Flowering this week is our 2019 seed collection from Texas of the Evening Primrose looking Milkweed, Asclepias oenotheroides. This odd clumping milkweed, which tops out at 18″ tall, only grows natively from Louisiana west to Arizona, and south into Mexico in very dry sites. Hardiness is most likely Zone 7b-10b.
by Patrick McMillan
The past couple of weeks the small, freakish flowers of one of the strangest of plants have begun to open in our gardens – pipevines. It’s difficult to believe that nature could summon up anything as strange as the flowers of pipevines. If you remember the “regular” aka actinomorphic and the “irregular” zygomorphic flowers from high school biology then you would have to consider the strange, inflated flowers of pipevines highly irregular.
These plants are related to wild gingers/heartleafs (Asarum) and are members of the basal angiosperms, which are plants with lineages that predate monocots and true dicots. Many of the early angiosperms have flowers that are pollinated by flies or beetles that they lure to the flowers with the pleasant smell of rotting meat or dung. Pipevine is no exception. They trick flies into entering the strangely shaped flowers which often have a funnel-like flare with a narrow opening and trap the fly in a chamber with the pollen and nectar to accomplish pollination.
The general shape of the pipevine flower also approximates the anatomy of a uterus and birth canal. As was all the craze in the early years of medicine, the resemblance to the uterus must mean it is good for treating issues with difficult pregnancies and childbirth. This archaic mode of determining herbal remedies is referred to as the doctrine of signatures – basically if a plant part looked like a part of the human anatomy it would be used to treat ailments associated with that organ. This avenue of medical care led us to the highly unsuccessful use of liverleaf (Hepatica) to treat ailments thought to be caused by the liver, like cowardice and freckles. Medical science has since progressed, maybe?
The pipevines include herbaceous upright perennials, short rambling vines, and enormous lianas (woody vines). The toxic chemical aristolochic acid is contained in all parts of the plant and though it is known to cause kidney failure (which probably didn’t decrease the problems with difficult childbirth) this chemical has also been shown to have antitumor properties. Don’t go munching on the leaves! Pipevine Swallowtails depend exclusively on pipevines for their larval food source and all the species we grow are host to large numbers of caterpillars in the summer.
The Pipevine Swallowtail accumulates aristolochic acid which deters predators like birds from wanting to consume them (they don’t want kidney failure either). This may explain why Spicebush Swallowtails and Red-spotted Purples look so similar to the Pipevine Swallowtail, they’re taking advantage of blending into the poisonous crowd.
These beautiful butterflies always seem to find your pipevines, no matter how secluded you think they are. Don’t worry, we can’t have enough swallowtails and the vines regrow without issue. These are great plants to include in your garden to support our butterflies. The caterpillars have another interesting behavior, when disturbed they have bright orange “horns” that are technically referred to as osmeteria that it pushes out of the front of its body and emit a very foul odor!
Three native pipevines are found in the Carolinas. Common Pipevine (Isotrema macrophyllum) can become a huge liana, reaching the canopies of old-growth trees and spreads through runners and can be difficult to keep contained. It grows best in cool climates and tends to suffer or not grow in warmer parts of the Southeastern US.
Woolly Pipevine (Isotrema tomentosa) grows very well in hot, humid climates and is known from only a few native populations in the Carolina coastal plain. Like its mountain cousin it is very difficult to restrain and may quickly outgrow the space you envision for it.
The only other pipevine is very dissimilar to the others, Virginia Snakeroot (Endodeca serpentaria), which is an upright herbaceous perennial that rarely gets a foot tall. If you’re wondering why these former Aristolochia are now in the genera of Isotrema and Endodeca, well, it appears to all be about genetics. They are closely related but currently in different genera.
One of the easiest to grow and showiest, best-behaved species in our garden hails from Brazil, Argentina and Bolivia, Fringed Pipevine or Fringed Dutchman’s-pipe (Aristolochia fimbriata). The plants form scrambling vines that act more like a groundcover than a vine and have beautifully silver-veined small leaves. The flowers are intricately patterned with lines and fringed with long “tentacles” to create one of the most bizarre flowers you’ll ever include in the landscape. Though you wouldn’t pick a plant from Brazil to be rock-hardy here in Raleigh, this one has been fully hardy (zones 7a-9a). For those of you looking to add some swallowtails but unwilling to devote the space to a monstrous mass of vines this one is for you. Fringed Pipevine is also incredibly drought-tolerant and perfect for part-sun to dappled dry shade.
As gardeners around the country are encouraged to plant more asclepias to encourage monarch butterflies, many folks are finding out that not all species of asclepias make good garden plants. As a genus, asclepias consists of running and clump forming species. There are number of horribly weedy garden plants like Asclepias speciosa, Asclepias syriaca, and Asclepias fasicularis. These plants are fine in a prairie garden, but are disastrous in more controlled home gardens.
One of our favorite clumping species is the easy-to-grow, Arizona-native Asclepias angustifolia ‘Sonoita’. This superb species was shared by plantsman Patrick McMillan. It has proven to be an amazing garden specimen, thriving for years, despite our heat and humidity. Did I mention it flowers from spring through summer?
This is the time of year when the tiger swallowtails feast on our many patches of the amazing native Stokes aster. Our favorite clone is the upright growing Stokesia laevis ‘Peachie’s Pick’. Moist soils are best, but stokesia tolerates some dry conditions on a short term basis as long as it has 2-6 hours of sun.
One of the little-known native asclepias, milkweed, is flowering in the garden this week. Asclepias variegata, redwing milkweed, is a widespread native, ranging from Canada and Virginia south to Florida, and west to Texas. So, why is this virtually unavailable commercially? Our plants typically range from 1.5′ to 2′ tall, although 3′ is possible. For us, it performs best in part sun to light shade.
The specific epithet “variegata” which refers to two colors on the flower was certainly a poor choice, since most asclepias have multi-color flowers. Of course, Linnaeus didn’t have the benefit of the internet back in 1753.
We wanted to create a buffet for local butterflies by our patio, and a mass planting of Eupatorium purpureum ‘Little Red’ did just the trick. Not bad for a highway ditch native.
The Pipevine Swallowtail butterfly caterpillars are munching away on any aristolochia (pipevine) in sight. This week, their favorite in the garden is the stunning Aristolochia fimbriata. Nature has created a wonderful balance where the catepillars each just enough to survive and grow, but not enough to damage the plant, which will quickly re-flush.
Hurricane Hermine brought some much needed rain over the weekend. Not only were there some happy gardeners, but the rain lilies are loving it too. Here is a picture of Zephyranthes ‘Heart Throb’ in the garden with its bright 2″ reddish-pink flowers and contrasting white eye. At a mere 6″ this Heart Throb is a real show-stopper.
Rain lilies got their common name from their charming habit of producing new blooms after it rains. Rain lilies come in a variety of colors to coordinate with your garden’s palette. Plant rain lilies near the garden path where you can enjoy their beauty from mid summer up until fall. Be sure to come check out our wide selection of rain lilies this coming weekend, Sept. 9-11, during our fall open house, and you can take home your very own Heart Throb!
Lobelia cardinalis is native to 41 out of the 50 states in North America. The cardinal flower is tolerant of many different soils from moist bogs to average garden soils, and is perfect for use in rain gardens. Cardinal flowers are also a magnet for hummingbirds and butterflies. Lobelia begins blooming in summer and will continue until fall with an array of flower and foliage colors to blend nicely in your garden, from the brilliant red flowers of the species, to the hot pink Monet Moment, or the burgundy foliage of Black Truffle.
You can order cardinal flowers online or visit us at our fall open house September 9-11 & 16-18 to see the cardinal flowers blooming in the garden and pick out that perfect plant for a spot in your garden.