Wednesday, April 14, 2021

Crenulate Leadplant - Amorpha crenulata

Flowers - Close up


Leaves close up - Note the crenulate edges to the leaf margin
Amorpha herbacea - Note the lack of crenulate edges on the margins

Crenulate leadplant (Amorpha crenulata) has also been described as a unique variety of the very common herbaceous leadplant (A. herbacea) but that is in error in my (and many others') opinion. They are very distinct from each other and quite easy to distinguish.  While crenulate leadplant is an upright evergreen woody shrub, herbaceous leadplant dies back nearly to the ground each winter and tends to grow horizontally more than it does upright. Crenulate leadplant can get to be at least 4-5 feet tall, while I've rarely seen herbaceous leadplant stand more than 2. There also are differences in the leaf margins - and I've photographed both above for your comparison.

In nature, crenulate leadplant occurs only in a few pine rockland areas in Miami-Dade County in extreme south Florida. It is endemic to Florida and listed as endangered by both the federal and state government. Its rarity is due, however, to the widespread loss of this special habitat. It was likely more widespread prior to development pressures.

Crenulate leadplant is an evergreen shrub that loses some of its foliage in the winter when planted north of its natural range. Each plant produces many upright stems that are rigid enough not to bend much as the clusters of blooms are produced at the ends. The stems and leaf veins are reddish  and the leaves are a deep bluish green - much different than in A. herbacea as shown above. Like many legumes the leaves are compound - composed of 20 or more leaflets. Each leaflet has crenulate edges along the margins.

Like many south Florida natives, blooming occurs over most months. The one photographed above in my Pasco County landscape, began flowering in early April. In contrast, the A. herbacea planted near it shows no signs yet of flower buds. The flowers occur on 2-3 inch long racemes and the flowers open from the bottom upwards over several weeks. Each flower bud is reddish purple in color and the open flowers are white with contrasting yellow stamens.  Like all members of this genus, they are eagerly visited by a wide assortment of pollinators. It also may be a host to the silver spotted skipper.

Crenulate leadplant is sometimes offered by native plant nurseries in the southern parts of Florida. I have found it to be an easy plant to both propagate and maintain in my central Florida landscape.  They do not require the types of alkaline soils that they occur in naturally and they are tolerant of a wide variety of soil moisture conditions. The one requirement seems to be adequate light to bloom. A specimen I planted at least a decade ago has never flowered though it is still alive after all of these years. This is a spectacular addition to a pollinator garden and should be more widely propagated. I have been doing so at Hawthorn Hill using the seed from my landscape specimen. I do not know how much cold this species can tolerate, butt it has not suffered negative impacts from temperatures in the mid-20's F.

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