Friday, May 19, 2017

Endangered Species Day: Conophytum herreanthus

Conophytum herreanthus ssp. herreanthus, Hardy #637, Umdaus, Northern Cape, RSA (Oct. 9, 1961). Greenhouse cultivation in Connecticut, May 2017.
In honor of Endangered Species Day, here is a South African succulent that is definitely endangered, and in fact very likely completely gone from the wild. Conophytum herreanthus subspecies herreanthus was known from a single population from an area called Umdaus, northwest of the town Steinkopf in Northern Cape Province. Subspecies herreanthus was apparently always confined to a single gneiss and quartzite hill, and although it was originally abundant, its numbers declined in the mid-twentieth century, probably because of overgrazing, and overcollection for the succulent plant trade. I visited the site with a group of botanists in 1997, and we could only find one, nibbled-looking plant. The plant has apparently not been seen since then, and Steve Hammer and Andy Young, in the latest South African National Biodiversity Institute Red List of endangered plants, list C. herreanthus ssp. herreanthus as extinct in the wild.

Subspecies herreanthus is actually not uncommon in cultivation, at least among Conophytum specialists, with a number of different collections and probably many different individuals in circulation. An effort was made in the 1980s to introduce fresh seed and a small number of plants back into the wild at Umdaus, but nothing established over the long term.

Conophytum herreanthus ssp. rex at Klipbok, south of Eksteenfontein, Northern Cape RSA. August 2004.
Conophytum herreanthus occupies a unique evolutionary position in the genus, with a number of probable ancestral characteristics like leaf pairs that are only fused at their bases and a highly xeromorphic (drought-adapted) epidermis with stomata sunken beneath the surface and protected by special hairs. Fortunately for conservation purposes, there is a second subspecies, C. herreanthus ssp. rex, which is merely "rare" in the wild, according to the Red List. Subspecies rex is a larger plant with longer leaves, that is reasonably abundant in the area of the Little Helskloof and the town of Eksteenfontein, occupying a far larger range than subspecies herreanthus, with multiple populations. There are recent reports of a third area where C. herreanthus is found, to the west of Eksteenfontein, occupied by very large plants with a bluish coloration and prominent dots on the leaves; these plants could probably be accommodated in C. herreanthus ssp. rex, but could conceivably warrant description as a new taxon.

Matt Opel with Pachypodium namaquanum: habitat of C. herreanthus ssp. rex at Klipbok.
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Hammer, S.A. & Young, A.J. 2015. Conophytum herreanthus S.A.Hammer subsp. herreanthus. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2017/05/20

Saturday, May 6, 2017

Nepenthes truncata Flowering

Nepenthes truncata with traps and flowers at the UConn EEB greenhouses, May 2017.
Nepenthes, the tropical pitcher plants, are carnivorous plants with passive pitfall-type traps. The traps are modified leaf blades, borne on the tips of long petioles and attached to expanded leaf bases that resemble the blades of more typical foliage. Nepenthes truncata, from the Philippines, is one of the largest tropical pitcher plants, with traps that can hold a liter or more of digestive fluid and probably catch the occasional lizard or mouse, in additional to more typical insect prey.

Nepenthes truncata, raceme of flowers on a male plant.
Nepenthes have small, dark or greenish flowers in tall racemes, with males and females on separate plants (Nepenthes are dioecious). All of the species that I have encountered produce a floral scent that is more or less unpleasantly musty. In N. truncata, the odor of the flowers is particularly offensive, and can permeate an entire greenhouse with a rank, surprisingly animal-like smell, reminiscent of something from a zoo.

Saturday, March 25, 2017

Odd Lichen Phenomenon

Shagbark Hickory (Carya ovata) with heavy lichen growth at the ends of the shag. Mansfield Center, Connecticut, January 2017.
Poking around the local woods during one of the many thaws this past winter, I came across a Shagbark Hickory with an unusual growth of lichen on its shaggy bark. The peeling strips of bark were heavily colonized by a big, gray foliose (leafy) lichen that I can't immediately identify.

Foliose lichen on Shagbark Hickory bark strip.
The lichen was mainly on the splayed tips of the bark. One could come up with an explanation of why the lichen was so vigorous on those spots: rainwater would flow down to the ends of the bark strips, keeping things moist and accumulating nutrients leached from the tree's surface. The problem is that there are hundreds of other Shagbark Hickories in the area, and it just seems to be this one tree that is festooned with such a heavy growth of this particular lichen. Maybe there is something especially conducive to lichen growth in the microhabitat of this one northwest-facing steep slope above a swampy hollow? It's difficult to say with just a single, isolated example. 

Another view of the licheny Shagbark Hickory.





Sunday, February 26, 2017

Late Winter in Connecticut

Sugar Maple and melting snow, Feb. 21, 2017.
 It's that time again: late winter in New England, when the sun is getting noticeably stronger, life in the woods is stirring, and a young man's fancy turns to thoughts of sap. It's been another mild season overall, but with periods of typical cold and a fair amount of snow. The Sugar Maple sap run was pretty good since Valentine's Day, but incredible warmth the past few days (a new all time high for the month of February in Boston yesterday, for example) has wiped out the snow cover and stopped the flow for the time being. There are some cold snaps in the forecast into early March, so maybe the sugaring season isn't quite done yet. My only boil so far was about 12 gallons of sap, yielding a quart and one cup of syrup, for a 38:1 ratio.

Honeybees bringing in Skunk Cabbage pollen, Feb. 25, 2017.
 Honeybee survival has been acceptable for the winter of 2016-17 to date, with six out of seven hives in the home yard doing well (and the one loss being a small colony that was looking troubled even back in October). I was surprised to see them bringing in fresh pollen yesterday, especially since just last weekend I was out snowshoeing in the woods.

Symplocarpus foetidus (Skunk Cabbage) with Huperzia lucidula (Shining Clubmoss), Feb. 25, 2017.
The pollen was coming in from Skunk Cabbage, always the earliest significant bee forage source in Connecticut. Skunk Cabbage produces only pollen as a pollinator reward, so the bees will probably have to wait several weeks at least, depending on the weather, for their first big nectar harvest of the spring, from Red Maple and willow flowers. They might get a little taste of nectar on warm days between now and then from early cultivated bulbs like snowdrops and crocus. 

Skunk Cabbage emerging from a quiet stream in Mansfield Center, Ct.
--
Maple Update, March 25: After a very warm February, winter did indeed make a strong comeback earlier in March. There has been weeks worth of seemingly optimal sugaring weather this month--hard freezes at night, thaws and bright sunny days, deep snow cover--but the sap has dried up completely and the season seems to be over. Apparently, too much unseasonable warmth early in the sugaring period can cause the sap flow to shut down for the year, even if conditions improve later on.

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.