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Showy milkweed (Asclepias speciosa): Mother Nature's Montrose Garden,
Montrose, Colorado
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Summer
blooming plants really come into their own in July, growing and flowering like
crazy with the long, warm days. One of
the prettiest in Mother Nature’s Montrose Garden is the Showy milkweed, Asclepias speciosa. The name speciosa
means ‘showy’, which certainly describes this native perennial. The scientific name is pronounced: ass-KLE-pee-us spee-see-OH-suh.
Showy
milkweed is a true native milkweed, of the genus Asclepias, in the subfamily
Asclepiadoideae of the Dogbane family (Apocynaceae).
There are over 200 species of milkweed
worldwide and 19 are native to Colorado. The Milkweeds are named for the milky ‘sap’
released when plants are damaged. This
sap contains toxic and medicinal chemicals (more on this later). The genus was named by Linnaeus to honor
Asclepias, the ancient Greek demi-god of medicine.
As
with most native plants, the Colorado Milkweeds of the Western Slope are
somewhat different from those of the Front Range and Eastern Colorado. Showy Milkweed is found on both sides of the
Rockies, and is a good garden choice throughout Colorado. The natives to Western CO (in addition to Asclepias speciosa) are: Asclepias asperula (Antelope-horn or
Creeping Milkweed), Asclepias
cryptoceras (Pallid or
Adobe Milkweed), Asclepias cutleri (Cutler's Milkweed), Asclepias hallii (Hall’s Milkweed), Asclepias
involucrata (Dwarf Milkweed), Asclepias macrosperma (Big Seed
Milkweed, Eastwood's Milkweed), Asclepias subverticillata (Whorled
Milkweed), and Asclepias tuberosa (Butterfly Milkweed).
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| Monarch butterfly larva |
Most
people know that Milkweeds are important food plants for Monarch
butterflies. The Monarch caterpillars
(larvae) eat the milkweed leaves and stems, ingesting the plant chemicals. The chemicals are not toxic to the caterpillars,
but they do make Monarch caterpillars unpalatable or toxic to their predators
(mostly birds and insects). Many
gardeners grow Milkweeds specifically for their Monarch habitat value. We don’t
have large numbers of Monarchs in Colorado, but they are seen occasionally. And
there is much current interest in the Monarchs of the Southwestern U.S. For
more good resources on Monarchs, see references 1-4, below.
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| Monarch butterfly |
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Showy milkweed (Asclepias speciosa): along
irrigation ditch, Montrose County, CO |
Showy
Milkweed is a common plant in the west.
It can be found growing wild from Minnesota to British Columbia, Canada,
in the north, and south to Texas, the Four Corners states and California. It grows in many plant communities, in sandy
to loamy soils, up to about 6500 ft. (1900 m.) elevation. It favors places that get a little extra water:
around lakes, streams and drainage channels, along roadsides and in other
semi-moist places. In Western Colorado,
it’s often seen on the banks of irrigation channels and streams. It’s common enough that it can appear
naturally in home gardens – as it did in Mother Nature’s Montrose Garden.
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| Showy milkweed (Asclepias speciosa): reseeded plants |
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| Showy milkweed (Asclepias speciosa): growth habit |
Asclepias speciosa is a bold and striking plant. It has stout,
upright stems, that are 3-5+ ft. tall.
The stems can be sparsely branched, though they are rarely so in the
Montrose plants we’ve seen. The leaves
are large (to 6 inches long and 3 inches wide), simple, oval-shaped and
opposite. The veins are prominent, and the leaves are thick and somewhat
succulent. The entire plant is an
attractive pastel green; a color that contrasts well with the flowers (or with the
darker foliage of background plants).
The stems and underside of the leaves may be covered by dense, white
hairs.
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| Showy milkweed (Asclepias speciosa): leaf, upper surface |
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| Showy milkweed (Asclepias speciosa): leaf, lower surface |
Like
most Milkweeds, Asclepias
speciosa is a perennial – coming back year after year. It sends up new
stems in the spring, spreading via underground stems (rhizomes). In time, a
single plant can form a large clump, given favorable conditions. In nature – and in drier gardens – the stems
die back after seeds are produced in late summer. In other gardens, plants may persist until
frosts kill the stems.
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| Showy milkweed (Asclepias speciosa): flowering plant |
Asclepias speciosa blooms in late spring to summer; depending
on climate and weather, this may be as early as May to as late as July or even
August. The flowers of the Showy milkweed are large for the genus. They grow in dense, mounded clusters, usually
at the top of the stem, but also in the upper leaf axils (where leaves connect
to the stem). Each flower can be up to 1
inch (2.5 cm.) across. The flowers are
very fragrant. They attract a wide range
of butterflies and other native pollinators.
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Showy milkweed (Asclepias speciosa): close-up
of flower, side view |
The
flowers themselves are rose-pink, fading to cream. The flower shape is typical for the
Milkweeds. If you’ve never closely
examined a milkweed flower, it’s well worth your time. The flowers are a marvel of Mother Nature’s
ingenuity. The flowers look like crowns.
The corona (crown-shaped structure
above the petals) is composed of five ‘hoods’ and ‘horns’ which are
modifications of the male sex organs. In
the very center is a complex structure (the gynostegium)
composed of fused parts of both male and female organs.
The
hoods and horns are appropriately named; as seen above and below, they indeed look
like hoods and horns. They point towards
the anthers (the pollen producing structures), which are fused to the female
stigma (the pollen-receiving structure) to form the gynostegium. For excellent labeled drawings of these
structures see reference 5, below.
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| Showy milkweed (Asclepias speciosa): close-up of flowers |
The
pollen is stored as pollen masses (pollinium)
rather than separate pollen grains. When
a pollinator insect visits the flower, its legs slip into the slits between
anthers on the gynostegium. If you look
closely, you can see these slits in the picture above; there are 5, radiating
out from the very center of the flower. When the leg is removed, it takes with it a
pollinium, which is deposited into the stigmatic slit of the next flower. From then on, it’s fertilization as usual.
Given
the unusual flower structure, you might expect pollination to occur only rarely. Quite the contrary: the highly modified structures,
and the lure of sweet nectar, ensure that Milkweed pollination is highly
efficient. For more on pollination see:
http://mother-natures-backyard.blogspot.com/2013/06/life-friendly-gardening-planning-for.html
.
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Milkweed (Asclepias): butterflies can function as
pollinators, but they're not as efficient as bees |
Showy
Milkweed is semi-incompatible, producing few viable seeds if
self-pollinated. Where plants are
plentiful (like Western Colorado), seed production is rarely a problem; but if
you’re growing Showy Milkweed elsewhere, you’ll need to plant several plants,
if you want fertile seeds. The
pollinators include a wide range of butterflies (not just Monarchs). But the
bees, including bumblebees, are often the most important pollinators. If you enjoy watching insect pollinators,
this is a plant to consider.
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| Showy milkweed (Asclepias speciosa): young seed pods |
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Showy milkweed (Asclepias speciosa): developing
seed pods
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The
seedpods are 3-5 inches long, inflated, and may be smooth or spiny (the local
ones are spiny – but not sharp to the touch).
As seeds develop, the pods dry from a pale green to tan. When fully dry, the pods split along their
seams, releasing numerous dark-brown seeds with silky ‘tails’.
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Showy milkweed (Asclepias speciosa): sometimes
reseeds in inconvenient places (just pull them up) |
The
seeds are wind-dispersed, so you may find new patches growing in favorable
locations. If plants appear in inconvenient places, just remove them (or remove
the seed pods before they fully develop). But if you want to collect the seeds, watch
the pods closely. The ripe pods can be
collected into a paper bag; the pods will then open in the closed bag,
releasing the seeds. The fluffy awns
(‘tails’) can then be removed by vigorously shaking the bag. You can then release the ‘fluff’; the heavier
seeds will remain at the bottom of the bag.
Plant seeds in fall or spring.
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| Showy milkweed (Asclepias speciosa): seedlings |
Showy
milkweed is fairly easy to grow (either from plants or seed), if given enough water.
Asclepias speciosa
grows well in most soil textures,
including clays. And it tolerates a wide
range of soil pH (about 5.0 to 8.5). Its
alkalinity tolerance likely explains its common occurrence on the Western
Slope.
It succeeds in full sun to part-shade, but often
looks its best in full sun. Consider the
location carefully before planting; plants have a long taproot and resent being
moved after becoming established. And
don’t worry if plants don’t look very impressive when small. Many native
perennials need a little time to develop their full character, and this is one
of them.
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Showy milkweed (Asclepias speciosa): can be grown
with non-native plants that have the same requirements |
Showy milkweed does need average to moist soils, at
least until after flowering is completed and seed pods are well developed. If you live in a dry area (or you’re experiencing
a dry spell) supplemental water will be required. Once the seeds have dispersed, you can
safely let the ground dry out. Cut back
the dry stems in fall or winter. That’s
really about all that’s needed – you won’t even need to fertilize, unless you
grow Showy milkweed in a container. And
don’t worry about insect pests; slugs and snails are about the only real challenges.
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Showy milkweed (Asclepias speciosa):
attractive summer perennial |
At this point, you may be wondering how to include
Showy milkweed in your garden. It’s hardy in regions from USDA Zones 3a to 9b,
and is a great perennial for any moist area: around a garden pond, in rain
gardens and infiltration swales, in moist irrigated areas, in mixed meadows
etc. It benefits from runoff, so it often does well along driveways, roadsides and
around patios. It can even be grown in a large container. It looks particularly
good when massed, and can be used mid-bed in mixed flower beds. It shows up particularly well against dark
backgrounds, including larger shrubs.
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Showy milkweed (Asclepias speciosa): pastel shades
contrast well with darker background foliage |
Of course, Showy milkweed is often included in pollinator
and butterfly gardens. But you might
want to plant it for other reasons. Of
all the local Milkweeds, this species produces the lowest concentrations of toxic
resinoids, alkaloids and cardiac glycosides (the chemicals for which Milkweeds
are famous). Native peoples throughout
the Four Corners states used young shoots, stems, flower buds, immature fruits,
and roots as cooked greens. That being said, this is a Milkweed
– we don’t advocate eating any part of milkweeds.
Not surprisingly, Asclepias speciosa has a long history as a medicinal
plant. The milky sap contains antiseptic
chemicals. Many native traditions favor it as a topical treatment for skin sores, cuts, warts and ringworm. A poultice of mashed roots is applied to
rheumatic joints to relieve pain and reduce swelling. Decoctions (teas) of the
roots were traditionally used to treat coughs. As with many natural medicines, Milkweeds should not be taken internally.
These are medicines – and all medicines have the potential to be
harmful, even lethal.
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Showy milkweed (Asclepias speciosa): particularly
effective when mass planted |
Showy milkweed was traditionally an important
source of fiber for cordage and rope. The fibers were also used in weaving and
for making paper. The tough fibers are
obtained from dead stalks gathered in the fall. Archeologic evidence suggests this
fiber has long been used in Southwestern and California cultures. The silky floss
from the seeds was traditionally used to line cradleboards and baby’s diapers. It
has also been used to stuff pillows and even life jackets (it’s water-proof). During World War II, gardeners, farmers and
school children collected Milkweed floss for the latter use [ref. 6].
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Showy milkweed (Asclepias speciosa): habitat
for many interesting insects |
So, why consider planting Showy milkweed in your
garden? First, it’s an interesting and
pretty perennial, bringing bold foliage and pretty flowers to the summer garden.
Second, it provides important habitat for interesting insects: butterflies,
native bees and colorful Milkweed bugs to name a few. And birds use the fiber for nest building.
Third, it’s an easy plant to grow in many types of
soils. Easy to grow perennials are a welcome addition to any garden. But perhaps most importantly, this is a plant
with a long tradition of use by inhabitants of the Four Corners states and
California. When you grow it – and use it – you become part of a tradition
rooted in our Colorado soil and our history.
And that’s something that’s hard to trump!
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Showy milkweed (Asclepias speciosa): Mother Nature's
Montrose Garden, Montrose, CO
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For a
gardening information sheet see: http://www.slideshare.net/cvadheim/asclepias-speciosa
For more
pictures of this plant see: https://www.slideshare.net/cvadheim/asclepias-speciosa-web-show-154917894
For plant
information sheets on other native plants see: http://nativeplantscsudh.blogspot.com/p/gallery-of-native-plants_17.html
_________
- https://pollinator.org/monarch?gclid=CjwKCAjwvJvpBRAtEiwAjLuRPc-d7a3Pe8By4uiL35Lui25oUb8aj8rNkRRc4xP-dU4GRjQHVgm6ohoCX-UQAvD_BwE
- http://khkeeler.blogspot.com/2015/10/milkweeds-monarch-butterflies-and.html
- http://khkeeler.blogspot.com/2016/06/where-to-buy-milkweeds-to-grow-in.html
- https://swmonarchs.org/
- http://waynesword.palomar.edu/termfl1.htm
- http://www.arhomeandgarden.org/plantoftheweek/articles/Milkweed.htm
We
welcome your comments (below). You can
also send your questions to: mothernaturesbackyard10@gmail.com
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