The genus digitalis
Digitalis is a genus of a couple dozen or so species (wikipedia says
about 20, GRIN lists only about 12 currently accepted species). As a group,
they are known as the foxgloves, named for their most popular species, the
common foxglove: Digitalis purpurea. The genus has recently migrated
from the figwort family (scrophulariaceae) to the plantain family
(plantaginaceae) – along with its cousins the penstemons – but
most references still place them in their former taxonomical position.
Common foxglove is a deservedly popular biennial
species, famous for its self-sowing habits in cottage gardens. Many cultivars
in different habits and colors have been developed, and are featured proudly
in lush photographs of English cottage gardens.
Another claim to fame for the
genus are the chemicals (called digitalins) which have medicinal value when
used judiciously, but render all parts of the plant poisonous when consumed by mammals and
humans and other mammals. Other references can tell you more details about how
these chemicals inhibit, attack, and affect the various organs; I'll leave it
at "just don't eat 'm!".
The "other" digitalis species
Although I've grown a few varieties of D. purpurea through the
years, they've never done as well for me as I hoped (based on the glorious
pictures in garden magazines and on seed packets), and for some reason they
never once self-seeded. So common foxglove doesn't figure very strongly in
our garden – but that is counter-balanced by a much greater emphasis
on its less frequently grown cousins. The "other" digitalis species are
typically listed as perennials, even though some are certainly more
long-lived in our garden than others. There's a good deal of confusion in
online references and among seed suppliers and traders as to the proper
identification and nomenclature of these various species; and when confusion
sets in, I often resort to a web page comparing and contrasting the various
plants we've grown, to see if I can make better sense of it all.
So on the rest of this page you'll find my comments and photos of several
digitalis species. Some of them are "official" species recognized by GRIN
and other references, while others came to me from nurseries and seed trades
with less well-established names. Any insights you may have on disentangling
the taxonomy would be welcome – I invite you to use the comment form at
the bottom of this page for this purpose.
Each of the species shown on this page also has its own plant portrait page
on this website, usually with larger and different photographs. Click on the
linked botanical names to access these portrait pages.
Cultivation and propagation
In my experience, most digitalis are pretty rugged plants. Some do fine
with full sun in our Pennsylvania garden, but most of them appreciate at least
part day shade, and I know of none that insist on all-day sun. The ones that
appreciate some shade also tend to be a little less tolerant of dry conditions,
but some supplemental water through dry spells is usually enough to bring them
through summer. As a group they are also quite hardy, some species surviving
as far north as USDA zone 2, others at least good to zone 5 or 6. Due to their
toxicity, foxgloves are generally regarded as resistant to rabbits and deer.
A few species have behaved like true perennials in our garden: D. lutea
and D. grandiflora being two prime examples. Others act more like
biennials, or may eke out a third year of performance before fading away. So
I try to collect seed for the species I appreciate – which luckily they all set
I've never divided a digitalis - they grow from non-spreading rosettes,
so they don't invite division, although I suspect that some species
can indeed be multiplied that way. But all of my propagation goes through
seed. They are easy to germinate: most species require no special attention
besides exposure to some light in order to sprout. Germination usually
occurs within two weeks of sowing. Details of my seed-starting trials are given
on each of the individual plant portraits linked from this page.
Because they grow slowly in their first
year, I start my Digitalis in February, growing the seedlings on in pots or
cell-packs under fluorescent lights in the basement. Even as seedlings they
can stand some light frost, so they go outside already in early spring to
harden off. By mid-late April, they are ready to be planted out in the garden,
where they will spend their first year growing into a sturdy rosette of
low-growing leaves. The following year, they will reach skyward, sending a
leafy stalk with flowers along its upper reaches to heights ranging from one foot
(D. thapsi) to four feet or more (D. ferruginea, among others).
The species in our garden
Strawberry foxglove is only half a step away from D. purpurea: it
is a hybrid between common foxglove and yellow foxglove (D.
grandiflora). It has handsome deep green crinkly leaves, with short
stalks carrying soft-hairy muted rosy pink flowers.
According to some references, it is more perennial than common foxglove,
but that must only apply to gardeners with just the right climate: I have
only ever enjoyed its flowers on second-year plants, no return in year
three. It's been a few years now since I last tried – maybe I'll try
to coax it into behaving like a perennial one last time (deadheading may
help; I seldom deadhead, because it means giving up those precious seeds).
Continuing with the brightly colored species, this is a pretty one from
the Mediterranean with smooth demurely pink flowers carried on one side of
the upright flowerstalk. The true species stays low (no more than two feet
tall), although through some garden promiscuity in action I've found taller
specimens in our garden. The little ones are the nicest, I think. The
leaves are mid-green and crinkly, broader than those of many other
foxgloves. A popular cultivar is 'Spanish Peaks' – in fact, my plants
may be offspring of that cultivar for all I know.
Willow-leaf foxglove, as its name suggests, has the narrowest
leaves of the species I've grown. It does not form as much of a rosette as
its cousins, instead holding most of its leaves in an alternating pattern
along the lower half of the flowerstalks. The leaves are somewhat evergreen,
although they tend to look quite dilapidated by the end of the cold season.
The other common name, dusky foxglove, derives from the flowers,
which are intriguingly colored, with red markings somewhere between a blush
and streaks overlaying a yellow background. They are larger than average,
and face downward. The stalks are not as sturdily upright, preferring to
grow in a curvaceous fashion to about 2 feet tall.
Now we're sliding into the yellow end of the color spectrum; while yellow
is featured in many Digitalis species, this is the clearest one of the bunch,
with larger pure pale yellow flowers; its common name is even "yellow foxglove".
The leaves on this plant are narrower, ending in a pointy tip; they are soft-
hairy, which gives them a dullish mid-green appearance: a good foil for the
masses of flower spikes (some upright, some nodding) that appear in late spring.
A reliable perennial, this is for sure one of my favorite foxgloves. In our garden
it reseeds occasionally, but certainly not rampantly.
Another entry into the yellowish end of things, straw foxglove has
smaller flowers than D. grandiflora, in a luscious buttery shade. Each
stalk holds dozens of flowers, neatly spaced, each perfectly formed into a narrow
tube opening to a mouth with a broad lower lip and a two-peaked upper lip. The
leaves are strap-shaped, pointy, and smoother than those of the species above,
in a darker shade of green.
Straw foxgloves in bloom look spendid in a partly shaded area, where the
flowers really pop. We grew ours in mostly shaded areas for years, until
some of them escaped and surprised me by doing quite well in mostly sunny
parts of the garden. They happily seed themselves around, only occasionally
making a nuisance of themselves. Each plant lasts for a good number of
years. All in all, a standby in the Lush Gardens.
And now we come to the first of the botanically muddled varieties on this
page. There are not many references to this species online; a search on
GRIN brings up a page that says it's a synonym for Digitaria, which is
clearly false (since that is a genus of grasses). But there are enough
mentions of the species that I'll continue referring to it by this name until
somebody convinces me it's something else.
The leaves on this one are somewhat narrow and pointed.
I grew my plants from seed, but for
some reason have not been able to collect any viable seed from them – which
is quite unusual for a foxglove.
The upright or slightly curving flowerstalks of the species are clothed
in an abundance of small flowers, each with a tuft of silvery hair attached
to its lower lip. I find the overall effect, when viewed up close, to be
comical. The flowers on ours are a rich chocolaty brown. Other photos of
the species sport some different color variations, including even redder
tints, and some lighter shades of orange. I'm pretty happy with our strain,
which I need to start from seed regularly, because the plants are
short-lived and do not self-sow in our garden. Even though these plants, at
about two feet height, are taller than most front-of-the-border perennials,
they are narrow enough to go close to the front. That way their flowers, which
can appear washed-out from a distance, can be appreciated up close.
We have now arrived squarely in the digitalis zone characterized by muted
earth tones – soft yellow, brown, and ochre figure prominently in many
species. Rusty foxglove features reddish-brown coloration in its
netted-interior flowers, which are arranged in abundance along tall, upright
spires. It's a rather easy-going perennial; individual specimens are not
particularly long-lived for us, but they do self-seed to keep themselves
represented in our garden. The leaves are darker green and narrow, climbing
up the flower stalk to a fine Christmas tree effect.
There are several named cultivars, including 'Gigantea' (which of course
grows particularly tall), and 'Gelber Herold', which has a more pronounced
yellow coloration. I'm pretty sure that whatever is growing in our garden
at the moment is either the plain species, or a bastard involving another
species or two. Which is unavoidable in a smallish garden featuring
multiple digitalis varieties.
A woolly complex of other creamy browny yellowy species
I've grown several other forms and varieties of digitalis through the
years. They usually came from seed trades (but sometimes from nursery
purchases), and were named D. lanata, D. lamarckii, and D. laevigata.
The plants are similar, with mostly upright stalks bearing strap-shaped
leaves and flowers with a creamy lower lip and a brown-netted interior, with
varying degrees of hairiness and floral density along the stalk, and ranging
in height from two to four feet. A botanist visitor to my website commented
in an email about one of the varieties I had put up that it belonged to the
"Digitalis lanata complex". So if even the scientists have a hard time
keeping the various similar species/subspecies/varieties apart, who am I to
try to bring order to the subject? All of these are attractive in an
understated way, and none have proven to be long-lived in our garden. The
captions for the photos shown here are the names under which they came to our
garden – I'm not suggesting they are correct.
D. laevigata 'Gracea'
I've attempted to grow D. viridiflora from traded seed,
but found myself with a pretty variety of D. lutea instead. The real
species, native to southeastern Europe, would be worth growing as well –
maybe I'll track it down one of these days.
I have also tried to obtain D. trojana; my attempts to grow the seed
labeled as such have not been successful, but in fact some of my plants in the
lanata complex may have been this species. I'll be trying again soon.
Other species recognized by GRIN include D. mariana and D. nervosa,
as well as a few that are synonyms for species now included in Rehmannia
and Isoplexis. I figure I'll have an opportunity to try a few of these,
as seed becomes available through seed trades and society exchanges. Do let me
know if you grow any distinct species not included on this page: I'd love to
grow as many as I can, at least once!
Visitors to this page have left the following comments
|agnes||Jul 29, 2012||thanks for showing all those digitalis. i just purchased one and the tag read: "digitalis" only, and showing a pink foxglove. i have been amending soil and i think she is ready to be put in the ground.
i will have to try some of the ones you are showing here.
|Judy||Feb 18, 2013||I've always been somewhat fond of D. lutea. Got tired of the lurid pink ones. But, I rather enjoy the parviflora for its small flowers and subtle nature. :-)|
|Patricia Shears||Sep 25, 2014||Very helpful page. Glad I'm not the only one who finds the murkier foxgloves both more appealing and difficult to identify. I suspect I have had the same problem of incorrect nomenclature. Here in SW France I can only grow the more robust, sun-loving species, although an unimpressive form of D lutea grows wild on our woods. D ferruginea does well, as does one of the hairy-lipped D lanata-type. I also have a smallish (30-45cm) orangey-yellow one, which makes a good basal leaf clump, with dark green veined leaves, semi-evergreen. I can send a photo if you would like. It does well here and seems to be slightly perennial, in addition of self-seeding.|
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March 04, 2012