Cold

Trachycarpus
Trachycarpus fortunei (Chinese windmill palm).  The 10 F (-12 C) forecast for Saturday night will probably be close to the minimum temperature tolerance for this species.

I shouldn’t complain when friends in Wisconsin are “enjoying” -14 F (-25.5 C), but the past week has been cold for North Carolina.  The days have hovered right around or just below the freezing mark, and nights have dropped as low as 11 F (-11.5 C).  We have several more cold days in store, with low temps on Thursday, Friday, and Saturday 10 to 13 F (-10.5 to -12 C).  These temperatures aren’t unusual for a North Carolina winter, but usually they are short lived, and generally the lowest temperatures are accompanied by an insulating layer of snow.  It is quite unusual for weather this cold to persist this long when the ground is bare (we finally had a little snow last night).  Consequently, the ground has almost certainly frozen deeper than it has for years.

During the past few years, when winters were mild, it has been tempting try various tropical and subtropical plants outside in the garden.  Come spring, it will be interesting to see how many of those plants, mostly South African and South American, have survived.

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Wintergreen orchids

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The winter leaves of Tipularia discolor in our woods.  Notice the purple pigment on their undersides.

Winter is the best time to look for several orchid species that grow in the North Carolina piedmont.  You can wander through the woods without worrying about ticks, spider webs and poison ivy.  Just watch out for deer hunters.

1. Tipularia discolor (cranefly orchid)

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T. discolor, a small colony of the typical spotted form

Tipularia discolor is one of the most common woodland wildflowers in our region.  They grow in almost every patch of woods, even where just a few trees have been left by developers.  The plants grow as scattered individuals or small colonies., and the drifting seed will also sprout in mulched flowerbeds that are shaded and dryish in summer.  T. discolor is very easy to find during the winter, when it bears a single leaf, and if you live almost anywhere in the piedmont, you could probably find a plant within a few minutes of stepping outside your front door.

They’re much more difficult to locate during the summer, because the foliage dies in spring and the midsummer flowers are small and dull.  The best way to find T. discolor flowers is to mark a colony in winter and return in July (hopefully avoiding the aforementioned ticks and spider webs).   You’ll be most likely to find flowers if you choose a colony that had the remains of inflorescences and dried seed capsules persisting in winter.  The flowers are pollinated by moths, and the column is twisted slightly to one side so that the pollen is deposited on the moth’s compound eye.

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T. discolor flowers lurking behind our shed, July 26, 2017.

Although the classic “textbook” description of T. discolor says that the leaves have dark purple spots on their upper surface and purple undersides (see above image), I have found considerable variation in the plants growing in central North Carolina.  All of the following photos were taken in Orange County, NC, and I monitored the unusually colored forms for several years to be sure that their appearance wasn’t a temporary fluke.

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No spots on upper surface.  This is the most common form growing on our property.
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Metallic purple-green
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Solid Purple.  I frequently see plants with leaves that emerge purple and fade to green, but rare clones like this plant retain the solid purple color all winter long.
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White spots/variegation.  I have only seen this color in one colony.  The white spots were stable over several years.

2. Aplectrum hyemale (Adam and Eve, putty root orchid)

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Aplectrum hyemale in Duke Forest

Aplectrum hyemale has a very similar growth habit, with a single leaf produced in autumn.  The leaves are slightly larger than those of T. discolor and are green with distinctive white stripes. We are near the southern edge of its range, and it is much less common than T. discolor.  I have only seen plants at two locations:  once in Duke Forest and once along the Eno River near downtown Hillsborough.

3.  Goodyera pubescens (downy rattlesnake plantain)

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Goodyera pubescens in our woods

Goodyera pubescens is evergreen, not deciduous, but like T. discolor it is easier to find in the winter.  It grows in the same habitat as T. discolor but seems to be somewhat less common.  Its foliage is very beautiful, and various sources report that it has suffered from over-collection for gardens, terrariums, and flower arrangements.  For terrariums, at least, its tropical relatives are much better suited.  Just be sure to seek out artificially propagated plants.  Several G. pubescens seedlings have sprouted in the hardwood mulch that we spread on flower beds, so if you’re lucky that’s a possible way to obtain plants for your garden.

Goodyera 2

Miracle Fruit

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Synsepalum dulcificum (miracle fruit)

There’s not enough going on in the garden and greenhouse to support a “Six on Saturday” post today, but I think the first fruit on a strange little plant warrants a post all of its own.

Miracle fruit (Synsepalum dulcificum) is a nondescript little west African shrub with nondescript little white flowers.  Its name and its claim to fame come from the red berries which contain a unique glycoprotein called miraculin.  Miraculin binds to taste receptors that are responsible for detecting sweet substances and functions as a pH-dependent agonist [1].  In other words, miraculin can activate sweet taste receptors, but only under acidic conditions.  The result is that sour (acidic) substances temporarily taste sweet.

This sounded like a lot of fun to me, so about a year-and-a-half ago, I purchased a small. S. dulcificum plant to grow in the greenhouse.  After a rocky start when it got badly sunburned, the plant has recovered nicely and recently produced two berries.  My initial plan was to cut the berries in half so that all four family members could try them.  However, it turned out that the berries consist of a thin layer of white pulp sticking to a large central seed that resists subdivision.  In the end, my wife graciously chose to wait for the next crop (or maybe she wanted to use us as guinea pigs).  I chewed on a small fragment of skin and pulp shaved off the largest berry, and the kids had one berry each.

The skin/pulp was tart and fresh but didn’t have much in the way of a distinctive taste.  After chewing on the berries, the kids and I tried sucking on wedges of fresh lemon and sipping apple cider vinegar.  The results were exactly as described in the literature, but it was still startling to experience the effect ourselves. The lemons tasted like wonderfully sweet fresh lemonade.  The vinegar was great.  I could still smell the volatile acetic acid, but the taste was sweet apple juice.  The overall effect was a complex, spicy apple cider.

I see more buds forming on the plant, so hopefully we will soon have a larger crop of berries to experiment with.

Reference

[1] Koizumi, A., Tsuchiya, A., Kakajima, K.-I., Ito, K., Terada, T., Shimizu-Ibuka, A., Briand, L., Asakura, T., Misaka, T., and Abe, K. (2011).  Human sweet taste receptor mediates acid-induced sweetness of miraculin.  Proc. Natl. Acad. Sci. USA 108: 16819-16824.

Colonists

cyclamen colony 1

Recently, I was walking along Morgan Creek in Chapel Hill, not far from the North Carolina Botanical Garden, when I noticed what I took to be an unusually extensive and dense population of Hexastylis arifolia, the little brown jug.

cyclamen colony 2

Closer inspection revealed that the plants were actually Cyclamen hederifolium, a native of Mediterranean Europe.  The plants were growing on a steep hillside, where rocks and loose soil have slowly slid down the slope.  A few plants extended onto the wetter, more compacted soil of the flood plain, but that was clearly not their favored habitat.

cyclamen colony 3

Nearby were a few plants of the real Hexastylis arifolia.

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Hexastylis arifolia (little brown jugs)

These Cyclamen hederifolium plants had clearly escaped from cultivation, but I don’t think they can really be considered invasive.  The true invasives are plants that form dense stands, choking out native species–things like Eleagnus species,  Ligustrum sinense (Chinese privet), Hedera helix (English Ivy), Pueraria montana (Kudzu), and Microstegium vimineum (Japanese stiltgrass).

Cyclamen seeds are distributed by ants, so the plants are unlikely to spread as far as those species with windborne seeds or berries that are eaten by birds.  The relatively sparse and low-growing leaves of C. hederifolium are also unlikely to smother other woodland plants–not that there is much else that likes to grow in the dry, unstable soil that the cyclamens seem to favor.

Not far from the cyclamens, I did see several other species with more potential to be invasive. Mahonia bealei (leatherleaf mahonia) and Ilex cornuta (Chinese holly) were naturalized in the woods, and of course, English ivy is ubiquitous.  The beautiful variegated leaves of Arum italicum stood out in the wet soil near the creek.  I had been thinking of adding A. italicum to my garden, but given its ability to spread and potential to be invasive in the mid-Atlantic region, I’m now not sure that’s a good idea.

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Arum italicum (lords-and-ladies) growing beside Morgan Creek

Although the C. hederifolium are probably no threat to native ecosystems, seeing them in an ostensibly wild area was a good reminder that the plants we grow in our gardens may not always stay there.

Eucrosia mirabilis

A couple of horticultural rules of thumb:

1. If an orchid is named after the Rothschild family, it is sure to have spectacular flowers.  cf. Vanda Rothschildiana, Paphiopedilum rothschildianum, Eurychone rothschildiana, Bulbophyllum rothschildianum.

2.  If a plant’s species epithet is some variation on “mirabilis” or “mirabile,” it is probably something special.  After all, “mirabilis” means wondrous, amazing.

Eucrosia mirabilis, blooming now in my greenhouse, lives up to its name.

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Eucrosia mirabilis inflorescence

E. mirabilis is a member of the Amaryllidaceae from South America.  Its sepals and petals are fairly small and a dull yellowish green color, and if that’s all there was to the flowers, it wouldn’t be worth growing.  But as you can see, the extremely elongated stamens and pistil are what make the flower amazing.  All of the flowers on an inflorescence open at the same time, giving the appearance of a large mop or head with long white hair.  The effect is very dramatic.

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Flowers just starting to open.  The folded stamens and pistil emerge limp and wrinkled, and slowly expand over several days.

The May 1, 2006 issue Curtis’s Botanical Magazine gives a good description of the ecology of E. mirabilis and its history in cultivation [1].  The species was described 1869 with notes indicating that it was from Peru, and it seems to have remained in cultivation until the 1870s–there is an herbarium record at Kew from 1876.  It was then lost for more than 100 years, and in 1997 was declared extinct by IUCN.  Surprisingly, researchers in Ecuador (not Peru) rediscovered the species in the same year that it was declared extinct, and seed, probably originating from Ecuadorian plants, entered cultivation in the late 1990s.

In nature, E. mirabilis grows on rocky hillsides among Opuntia cactus (prickly pear), so it needs bright light and very well drained soil.  I attempt to replicate this habitat by growing the bulb in an 8″ diameter terracotta pot with a well-drained mix of sand, permatill, and a little commercial potting soil.  During the spring and summer, I grow it outdoors in full sun, and it produces a pair of large, paddle-shaped leaves.  When the leaves start to wither in early autumn, I move it into the greenhouse for several months of warm, dry dormancy.  My plant always flowers in December or January, consistent the bloominng season in the wild, but plants in England are reported to bloom in April and May [1].  It is completely leafless while flowering, and the long inflorescence emerging from an apparently empty pot adds to the bizarre appearance.

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My bulb has shown no inclination to form offsets, so I suspect it must be propagated by seed.  Luckily, the plant is self fertile, and I have several second generation seedlings coming along.  I have donated extra seed to the Pacific Bulb Society seed exchange,  and I’ll probably be sending more to the SX in a couple of months.

Reference

Matthew, B. and Lewis, G. (2006).  557. Eucrosia mirabilis (Amaryllidaceae).  Curtis’s Botanical Magazine 23:157-164.