North America's Pachysandra

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In the interest of full disclosure, I have never been a fan of garden variety Pachysandra. Long before I had any interest in plants or gardening, there was something about this groundcover that simply did not appeal to me. Fast forward more than a decade and my views on the use of Asian Pachysandra in the garden have not changed much. You can imagine my surprise then when I learned that North America has its own representative of this genus - the Allegheny spurge (Pachysandra procumbens).

My introduction to P. procumbens happened during a tour of the Highlands Botanical Garden in Highlands, North Carolina. I recognized its shape and my initial reaction was alarm that a garden specializing in native plants would showcase a non-native species. My worry was quickly put to rest as the sign informed me that this lovely groundcover was in fact indigenous to this region. Indeed, P. procumbens can be found growing in shady forest soils from North Carolina down to Florida and Texas.

This species is yet another representative of a curious disjunction in major plant lineages between North America and eastern Asia. Whereas North America has this single species of Pachysandra, eastern Asia boasts two, P. axillaris and P. terminalis. Such a large gap in the distribution of this genus (as well as many others) seems a bit strange until one considered the biogeographic history of the two continents.

Many thousands of years ago, sea levels were much lower than they are today. This exposed land bridges between continents which today are hundreds of feet under water. During favorable climatic periods, Asia and North America likely shared a considerable amount of their respective floras, a fact we still find evidence of today. The Pachysandra are but one example of a once connected distribution that has been fragmented by subsequent sea level rise. Fossil records of Pachysandra have been found in regions of British Columbia, Washington, Oregon, Wyoming, and North and South Dakota and provide further confirmation of this.

As a species, P. procumbens is considered a subshrub. It is slow growing but given time, populations can grow to impressive sizes. In spring, numerous fragrant, white flower spikes emerge that are slowly eclipsed by the flush of spring leaf growth. The flowers themselves are intriguing structures worthy of close inspection. Their robust form is what gives this genus its name. "Pachys" is Greek for thick and "andros" is Greek for male, which refers to the thickened filaments that support the anthers.

It is hard to say for sure why this species is not as popular in horticulture as its Asian cousins. It tolerates a wide variety of soil types and does well in shade. What's more, it is mostly ignored by all but the hungriest of deer. And, at the end of the day, it took this species to change my mind about Pachysandra. After all, each and every species has a story to tell.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2]

Meet the Sweetfern

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I remember the first time I laid my eyes on Comptonia peregrina. I was new to botany at that point in my life so I didn't have a well developed search image for these sorts of things. I was scrambling down a dry ridge with a scattered overstory of gnarly looking chestnut oaks when I saw a streak of green just below me on a sandy outcropping. They were odd looking plants, the likes of which I had never seen before.

I took out my binoculars to get a better look. What were these strange organisms? Were they ferns? No, they seemed to have woody stems. Were they gymnosperms? No, I could make out what appeared to be male catkins. Luckily I never leave home without a field guide or two. Using what little terminology I knew, I was able to narrow my focus to a plant commonly called a "sweetfern."

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This was one of the first instances in which I grasped just how troublesome common names can be. C. peregrina is mostly definitely not a fern. It is actually an angiosperm that hails from the bay family (Myricaceae). Comptonia is a monotypic genus, with C. peregrina being the only species. It is a denizen of dry, nutrient poor habitats. As such, it has some wonderful adaptations to deal with these conditions.

To start with, its a nitrogen fixer. Similar to legumes, it forms nodules on its roots that house specialized nitrogen-fixing bacteria called rhizobia. This partnership takes care of its nitrogen needs, but what about others? One study found that not only do the roots form nodules, they also form dense cluster roots. Oddly, closer observation found that these clusters were not associated with mycorrhizal fungi. What's more, they also found that these structures were most prevalent in highly disturbed soils. It is thought that this is one way that the plant can maximize its uptake of phosphorus under the harshest growing conditions. 

Flowering in this species is not a showy event. C. peregrina can be monoecious or dioecious, producing male and female catkins towards the ends of its shoots. After fertilization, seeds develop inside bristly fruits. Seed banking appears to be an important reproductive strategy for this species. One study found that germinated seeds had lain dormant in the soil for over 70 years until disturbance opened up the canopy above. It is expected that seeds of this species could exhibit dormancy periods of a century or more. 

In total, this is one spectacular species. Not only does it have a unique appearance, it is also extremely hardy and an excellent species to plant in drought-prone soils wherever it is native. I do see it in landscaping from time to time. If you encounter this species in the wild, take the time to observe it in detail. You will be happy you did!

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

So Many Goldenrods, So Little Time

Nothing says late summer quite like the blooming of the goldenrods. These conspicuous members of the aster family get a bad rap because many folks blame them for causing hay fever. This is simply not true! In this video we take a closer look at a small handful of goldenrods as a way of celebrating this ecologically important group.

Music by: Artist: Ampacity

Track: Encounter One

https://ampacity.bandcamp.com

https://www.facebook.com/ampacityband

In Search of a Parasitic Orchid

In this episode, In Defense of Plants goes looking for a tiny parasitic orchid called the autumn coralroot (Corallorhiza odontorhiza - http://bit.ly/2xQhzbc). It has no leaves and does not photosynthesize. Instead, it makes its living completely off of mycorrhizal fungi, digesting its hyphae within the cells of its highly derived roots. Along the way we meet plants such as:

 Music by: Artist: Ampacity

Track: Asimov's Sideburns

https://ampacity.bandcamp.com https://www.facebook.com/ampacityband

The Curious Case of Hawaii's Endemic Orchids

Orchids and Hawai'i are nearly synonymous. It may come as a surprise then to learn that only three species of orchid are native to this lush archipelago. In fact, there are more non-native species of orchids growing in Hawai'i than there are native. Like much of Hawai'i's endemic flora and fauna, these three distantly related orchid species find themselves on the brink of extinction. How and why only three species of orchid came to call Hawai'i home is a great mystery and it is one that conservationists are struggling to understand before it is too late. 

Orchids produce the smallest seeds of any plants. These dust-like propagules can travel far and wide on the slightest breeze. If any plants were to make it to one of the worlds most remote island chains my bet would be on the orchids. Alas, until settlers arrived, Hawai'i was home to only three - the Hawaiian bog orchid (Platanthera holochila), the Hawai'i jewel-orchid (Anoectochilus sandvicensis), and the Hawai'i widelip orchid (Liparis hawaiensis). The ancestors of these plants must have traveled quite a distance to get to these islands. The Hawaiian bog orchid, for instance, can trace its ancestry back to a related species of Platanthera native to the Aleutian Islands whereas the other two likely blew in from Asia. 

These three species were once found in a variety of locations. Today, however, all of that has changed. Populations of each of Hawai'i's endemic orchids are declining at a rapid rate. In fact, the Hawaiian bog orchid is considered one of the most endangered orchids in the world. The causes of their decline is what one would expect from an island species - habitat destruction, the introduction and subsequent spread of invasive species, and just poor land management in general. It is strange though that so many orchid species from elsewhere in the world are thriving as their endemic cousins are declining. 

Though the exact reasons for this remain uncertain, some of it has to do with another invader - honeybees. Honeybees are native to Europe and are generalists in their foraging abilities. Until bees were were brought to Hawai'i, many introduced orchid species behaved themselves. There simply wasn't anything around to pollinate them. Once honeybees came onto the scene, a few of these introduced species such as the bamboo orchid (Arundina graminifolia) were suddenly able to reproduce. The tropical climate made the land ripe for the taking. But this is only part of the picture. There is another, more interesting conundrum that remains to be solved. 

Orchids absolutely require mycorrhizal fungi to germinate and grow. Why is it then that introduced orchids seem to be doing so much better than the Hawaiian endemics? Good question. Some orchids can be very specific about the fungi they will partner with whereas others are not. It could be that all of the introduced orchids that are naturalizing are generalists whereas the endemics are specialists. It could also be that the endemics simply can't handle the altered disturbance regimes brought on by modern society.

The real reason is probably some combination of these and many more but the fact of the matter remains, Hawai'i's native orchids are in trouble. Since they are not nearly as showy as other orchids they are rather overlooked. This is a shame because if they are lost from their native range, they are gone from the world forever. Luckily there are people out there like Dr. Nicole Hynson of the University of Hawai'i and Dr. Larry Zettler of Illinois College who are working to understand, propagate, and conserve these unique species. 

Photo Credits: University of Hawai'i Museum (http://bit.ly/1K8pjKC), Arkive (http://bit.ly/20kxg17), and G. Daida (http://bit.ly/1K8phCw

Further Reading:
http://bit.ly/1PKOV0C

http://s.si.edu/1QRn0el

http://s.si.edu/1Rjwd1g

http://s.si.edu/1W8bGMb

http://www2.hawaii.edu/~nhynson/Hynson_Lab/Welcome.html

http://www.ic.edu/LarryZettler

Growing Ferns

I am finally having some success intentionally growing ferns from spores. I collected and sowed spores from some interrupted ferns (Osmunda claytoniana) over the summer. They have been hanging out as gametophytes for months now and some are finally starting to grow sporophytes. Here is how it worked for me:

I kept my eye on a batch of adult plants this summer. Once their fertile fronds developed I would flick them every now and then to see if they were releasing spores. Once I saw that they were I shook the fronds over some paper to collect the spores. I then took some old potting soil and sterilized it with boiling distilled water. I use old takeout containers because they are small and have clear lids that form a seal which keeps the humidity high.

Once the soil was cool I sprinkled the spores over it and then placed it on a shelf where it gets a small amount of ambient light every day. The rest they did themselves. You just have to remember to check on them and keep the humidity quite high because they can dry out really fast. They seemed stuck as gametophytes for months. I just noticed the start of these sporophytes the other day.