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Strawberry Clover

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Summary

Common Name
The common name is strawberry clover (Duke, 1981).

Scientific Name
Trifolium fragiferum L is its scientific name (Duke, 1981).

Cultivar
There are several varieties available: 'Palestine,' developed in Australia, is large and productive, but is susceptible to frost; 'Salina' is better adapted to California (Duke, 1981). Other varieties include 'Fresa' (Slayback, pers. comm.) and 'O'Conners,' an Australian variety (Miller et al, 1989). Gillett (1985) listed five botanical varieties, distinguished by morphological characters: majus, modestum, pulchellum, orthodon, and fragiferum.

Seed Description
According to Duke (1981), seeds are ovoid-truncate and spotted with light brown, there are 661,000 seeds/kg, and seed may be 40-75% hard even after hulling. Gillett (1985) described the seeds as 1-1.2 mm long, reniform, and brown spotted.

Seedling Description
Seedlings are vigorous (Slayback, pers. comm.) but less so than those of white clover (Townsend, 1985). Seedlings express salt tolerance better when weather is cool (Duke, 1981).

Mature Plant Description
Based on the account by Gillett (1985), strawberry clover is a pubsecent or glabrous perennial with prostrate or creeping branching stems 0.5-5 dm long, rooting at the nodes and with erect petioles and peduncles. Leaves congested or loose; petioles long, pilose. Stipules long, lanceolate, dilated and white chartaceous towards the base and with subulate free part. Corolla white to pink.

Temperature
Strawberry clover tolerates mean annual temperatures of 6.6-21.8 C, with a mean of 20 cases of 11.9 (Duke, 1981). McLeod (1982) listed it is a warm-season plant that will tolerate temperature extremes. 'Salina' is not so winter hardy as common strawberry clover, which can withstand snow cover (McLeod, 1982). Yet 'Salina' strawberry clover is more cold tolerant than the Australian cultivar 'Palestine', from which it was derived (Carlson et al., 1985).

Peaceful Valley (1988) and Miller et al. (1989) remarked that the species is tolerant of heat and full sun exposure.

Seedlings express salt tolerance best when weather is cool (Duke, 1981).

Geographic Range
According to Duke (1981), strawberry clover is native to Eurasia and inhabits the Cool Temperate Steppe to Wet through Warm Temperate Thorn to Moist Forest Life Zones. It is assigned to the Eurosiberian and Mediterranean Centers of Diversity, and has been introduced to Australia, New Zealand, and to the United States, where it is naturalized in the North. With irrigation, it does well in most of California (Slayback, pers. comm.), but it was not listed by Munz (1973) as naturalized in California.

Water
According to Duke (1981), strawberry clover tolerates mean annual precipitation of 4.4-11.6 dm, with a mean of 20 cases of 7.0. It is tolerant of wet, waterlogged soils, and survives flooding for 1-2 months; it can also survive in dry areas and tolerates short droughts. According to Munoz & Graves (1988) it requires 30 inches of water. It grows best where moisture is plentiful (McLeod, 1982), yet requires fewer irrigations than ladino clover when soil is porous (McLeod, 1982).

In Californian regions with 36 to 40 inches of rainfall per year and a rain-free period of 90 to 100 days, strawberry clover will produce continuously without irrigation (McLeod, 1982).

Strawberry clover is tolerant of infrequent irrigation (Miller et al., 1989) and as of 1992 had survived for 3 years in unirrigated roadside prairie plantings at John H. Anderson's Hedgerow Farms, Yolo County, California (Bugg, pers. comm.).

Prichard et al. (1989) found that almond orchards with strawberry clover as a cover crop required up to about 1/3 more irrgiation water on average than those using 'Blando' brome as a cover crop or those with residual herbicide or chemically-mowed resident vegetation.

Nutrients
Duke (1981) reported that strawberry clover is tolerant of alkalinity, salinity, and waterlogged soils. P2O5 is sometimes added to soils to compensate for P deficiency (Townsend, 1985).

Kanyama-Phiri et al. (1990) found that in strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, the clovers were most productive with 60 kg/ha of N added. Strawberry clover and ladino clover are similar in morphology and growth habit, but differ in response to different nutrient and grazing regimes. In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, with no added nitrogen, ladino clover peaked in dry matter production in October, then fell off during November. Strawberry clover peaked in November. By contrast, when nitrogen was added (60, 120, and 180 kg/ha of N added), these situations were reversed.

Soil pH
Strawberry clover tolerates soil pH of 5.3-8.2, with the mean of 19 cases being 6.8 (Duke, 1981). The species is tolerant of alkali (Duke, 1981; McLeod, 1982; Miller et al., 1989). Cv 'Salina' has been called the most alkali-tolerant perennial clover (Peaceful Valley, 1988).

Soil Type
Strawberry clover is adapted to a wide range of soils (Duke 1981; McLeod, 1982), from loam to clay (Munoz & Graves, 1988). It is said to be tolerant of alkali, high pH, salinity, short-term drought, and waterlogging (Duke, 1981). It produces best on fertile, well drained soil (McLeod, 1982), and cv 'Salina' is said to be well adapted to all orchard and vinyard soil conditions (Finch & Sharp, 1983).

Shade Tolerance
Strawberry clover will tolerate shade (Munoz & Graves, 1988) but is usually paired with Dutch white (ladino) clover in orchards because the latter is more shade tolerant (Bugg, pers. comm.).

Salinity Tolerance
This species is tolerant of salinity (Duke, 1981; McLeod, 1982), showing good growth in combination with saltgrasses and sedges at 1% salinity and with established stands persisting in the face of salinity of over 3%. In overly-saline pastures, strawberry clover may look overgrazed, and flower heads are short stalked (Duke, 1981). Seedlings express salt tolerance better with cool weather (Duke, 1981). The species will grow on salty soils along tidal streams (McLeod, 1982).

Herbicide Sensitivity
Strawberry clover is highly tolerant to 2,4-D and glyphosate applications as well as other herbicides. (Fred Thomas, pers. comm.)

Life Cycle
Strawberry clover is a long lived perennial (Peaceful Valley, 1988) that roots at the the nodes of stolons (Gillett, 1985) and grows principally during the summer (McLeod, 1982). Flowering is during June and July (Duke, 1981). From 40-75% of seed may be hard. The species can be seeded in fall or during spring where moisture is adequate.

Seeding Rate
Seeding rates were variously given as 2-5 kg/ha (Duke, 1981), 3-6 kg/ha (Townsend, 1985), 5-15 lb/acre (Munoz & Graves, 1988; Miller et al., 1989), 6-10 lb/acre (McLeod, 1982), 9 lb/acre (Finch & Sharp, 1983), and 12-15 lb/acre (Peaceful Valley, 1988).

Seeding Depth
Recommended seeding depths are 1 cm (Townsend, 1985), 1/4-1/2 inches (Peaceful Valley, 1988), and 1/2 inch (Slayback, pers. comm.).

Seeding Method
Drill or broadcast methods are suggested (Slayback, pers. comm.); drilling scarified seed gives the best stands, but unscarified seed may be sown on unprepared seedbeds in the late winter (Townsend, 1985). If seedbeds cannot be prepared, existing vegetation should be mowed or removed before seeding (Townsend, 1985).

Seeding Dates
Sow seed fall-spring (Munoz & Graves, 1988; Peaceful Valley, 1988). According to McLeod (1982), sowings in the fall, before cold weather, germinate better than spring sowings; Townsend (1985) stated that fall sowing is usually preferred in California. By contrast, McLeod (1983) mentioned that weed control in the spring sowings may be easier since weeds can be mowed at the proper time; mowing for weed control in fall sowings may often be delayed because of wet soils.

Inoculation
Strawberry clover requires a special strain of Rhizobium trifolii, "Trifolium Special Culture No. 6" (Nitragin Co.) (Burton and Martinez, 1980; Duke, 1981).

Seed Cost
Seed cost was $4.00/lb (Munoz & Graves, 1988). Fred Thomas (pers. comm.) listed the market retail price for cv 'Salina' as $2.67/lb in 1993.

Seed Availability
Seed availability is fair to good (Slayback, pers. comm.).

Days to Flowering
Flowering of this perennial occurs principally in May and June (Duke, 1981).

Days to Maturity
Seed presumably is mature in July (Bugg, pers. comm.).

Seed Production
Although common strawberry clover is self-fertile, the 'Salina' variety is self-sterile and needs cross pollination (McLeod, 1982). Duke (1981) mentioned that strawberry clover is a good honey plant, so cross pollination is presumably by bees.

Duke (1981) discussed seed production and harvesting as follows. Cattle should be removed by June 1 to allow flowering and seed development. Cut the heads when most seed envelopes are light brown, and slightly damp, to avoid loss of seed due to shattering. Closely-set windrowing attachments or bunchers on mowers are useful in reducing the number of times a crop must be handled, and thus reducing losses due to shattering. Vacuum collection of seed can be done if the soil surface is smooth. Seed yields range from 40-300 kg/ha, and the mean is about 100 kg/ha.

Seed Storage
Even after seed are hulled, 40-75% may be hard (Duke, 1981). Seed remains viable for a relatively long time (McLeod, 1982).

Growth Habit
Strawberry clover has a prostrate, spreading habit (Munoz & Graves, 1988); its thick growth allows it to smother weeds (Peaceful Valley, 1988). It is stoloniferous (Miller et al., 1989); stolons root at the nodes (Gillett, 1985), and roots may extend to a depth of 1 m (Townsend, 1985).

Maximum Height
'Salina' attains a height of 8 to 12 inches (Finch & Sharp, 1983), or up to 14 inches (Peaceful Valley, 1988). Bugg et al. (unpublished) found that cv 'Salina' seeded in October had by the following May attained a mean height of 31.12 +/- 4.91 cm (mean +/- S.E.M.) (12.25 +/- 1.93 inches) in a Mendocino County organic vineyard.

Root System
According to Townsend (1985), on dry soils, strawberry clover roots penetrate to about 1 m, but are confined to the upper 8-10 cm on wet, saline soils. McLeod (1982) stated that taproots will descend 2 to 4 feet when there is no sub-surface hardpan.

Establishment
The following is based on Duke (1981). If moisture is adequate, strawberry clover may be spring sown with a companion grain crop. Barley is suitable on saline sites. On prepared seedbeds, competition from other plants is seldom a problem during establishment. If seed is broadcast with no seedbed preparation, rushes and sedges should be mowed. Strawberry clover withstands trampling and grazing better than other, competing plants.

Strawberry clover requires 25 days to germinate, therefore in sandy soils, sufficient irrigation will be needed to keep the seedling from dying, especially with a spring planting. (Fred Thomas, pers. comm.)

Maintenance
Grazing (or, presumably, mowing) can be used after strawberry clover is established, to reduce competition by barley or other plants (Townsend, 1985).

In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, close mowing alternating with 30-31 day regrowth periods apparently favors the two clovers and the perennial ryegrass (Kanyama-Phiri et al., 1990).

Strawberry clover and ladino clover are similar in morphology and growth habit but differ in response to different nutrient and grazing regimes. In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, with no added nitrogen, ladino clover peaked in dry matter production in October, then fell off during November. Strawberry clover peaked in November. By contrast, when nitrogen was added (60, 120, and 180 kg/ha of N added), these situations were reversed (Kanyama-Phiri et al., 1990).

On P-deficient soils, P2O5 addition increases production (Townsend, 1985).

Mowing
Strawberry clover tolerates mowing (Finch & Sharp, 1983; Munoz & Graves, 1988; Peaceful Valley, 1988; Miller et al., 1989) and grazing (Peaceful Valley, 1988). Grazing (or, presumably, mowing) can be used after strawberry clover is established, to reduce competition by barley or other plants; strawberry clover tolerates close, continuous grazing (Townsend, 1985).

In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, close mowing alternating with 30-31 day regrowth periods apparently favors the two clovers and the perennial ryegrass (Kanyama-Phiri et al., 1990).

According to Kanyama-Phiri et al. (1990), strawberry clover and ladino clover are similar in morphology and growth habit, but differ in response to changes in nutrient and grazing regimes. In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, with no added nitrogen, ladino clover peaked in dry matter production in October, then fell off during November. Strawberry clover peaked in November. By contrast, when nitrogen was added (60, 120, and 180 kg/ha of N added), these situations were reversed.

Incorporation
No information is available in this database on this topic.

Harvesting
Seed crop should be cut when seed envelopes are light brown. Ripe heads shatter readily, so cut when heads are damp and envelopes are tough. Mow, then pick up from swath or windrow. Vacuums have been used for harvest, where soil surface is smooth. Seed crop may be cured in windrows or stacks, then picked up from these and threshed by clover hullers or combines having hulling attachments (Duke, 1981).

Equipment
A seed crop may be cured in windrows or stacks, then picked up from these and threshed by clover hullers or combines having hulling attachments (Duke, 1981).

Uses
Strawberry clover is seldom used for hay because of its low stature, but it is used in lawns, permanent pasture, green manure, and is a good bee plant (Duke, 1981).

Strawberry clover is viable on swampy ground because it tolerates waterlogging (McLeod, 1982), and it is the hardiest perennial clover species available for Californian orchards and vineyards (Miller et al., 1989). Its forage production is poor in the summer (Finch & Sharp, 1983), yet cv 'Salina' is usable in orchards, vineyards, and other perennials where a low-growing, heat tolerant year round clover is desirable (Peaceful Valley, 1988).

Mixtures
Duke (1981) stated that strawberry clover does well in mixture with saltgrasses and sedges at 1% salinity and is tolerant of weeds, and that barley is the only salt-tolerant annual suitable for mixed seedings on saline sites. In Californian orchards, the heat-tolerant strawberry clover is often grown in mixture with shade-tolerant white or ladino clover (Bugg, pers. comm.).

In roadside prairie mixes at John H. Anderson's Hedgerow Farms (Winters, Yolo County, California), strawberry clover has persisted for 4 years in combinations with sheep fescue (Festuca ovina cv 'Covar'), meadow barley (Hordeum brachyantherum) or perennial ryegrass (Lolium perenne), without irrigation (R.L. Bugg, pers. comm.).

In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, close mowing alternating with 30-31 day regrowth periods apparently favors the two clovers and the perennial ryegrass (Kanyama-Phiri et al., 1990).

Kanyama-Phiri et al. (1990) further found that in strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, the clovers were most productive with 60 kg/ha of N added. Strawberry clover and ladino clover are similar in morphology and growth habit, but differ in response to different nutrient and grazing regimes. In strawberry clover - white clover - perennial ryegrass - orchardgrass mixtures, with no added nitrogen, ladino clover peaked in dry matter production in October, then fell off during November. Strawberry clover peaked in November. By contrast, when nitrogen was added (60, 120, and 180 kg/ha of N added), these situations were reversed.

Biomass
Biomass harvests were made on May 15-16, 1991 for cover crops seeded during October, 1990, in a replicated study (r=4) at Blue Heron Vineyard, Fetzer Vineyards, Hopland, Mendocino County, California. Dry above-ground biomass was 1.866+/-0.607 Mg/ha, Mean +/- S.E.M. for 'Salina' strawberry clover (Bugg et al., unpublished data); this was only 37.9% of the weed biomass in unseeded control plots. When weeds were included, biomass was 5.405+/-0.620 ( Mg/ha, Mean +/- S.E.M.) (Bugg et al., unpublished data). In the same trial, biomass of strawberry and white clovers in mixture was 3.941 +/-0.872 Mg/ha.

When strawberry clover is grown in mixes with grasses such as dallis grass (Paspalum dilatatum Poir.), total biomass production can be 18 Mg/ha-year (Townsend, 1985).

N Contribution
Nitrogen content of strawberrry clover has been estimated at 125 lb/acre for 'Salina' (Peaceful Valley, 1988), and from 100-300 lb/acre (Munoz & Graves, 1988).

Non-N Nutrient Contribution
As summarized by Townsend (1985), strawberry clover grown on saline soils shows elevated Mg, Na, K, and P concentrations, but reduced N and Ca as compared with the same species on non-saline soils. AU Townsend, C.E. YR 1985 TI Miscellaneous perennial clovers. SO Chp. 26, pp. 563-578 in: Taylor, N.L. Clover Science and Technology. Agronomy Monograph No. 25, Agronomy Society of America, Inc., Crop Science Society of America, Inc., and Soil Science Society of America, Inc., Publishers. Madison, Wisconsin. TY PUB IN Crops Research Laboratory, USDA-ARS, Colorado State University, Fort Collins, Colorado.

Effects on Water
Prichard et al. (1989) found that a cover crop of strawberry clover in almond orchards could increase water use by about 25% over that observed in bare orchards.

Field observations on clay soils suggested that strawberry clover will greatly (25-40%) improve water infiltration due to the shrinking and swelling of the taproot opening up channels. (Neil Phillips, pers. comm.)

Effects on Microclimate
There can be reduced sunburning and sandblasting where strawberry clover is grown as a cover crop. (Fred Thomas, pers. comm.)

Effects on Soil
Taproots open up compacted soil. (Fred Thomas, pers. comm.)

Effects on Livestock
Strawberry clover is as good a livestock feed as white clover; used with good results by poultry and mammalian livestock (Duke, 1981)

While noted as a non-bloating clover, Monte Bell did observe bloat in a pure stand at Williams, CA at the La Grande Ranch ca. 1985. Otherwise strawberry clover is a primary component of all non- bloating pasture mixes in California. (Fred Thomas, pers. comm.)

Effects on Workers
No information is available in this database on this topic.

Pest Effects, Insects
Cv 'Salina' has been termed a good beneficial insect attractor (Peaceful Valley, 1988), but Bugg (pers. comm.) stated that it appears to harbor relatively low densities of key beneficial insects.

Pest Effects, Nematodes
McKenry (pers. comm.) found that cv 'Salina' is a host for Meloidogyne hapla but does not appear to be a good winter host for M. javanica, M. incognita or M. arenaria.

Duke (1981) reported that the following nematodes have been isolated from strawberry clover: Ditylenchus dipsaci, Heterodera galeopsidis, Heterodera trifolii, Meloidogyne javanica,and Pratylenchus penetrans.

Pest Effects, Diseases
Strawberry clover is more susceptible to Sclerotinia (McLeod, 1982; Townsend, 1985) and crown rot (Townsend, 1985) diseases than is ladino clover; the Sclerotinia fungus is favored by cool, wet conditions. Duke (1981) reported 12 species of fungi as having been isolated from strawberry clover.

Pest Effects, Weeds
Cv 'Salina' shows a low, thick, weed-smothering growth habit (Peaceful Valley, 1988).

Strawberry clover cv 'Salina' was sown as a vineyard cover crop in Mendocino County, California, in late October and harvested in mid-May. Weed biomass was 3.540+/-0.704 Mg/ha, Mean +/- S.E.M. (Bugg et al., unpublished data). Dominant winter annual weeds were chickweed, shepherds purse, rattail fescue, and annual ryegrass. Vegetational cover by the clover was 62.50+/-10.51% (Mean +/- S.E.M.) (Bugg et al., unpublished data).

Pest Effects, Vertebrates
Based on observations at John Anderson's farm in Winters, CA, strawberry clover attracts gophers; it is not clear whether this increases pest problems from gophers, or diverts them from feeding on crop plants (Bugg, R.L, Pers. Comm.).

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