OREGON STATE UNIVERSITY
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Herbaceous, highly productive, cool-season winter annual clover suitable for hay, grazing, seed production, soil improvement, and wildlife forage. Well-adapted to overseeding of perennial warm-season grasses. Produces forage later in the spring than crimson and sub clover. Upright growth habit, to 40-50 inches (100-130 cm) under favorable conditions.
Inflorescence: Large conical flower head up to 2 inches (5 cm) long has white to pink flowers opening from bottom to top, browning when mature.
Mostly upright stems grow to 3-4 feet (90-120 cm), are glabrous (not hairy), hollow, smooth, and often purple.
Palmately trifoliolate, arrow-shaped leaves have a characteristic large, white V mark.
Stipules are white, long, narrow, and pointed, with prominent veins.
Deep taproot can penetrate up to 4.5 feet (140 cm).
Seeds are about twice the size of white clover, with 400,000 per lb (880,000/kg). Nearly 70% are hardseeded, seed requires scarification for satisfactory germination.
Mostly upright stems grow to 3-4 feet (90-120 cm). Annual.
Grown throughout the mid-south and southeastern United States (USDA Plant Hardiness Zones 9a-8a). It requires 18-25 inches (450-650 mm) minimum precipitation or irrigation.
Tolerates moderately acid to moderately alkaline soils (pH 5.6-8.4) that are well- to moderately well-drained. Not suited to sandy, droughty soils with low fertility. Will not survive poorly drained soils. Moderately sensitive to salinity (1.5-3 dS/m).
Arrowleaf Clover Suitability Tolerance Values
|
Suitability Class |
Jan Min (°C/°F)* |
July Max (°C/°F) |
Annual Precip (mm/in)** |
Soil pH*** |
Soil Drainage† |
Soil Salinity (dS/m)# |
|
Well-suited |
-10/14 |
32/90 |
1524/60 |
5.8-7.5 |
MWD-WD |
<2 |
|
Moderately suited |
-12/10 |
34/93 |
1270/50 |
5.5-8.0 |
SPD-SED |
2-3 |
|
Marginally suited |
-15/5 |
36/97 |
1016/40 |
5.0-8.5 |
SPD-ED |
3-4 |
*Cold temperature tolerance: USDA Plant Hardiness Zones - based on average annual extreme minimum temperature; 7a-9a as a winter annual.
Heat Zone - based on Mean Max July Temperature: 92-96 °F.
Latitude delimitations: 30-35 degrees N, 99 degrees West boundary.
**Precipitation minimum requirements important for fall, winter, spring seasons, since planted as a winter annual in the southeast. Zone: 36-40 inches and greater.
Rooting: tap, to 150 cm.
*** Soil pH tolerance: NRCS Range and Pasture Handbook, Chapter 3 classification for arrowleaf clover is moderately acid to moderately alkaline (5.6-8.4).
† Soil drainage: NRCS Range and Pasture Handbook, Chapter 3 classification for Arrowleaf Clover is WD-PD. 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 for Arrowleaf Clover for the classes 1-7: 5, 20, 55, 100, 100, 55, 20, respectively.
Flooding Tolerance: Brief (3-6 days). [Not listed in NRCS documents.]
# 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). Arrowleaf is not listed.
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.
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. The procedure used to produce these suitability maps is described below.
Suitability curves were developed for each clover species for three climate variables (average annual precipitation, average July maximum temperature, and average annual extreme low temperature) and three soil variables (drainage class, pH, and salinity). For each variable and each species, the curves were fit using estimated yield data across the full range of values for the given variable.
The coefficients for the model equations were applied to spatial data layers representing each climate and soil variable, resulting in spatial outputs of percent yield for each of the clover species and each climate and soil variable. The percent yield layers were then classified into four suitability classes, as follows:
| Classification | Relative Yield (RY) % |
| Unsuited | 0-25 |
| Marginally unsuited | 26-50 |
| Marginally suited | 51-74 |
| Well suited | 75-100 |
Finally, three "hybrid" suitability layers were produced for each clover species based on combinations of 1) the three climate variables, 2) the three soil variables, and 3) all six climate and soil variables together. These combined suitability layers were created by selecting for each location the lowest suitability value of the included variables, with the idea that the overall suitability for a species will be limited by the most restrictive factor.
Data sources
----------------
Climate data: 800m PRISM 30-year normals for years 1981-2010 (PRISM Climate Group, Oregon State University, http://prism.oregonstate.edu, accessed 2018-01-17)
Soils data: NRCS STATSGO (Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. U.S. General Soil Map (STATSGO2). Available online at https://sdmdataaccess.sc.egov.usda.gov. Accessed 2018-01-10.
|
Climate Factors |
Soil Factors |
Combined Factors |
|
Minimum Temperature
|
pH
|
All climate and soil factors (most limiting)
|
|
Maximum Temperature
|
Drainage
|
All soil factors (most limiting)
|
|
Precipitation
|
Salinity
|
All climate factors (Most limiting)
|
Click on the thumbnail image to view a larger map.
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature
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pH
|
Climate and Soil
|
|
Maximum Temperature
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Drainage
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All Climate
|
|
Precipitation
|
Salinity
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All Soil
|
Hawaii
| Climate Factors | Soil Factors | Combined Factors |
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Minimum Temperature
|
pH
|
Climate and Soil
|
|
Maximum Temperature
|
Drainage
|
All Climate
|
|
Precipitation
|
Salinity
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All Soil
|
| Climate Factors | Soil Factors | Combined Factors |
|
Minimum Temperature
|
pH
|
Climate and Soil
|
|
Maximum Temperature
|
Drainage
|
All Climate
|
|
Precipitation
|
Salinity
|
All Soil
|
Planted during the autumn in the southeastern USA with annual ryegrass or other annual grass or interseeded into warm season grass pastures where winter and spring temperatures are sufficiently warm to allow growth during this period. Arrowleaf is later maturing than crimson clover, and continues to grow into early July.
Select a cultivar that has been shown in local university trials to have improved resistance to virus complex, crown rot, and alfalfa weevils and aphids. ‘Blackhawk’ was released by Texas A&M in 2013. It matures earlier than ‘Apache’ (medium) and ‘Yuchi’ (late) cultivars. ‘Arrotas’ is a late-maturing, high yielding cultivar released by the Tasmania Institute of Agriculture.
High quality forage; improves pasture quality when overseeded into warm-season (C4) grasses.
Minimal bloat risk.
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