Sunday, May 13, 2012

Mock Bishop's Weed - Ptilimnium capillaceum


Mock Bishop's Weed (Ptilimnium capillaceum) is a member of the carrot family.  It occurs statewide in Florida, in a wide variety of moist to wet soil habitats, but is also well adapted to average soils and can be found as a lawn or old-field weed.  Mock bishop's weed occurs in much of the Southeast and Midsouth to about Ohio.   Throughout this range, it is an annual that prospers by producing large numbers of seeds.
As a "wild carrot", this species produces a deep taproot, highly fragrant foliage, and umbels of tiny white flowers.  The taproot provides it with good drought tolerance once it is established and the foliage feeds the caterpillars of eastern black swallowtail butterflies.  In our landscape, mock bishop's weed shows up everywhere we water - especially around our potting benches, inside our flats of wildflowers, and in the wetland garden.  We weed some of it or we'd be overrun by this plant in just a few years, but we leave the rest for the butterflies. 
Mock bishop's weed rarely stands taller than 18 inches at maturity. Like many other "carrots" (e.g. dill, fennel), the main stem is hollow and a great many leaves attach to it and off the many side branches.  These leaves are compound with finely dissected leaflets.  The flower heads arise from the ends of every stem.
Many "carrots" produce flowers in specialized heads - called umbels.  Mock bishop's weed is no exception. Each bloom is tiny and bright white.  At full bloom, mock bishop's weed is attractive. This is a spring/very early summer bloomer.
This plant is rarely offered for sale by commercial sources; its main draw being butterfly gardeners interested in adding larval food plants.  Because it blooms early, it is one of the best larval food plants for eastern black swallowtails.  From my experience, it is their preferred spring plant and a great majority of 1st generation butterflies are produced from it.  If you add it, you are likely to have it forever if you plant it in a moist to wet location.  Just make sure you give it some bare soil for the seed to land on. 

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