Tough-as-Nails Perennials
by Carole Ottesen

Tired of coddling temperamental plants? Garden expert Carole Ottesen profiles 10 resilient perennials that have survived drought, deer, and neglect in her Maryland garden.

Given plenty of water and a bit of coddling, any plant can look good despite hellish weather and rapacious deer. But what happens if you go away for three months and leave your unirrigated garden in the heart of deer country untended during a prolonged drought? If your first thought is “plants will die,” you’re right. Without the water and TLC, there will be losses.

I experienced this firsthand because for the last two summers I have abandoned my sultry Maryland garden to the elements and escaped north to a cool maritime haven in Nova Scotia. After last summer’s record-breaking drought in the eastern United States, and recalling that my house-sitter is not a gardener, I expected the worst when I returned in September.

The Upside of Neglect

Shocking as it is to return to a neglected garden, there is an upside to this experience. After my garden had endured these harsh conditions, I discovered which plants made it through and, more interestingly, which came through the ordeal with flying colors. A rare few plants not only survived, but did so with aplomb.

Generally speaking, well-established shrubs and trees made it - if a bit less perkily than usual. Not so the perennials, which are more susceptible to deer damage and drought. And forget annuals and thirsty tropicals.

The first thing I noticed on my tour of the garden was that the ground seemed strangely empty - even of weeds! A prolonged drought not only stresses plants, it stresses deer, so they eat more and different plants than their usual fare. As a result, I found spots of bare soil in my woodland garden and perennial border where plants used to be.

The next thing I observed was that some of what had survived didn’t look the way it’s supposed to. Asters are a case in point. Although it’s hard to kill an aster, deer browsing can make it look like the product of a breeding experiment gone awry. That gracefully arching mass of starry flowers becomes a bunch of sticks with a few blooms jammed at the ends. Likewise, deer browsing reduced the seemingly invincible prairie dock (Silphium terebinthinaceum) from a monumental clump of three-foot-long, sandpapery leaves to a giant pin-cushion of shredded stems.
When I got over the initial shock, I noticed, here and there, a few dust-encrusted individuals that appeared intact. After dousing them with a hose, I found (my heart swelling with profound gratitude) a few of these plants appeared to be totally unscathed. They may not have grown overmuch during the summer, but neither did they lose significant biomass.

The following are plants in my Maryland garden (USDA Zone 7, AHS Zone 7) that came through the Summer from Hell with grace and good looks. (See page 29 for a list of dependably drought-tolerant plants from other regions of North America, or visit the web special linked to the online version of this article at www.ahs.org for a more detailed list.)

Perennials For Sun

Arkansas Bluestar
(Amsonia hubrichtii, USDA Zones 5–9, AHS Zones 9–5)

Completely unscathed from its summer of neglect was Arkansas bluestar, which is endowed with a milky latex sap that makes it unappealing to deer. Its other fabulous quality, once well-established, is its drought tolerance.

Although the delicate ice-blue spring flowers are what give this plant its common name, the autumn color of its feathery leaves is the reason people grow it. The stems grow long and billowy and put on a fine show in October when the leaves turn a stunning pale pumpkin color. Great in both sun and part shade, Arkansas bluestar is native to Arkansas and Oklahoma. It grows into mounds of arching foliage that reach three feet and slightly more in height and breadth. Downy bluestar (A. ciliata, Zones 6–10, 10-6) and common bluestar (A. tabernaemontana, Zones 3–9, 9–1) are not quite as drought tolerant but still worth considering.

Butterfly Weed
(Asclepias tuberosa, Zones 4–9, 9–2)

Butterfly weed’s other, less appealing, name is “pleurisy root,” because its deep-reaching root was once used to treat lung inflammation. That taproot is one reason this plant easily tolerates heat and drought. In fact, this two-foot-tall native perennial seems to flourish in the sunniest, hottest spot in the garden where it will flower in mid- to late summer. Butterflies flock to the flat, bright orange flower heads for nectar, and the larvae of monarch butterflies feast on the leaves, a short-term phenomenon that doesn’t harm the plant. Selections include the Gay Butterflies series and ‘Hello Yellow’.

This super-tough perennial has a couple of quirks. It is late to emerge from dormancy in spring, so forgetting its presence is easy. When trying to plant something else near butterfly weed, be careful to avoid digging into and damaging its hidden roots. Its other quirk is that it so dislikes transplanting; it may disappear for nearly a season after being moved. Depending on where you live, other milkweed species are worth considering, among them swamp milkweed (A. incarnata).

Japanese Roof Iris
(Iris tectorum, Zones 5–9, 9–3)

Yes, Japanese roof iris can actually grow on a thatched roof. It can take anything the climate throws at it and still look like it spent the summer at a spa. Divisions I set out the fall before the terrible summer still provided a river of texture through my garden. In fact, the river has become a veritable torrent of light green fans, 18 inches high by at least two feet across.
The flowers, usually white to pale blue-lavender with serrated crests, bloom for a fleeting week or two in late spring or early summer, but the dramatic foliage lasts until a hard frost. The selection ‘Alba’ has white flowers with yellow-tinged crests.…

Rosemary
(Rosmarinus officinalis, Zones 7–9, 10–1)

Technically rosemary is a subshrub rather than a perennial, but I’m including it because its heartwarmingly splendid appearance makes it the poster child for all herbs. Despite months of heat and drought, rosemary still stood upright in my garden, bursting with good health and bright green vigor; the drought must have reminded it of its native Mediterranean region.

I grow the cultivar ‘Arp’, which is hardier than most, but still susceptible to wet feet in winter. Mine is sited on a hill with excellent drainage where it will grow, hopefully, to its six-foot potential.
Several of rosemary’s fellow herbs fared almost as well. Purple sage (Salvia officinalis var. purpurea), lemon thyme (Thymus 5citriodorus), Italian oregano (Origanum 5majoricum), lesser calamint (Calamintha nepeta), and lavender (Lavandula spp.), were all presentable when I returned. Cardoon (Cynara cardunculus), a silvery Mediterranean plant related to artichoke, had grown berserk—sending up six-foot flower stalks all over the garden.

Hellebores (Helleborus spp.)

Deer-resistant, shade-tolerant, evergreen, and early-blooming, hellebores (Helleborus spp.), are as near perfection as plants can be. True to expectations, they survived the long, dry summer, but some did so with more élan than others.…

Perennials For Shade

Autumn Fern
(Dryopteris erythrosora, Zones 5–8, 9–5)

People tend to think of ferns as delicate inhabitants of moist woodlands. While the “moist woodland” part of that statement is mostly true, ferns are anything but delicate. Among the oldest plants on earth, ferns are true survivors. In forms almost identical to those of today, they’ve been around for more than 300 million years. Once established, they make it in shade that isn’t always moist.
Autumn fern, a bold, two-foot-tall, evergreen plant with shiny fronds, is one of the toughest. Situated under a big yellowwood (Cladrastis kentukea) a ground-covering mass of these ferns defies drought and deer. The fern gets its name from the red-orange color of the new fronds emerging in spring. It spreads slowly into big clumps and works well underplanted with spring- or early summer-blooming bulbs such as camas lilies (Camassia spp.).
Other ferns in my garden that came through the drought unscathed include Christmas fern (Polystichum acrostichoides), Makino’s holly fern (P. makinoi), sun-tolerant southern shield fern (Thelypteris kunthii), holly fern (Cyrtomium falcatum ‘Rochfordianum’), Goldie’s wood fern (Dryopteris goldieana), Mexican male fern (D. pseudo filix-mas), and the spectacular, evergreen, thick-stemmed wood fern (D. crassirhizoma). However, maidenhair fern (Adiantum pedatum) and ostrich fern (Matteuccia pensylvanica), responded to drought by going dormant.…

A Lesson Learned

Now, as the memory of that killing drought fades and a wetter-than-normal spring plumps plants to luxuriance, it’s easy to drop one’s guard. But I learned the hard way that a garden needs a backbone of tough, reliable plants that can take pretty much anything our climate can dish out. Over the next few years, I intend to add more of the plants that did well, and seek out other resilient gems that will offer my garden both durability and diversity.

Carole Ottesen is a contributing writer for The American Gardener. Her gardens in Maryland and Nova Scotia are thriving on benign neglect.


Photo credits: Amsonia hubrichtii by Carole Ottesen; Iris tectorum Courtesy of ItSaul Plants
 

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