Gerald Klingaman, Ph.D., is an emeritus professor of horticulture at the University of Arkansas. He is now working full time as Operations Director at the Botanical Garden of the Ozarks. He gardens in Fayetteville.

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Foxgloves in the Southern Garden
by Gerald Klingaman       #Flowers   #Ornamentals

 


Common foxglove is most often seen in shades of purple or rose with blooms produced in the late days of spring.


The cottage garden would not be complete without the spiky flowers of the common foxglove.


Foxglove breeders have been able to put together all sorts of attractive color variants for the spring garden.


Digitalis grandiflora has yellow-tinged nodding flowers that are as large as seen on the best common foxglove hybrids.


Digitalis lanata, the Grecian foxglove, is the commercial source of the drug digoxin.


 Digitalis davisiana blooms in early summer and has been a good reseeder in a sunny and dry part of my rock garden.


The willowleaf foxglove is a spreading perennial foxglove from Spain that can be used in the rock garden.

The transition from the riot of color during spring’s awakening of the garden to the lazy days of summer is one of my favorite periods. Though the calendar tells us it is still spring, the flowers and the warmer temperatures inform us another spring will soon pass into the record books. It is during this transitional period that many old-fashioned favorite garden plants bloom. Irises, peonies, hollyhock and especially foxgloves make their presence known during this period.

The spiky nature of foxgloves makes them easy to spot in the border where their colorful blooms punctuate and help define the rest of the border. For many gardeners, foxgloves begin and end with the common foxglove, Digitalis purpurea, but there are about 20 species in this Old World genus and nearly all have some merit in the garden. Let’s explore the foxgloves in more detail.

Foxgloves are by nature biennial or short-lived perennials. A few, such as the 1967 All-America Selection called ‘Foxy’, will bloom from seed in one year and behave as an annual, while Digitalis lutea, the yellow foxglove, will grow quite well as a perennial if planted in a site of its liking. But these are the outliers to this group; most are biennial. Reseeding is a mixed bag. In my Zone 7 garden, I’ve had D. davisiana reseed freely while D. purpurea has never done so for me, but is said to do so readily in northern gardens.

During their first year, foxgloves grow in a ground-hugging rosette of leaves that may be as much as a foot across. The better growing conditions provided these vegetative plants the first season, the larger and more robust will be the spiky shoots produced in the second year. In mid to late spring of the second year, the rosettes send up a tall, sparingly branched spike that produces smaller, alternately arranged leaves up the stem.

The flowers are terminal and arranged on one side of the scape, or, depending on the species, spirally around the stem. The tubular flowers are obviously made for bee pollination with broad, tubular corollas often seen with elaborate markings in the throat of the bloom that surely must look like landing lights for the average bee brain. Flower colors vary according to the species with the common foxglove predominately in shades of purple or pink, but with some cultivars available in white or as bicolors. Many of the other less common species have flowers in shades of yellow or rusty-tan.

Foxgloves have long been classified in the “scroph” family by botanists because of their close physical resemblance to plants such as snapdragons, penstemons, monkey flower, Indian paintbrush, mullein, toadflax and others. These plants share the erect architecture, distinctive tubular insect-pollinated flowers and the characteristic many-seeded capsule. But since DNA testing came to the fore in taxonomic circles in the 1990s, the Scrophulariaceae (Figwort) family is no more. Instead – because of complicated taxonomic rules – this once homogenous group has now been merged into the overly large Plantain family, which even to the botanists supporting the change is so dissimilar it defies a logical description. While this change in classification makes not a whit of difference to the foxgloves or the average gardener, it does frustrate those of us who try to keep an eye on what the botanists are up to.

The name foxglove is a curious one that has been in use in English since at least the 16th century; in German it is called fingher kraut (finger hut, or thimble); in Latin, Digitalis. All of these names refer to fingers and are a direct inference to the large, tubular flowers of Digitalis purpurea. Though foxglove is the name handed down to us by herbalists such as John Gerard, an even older name used in the 13th century was “folkglove,” or literally the gloves of the wee folk (fairies) living in the woods. Some folklorists hold that legends existed that foxes donned slippers of Digitalis flowers to allow them to stealthily steal chickens from the coop, but it seems more likely to me that foxglove is merely a corruption of folkglove, possibly exacerbated by some of the Old English fonts that could easily cause a misreading of an “lk” as an “x”. Leonhard Fuchs, the German herbalist after whom Fuchsia is named, first used the name Digitalis in 1542 to describe the plant, borrowing from the Latin name for a thimble or glove, digitabulum. Apparently the plant was never given a name by Latin or Greek authors, or at least one that survived until the Renaissance when European botanists/herbalists began writing about plants and their uses.

The common foxglove (D. purpurea), though familiar to every gardener, is not so common in today’s gardens that it can be considered commonplace. It is a common sight in cottage gardens or heirloom plantings, but in contemporary garden borders it is a bit more rare. This species typically grows 4 to 6 feet tall with large purple, pink or rose-colored blooms that open from the base of the spike towards the apex. Colors center around purple or pink but white and yellow selections are also available. Plants usually are in bloom for 4 to 5 weeks in late spring but are most effective during the first three weeks of the display. Cutting the flower spike back before all of the blooms have opened on the first spike will usually result in a second, though admittedly less spectacular, secondary spike.

Common foxglove is best in bright light but has a preference for cooler areas so planting them on the north side of the house, on a north-facing slope or in an area that gets dappled or afternoon shade works best in Southern gardens. They grow best in a uniformly moist but well-drained garden soil with a high organic matter content. Nurserymen report a general difficulty in selling “green” plants – plants without flowers. Unfortunately, foxgloves bought in flower in the spring in gallon nursery pots never perform as well as plants planted in the fall and overwintered in place. This species is best in Zones 4 through 8. Foxgloves are shunned by deer.

Foxglove seed is tiny but germinates easily. I like to plant in early summer so the plants can be grown outside in pots so they will be ready to plant into the garden in the fall. The seeds need light for germination, so sprinkle the seeds onto any good quality potting soil and press them firmly into place. Keep the medium moist and in 4 weeks the seedlings will be large enough to transplant into 6-inch plastic pots. Water and fertilize the plants during the summer and by fall they will be ready to go to the flower border for their spring display. For mass effect, plant them on 12-inch centers or, if they are to be used as accents, scatter them out amongst the other perennials.

A number of different strains and hybrids are offered in the seed trade. Thompson and Morgan has one of the best offerings of foxgloves with the ‘Excelsior Hybrids’ being one of the best offerings for high quality, uniform-sized plants in an array of colors. Their ‘Mountain’ series have upward facing blossoms that are supposed to be more colorful from a distance but to me look a bit contrived and unnatural. Their Camelot hybrids compete with ‘Foxy’ as being able to dependably bloom from seed the first season. However, to get foxgloves to bloom from seed in one season requires the use of a greenhouse and planting the seeds in midwinter. The strawberry foxgloves (D. xmertonensis) are actually hybrids with D. grandiflora and grow about a 3 feet tall with large inflated blossoms that are usually in shades of apricot or dark rose.

Because common foxglove is nearly always biennial, it must be mindfully replanted each season or it will disappear from the perennial border. In northern gardens it reseeds more freely than in the South; in fact it is naturalized in wide swaths of the northeast and Pacific Northwest and the USDA considers it an invasive weed in those areas. Because the natural range of this species is in the mountains of Europe and throughout the British Isles, it has not been able to establish itself as an escapee in the 400 years it has been grown in Southern gardens. 

Digoxin
Though foxgloves were included as possible remedies by many early herbalists, its use was primarily as a purgative (a laxative). It was not until the mid 19th century that two French scientists discovered the effect of digitalis extracts on heart problems, and it took another 25 years before the active ingredient, digoxin, was identified.

For many years digoxin-based drugs were the standard treatment for congestive heart failure, but cardiologists have shifted away from the drug because it has not been found to extend the life of patients.

However, it has been shown to reduce hospital visits and improve the quality of life for patients suffering from heart disease. In 2003, Charles Cullen – the kind of nurse we hope to never meet up with in a hospital – confessed to a string of almost 40 serial murders while working for 16 years as a nurse in various East Coast hospitals. His weapon of choice was overdose of digoxin in the ever-present IV line.

Digitalis grandiflora, the yellow foxglove, has the largest flowers of the commonly offered foxglove species. It grows to 3 feet tall and produces, instead of a rosette of leaves as seen in common foxglove, a branched perennial crown which gives rise to basal clusters of lanceolate–elongate leaves. Its flowers appear in late spring on one-sided racemes and are either downward facing or, in some of the better selections, more horizontally aligned along the stem. Similar to it, and also called yellow foxglove, is D. lutea which has half-sized blooms of the two yellow species. This species is native to Spain and Portugal and has been more perennial for me than D. grandiflora, though admittedly the first mentioned species is the showier of the two. Both will grow in the open woodland but D. lutea appears to tolerate summer drought better than D. grandiflora. Both plants are considered hardy from Zones 4 through 8.

The Grecian foxglove, D. lanata, is native in southern and western Europe and is hardy from Zones 7 through 9. It grows about 3 feet tall and has brownish yellow, finger-sized blooms that do not flare at the end of the floral tube. It is a biennial and grows in open, often rocky ground in the same kind of habitat where mullein might be found. For me it has bloomed nicely but never reseeded. This species was the original source of the drug digoxin (see sidebar). It has become naturalized in some of the Northeastern and Midwestern states.

Rusty foxglove (D. ferruginea) is native to southern Europe and Asia Minor where it grows as a biennial. Plants flower in midsummer with narrow, erect spikes of yellowish-brown flowers borne up the stems that reach 4 feet in height. About eight years ago I received seeds of D. davisiana from the North America Rock Garden Society in the seed exchange. It too is biennial and similar in form to rusty foxglove but flowers are somewhat smaller and the plants are narrower. It has reseeded in a bright but dry bed next to my driveway and makes a nice display in early June.

Digitalis obscura, narrow-leaf or willowleaf foxglove, is a Spanish native hardy from Zones 4 through 7 that forms perennial clumps 18 inches across with plants attaining about 12 inches in height when in bloom in May. It has rusty yellow blooms about 1 ½ inches long on an arching, one-sided spike. It requires a sunny, extremely well-drained site in the rock garden. It has made the rounds some in the nursery trade of late because it was named as one of the Colorado PlantSelect plants and is well adapted to the mountainous conditions of that state.

All parts of all Digitalis species should be considered poisonous. Young children from an early age should be taught not to randomly graze on plants in the garden or in the wild. The poisonous principle in Digitalis is various cardiac glucosides that are also found in oleander, lily-of-the-valley, dogbane, wallflower, squill and many other plants. In a 2006 analysis of 1.33 million non-pharmaceutical poisonings reported to emergency rooms, 0.1 percent of these involved plants containing cardiac glucosides. The number of foxglove related incidents is not reported but the report does go on to say that, while fatalities from accidental ingestion of plants containing cardiac glucosides are known, they are not common. Crime show dramas portraying murder via slipping a bit of foxglove into the salad are gross exaggerations. Because foxgloves do not have attractive and inviting berries, there is a low probability of accidental ingestion by children.

Foxgloves are beautiful and interesting plants in the garden that can be massed or used to brighten up the late spring border. They have about them an elegant charm that gladdens the hearts of all that see them.  With a little pre-planning, they can be a welcome addition to any Southern garden.

 

 

Posted: 05/16/11   RSS | Print

 

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