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.

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.