Posts Tagged Swamp Milkweed
In my region of central North Carolina, it has been a very sparse year for butterflies and moths. The local lepidopterists (folks who study this group of insects) suspect that an especially severely cold winter followed by a wet early spring may be responsible for the dearth of this insect group. This is not just bad news for those of us who enjoy watching colorful butterflies drift in clouds from flower to flower. It is very bad news for the ecosystem, because myriad species of animals — most especially nesting birds — rely exclusively on the larvae of this group (caterpillars) to feed their young. Caterpillars are the perfect baby bird food — packed with protein and other key ingredients that insure that chicks grow quickly to fledgling stage, where they become less vulnerable to predators. In fact, caterpillars are the only food parent birds of familiar species such as Eastern Bluebird, Carolina Chickadee, and Carolina Wren can use; their chicks require the specific nutrients in those proportions to grow and fledge.
The well-known classic, Silent Spring, by Rachel Carson warned the world about what happens when insects disappear from ecosystems. The banning of DDT saved our birds that time. A more recent classic, Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens, by Douglas W. Tallamy, details specifically which species of insect rely on which species of native plants. The list is long and alarming — at least to me — because many species of insects rely exclusively on only one species of plant to feed their larvae. If that plant species is unavailable, the insects that rely on it cannot complete their life cycles. If the host plant species becomes widely unavailable (as species of Ash trees are becoming now, due to devastation by the non-native Emerald Ash Borer), insects that rely on those species will disappear.
I was delighted to spot this fresh-looking Juniper Hairstreak dining on Swamp Milkweed in my pollinator garden yesterday. This small butterfly is often overlooked, because of its soft green color, but it is relatively common in the Piedmont region of North Carolina because its larval food plant — Eastern Red Cedar (Juniperus virginiana) is also relatively common. On my five acres, we are lucky to have a number of 40-foot mature specimens. They provide shelter for birds and other creatures, their bluish “berries” (actually cones) are beloved by Cedar Waxwings and other birds, and their sturdy shade and deep green color make this evergreen species well-suited for any landscape. If sited where air flow can stagnate, a colorful fungus that uses this species as an alternate host can appear, but I solved this issue in my yard simply by limbing up the trees to permit better air circulation.
References tell me that male Juniper Hairstreaks linger on branch tips of their host tree until a female is attracted. Females lay single eggs on the tips of branches, which eventually hatch to become very well-camouflaged caterpillars similar to the one in this link. I’ve never seen one on my trees, but then again, I’ve never gone looking for them either.
But the presence of this fresh-looking specimen on my Swamp Milkweed yesterday tells me that my Red Cedars have been playing host to green caterpillars that have likely been helping to feed the three broods of Eastern Bluebirds reared by the ambitious parents that nested on my property this year.
In a world so filled with darkness these days, the appearance of this petite green butterfly gives me at least small hope for my planet’s future.
In the southeastern US piedmont region where I live, I am happy to report that more and more homeowners are adding native pollinator gardens to their landscapes. By providing sources of pollen, nectar, and leaves of plants that native bees, butterflies, moths, wasps, etc. rely on, we are all helping to replace at least some of the native ecosystems obliterated by urbanization that once fed these insects. As Douglas Tallamy explains in his book, Bringing Nature Home, if we lose our native pollinators and other insects, we also lose the native wildlife that eats these insects — birds, bats, frogs, etc.
One of the poster-insects for the plight of our native pollinators is the Monarch Butterfly. Reports seem to vary every year recently regarding the status of this beautiful species, but it seems clear that we should all continue to add to our landscapes the native food plants that this butterfly relies on: milkweeds (Asclepias spp.)
Milkweeds are a test of patience for gardeners. New transplants don’t usually bloom prolifically the first year after planting. These plants spend that first year establishing healthy root systems. But by their third year in your garden, you will agree that milkweeds are worth the wait — for the beauty of their prolonged flowering, for their fat, brown pods from which seeds escape on silken parachutes, and for the diversity of pollinators that dine on their flowers, and the Monarch Butterfly caterpillars that devour the plants.
For gardeners wondering which species of milkweed to try in their gardens, I recommend three options. These are the easiest to grow, and also the most readily available in the trade.
- Swamp Milkweed (A. incarnata) is native to moist areas and can handle some shade. However, it thrives in standard garden beds, as long as you water it during droughts, and perhaps a bit extra during its first year as it is establishing. In return, you will get three-foot-tall plants covered in clusters of pink flowers. There’s also a white-blooming variety of this species, but I think the pink forms are much lovelier. A well-established plant will bloom for at least a month, and will be visited dawn to dusk by happy pollinators. If you’re lucky, these visitors will include some Monarch butterflies.
- Butterfly Weed (A. tuberosa) is native to hot, sunny hillsides. It’s not unusual to see it growing on unmowed road banks in my region. The trick to this species that produces bright orange flowers is excellent drainage. If it sits for long in too-moist soil, it will forsake you. The plants I’ve added grow bigger every year, producing more and more flowering branches literally abuzz with happy pollinators.
- Common Milkweed (A. syriaca) thrives in moist, sunny places. It is not as showy as the first two species above, but it seems to be the favorite food plant of Monarch Butterfly caterpillars, perhaps because it is the most commonly occurring milkweed species on patches of undeveloped land. I tucked mine toward the back of a flower bed, where they can grow tall while waiting for Monarchs to find them. I planted mine in my boulder bed, and they haven’t bloomed for me, possibly because they don’t get quite enough sun. But they grow well, producing tall, green plants, and last year Monarch caterpillars ate them literally to the ground. However, the plants returned in greater numbers this year, which is when I realized that this species spreads via running rhizomes. As Matt Gocke, Greenhouse and Nursery Manger at the North Carolina Botanical Garden told me, you plant this species once, and you will never need to plant it again, because of its ability to spread itself via rhizomes.
Milkweeds are slow to emerge in spring, far later than many other native perennials. But once they appear, they grow quickly, and soon the pollinator visits begin. Two pests will also eventually show up.
Bright orange Oleander aphids inevitably appear on every milkweed species I grow, but they seem to favor Common Milkweed. So-called because they also feed on oleanders, these aphids are orange to warn potential predators that they are poisonous, having ingested the toxins in milkweed that cause deer, rabbits, and other plant-eaters to pass them by. These aphid infestations can get pretty ugly. I control mine by donning garden gloves and simultaneously spraying the stems with a strong jet of water while rubbing off the aphids with my fingers. Aphids are poor climbers; once knocked down by the water, they have trouble getting back up the stems.
Milkweed bugs usually show up eventually on some of my milkweeds. These can be destructive to developing seed pods, because they suck out the nutrients in the pods, thereby stunting them. If they get out of hand on my plants, with my gloves on, I pick them off and drop them in a jar of soapy water, where they quickly die. Most years, I never see very many of these insects, which makes me wonder if some bird eats them despite their possible toxicity.
A Few Other Milkweed Species
Being a somewhat obsessive gardener, if I like a genus of native plants, I’ll often try to grow as many different species as I can. Thus, I grow a few additional species of milkweed. This is the second year for my Whorled Milkweed (A. verticillata). Until it blooms, you wouldn’t even believe it’s a milkweed. That’s how un-milkweed-like its leaves look, at least to me. But its small white clusters of flowers are unmistakably milkweed blooms, and this year the plant has formed a lovely small shrubby plant that continues to produce flowers popular with an array of pollinators.
The flowers of Red Milkweed are similar to those of Swamp Milkweed, and they share a preference for the same growing conditions. I grow mine in a pot that sits in my summer water feature. It blooms in early spring, but doesn’t re-bloom.
Fewflower Milkweed is native to swampy parts of the coastal plain region up and down the eastern coast of the US. I planted this in one of my summer water feature pots last year, but it didn’t bloom. But this year, beginning about two weeks ago and still going strong, the plant began to produce clusters of peachy-orange flowers. The color is not as in-your-face as that of Butterfly Weed flowers, but as the common name implies, each flower cluster contains a relatively small number of flowers. They are as popular with pollinators as the other milkweed species, but probably not a practical choice for most piedmont gardeners.
I think native milkweeds should be on every gardener’s list of must-have perennials. For an investment of some patience on your part, you will be rewarded with prolonged, colorful blooms visited by swarms of bees and butterflies. And if you’re really lucky, perhaps you’ll get the chance to watch a Monarch caterpillar transform into a chrysalis, and then a butterfly, as I did last year.
Fall is a great time to plant milkweeds in your garden, and you can get the three species I suggested — plus perhaps a few more — at the North Carolina Botanical Garden’s Fall Plant Sale next month. I’ll be there on Member’s Night to get first crack at all the wonderful plants that will be offered. I hope I’ll see you there!
Readers of my blog may remember that about this time last year, I acquired one or two plants of every species of milkweed being offered at the NC Botanical Garden’s Fall Plant Sale. I thought it would be useful to write up an evaluation of how those plants performed in my garden during this year’s growing season. Recall that I divided my new acquisitions into two groups – those native to drier, well-drained habitats, and those preferring moist, even swampy conditions.
Boulder Garden Milkweeds
As I described in my original milkweed-related post, my boulder garden is a sunny, hot spot full of diabase boulders of varying sizes that are slowly eroding into smaller chunks, leaving a sandy, relatively thin soil surrounding them. Any plants that love heat and good drainage get a trial here, so this is where I planted
- Clasping Milkweed (Asclepias amplexicaulis)
- Whorled Milkweed (A. verticillata)
- Common Milkweed (A. syriaca)
- Poke Milkweed (A. exaltata)
- Butterfly Weed (A. tuberosa)
All of these plants are still alive and apparently healthy, but two of the species never bloomed.
Clasping Milkweed – This plant is still alive and green, but it never grew. At all. Usually, when a plant is unhappy, it eventually fades away, and the drought-plauged, hot summer certainly gave it plenty of excuses. But it persists, looking almost exactly as it did when first planted nearly a year ago. I know that some plants – usually woody ones – spend their first year after transplanting maximizing root growth while producing minimal top growth. But I’ve never seen this in a perennial. As long as it remains green, I will think positive thoughts about it. Perhaps next spring, new growth will appear.
Whorled Milkweed – This is the most un-milkweed-looking milkweed I’ve ever met. Its needle-like leaves give it a softer appearance than the other milkweeds. It never grew more than about 12 inches high, but it seems healthy.
About mid-July, it produced many tiny flower buds in the leaf axles. Eventually, these grew into the typical milkweed bud clusters I knew from other species.
In early August, they opened to produce waxy greenish-white flowers in a typical milkweed-looking inflorescence. The flowers were small, proportionate to the size of the plant, but they managed to draw a wide range of pollinators while they bloomed.
Despite all those pollinator visits, I have not seen a single seed pod on this species. But the plant itself still looks healthy, so I’m hoping it will survive the winter again, perhaps producing a more robust plant next year, since it will be starting from a larger size.
Common Milkweed – This was my other non-blooming milkweed in this bed. But unlike Clasping Milkweed, my Common Milkweed plant grew robustly, and still looks very vigorous. Interestingly, while the orange oleander aphids that notoriously plague milkweeds are all over my other milkweeds, they’ve barely bothered this one.
It grew to a height of about 2.5 feet, but has never shown any signs of flowering.
Poke Milkweed —This taller milkweed grew early and quickly in the spring. I was befuddled by its first blooming attempt in late May, which yielded one single flower. Not an inflorescence – just one pinkish-white flower.
My research confirmed that it should have produced a typical milkweed inflorescence. I decided to be grateful it managed at least one flower during its first year in my garden.
But then in early July, I noticed more flower buds! These produced typical milkweed inflorescences by mid-July.
As with my Whorled Milkweed, many pollinators visited, but no seed pods were produced.
Butterfly Weed – There is a reason that this milkweed species is sold often in plant nurseries. Its showy, bright orange flowers laugh at heat and drought.
One of my plants produced one round of blooms, but the other one is currently on its third round of blooms, and is simultaneously sporting a number of growing seed pods. Score!
It began blooming in early June, produced another round in July, and started up with a third blooming cycle in early September. Pollinators cannot get enough of this plant, and neither can I!
Water Feature Milkweeds
Three of the milkweed species I acquired last year are native to swampy habitats, so as I explained in my original post, I planted them in pots, which I inserted into my front water feature after danger of frost this spring. They were:
- Swamp Milkweed (Asclepias incarnata)
- Few-flowered Milkweed (A. lanceolata)
- Purple Savanna Milkweed (A. rubra var. laurifolia)
Two of these did beautifully, and one was a failure.
Swamp Milkweed – This is the other native milkweed you will find commonly in plant nurseries, because like its cousin, Butterfly Weed, it reliably produces beautiful clusters of blossoms that persist well in our summer heat while attracting myriad pollinators.
My two plants both grew to heights of about 3 feet, and produced two rounds of blossoms, first in early June, then again in late July. Now they are full of many expanding seed pods.
There’s a white-flowering form of this species, but I prefer the more common pink-blooming variety.
If you can provide an evenly moist garden bed, you can add this beauty to your garden. It doesn’t require as much water as I gave it. But in my yard, water almost always becomes a scarce commodity as summer progresses, so I stacked the deck in my favor by growing my Swamp Milkweeds in pots immersed in my water feature.
Few-flowered Milkweed – This is my only full-out failure. It stayed green and grew a bit through May, but then it began dying back, leaving nothing but a brown stem. Oh well, nothing ventured, as the saying goes.
Purple Savanna Milkweed – This native milkweed grew to about the same height as the Swamp Milkweeds. It also produced two rounds of blooms for me – one in early June, and again in early August. I would not characterize the flower color as purple.
To my eye, the flowers on my plant were more of a deep pink or mauve – very lovely – and very attractive to pollinators. This species did not set seed either, alas.
Where have all the Monarchs gone?
The only great disappointment I’ve had with my milkweed garden is the complete absence of Monarch butterflies. They’ve been reported nearby, and one even had the audacity to fly in front of me as I drove down my road about a mile from my house. But I have not seen a single Monarch in my garden and yard anywhere, and no caterpillars either. It was a rough year for butterflies in my area anyway, apparently due to an unusually cold and wet spell late last winter. I’m hoping that my milkweeds will return next spring even more vigorously, perhaps finally serving the visiting Monarchs for which they were planted. But even without the Monarchs I’d hoped for, I consider my milkweed garden to be a success. The pollinator diversity they attracted was exciting, and I’m hoping that the seed pods the Swamp Milkweeds and Butterfly Weeds are developing will yield new plants for my gardens.
But wait, there’s more!
You may recall that one of the flower varieties from Renee’s Garden I tried last year was an annual tropical milkweed variety called Butterfly Bright Wings. Last year, many of these plants produced seeds that floated everywhere. A number of those seeds produced plants that germinated in the boulder bed this year, where their mother plants had grown. It took them until last week – probably because of the drought – but these volunteers have finally begun to bloom. All appear to be the red form, which is the one I liked best anyway. I’m hoping they will again produce seed pods and perpetuate themselves next year.
For ornamental reliability, I recommend piedmont gardeners stick with Butterfly Weed and Swamp Milkweed. I have a feeling the other species that bloomed for me may be a bit more temperamental, and except for Purple Savanna Milkweed, they don’t produce very showy flowers.
I think perhaps the Greenhouse and Nursery Manager at the NC Botanical Garden may have reached the same conclusion, because he’s only offering Butterfly Weed and Swamp Milkweed at the upcoming Fall Plant Sale.
If you’re looking for vigorous, re-blooming flowering milkweeds that can handle our hot summers and might attract Monarch butterflies, you should stop by the sale and pick up some of these beauties. For the best selection, come on Members’ Night on Friday, October 2. Members can use their 10% discounts and get the best selection of plants. Plus there’s free food, beverages, and live music – and you can join at the door that night. I hope to see you there!
Those of you who have read my blog for a while may have noticed that when I fall in love with a native genus of plants, I tend to want to grow at least several different species in that genus, usually because I think the plants are beautiful, and because I like to see how many of these natives I can site well enough to flourish in my yard. Basically, I like to experiment. I’ve done this with southeastern US native deciduous Magnolia species, and with southeastern native deciduous azalea species. In both of these cases, the plants are beautiful and provide three or four seasons of visual interest.
Not so for my latest experiment. At this year’s plant sale at the NC Botanical Garden, I took advantage of their offerings of native milkweed species, because I’m eager to try to help the Monarch butterfly population. As I wrote here, Monarch butterfly populations appear to be declining precipitously, probably mostly due to habitat destruction, although other factors are also relevant. Monarchs only lay their eggs on species of native milkweeds. These plants contain toxins that Monarch caterpillars can process, but avian predators find the toxins make the caterpillars inedible, even when they metamorphose into winged adults.
A few of our native milkweeds produce flowers worthy of any garden. Butterfly Weed (Asclepias tuberosa) and Swamp Milkweed (A. incarnata) can be found in many plant nurseries. With proper siting, both will thrive in most Piedmont gardens. The flowers attract numerous pollinators, and in my yard, the Monarch butterflies usually show up in early autumn to lay eggs on the plants, usually after the flowers have morphed into the long seed pods characteristic of the genus. The caterpillars usually strip almost every leaf off the plants, then turn into emerald chrysalises attached to nearby vegetation.
As a gardener, I routinely assess plants not only for their visual impact in my landscape, but also for their growing requirements. In the case of native milkweeds, I soon realized that they fall roughly into two groups, based on growing conditions. Butterfly Weed represents one group — the milkweeds that require excellent drainage and lots of sun. Swamp Milkweed represents the moisture-loving milkweeds. Some of these can tolerate a bit more shade, but not much; all of them need a constant supply of moisture.
I have a wonderful sunny flower bed built around a stand of diabase boulders beside my driveway. The soil is sandy and full of rocks, bits of boulder slowly breaking down. Drainage is excellent, and I’ve had good success there with plants that need these conditions. This is where I planted my new native milkweeds that need good drainage and hot sun:
- Clasping Milkweed (Asclepias amplexicaulis)
- Whorled Milkweed (A. verticillata)
- Common Milkweed (A. syriaca)
- Poke Milkweed (A. exaltata)
- Butterfly Weed (A. tuberosa)
All of these milkweeds produce similar flower clusters, and they’re all pretty, mostly in an understated way. Some of them — Poke and Common Milkweeds — grow quite tall, and likely will look a bit unkempt as they mature, which is why I put them toward the back of my bed, where they won’t be particularly conspicuous. Poke Milkweed may need a bit more moisture, so I sited it on a downslope, where it should receive more water.
Even the less showy flowers will attract numerous pollinators, and I’m hoping Monarch caterpillars will appear to devour them next summer/fall. My newly planted good-drainage-loving milkweeds are not mulched. I put small rocks around their bases to help me remember where they are after these perennials die back later this fall. I planted two Butterfly Weeds toward the front of my boulder bed. They are smaller plants at maturity, and their showy, bright orange flowers will look lovely against the boulders.
You may notice a flowering plant amidst all the greenery in one of the pots in the above photo. That was my one impulse buy at the plant sale. I had gone there fully intending to buy only milkweeds, but this lovely native orchid caught my eye. I have always loved the Nodding Ladies’-tresses (Spiranthes cernua) that bloom in the NC Botanical Garden’s carnivorous plant display this time of year. So when I spotted this healthy specimen — actually two blooming plants in one pot — I had to have it.
I’ve had great success growing other wetland plants, including carnivorous pitcher plants, in pots that I then place inside my shallow water feature during the growing season. These plants overwinter in their pots inside my little greenhouse, where they sit in saucers of water that I refill as needed to maintain the constant moisture levels they require.
I decided to plant my newly acquired wetland-loving milkweeds in pots that I will treat like the ones currently still sitting in my water feature. Because I’ll be draining that little pond soon, I decided to simply put the new pots in water-filled saucers for now. Next spring after frosts are gone, they will go into the little pond with the other moisture-loving plant pots.
As with the showy Butterfly Weeds, I acquired two Swamp Milkweed plants. Their bright pink flowers will look great amidst the other water plants next growing season. The moisture-loving milkweeds in my new pots are:
- Swamp Milkweed (Asclepias incarnata)
- Few-flowered Milkweed (Red Milkweed) (A. lanceolata)
- Purple Savanna Milkweed (A. rubra var. laurifolia)
These, plus the Nodding Ladies’-tresses, left a bit of room in the pots, so I popped in a few Cardinal Flowers (Lobelia cardinalis) that I had in pots elsewhere. Cardinal Flowers can tolerate drier soils, but they planted themselves in my wetland pots some time ago, and the bloom stalks on those wetter plants are always the tallest in my yard.
I am hopeful that my milkweed experiment will add visual interest to my landscape, attract copious pollinators, and most of all, be utilized by hungry Monarch butterfly caterpillars. Nurturing Beauty in all her guises will always be the greatest reward for this gardener.
Butterflies add moving color to otherwise static gardens. During peak butterfly season in my yard, dozens upon dozens of winged beauties drift from flower to flower, sometimes even bumping into me as I admire them. Planting flowers that attract these mobile garden ornaments is one sure way to bring them to your yard. But if you really want them to stick around, they need to be fruitful and multiply. And for that, they need caterpillar food plants.
In the case of Monarch butterflies, we’re in luck, because a number of their caterpillar food plants — members of the milkweed family — also produce lovely long-lasting flowers. One of my favorite milkweeds is Swamp Milkweed (Asclepias incarnata). As its common name implies, it thrives in moist soil, but you can keep it happy in a well-mulched garden bed. For lots of flowers, give it a minimum of fours hours of sun. If it gets hot afternoon sun, it will need more water. In return for meeting its minimum requirements, you’ll be rewarded with lovely pink flowers like this:
Group a few of these beauties together for more visual impact — and to make it easier for the Monarch butterflies to find them. Every late summer, I watch female Monarchs lay individual eggs on my Swamp Milkweeds. Soon the hungry larvae emerge and pretty much devour the entire plant before they create their emerald cocoons.
By the time the Monarch caterpillars are decimating my milkweeds, the flowers have finished for the season, leaving long seed pods to ripen by fall. The caterpillars don’t eat the seed pods, so I get new plants from seed, and because milkweeds are perennial, the devoured plants resprout every spring.
Personally, I don’t think you can ever have too many Monarchs, and I think the caterpillars have almost as much visual impact as their adult winged forms. See what I mean:
And if you’ve got children in your household, planting milkweeds will provide you with an instant outdoor laboratory to teach them about the Monarch life cycle.
Last year, I managed to grow fourteen new Swamp Milkweeds from seeds I collected from pods on older plants in my yard. I planted them on three sides of my yard to ensure that I’ll have enough food for all the Monarchs that I hope will stop by.
To learn more about Monarch butterflies, try this site.