Plant Highlight · Conradina verticillata · The Cumberland Plateau

Cumberland Rosemary, and Why We Only Sell One in South Carolina

A low, rosemary-scented shrub from the river bars of Tennessee and Kentucky, federally threatened since 1991, propagated on our benches in Aiken, and bound by law to stay inside the state where the plant was grown. The plant, the rule, and why we think the restriction is worth explaining rather than hiding.

8 min read · By Fiona von Grey · Aiken, South Carolina

IA rosemary that lives by the flood

Almost every false rosemary in the genus Conradina belongs to the hot white sands of Florida and the Gulf Coast. Conradina verticillata took the road nobody else did. Cumberland rosemary grows on the Cumberland Plateau, in Scott, Morgan, Cumberland, White and Fentress counties in Tennessee and in McCreary County, Kentucky, on the sand and cobble bars of rivers in the Big South Fork, Emory and Caney Fork watersheds. The Obed, Daddy's Creek and Clear Creek all belong to that story. Cumberland rosemary is the only member of the genus that never reached Florida, and the only one hardy in a zone 5 winter.

The river bars are a hard place to live, and Cumberland rosemary depends on exactly that hardness. Spring floods scour the bars, stripping away the trees, shrubs and taller perennials that would otherwise shade a low plant out. By late summer the same bars bake dry in full sun. Floods also break off pieces of stem and carry them downstream to root in fresh gravel, which matters more for this species than for most, because Cumberland rosemary is the only triploid in the genus. Triploid plants tend to set little viable seed, and seed germination in this one is very low, so the plant spreads mostly by rooting along stems and by those downstream fragments. What looks like a colony of separate plants on a gravel bar may be one individual, spread out.

Pick a needle and crush it, and you will understand the common name immediately. The scent is uncannily like the kitchen herb. A 2022 study from the University of Tennessee, published in the Journal of Agricultural and Food Chemistry, identified 1,8-cineole and eugenol among the aroma compounds, giving eucalyptus and clove notes, and found that the most potent single odorant was 1-octen-3-one, a compound that on its own smells of mushrooms. River sand, rosemary and a little forest floor. It is a fitting smell for a plant from that country.

This is a plant that needs the river to behave like a river.

IIHow a plant comes to be threatened

The US Fish and Wildlife Service published the final rule listing Cumberland rosemary as threatened on November 29, 1991, and the listing took effect at the end of that December. The recovery plan that followed in 1996 counted 91 colonies, 79 in Tennessee and 12 in Kentucky. The Service has since reviewed the species' status in 2010 and again in 2023. Tennessee lists the plant as threatened; Kentucky lists the plant as endangered.

The pressures on a river-bar plant are easy to picture once you know how the plant lives. Dams and reservoirs change how often and how hard a river floods, and a bar that no longer floods grows over with woody plants. River bars are also where people go: to put in canoes, to camp, to cross, to drive, and all of that tramples a low mat. And the whole population lives along a small number of streams on one plateau, which leaves little margin for a bad decade. The Service declined to designate critical habitat at listing, in part out of concern that publishing precise maps would show collectors where to look. For a plant this local, a single dug-up colony is not a small loss.

IIIWhat the law says

Here is the part people ask about, set out as plainly as we can. This is our general understanding and not legal advice.

Put together: a nursery in South Carolina, selling nursery-propagated Cumberland rosemary to a customer in South Carolina, is doing something the Act does not prohibit. The same nursery selling the same plant to a customer in Georgia, North Carolina or Tennessee is not. The plant's home state makes no difference. Tennessee gardeners, alas, are as out of luck with us as anyone else outside South Carolina.

IVHow we handle an order

We did not want this to depend on a line of small print that someone might skim past at midnight. Cumberland rosemary is set up in our shop so that checkout only offers delivery to a South Carolina address. If you are in South Carolina, order as you would any other plant, or choose one in person at the nursery. If you are not, the plant will not ship to you, and we would rather explain why here than surprise you at checkout.

Every plant we sell was propagated here at the nursery. We checked our approach with counsel before listing the plant, and we will keep checking, because the rules for listed species do change. If they change in a way that affects this plant, we will update this page.

VGrowing Cumberland rosemary

Think of the river bar and you will have most of it. Full sun. Sharp drainage, which means sand, gravel or gritty loam, a slope, a raised bed, a rock garden, or the top of a stone wall the stems can spill over. No competition from taller plants crowding in. No fertilizer, which brings soft, floppy, short-lived growth. Regular water through the first season while roots establish, and then very little.

In a Southern garden the enemy is wet more than cold. Heavy clay, a low spot, a bed on the lawn irrigation schedule, or a thick layer of mulch against the stems will lose you the plant faster than any winter. Plant in fall into native sand without amending the hole, keep any mulch thin and gritty, and let the mat creep. Our notes on gardening in sand cover planting in detail.

For companions, echo the river bar: low grasses, stone, and other small plants that want the same lean, bright ground. At the front of a gravel bed with Georgia savory and the peppermint-scented 'Desi Arnez', Cumberland rosemary makes a planting you can smell from a few steps away on a warm day.

VIWhy grow a threatened plant at all

A reasonable person might ask whether a rare plant belongs in a garden at all, or whether selling one sits uneasily with protecting the species. We have thought about it, and our answer is yes, with care.

Garden plants are not a recovery program. Restoring Cumberland rosemary in the wild depends on river management, protected bars, and careful work with wild genetic stock by the agencies and botanists responsible for the species, and nothing in a garden bed replaces that. What gardens can do is quieter. When a plant can be bought, nursery-grown and legal, no one has a reason to dig one from a river bar. When a plant grows in gardens, more people know the species exists and care what happens to the rivers. And a species kept in cultivation in many places is a little less fragile than a species kept in one.

So we grow the plant, we sell the plant where we are allowed to, and we tell everyone else the story. The restriction is not an embarrassment. We think the restriction is one of the more interesting things about the plant.

VIIQuestions we get asked

Can I send one as a gift to someone outside South Carolina?

No. The restriction is on where the plant is sold and shipped, so an order can only go to a South Carolina address.

I live outside South Carolina. Can I pick one up at the nursery?

Please get in touch with us before you make the trip, and we will talk it through with you.

Can I cook with the leaves?

We would rather you did not. No culinary tradition is documented for any Conradina, and this one is a federally threatened species. Grow Cumberland rosemary for the scent in the air, and keep true rosemary, now Salvia rosmarinus, for the kitchen.

Will Cumberland rosemary grow in the heat of the coastal plain?

The plant is rated through zone 9 and grows here in Aiken. Drainage is the deciding factor; give sand or gravel and full sun, and keep irrigation away.

Why don't you sell Etonia, Apalachicola or short-leaved rosemary in South Carolina too?

Those three are federally endangered Florida endemics that we list as reference plants rather than offer for sale. They belong to our history, and you will find each of them in our field guide to the scrub mints. If that ever changes, the guide will say so.

Further reading on The Node

Every scrub mint we grow or have grown is in the field guide to the scrub mints. For the scent, the names and the history, read The Rosemary That Isn't. Our earlier exploration of the Conradina genus covers the rest of the family.