Amsonia — blue star
Amsonia — a genus of about twenty species, native to
temperate climates in North America, Europe, and Asia. Named for Charles
Amson, a U.S. traveler-scientist who lived in the 18th century. The latest
taxonomical wisdom places them in the apocynaceae family, which they share
with several hundred other genera, including Asclepias and Vinca. The
plants, while commonly featured in books about perennials, don't usually
make it to the top of must-grow lists — but perhaps they should.
As is often the case, this page started because I was eager to learn a
little more about a few of the plants growing in our garden. The species we
grow have many similarities — the differences are most apparent when they
are contrasted side by side on a dedicated page. Compared to other genuses
in our garden, for which I have lots of material, amsonia is less
represented: we grow only a few species/varieties, most of which
are native to the United States.
In my experience, amsonias are slow to get going in the garden —
but once they are established, they stick around, growing more robust (but
not spreading too much) year after year. They certainly don't seem to mind
our clay-based soil. While none of ours are planted in areas that get
parched, I've never seen them wilt even during dry spells, so I judge them
The amsonias in our garden are all planted in
fairly open areas, receiving full sun to part shade. The ones that get a
little more shade bloom a little less, so full sun is probably best.
Due to their milky sap, amsonias are often bypassed by foraging mammals,
which makes them somewhat resistant to deer and other pelted pests.
A ripe seedpod from A. hubrichtii, ready to split open lengthwise...
...and several of the log lookalike seeds that were inside.
Amsonias have some of the funniest-looking seeds around — the seed pods are long
tubes that are filled with cylindrical brown seeds arranged end-to-end. When
you first see them, it appears as if you've inadvertently broken a "whole" seed
into a bunch of fragments — but indeed each cylinder is a seed. The seeds ripen
in the middle of fall — quite a long time after the plants bloom. I harvest
them when the pods are quite dry and tan in color, but before they split apart
lengthwise to drop their seeds. For the ones we grow, that's in October and
Germination can be a little tricky, especially for the inexperienced
seed-starter (as I was, when I first tried). My first attempts were with
A. tabernaemontana; I remember trying to start them indoors, having
no luck, and finally, having just about given up, setting the cell-pack in
my unheated greenhouse (RIP) in early spring. A few weeks later, the seeds
germinated nicely — the resulting plants still grace our garden.
I now know that amsonia do best with an extended cold period — 8-10
weeks seems to do the trick — before germination at room
temperature. I also realized recently that the final stage of germination
sometimes requires somewhat warmer than room temperature, so I've started
providing some bottom heat this year, with great results. I've had good luck
with the baggy method, as well as with
winter-sowing in November. Some sources also
suggest to soak the seed overnight, but I've not found this to be necessary.
Since the plants don't spread out much, and stay put as a healthy clump,
they do not require division for good performance. But they can be
divided in spring, as a means of propagation.
For most of the year, the leaves and branching structure provide the best
clues to tell the different species apart. The flowers are, at least
superficially, more similar, as are the seedpods. So let's start with the
leafy material. The three species growing in our garden are shown in three
|A. illustris has grassy-green leaves
resembling those of willows or some milkweeds. The stems are somewhat lax,
and the plants maintain a graceful appearance throughout the growing season.
Although they are a bit late to appear in spring, they quickly make up for
it through fast growth in late spring.
||A. tabernaemontana also has lanceolate
leaves, but not quite so long and floppy as A. illustris, and a darker shade
of green; the overall plant
has a more upright, bushy habit. Stems are tinged with red.
||A. hubrichtii is quite different from
the first two, with threadlike leaves arranged bottle-brush-style around
upright stems. The habit is very upright on young plants with just a single
stem, and gets more relaxed as the plants mature and become
|A. elliptica, native to China, is
superficially similar to A. illustris, its leaves perhaps arranged more sparsely
along the upright stems. The difference is easier to make out when leaves first
emerge in spring: the new leaves are stubbier and more rounded, in a bright
shade of green.
||A. 'Blue Ice' is of hybrid origin, found
as a chance seedling at White Flower Farm years ago (read more at the
page). Our plant's leaves have a blue-green cast, and a distinctively pointy
shape. They do not set seed, but it is the only one of our amsonias that spreads
by its roots (fortunately, not invasively so).
Flowers and seedpods
I've not been so diligent just yet taking photos of all the species. The
ones on 'Blue Ice' are shown at right; my photos of two species are shown
below, but not in a format that makes it easy to compare them. I'll venture out
with my camera next spring and fill in the gaps.
|This photo of A. illustris shows its clusters of powder-blue flowers, each with five slender petals.
||A photo of A. tabernaemontana shows
the same basic flower shape, along with oddly fuzzy buds.
This is A. elliptica, again with fairly
similar flower shape. At least on our plant, the flowers don't cluster nearly as
densely as those on other species.
The seed pods are superficially similar — all the species in our garden hold
them stiffly upright, and they mature to a tan brown. I'm pretty sure there
are more subtle differences between the species (for example, both the pods and
the seeds seem shorter and stubbier in tabernaemontana than in illustris and
hubrichtii), but I haven't explored them systematically yet.
The image at left shows pods for A. tabernaemontana.
Among the gardenworthy characteristics of amsonia, brilliant fall foliage
is often cited. Unfortunately, the first species to inhabit our garden, and
apparently the easiest one to come by, was A. tabernaemontana, which is not
a stellar performer in that respect. Some years, it colors up a bit — others,
leaves just wither to a tan and drop. The same goes for 'Blue Ice', but the
other species have more potential.
|Even in one of its better years, A. tabernaemontana just barely manages to produce a bit of color.
||A. illustris does not color up till the
middle of November, but when it does, its golden yellow leaves are set afire
by the low autumn sunbeams to great effect.
||By early to mid November, A. hubrichtii
reaches its peak color. The mass of fine leaves all turned rich yellow is a
A. orientalis is native to the Eastern Mediterranean. Its description
sounds rather like that of species we grow, although the leaves are more
gray-tinted. A United States native we don't yet grow is A.
ciliata, whose description sounds most like our hubrechtii.
Eventually, I figure we'll give most of them a try — and as we do,
I'll update this page with all the latest information.
Amsonia hasn't inspired many dedicated websites or pages, but there's a lot
of information out there on the web about individual species. My PlantLinks page is
not a bad place to start exploring. There's also a nicely illustrated article by
Rich Darke (in PDF format) that highlights various species – including
a few that I've yet to add to my collection.
Visitors to this page have left the following comments
|christy shivell||Mar 11, 2008||what a great web site! I have seed for A. salicifolia. Would gladly trade for A. illustris seed. Is illustris a us native? Hadn't heard of it before your page. Love the fall color. salicifolia does have much more narrow leaves than tabernaemontana, but they aren't like hubrechtii, either. More like illustris in shape. I think my plant originally came from native gardens in greenback tn. was mislabeled tabernaemontana, but obviously not. bob woodward of woodlanders ided it, but who knows. they obviously hybridize. visit my site, if you like. not as detailed or well done as yours, though, but some pretty pics, mostly of natives. www.shyvalley.com|
|Heidi||May 27, 2011||Bluestar amsonia may be the perfect plant.
A. hubrichtii is the opposite. State of Delaware grew a bank of it by the capital building and it looked bad all the time. Now it's gone.|
I've seen marvellous specimens of A. hubrichtii (and my own don't look half bad either). I guess it all depends on how they're used, and the conditions they have to contend with.
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May 18, 2014