Monday, February 13, 2017

Dodder Cultivation

Cuscuta europaea on a sad Coleus, with flowers and mature fruits.
Dodders (genus Cuscuta) are twining parasitic plants in the morning glory family (Convolvulaceae). Cuscuta plants are holoparasites, which have non-functional scale leaves and have lost the ability to make chlorophyll, and thus are completely dependent upon host plants for all of their nutritional needs. Cuscuta europaea is an annual species that thrives on a wide variety of hosts, and is one of the easiest parasitic plants to cultivate indoors or in a greenhouse.

Cuscuta europaea seeds and one week seedlings.
Dodder has small seeds, and the nearly rootless, filamentous seedlings must attach to a host plant soon after germination, or they will quickly exhaust their resources and die. It seems to be beneficial to scarify the seeds by rubbing them lightly on sandpaper; otherwise germination can be poor. The seeds can be sown on the soil surface next to an appropriate host plant. I've used Coleus hybrids with good results, but C. europaea isn't picky and a wide variety of common garden plants work, including Impatiens, sunflowers and tomatoes. Cuscuta seedlings latch onto smaller, tender shoots more easily than to older host growth, so freshly established Coleus cuttings are a good starting point.

Cuscuta europaea, young seedlings establishing on Coleus.
Only a fairly low percentage of dodder seedlings manage to wrap around a host stem and form haustoria--the nutrient-absorbing connections to host vascular tissues. If successful, the peg-like vestigial root and lower parts of the dodder seedling wither away, while the portion in contact with the host remains alive. The live portion of an establishing seedling spends a week or so as a tiny yellowish ring around the host stem, not putting on much obvious growth, perhaps while the haustoria are working their way into position. After they get organized, though, young dodder plants explode into growth, sending branching stems in every direction and establishing new haustorial connections to their host plant wherever they make contact, and eventually reaching outwards to infest other compatible plants within reach.

Cuscuta europaea, one month old and spreading.
Cuscuta europaea reaches maturity within a month or two of germination, producing clusters of small, pale, non-showy flowers. These are self-pollinating, and almost all of them yield papery fruits containing several viable seeds, even in the absence of any pollination agents. This particular dodder species is short-lived, and begins to slowly decline as the seeds start ripening and the host plant loses vigor. The plants will hang on for six months to a year before dying out completely, assuming they don't kill their host outright, but need to be restarted from seed periodically. Dodder stems trained onto fresh hosts can be severed from the original plant after they have formed haustoria, and these cuttings often seem to be reinvigorated, at least temporarily. Dodders are potential invasives, so old plants with seeds should be disposed of in a way that the seeds will be destroyed or not potentially spread into the environment.

Ironically, C. europaea is itself easy pickings for common greenhouse insect pests like aphids and mealybugs. It's possible to control these with the usual insecticidal soap or appropriate pesticides, but often it seems to make more sense to just start over with a fresh sowing of seeds, given how quickly C. europaea grows. Many aphid species can be controlled with a minute parasitic (technically a parasitoid, since it invariably kills its host. Like Aliens.) wasp, Aphidius spp. Aphidius themselves are sometimes subject to infection with hyperparasite wasps such as Dendrocerus. Parasites on parasites on parasites on parasitic plants on hapless green plants; an appropriate vignette of how the natural world works, to think about during this Darwin Day season.

Sunday, January 8, 2017

Spanish Moss Cold Hardiness II

Tillandsia usneoides that spent much (but not all) of the winter of 2015-16 outdoors in Mansfield, Connecticut.
A while back I wrote about the cold hardiness potential of Tillandsia usneoides (Spanish Moss). Last winter was a very warm one, and for a while it looked liked some experimental clumps of T. usneoides, the hardiest bromeliad, might make it through a whole year outdoors in New England. A specimen brought indoors on February 10, 2016, perked up in a cool greenhouse with no sign of frost damage.

However, one of the worst cold snaps in recent years started just a few days later, with five days around the weekend of February 13 not seeing temperatures above freezing at all. The arctic outbreak reaching a nadir with a day with high temperatures only reaching 10°F (-12°C), lows of -10°F (-23°C), and howling winds. Although this was only a brief interlude in a record warm season, it was enough to kill all the T. usneoides material that was left outdoors.

Periods of more than a week with constant sub-freezing temperatures, or absolute low temperatures below 0°F (-18°C), seem to cause severe or fatal damage to unprotected Spanish Moss. This winter in Connecticut we've already experienced enough cold weather to cause almost total dieback, but I wonder if some year soon we'll have conditions where T. usneoides survives an entire southern New England winter, and resumes normal growth in the spring?

Monday, November 14, 2016

Conophytum Flowers

Conophytum plants in flower. Conophytum cubicum up front with white flowers, C. burgeri pink at left, C. irmae yellow at front right, etc. etc.
  Here in New England, we're just reaching the end of the main flowering season for Conophytum (family Aizoaceae), my favorite group of dwarf succulents from South Africa (and slightly into Namibia). These plants grow during the cooler, shorter-day part of the year, and the majority of species bloom at the start of the growing season. For me, that's October, but in their native Southern Hemisphere habitat, they mostly bloom in April. A few species bloom earlier or later in the year, and a couple, like Conophytum bachelorum (purple plants at front left in the photo above), strictly flower in the late winter and spring.

More Conophytum flowers at a University of Connecticut greenhouse, October 2016.
The 100 or so species of Conophytum show a tremendous range of floral colors, but in all cases have a floral tube with a supply of nectar as a reward for pollinators. The tube is formed by the fused bases of the petals, which, technically, are thought to be modified stamens ("petaloid staminodes") in this family. The brightly colored daytime flowers that are most obvious in these photos are probably pollinated primarily by bees, long-tongued nectar drinking flies, and butterflies. They open on sunny days, close up at night, and tend to have only a faint, pleasant smell.

A number of species, like Conophytum calculus (grey-green spheres at lower left in the second photo), have nocturnal flowers that open fully after dark and produce strong sweet and spicy fragrances. Nocturnal Conophytum flowers are frequently a pale, dull yellow or straw color, but white, pale pink and dark bronze also occur. Nocturnal Conophytum flowers will only open properly at night if it has been sunny during the day. On the night after a dark, cloudy day, they remain closed, in what could be an adaptation to prevent the flowers from getting ruined by rain.

Monday, October 31, 2016

A Trip to Boston Hollow

Westford, Connecticut
I'm located in a more or less suburban neighborhood close to the University of Connecticut, which is practically a small city. The northeast quadrant of Connecticut is called the Quiet Corner for a reason, though, and if you travel just a few miles to the north and east, the landscape becomes pretty rural for the Nutmeg State. Westford, Connecticut is a tiny cluster of nineteenth and eighteenth century houses and a church within the town of Ashford. Taking the road east from Westford, the houses thin out and you enter an almost unpeopled landscape of swamps, overhanging cliffs and dark hemlock groves: Boston Hollow.

Campaign sign spotted by the road in Westford. "Sunken R'lyeh has the best leaders, tremendous, not like we have in this country. Great Cthulhu says nice things about me, folks, nice things, believe me. A strong leader, I hear him in my dreams, not like the dishonest media says. The Old Ones don't win anymore. Sad."
New England horror author H.P. Lovecraft's most famous creation is probably the invertebrate deity-whatzit Cthulhu, who is also a perpetual third party candidate for president (slogan: "Why settle for the lesser evil?"). Lovecraft was a Providence native, and his decadent hill towns with terrifying secrets were based mostly on certain backwards settlements around Springfield, Massachusetts. But he certainly was also familiar with eastern Connecticut, and parts of Ashford have a definite Lovecraft Nation feel about them.

Ashford was a prosperous farming community in the early nineteenth century, with 2661 residents in the 1830 census. It entered a steep decline in the mid-1800s, however, and was down to less than 700 residents around World War I. The region might have been very nearly abandoned in the early twentieth century, if it hadn't been for an influx of Eastern European immigrants looking for cheap farm land. The town has made a comeback since the mid-twentieth century, but as late as the 1970s, there were houses without electricity or indoor plumbing in the area, and some old-timers made a living with activities like burning piles of logs encased in earth to make charcoal, and cutting Witch Hazel branches for medicinal preparations.

Road through Boston Hollow
The history of Boston Hollow has also followed a Lovecraftian trajectory, from bustling center of activity, to nearly forgotten backwater. An important Native American route, the Old Connecticut Path, passed through the area, and the Hollow was part of the Center Turnpike, a major thoroughfare between Boston and Hartford at the peak of Ashford's first period of prosperity in the 1830s. Today Boston Hollow is part of the Yale Myers Forest, the road receives barely any traffic at all, and the Hollow is probably about just about the quietest corner of the Quiet Corner of Connecticut.

Not-quite the Old Man of the Mountain, in Boston Hollow.

Hemlock forest on the steep sides of the Hollow.
The deep, shaded ravine in the heart of Boston Hollow is cooler and damper than surrounding areas, and just about all available surfaces on the forest floor seem to be covered with ferns, mosses and lichens. Striped Maple, an understory shrub or small tree that is common in the north woods of New England, occurs all over the steep slopes of the Hollow, but is otherwise an uncommon sight this far south.

Peligera cf. canina, Dog Lichen
Umbilicaria mammulata, Smooth Rock Tripe
I noted a couple of interesting lichens on a recent foray into Boston Hollow. Rock Tripe is large and impressive (as lichens go) lichen that is not uncommon in the right sort of habitats in Connecticut: shaded and undisturbed rock faces and large boulders. It gets especially abundant and luxuriant in Boston Hollow, though, along with Rock Polypody (Polypodium virginianum), a poikilohydric or "resurrection" fern, which can dry to a crisp in drought, then rehydrate and reanimate itself when rain returns. There were also some blackish patches of Dog Lichen, with reddish sporocarps (fruiting structures), which I haven't seen very often, but which does also grow in a bare spot in my yard, for some reason.

There is a lot to explore around Boston Hollow, with close to 8,000 acres of forest preserved for research by Yale, a number of nearby state parks, and large additional parcels of forested land owned by a local timber company. But, and maybe it's just because I'm originally a New York City native, it's hard to shake the feeling that the place is just a little too far from the madding crowd, and decidedly not the sort of woods where you would want to be caught after dark on Halloween.

Sunday, August 14, 2016

Albino Woodland Plants

Albino Fagus grandifolia, Meredith, NH, July 2016.
Albino plants, which have lost the ability to make the green pigment chlorophyll, show up occasionally among seedlings or as abnormal growth from an established plant. This summer, I've noted a couple of photosynthetically-challenged native plants in my travels, including the American Beech (Fagus grandifolia) above. American Beeches send up root-borne shoots as a method of vegetative reproduction; in this case something went wrong with chlorophyll synthesis in part of the root system of a normal mature beech, and there were several pale shoots like this in a small area of the forest floor. The albino shoots are supported by sugars produced by the original green, photosynthetic portions of the clonal grove of trees. The albino beeches were in a pine/maple/hemlock forest near Winnesquam Lake in New Hampshire.


 Albino Cypripedium acaule, Mansfield Center, Ct, May 2016.
Back in Connecticut, I discovered an immature Pink Lady's Slipper with a completely albino leaf. This was the first time I've seen a true albino form of this woodland orchid, though apparently others have been photographed, including one that grew to flowering size. Almost all orchids have minute seed and seedlings that cannot survive on their own at first, relying on symbiotic fungal hosts from which they absorb the nutrients they need to grow. All Pink Lady's Slipper seedlings go through a subterranean phase that can last several years, when they produce no foliage at all. Presumably, an albino Cypripedium seedling can survive for an indefinite period, by relying on its parasitic relationship with fungi long after normal green plants would be making most of their own food. 

White flowered Cypripedium acaule, Mansfield Hollow.
Back around Memorial Day I revisited the white-flowered Pink Lady's Slipper that I found two years ago in Mansfield Center, Ct. It's still doing well, although I looked last year and couldn't find it; possibly it skipped a year without blooming.