Plant Profile: Eryngiums

By Craig Huegel

Reprinted from The Understory, Nov.–Dec. 1993

The genus Eryngium, sometimes commonly called the button snakeroots is one of many within the carrot family. Those of us who garden for butterflies recognize this family as important because it provides larval food plants for the black swallowtail butterfly. Non-native species that we frequently use include carrots, parsley, dill, fennel, and lovage. Other members, such as water hemlock, are equally as famous because of their toxicity to humankind. The hemlock potion that poisoned Socrates was made from a member of the carrot family; not from the hemlock tree as some suppose.

We are restricted a bit if we wish to use native carrot family plants in our butterfly gardens because most members are either aquatic or wetland species. This may be fine if you have these conditions in your yard, but most of us cannot easily accommodate their requirements. This is where the eryngiums come in.

Eryngiums are a varied genus that contain four species native to Pinellas County and three others that occur elsewhere. One of these three, E. cuneifolium, is an extremely endangered scrub species that occurs naturally only in a few localities in Highlands County along the Lake Wales Ridge. Within this diverse group are both wetland and upland, large and small, and colorful and inconspicuous species. In other words, it contains something that should fit your needs.

Members are either biennials or perennial. Many other characters are varied, but all have flowers in heads with stiff spiny bracts surrounding their base. The flowers often are fragrant and attract many pollinating insects. Although not greatly used by butterflies as a nectar source, some species definitely are used by black swallowtails as a larval food. Others may be used, but I know of no data on these natives besides my own observations.

corn snakeroot

Corn Snakeroot (E. aquaticum) is a native of fresh and brackish water wetland edges in north and central Florida. Its coarse sedge-like leaves stand about 12 inches high. Flower stalks appear in summer and reach 2-3 feet. Flowers bloom in early September. They are rather large and showy for this genus, the heads being nearly 1 inch across and individual flowers being powder blue in color. Corn snakeroot is a very attractive plant for moist locations and should be more widely used.

Fragrant Eryngium (E. aromaticum) is a low-growing perennial native to dry flatwoods and sandhill habitats throughout Florida. The small, sharply-toothed, wedge-shaped leaves are nearly inconspicuous during most of the year, but the 1- to 2-foot long flower stalks appear in summer and sprawl along the ground. Individual flowers are extremely tiny, but are an attractive powder blue. As the name implies, they also are very fragrant. This is one eryngium that I've observed being used by black swallowtails. It also is probably the most adaptable member for use in a typical butterfly garden setting, but regrettably I know of no one currently propagating it.

Baldwin's Eryngium (E. baldwinii) is a small, prostrate, broad-leaved species with tiny, light-blue flowers. Native to wetland edges throughout Florida, its nature and habitat requirements do not make it a good candidate for the home landscape. In most situations, its presence goes unnoticed. I have seen Baldwin's eryngium in the wild, but have no experience growing it.

Photo by Dan TenagliaRattlesnake Master/Button Snakeroot (E. yuccifolium) is a medium-sized perennial with 1-foot long yucca-like leaves--complete with spines. Native to wet flatwoods and marshy edges, it sends up its 2- to 3-foot tall flower stalk in summer. Its fragrant, greenish-white flowers open in September. This is a very interesting wildflower for moist areas and as an accent it could be quite useful. But as a larval food, the jury is still out.

Currently, the eryngiums are not widely grown by native plant nurseries. Since the publication of my butterfly book (Butterfly Gardening with Florida's Native Plants), a couple of nurseries have begun growing E. yuccifolium and The Natives have offered E. aquaticum. All of them may be propagated by seed, however, should you find a seed source. Below are descriptions of the species native to Pinellas County. Several of these, plus the endangered wedge-leaved button snakeroot, E. cuneifolium, can be seen at the Pinellas County Cooperative Extension Office.

Published on  07.30.2012