Saturday, July 31, 2010

Mock Bishop’s Weed—An Overlooked Native Annual

Mock Bishop's Weed - Ptilimnium capillaceum

Mock bishop’s weed is a prosaic and rather unattractive name for a highly attractive little annual in the carrot family. It has been recorded as a native plant in all but six of Florida’s counties where it occurs in moist situations such as ditches and pond margins. It is both common and adaptable yet it is inexplicably overlooked by native gardeners. This has always puzzled me since I have often wondered how a garden can be considered “native” if it lacks common plants native to the area where the garden is located.

Scientifically known as Ptilimnium capillaceum, mock bishop’s weed has perhaps the daintiest and most delicate appearance of any plant native to Florida. As is typically the case with winter annuals, its life begins when the seeds, which have lain dormant throughout the summer, germinate with the onset of cooler weather in the autumn or early winter. At first, the seedlings resemble nothing more than wispy green threads. Throughout the winter and early spring, the little plants grow vigorously and soon resemble beautiful masses of the finest green lace. This singular appearance is the result of each leaf being divided into numerous, hair-thin segments. With the approach of warm weather, the plants begin to flower and they produce prodigious masses of tiny white flowers about as large as a pinhead. Both the “green lace” and flowering stages are equally beautiful but they are followed by an awkward final stage. As warm weather arrives in late spring, seed production ensues and the little plants wither as all their energies are focused on producing the next generation. The exhausted plants soon turn yellowish or brown, they completely dry up and, when summer arrives in full force, they survive only in the form of dormant seeds that await the coming of cold fronts in autumn.

Mock bishop’s weed is a useful butterfly plant and is highly recommended for butterfly gardens as food for the caterpillars of the black swallowtail butterfly, Papilio polyxenes. The caterpillars are interesting little creatures that mimic bird droppings when young but soon grow into beautiful green caterpillars with narrow black bands on each segment of the body, with each black band variously adorned with yellow spots. For best results in attracting black swallowtails, mock bishop’s weed should be grown in large masses. In spite of their small size, the tiny flowers play an important ecologic role in both natural communities and in our gardens. The tiny flowers have easily accessible nectar that is offered freely to all insects. Among these are tiny wasps and flies that parasitize other insects such as aphids, scales, and mealy bugs. Studies have shown that these diminutive biological control agents lay more eggs and stay in a given area longer if there are miniature flowers to provide much needed fuel in the form of nectar.

Growing mock bishop’s weed is simplicity itself and involves nothing more than spreading the seeds in late spring or early summer in a moist part of the garden. Gardener’s in dry areas can still grow a small colony of this plant if they can find a spot that stays moist during winter and early spring. For example, a colony may be started near the base of a potted plant that gets regular watering or where the water from a bird bath spills onto the ground. For many years, this endearing and charming little plant has provided months of beauty during the winter and early spring—and my only investment for this rich reward was the scattering of a few seeds in a spot where I occasionally aim the watering hose as I water my potted plants.

Finally, a word of warning is called for since there is a non-native impostor that frequently infiltrates gardens disguised as mock bishop’s weed. It is an equally common, lacy-leaved winter annual known as Cyclospermum leptophyllum. This interloper may be recognized by the position of its flower clusters, which occur along the stems opposite the leaves. In the native Ptilimnium capillaceum, the flowers terminate at the end of the stems and are held above the leaves.

© 2009 Rufino Osorio. All rights reserved.

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