Lacy phacelia

Description

Lacy phacelia is an attractive, non-native, flowering plant. It is native to southwestern United States and northern Mexico. It has been intentionally introduced throughout the United States, southern Canada, and Europe. It is adventive in Minnesota, occasionally escaping, and possibly establishing a local population. However, neither the plants nor the seeds survive the winter.

In its native range, lacy phacelia is found on sandy to gravelly slopes and in open areas. In other areas it is cultivated as a garden ornamental, a cover crop, a green manure, and as a bee plant for honey production. It attracts beneficial insects, including hoverflies (family Syrphidae), which feed on aphids and are a useful biological control agent.

Lacy phacelia is an annual, herbaceous, scorpionweed. It rises on an unbranched or few-branched stem from a taproot and dense fibrous roots.

The stem is erect and 6″ to 40″ (15 to 100 cm) in height. It is covered with more or less short, stiff hairs and with minute, fine, short, glandular hairs.

The leaves are alternate, oblong to egg-shaped, and ¾″ to 8″ (20 to 200 mm) long. The leaf blades are longer than the leaf stalks (petioles). They are usually pinnately divided into leaflets arranged on opposite sides of a central stalk (pinnate). They look much like the leaves of common tansy. This is the feature that gives the plant both its species epithet, tanacetifolia, and one of its common names, tansy scorpionweed. The leaflets are toothed to pinnately lobed

The inflorescence is a dense, flat or rounded, usually 2 to 4 branched flower cluster at the end of each stem. Each inflorescence branch is a coiled, one-sided, dense, fiddle-head arrangement (cyme) of many short-stalked flowers. The flowering time is March to May in its native range, but in other areas it flowers as late as October.

Each flower has 5 outer floral leaves (sepals), 5 petals, 5 stamens, and 1 style. The sepals are united at the base, forming a short tube (calyx), and separated into 5 more or less linear, ⅛″ to ¼″ (4 to 6 mm) long lobes. The lobes are densely covered with long hairs. The corolla is widely bell-shaped, blue, lavender, or bluish purple, and ¼″ to ⅜″ (6 to 9 mm) in diameter. The petals are fused at the base into a short tube then separated into 5 lobes. The lobes are densely hairy outside, hairless inside. The margins are entire, not notched or irregular (erose). The stamens and style are very long, extending far beyond the petals. The stalks (filaments) are ⅜″ to ⅝″ (9 to 15 mm) long, purple at the base, fading to almost white at the tip. There is a pair of small scales fused to the base of each filament. The style is 7⁄16″ to ⅝″ (11 to 15 mm) long. It is split (cleft) for two-thirds to three-quarters of its length.

The fruit is a more or less egg-shaped, ⅛″ (3 to 4 mm) long capsule, usually with just 1 or 2 seeds, sometimes up to 4 seeds. The capsule is minutely hairy to short hairy toward the end. The calyx and the corolla persist as the fruit develops. The persistent calyx lobes are ¼″ to 5⁄16″ (6 to 8 mm) long.

Height

6″ to 40″ (15 to 100 cm)

Flower Color

Blue, lavender, or bluish purple

Similar Species

Habitat

Sandy to gravelly slopes, open areas

Ecology

Flowering

March to October

Pests and Diseases

Use

Garden ornamental, cover crop, and to attract beneficial insects