Know Your Natives – Hairy Phacelia

Hairy phacelia (Phacelia hirsuta) of the Borage (Boraginaceae) family [formerly of the Waterleaf (Hydrophyllaceae) family] is a beautiful annual forb with blue flowers.  In the U.S., it is found naturally in Arkansas, Louisiana, Texas, Oklahoma, Kansas, and Missouri, as well as introduced in Kentucky and Pennsylvania.   In Arkansas, it is found throughout much of the state but sparser in the Mississippi Alluvial Plain.  Its habitats include rocky to sandy, moist soils in open woods and woodland margins, as well as in prairies, glades, and along roadsides.  The genus name is from Greek for “bundle”.  The specific epithet is from Latin for “hairy”.  Another common name is “hairy scorpion-weed”.

Hairy phacelia, whose basal leaves appear in late winter, develops a main stem and several long to short secondary stems.  The longest secondary stems grow from lower leaf axils of the main stem, with shorter stems growing from mid-stem axils.  Plants have a tap root and a few fibrous roots.  The main stem and secondary stems reach a similar maximum height of up to 1 to 1½ feet.  Stems, which are weakly erect, are yellowish-green with the lower portion having a reddish cast.  Stems are very hairy (hirsute).

Hairy Phacelia - Phacelia hirsutaPhoto 1:  In this April 2nd photo, several secondary stems have developed and developing inflorescences can be seen at the ends of stems.

Alternate hirsute leaves, with three to seven leaflets or lobes, are widely spaced on a mature plant and are medium green on upper surfaces and light green on lower surfaces.  Leaves feel soft and venation is not especially distinct.

Lower leaves, which have long, grooved petioles, have blades from ¾ inch to 1¼ inch long, with maximum width of about ¾ inch.  These leaves typically have a lower lateral pair of opposite, oval leaflets and, higher up the leaf blade, one to three pairs of mostly opposite, lateral leaflets that may have widened bases, becoming lobes.  Additionally, a large, broad terminal lobe is partially cleft on both sides so that it is three-lobed.  Lower leaflets (or lobes) are set perpendicular to the rachis while upper lobes (including those of the terminal lobe) are angled toward the apex.   Lobes of these lower leaves may be wide or narrow with rounded tips.

Upper leaves (from mid-stem into the inflorescence), have blades that decrease in size up-stem to uppermost leaves that may be ¾ inch long and 3/8 inch wide.  Transitioning up-stem,  lobed leaves gradually change shape from petiolate to sessile and lobe blade tissue increasingly extends along the rachis.  The uppermost leaves have two or three pairs of lateral lobes that may be either narrow-rounded and angled toward the leaf apex or narrow-acuminate and out-flared.   The shape of terminal lobes is similar to lateral lobes.  Petioles of mid-stem leaves (when present) are wide and broadly grooved.  Smaller leaves are sessile.

Hairy Phacelia - Phacelia hirsutaPhoto 2:  Leaf display shows changing leaf shape from basal to upper stem leaves (left to right).  Note that leaves change from petiolate to sessile and from having some leaflets and lobes to having all lobes.

Inflorescences, in mid-spring, grow from uppermost leaf axils of main and secondary stems.  Appearing first as round clusters (or “bundles”) of compacted sepals, with growth, the coiled nature of the inflorescence becomes apparent.  Coils consist of a peduncle with up to twenty or more flowers alternately arranged along the upper side of the inflorescence axis (rachis).*  Flowers are each on a short pedicel.  Peduncles and pedicels have short hirsute pubescence.  As the coil straightens, flowers reach anthesis from lowermost to uppermost.  When fully straightened and the last flower has bloomed, the inflorescence may be 3 inches long.   The entire plant continues to stretch out (grow) until the final flowers have bloomed.

Hairy Phacelia - Phacelia hirsutaPhoto 3:  Developing inflorescence appears as rounded clusters of loose, hirsute sepals at ends of stems.

Flowers, about ½ inch in diameter, have a deeply divided calyx with five long, narrow, spreading lobes with hirsute exteriors, and a bowl-shaped corolla notched to create five broadly-triangular but rounded lobes.  The exterior of the corolla is pubescent.  Corollas are typically a light blue to lavender overall, but may have a lighter or white center.  Just below mid-corolla, ten dark purple, round to three-sided spots encircle the flower’s center, two spots below each lobe.  These purple spots are surrounded by a haze of lighter color.  Five spreading stamens have white filaments, with anthers at first bearing light yellow pollen that become black.  Filaments, adnate at the base of the corolla, are covered by long radiating white hairs.  The pistil, also white, has a forked and pointed style whose stigma does not become receptive to pollen until after the pollen from the same flower has been shed (protandry–an adaptation that reduces self-pollination).   Stamens and pistils, all about the same length, extend slightly beyond the rim of the corolla.  A light green, superior ovary, also hirsute, has the shape of an elongated, round cone.

After producing seed capsules containing a small number of brown seeds, these annual plants quickly die.

Hairy Phacelia - Phacelia hirsutaPhoto 4:  Flowers reach anthesis at the top of a coil in sequence (from left [bottom of coil] to right [top of coil] in this photo) as coil straightens.  “Newest” flower at right bears pollen.  Forked styles can be clearly seen in the lower two flowers.

Hairy Phacelia - Phacelia hirsutaPhoto 5:  In this May 1st photo, plant is nearing the end of its life cycle.  Plant being collected by botanist Eric Sundell (a reviewer of these articles), accompanied by Milanne Sundell.

In addition to hairy phacelia, six other native phacelia species occur in Arkansas.  Hairy phacelia is the most common and widespread.  Three of the others are rare to very rare in the state and are tracked by the Arkansas Natural Heritage Commission.  Hairy phacelia can be distinguished from the other six by several characteristics, including 1) high degree of pubescence and 2) light blue to lavender, bowl-shaped, 10-spotted corollas, 3) stamens and pistils that are only slightly exserted from corolla, and 4) rounded, non-fringed corolla lobes.

Another species in the borage family that can occur in the same habitats as hairy phacelia and with some similar characteristics is “large-flower baby-blue-eyes” (Nemophila phacelioides).  It occurs in the west-central part of the state.

  • This inflorescence style is referred to as a scorpioid (resembling the coil of a scorpion’s tail) or helicoid cyme which is typical of the borage family and the source of one of the general common names, “scorpion-weed”, for some members of the genus Phacelia.

Article and photographs by ANPS member Sid Vogelpohl

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