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Friday, May 25, 2018

Distinctly Different Milkweeds

Pearl Milkvine
Much ado has been made of the more common and widespread milkweed species, but there are a handful of milkweed vines that are less common but more distinct, and just as useful as native host plants for Monarchs and related butterflies.

A fairly robust, twining vine 6 to 12 feet long growing in dry, light shade in thickets on rocky hillsides and woodland edges, Pearl Milkvine (Matelea reticulata) is best known for its heart-shaped leaves and flat, greenish-white flowers ½ to ¾ of an inch across with pearly, iridescent centers.   Also called Green Milkweed Vine, Net Vine Milkvine, and Netted Milkvine, its curious flowers have tiny white veins forming an intricate pattern on the surface of the petals, adding to their unusual look. In fact, ‘reticulata’ refers to this pattern, which mans ‘resembling a net or network’.  It blooms from April to July, especially in full sun, giving way to fairly large, interesting prickly follicles filled with seeds attached to silky threads.  This native species is a host plant to Monarch butterflies.

Plateau Milkvine

Both the Pearl Milkvine and Plateau Milkvine have prickly seed follicles
Often mistaken for Pearl Milkvine is Plateau Milkvine (Matelea edwardensis), endemic only to the Edwards Plateau of Central Texas.  This uncommon vine shares the same twining habit of Pearl Milkvine, but its leaves, while similar, generally have a somewhat wavy edge, and its flowers are bell-shaped instead of flat.  Additionally, its greenish-white flowers do not have a pearl center, and its petals are not solely reticulate-patterned, having parallel veins in their lower halves and centers, and reticulate or networked veins only on the edges or margins.  Blooming in April and May, this species can be found on gravelly soils in open woodlands, often climbing on other plants, and it is a native host plant for Queen butterflies.

Pearl Milkvine Flowers
Plateau Milkvine Flowers
Purple Milkvine
Usually found in the chalky soils of pastures and open ground, Purple Milkvine (Matelea biflora) has low-growing stems that radiate along the ground from a woody rootstock, and along with its opposite, triangular leaves, are covered with long, spreading hairs.  From March to June, pairs of star-shaped, five-petaled, dark purple-brown flowers rise from the base of the leaves, which gives this plant its other common name of Star Milkvine.  While its trailing stems can grow up to 2 feet long, it inhabits grassy areas and as such is often hidden and overlooked, except by Queen and Soldier butterflies who use it as their native host plant.

Talayote
Named for a small town in Chihuahua, Mexico, Talayote (Cynanchum racemosum) or Milkweed Vine is a climber that grows to 15 to 20 feet in full sun to part shade, and is a native host plant for both Queen and Soldier butterflies.  Talayote produces clusters of small cream and green flowers that are held above and among the heart-shaped leaves, blooming in the hotter months from summer into fall, and attracting a host of other small but beneficial pollinators.  Growing only in Central, South, and West Texas in the United States, this vine produces plump, smooth follicles 3 inches long, filled with silk-topped seeds, often remaining on the vine well into winter. 

Take the time to seek out and appreciate these lesser known members of the Milkweed family, as they are beautifully and distinctly different!

Tuesday, May 1, 2018

A Horse of a Different Color

Horsetail or Scouring Rush

Few plant species that grow naturally today have been around for over 100 million years, but one of the best known are plants in the genus Equisetum, which is the only living genus of the entire family of Equisetopsida, most commonly known as horsetails.  They are recognized as close relatives of ferns, typically growing in wetter areas with whorls of needle-like branches radiating at regular intervals from each single vertical stem.

The common name of horsetail is used for the entire group of plants, since the branched species resemble a horse’s tail.  In fact, the genus Equisetum comes from the Latin equus or ‘horse’ and seta or ‘bristle.’  Another common name is scouring rush, referring to the upright rush-like appearance of the plants, and the fact that the longitudinal ridges of the stems are coated with abrasive silicates, making them useful for scouring or cleaning metal items.  It is still used today as a traditional polishing material in Japan.

The primary species of horsetail that occurs natively in wet or moist areas of Texas, most commonly on the Edwards Plateau and in Blackland Prairie, as well as most of the non-tropical northern hemisphere, is Equisetum hyemale.  A spreading, reed-like perennial growing to 3 feet tall, each stem is evergreen, cylindrical, jointed, hollow, and about 1/4 of an inch in diameter.  In this species, the needle-like branches appear non-existent, but are actually small and fused around the stem at each joint or node, forming a blackish-green band or sheath.  Interestingly, the pattern of spacing of the nodes in these plants, which grow increasingly close together toward the apex, is precisely what inspired Scottish mathematician John Napier to discover logarithms in the late 16th century.

Dragonflies, like this Neon Skimmer, love to perch on the cones of
the horsetail’s upright stems.

Horsetail prefers open or wooded areas along streams, moist flats, and wet ledges. Like ferns and other related species, horsetails reproduce by spores rather than through seed-producing flowers. These spores are borne in cone-like structures at the tips of some stems, and are mostly homosporus, meaning of the same size and type.  The tiny spores have four elaters or structures that alter shape in response to changes in moisture, effectively acting as moisture-sensitive springs that assist spore dispersal through crawling and hopping motions once released from the cone.

Horsetails reproduce by spores borne in the cone-
like structures at the tips of some stems.

The upright, evergreen, segmented foliage of horsetail is an appropriate plant for a rain garden, pond edge, water feature, or area with moist soil, and is an excellent perching plant for dragonflies. While it can spread quickly by underground or underwater runners, it is easily kept in check by periodic pulling or by planting it in a container.  Few plants add as much interest or vertical structure to a wildscape as this living fossil, which is clearly a  ‘horse of a different color’!