Phacelia

• Cool-season annual forb
• Native to California, but developed in Germany
• 12-36" tall
• Biomass 3,300-6,000 lb/a
• N content 4%
• Flowers March-May
• Matures April-June
• Grown as a nitrogen catch crop and as a nectar source for honeybees and hover flies
• Harbors lygus bugs

Common Name

Phacelia (Sengonca and Frings, 1988), tansy phacelia (Niehaus and Ripper, 1976).

Scientific Name

Phacelia tanacetifolia, Benth., Hydrophyllaceae (Munz, 1973).

Mature Plant Description

Tansy phacelia is a cool-season annual 2-8 dm in height (Munz, 1973). Phacelia is a bushy plant with fern-like foliage and blue flowers (Pears et al., 1989).

Life Cycle

Broadleafed annual (Sengonca and Frings, 1988), flowering from March through May (Munz, 1973).

Seed Cost

Seeds can be expensive (Pears et al., 1989).

Root System

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Both phacelia and cereal rye cover crops developed extensive fibrous root systems reaching depths of 75cm.

Biomass

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. For phacelia, biomass production was 3,640 +/- 283.8 kg/ha and N content 106 +/- 10.4 kg/ha. The corresponding values for cereal rye were 3,727 +/- 1.29.2 kg/ha and 136 +/- 9.5 kg/ha.

Effects on Water

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Cover-cropped soil showed lower soil moisture than control from mid- to late March.

Effects on Soil

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Phacelia led to significantly higher soil microbial biomass C and N than cereal rye or control on several dates in late March and early April. Cover-cropped soil showed lower soil moisture than control from mid- to late March.

Pest Effects, Insects

In a two-year, replicated study, Sengonca and Frings (1988) grew tansy phacelia (Phacelia tanacetifolia, Hydrophyllaceae) on the corners, in interior strips, and in "islands", in conjunction with 200-m2 plots of sugarbeet. Control plots featured monocultures of sugarbeet. Densities of bean aphid (Aphis fabae) and eggs and larvae of aphidophagous hover flies (Diptera: Syrphidae) were highest in control plots. On the other hand, sugarbeet yields were significantly higher, and adult syrphids (which feed on floral nectar and pollen of phacelia) were significantly more abundant in the plots with phacelia. Syrphids were credited with reducing the aphids in plots with phacelia. Aphidophagous syrphids observed included Episyrphus balteatus, Metasyrphus corollae, Sphaerophoria scripta, Scaeva selenitica, and Melanostoma scalare..

Tansy phacelia is an annual plant native to California and introduced as a bee plant to Europe during the early 1900's. It is used as a cover crop in Europe, but (at least in California) harbors high densities of Lygus spp. and should be used with care (Bugg, pers. comm.). When tansy phacelia was grown in a commercial flower garden in Capitola, Santa Cruz Co., during 1980, the plant harbored high densities of Lygus spp. When the plant died during spring, the Lygus dispersed and caused damage to other flowers in the garden (Richard Reed, pers. comm.).

Flowers of tansy phacelia are attractive to bees (Pears et al., 1989).

Wyland et al. (1996) during winter in Salinas, CA, grew tansy phacelia (cv. 'Phaci') and cereal rye (cv. 'Merced') both preceded and followed by broccoli; control plots were fallow. There were three replications. Plots were managed by th reduced-tillage "Sundance System." Both cover crops were tilled under in mid-April and broccoli was planted in late April. Phacelia led to significantly higher densities of bulb mite (Rhizoglyphus echinopus) on the soil surface than did either cereal rye or bare plots, during broccoli growth.

Pest Effects, Weeds

Tansy phacelia grows quickly and suppresses weeds (Pears et al., 1989).

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