Plant of the Week: Dutchman's pipe or pipevine (Aristolochia macrophylla)

In the movie "Field of Dreams" an Iowa corn farmer hears a voice that commands "if you build it, he will come" and he interprets the vision that he should plow under the corn field and build a baseball diamond for the Chicago Black Sox, which of course he does and we all know the rest of the story.  This plant of the week is one of those, if you plant it, they will come stories.  My first personal narrative came when I planted a sole Dutchman's pipevine in the backyard and on July 4, went out to browse around the garden and low and behold, I found caterpillars, dozens of them, all sizes, eating those large heart-shaped leaves like there was no tomorrow. Those caterpillars were of the pipevine swallowtail that I had observed visiting the garden some weeks before.  What a thrill it was to know that there actually was order in the universe!  What amazed me so much was that native populations of this plant were many, many miles away from my urban landscape in Lexington.  Since that time I am not sure I can remember not visiting yards or nurseries and not seeing caterpillars eating pipevine leaves.  This is not a showy vine in the least and of course it gets its name from the pipe shaped flowers, that are often hidden and inconspicuous, that appear in early summer.  It is a rapid grower, up to 75' in some cases, given some good garden soil (it can't tolerate dry, clay soils) and full to part sun and something to climb on like a trellis, stout tree, or even along the top of a wooden fence.  It is the primary plant that attract pipevine swallowtail butterflies, which consume the leaves and are then somewhat toxic to other predators because of the alkaloids contained within the leaves that the caterpillars consume. One of the really fascinating things about the flower is that the strong scent attracts insects, usually flies or gnats, and get caught in the fine hairs of the tube and are eventually released as the hairs wither, releasing the insects covered in pollen.  There are three species native to Kentucky: A. macrophylla, A. serpentaria, and A. tomentosa and they are members of the birthwort family which was so named because of the medicinal properties related to aiding childbirth.  This is a species that can be grown quite easily from seed.  If you are looking for a fast growing species that can quickly cover a porch, this would be the ideal plant.

Plant of the Week: White Sassafras (Sassafras albidum)

Everyone has probably heard about drinking sassafras tea or root beer, elixirs that were historically made from the roots and shoots of the sassafras tree.  However, the primary ingredient in sassafras oil is safrole which has been banned by USDA as a food additive since 1976 when it was discovered to be carcinogenic.  Today the U.S. Drug Enforcement Agency monitors safrole and sassafras oil because it is used to make three different psychedelic drugs including "ecstasy".  Hence today root beer gets its unique odor and fragrance from esters found in wintergreen and black birch (methyl salicylate) and the other aroma for food additives are made artifically. Other uses of sassafras include using the dried leaves to make file' for use in Creole and Cajun cooking (most notably gumbo), for aromatherapy, and for fragrance in perfume and soap.  As a landscape tree it is best used where sprouting by new individuals is not a problem because this species has a tendency to root sucker forming a clump of small trees as a result of its shallow root system.  The main stem does have a deep taproot making this a drought tolerant species. This species is adapted to a wide variety of habitats but it must have very well drained soils, usually sandy loam but not heavy clay.  It has outstanding fall color ranging from orange to deep red and the pyramidal shaped tree can be quite stunning when it reaches its maximum height of 60' tall. It has small inconspicuous flowers that appear in March and April followed by small bluish black fruits in September.  The leaf shape of this species is variable and ranges from ovate to mitten-shaped to three-lobed. Young leaves have a soft downy appearance.  The plant does well in full sun but can take some partial shade.  In terms of wildlife use, the berries are eaten by birds and it serves as a host plant for the spicebush swallowtail.

Plant of the Week: Snow Trillium (Trillium nivale)

The smallest and earliest flowering of all the Trillum or Wake Robins, the snow trillium, is considered rare throughout much of its range.  It is a diminutive little gem that can be challenging to find in the nursery trade, but it is available from several specialty nurseries and it can be expensive.  This species loves limestone soils and reaches a total height of 2 - 4" tall.  It typically flowers in March in Kentucky and is one of the early, showy spring ephemeral wildflowers.  It reproduces from seed, but most often via underground rhizomes.  Thus when you typically find this species in the wild it is often observed in a large colony.  The seeds are dispersed by ants and it takes up to 4 years to grow this from seed (which is why it is so expensive in the trade). This is a long lived species and individual plants can live for more than 8 years, and usually much, much longer giving rise to large colonies.  Unlike other shade or woodland garden plants, this species does not like heavy leaf mulch and so in the garden it should be planted in good loamy, fertile limestone soil where it gets filtered sunlight but where the leaf litter doesn't accumulate. Another unique feature is that this species doesn't appear to like competition and hence it should be planted in an area that will not be over-taken by other woodland species like wood poppies, bluebells, asters, etc.   This is an easy trillium to identify because it flowers earlier than all the other trilliums, is small growing to 4" in height, has a single stem that produces a single flower with 2" long petals and sepals and is usually white to off-white in coloration and the leaves often have a grayish tint to them.  Like other trilliums, deer love these plants and they should be protected if you have deer present in the surrounding area.  Because this plant is so uncommon in nature and is endangered in Kentucky, do not dig plants from the wild and purchase only nursery propagated, not nursery grown, plants from reputable nurseries.  Even though this species doesn't like competition, you can put some companion plants next to areas where your colonies develop and a couple of these are quite showy as well and include hepatica and rue anenome.

Plant of the Week: American Snowbell (Styrax americanus)

I will never forget the first time I encountered this beautiful deciduous shrub in the wild.  I was working on the rare wildflower book and was out at Land Between the Lakes looking for Trepocarpus (not a very showy plant at all).  As I was walking along the shore next to the woods I saw a beautiful shrub that at first glance looked like a honeysuckle because it was covered in dainty white flowers and it smelled fantastic.  As I approached I realized it wasn't a honeysuckle at all, rather the American snowbell. This shrub does very well in the landscape because it is a wetland species that likes moist soil and partial shade, although it will grow in full sun.  It has a preference for acidic soils but does just fine in the limestone soils of central Kentucky.  While it can reach heights of 10 to 15' tall, I rarely see it get over 6 to 8' tall and it has a very open canopy form with simple, alternate elliptical shaped leaves that are smooth below and slightly hairy above. While the bark is generally a gray color on the main stem, individual branches can vary in color from reddish to brownish to greenish and as they age the go from slightly hairy to smooth.  The showy flowers are quite fragrant and are pollinated by bees and this is a primary host plant for promethea moth (Callosamia promethea). This is a relatively fast growing shrub and it is easily propagated from softwood cuttings.  A number of nurseries sell this species and some even carry large balled and burlap specimens.  This is a wonderful addition to a woodland garden and would work nicely with Carolina Silverbell and Flowering Dogwood as understory species because it flowers in April.