
Precipitation Wet |
Salinity Wet |
All Climate Wet |
|
Precipitation Dry |
Salinity Dry |
All Climate Dry |
Produces rosette in autumn following late summer seeding or reseeding germination. Primary production is spring to early summer with later maturing cultivars providing forage into early summer if soil moisture is available.
Subterranean clover has three sub-species: subterraneum, yanninicum, and brachycalycinum. Subspecies subterraneum is the most common and widely grown. Yanninicum is adapted to spring waterlogged soils. Brachycalycinum tolerates more calcareous soil.
Cultivars differ in persistence, productivity, flowering time, seed maturity, hardseededness, pest and disease resistance, and estrogen content. Select late flowering cultivars if moisture extends into summer, early flowering types for early spring biomass. Low growing - hardseeded types tolerate low temperatures; use small-leaved prostrate types for set stocking grazing management.
Quality: Highly palatable and digestible forage in late winter and spring.
Antiquality: Older cultivars produce compounds with estrogenic activities that can interfere with livestock breeding. Select low phytoestrogen-containing cultivars.
Journal Papers
Teixeira, Carmen, John Hampton, and Derrick Moot. 2021. Phenological development of subterranean clover cultivars under contrasting environments. Ann Appl Biol. https://doi.org/10.1111/aab.12693
Enriquez-Hidalgo, Daniel, Trinidad Cruz, Dayane L. Teixeira. 2020. Phenological stages of Mediterranean forage legumes, based on the BBCH scale. Ann Appl Biol. 176: 357–368. https://doi.org/10.1111/aab.12578
Books and Book Chapters
Clover Science &Technology (Agronomy Monograph No. 25, 1985)
Extension Fact Sheets and Circulars
Lincoln University
Guide for subterranean clover identification and use in New Zealand
