Holiday Flowers: Crassula ovata

Windowsill-grown Crassula ovata, December 25, 2017. 

Crassula ovata, the Jade Plant, is a familiar windowsill succulent, but it seems to be pretty unusual to have one flower as well as my plant has this winter. I'm not quite sure what I did to bring on this display, which is much better than I've ever achieved before with C. ovata as a houseplant. It spent the summer outdoors in quite a sunny spot (after adjusting to life out of the house for a week or two under a tree in dappled shade), and then stayed out late into autumn. By the time it came in, around Halloween, there had been a little light frost, and the flower buds were just starting to appear. Abundant sun and an autumn chill may have helped; it also probably got a bit more fertilizer than usual over the summer (a typical balanced water-soluble houseplant food).

This Jade Plant is not tremendously old, about six years from a cutting from a landscape plant in southern California. It has flowered before, but nothing like this year's show. Another member of the Connecticut Cactus and Succulent Society also reported excellent flowering in his C. ovata plants this month, so it's possible that the weather this year was particularly favorable. It was a relatively mild and sunny fall.

Mystery Stone Structures in Connecticut

Fieldstone cairns at the Werge Easement, Thompson, Ct. November 4, 2017

 Much of the landscape of Connecticut is pretty abundantly supplied with rocks. During the nineteenth century, after the primordial forests were for all intents and purposes completely cut, farmers clearing fields for crops or grazing would use the stones for walls and foundations. 150 year old stone walls are a ubiquitous feature of the Connecticut woods today. The eastern part of the state is also famous in certain circles for other, more puzzling fieldstone structures: cairns, piles, small towers, niches and even a few underground chambers, old but no one knows exactly how old, built by unknown people for dubious purposes. I recently got out for a tour of one of these "lithic sites," organized by The Last Green Valley and led by Joe Iamartino of the Thompson Historical Society, who tempted hikers with a quote from researcher J.P. Whittal: "There are more unexplained crude stone monuments in Thompson than anywhere in New England."
 

Hillside with about 10 cairns visible among the trees.

 After a slide show at the old Thompson town hall, a group of about 40 adjourned to the Werge Easement, a tract of private land set aside for conservation purposes and not normally accessible to the public. Anyone who has spent much time at all in the Connecticut woods has come across piles of loose rocks, in addition to the usual stone walls, in situations where it seems likely that a farmer was just disposing of stones picked from a field. The cairns in Thompson definitely looked more purposeful than that, more carefully put-together, and there were dozens of them dotting a ridge and an adjacent valley. I haven't run across anything remotely like it before.

Somewhat tumbledown stone pile with a niche at ground level.

 Several of the structures have niches in their bases, but nothing large enough for a person to get into. These seem like they might have been used to store something, but what isn't clear. Colonial records indicate that the native Americans built root cellars and underground sweat lodges, which could explain some of the larger stone chambers found elsewhere in New England, but not these dorm-fridge-sized cubbyholes. Cairns in the area have been excavated (often by looters and treasure hunters, unfortunately), but it seems that very little in the way of artifacts have ever been recovered.

A small stone tower

 There is one stone tower on the site, or perhaps a particularly tightly-constructed, skinny cairn. This was only about five feet tall, but another locality in the area has several towers of similar construction, but twice as high.

The "whale," an immobile boulder or bedrock outcrop with piled stones trailing behind it.

 A few of the structures, perhaps somewhat fancifully, might be said to represent animals, possibly turtles or whales. This struck me as a bit of a stretch.

Stone pile in poor condition, with trees growing out of it.

 A mature White Oak growing on top of a fallen-over cairn provides some indication of the age of the lithic site. I'd guess that the tree sprouted more than a century ago and could be 150 years old. The cairn, which looked like it was being overgrown by the tree's roots and not simply piled up against an existing trunk, should be older than that at a minimum. One New England stone chamber has reportedly been determined to be at least 800 years old, based on carbon dating of material found within, but in the absence of any surviving organic artifacts like bone, charcoal or wood, it would not be possible to carbon date the Werge Easement structures.

Stone pile arranged atop a large glacial erratic (the whale stone is in the background).

The majority of the crude stone monuments seemed to built on open ground, but a few were constructed on top of large boulders, the boulders being of such a size that they themselves probably were never moved. There were only two or three cairns built like this, out of the dozens that I saw on the walk.

The smaller boat-shaped stone structure at the Werge Easement.

The site has two examples of another type of mysterious stone structure: boat-shaped mounds, the size of mobile homes, with larger stones piled to make walls around the perimeter and the interior filled with a mix of smaller stones, creating a level, raised platform, three or four feet high. The two "stone boat" platforms, one large and one smaller, are fairly close to each other, but on a different part of the property than the majority of the cairn-type constructions. 

The "prow" of the larger boat-shaped platform.

As to what the Thompson lithic sites actually are, when they were built and by whom, that seems to be very much up in the air, without much indication that definite answers might be forthcoming. Our guides favored the theory that they are largely or entirely the work of Native Americans (the Nipmucs), and date to before European contact or the earliest colonial times. In this interpretation, the cairns are ritual objects or memorial markers, and may indicate the location of deaths in battle or other notable events. Some Native American tribes apparently had a tradition of marking the location of the death of an ancestor with a pile of stones, which subsequent generations would add to when they were in the area. The stone platforms could also be ritual sites, or they might be the foundations of raised wigwams. 

The view across the "deck" of the larger platform.

Another explanation that is maybe not as romantic, but at least as viable, is that the site is a sort of rustic art installation constructed by bored Yankee farmers, less than 200 years ago. Farming in New England is a difficult business and early efforts at cultivating fields or improving pastures involved a lot of moving rocks out of the way. In general, fieldstone was used to make walls, or sometimes thrown into heaps in out of the way spots or at property lines. But, there wouldn't be anything stopping a farmer with a more creative disposition from sequestering his extra rocks in neat little cairns and towers around his property.

 It is interesting to note that the Werge cairns and platforms occur in the neighborhood of perfectly ordinary stone walls from the 1800s, and sometimes the walls and the mysterious lithic structures are practically on top of each other, separated by just a few yards. So, if one contends that the lithic site is an ancient survival from pre-contact times, one also has to reckon with generations of nineteenth century Connecticut sheep farmers carefully working around the old monuments, and not deconstructing them for wall material or to get them out of the way. Which is entirely possible, but maybe not much more probable than imagining a farmer with a funny aesthetic sense building the stone monuments himself.

A Thompson, Ct lake in late autumn.

Lots of what might charitably be called exotic theories exist for Connecticut lithic sites, of course: they were built by wandering Celts on ley lines, or they were left by Vikings and the boat-shaped platforms are symbolic long-boat burials, or they're evidence of Phoenician sailors navigating the Quinebaug River. I'm not sure if anyone has claimed that they're the ruins of Sasquatch encampments, but that would probably be at about the same level of likelihood.

Ultimately, much of the interpretation of the Thompson stone monuments depends on their age, but there doesn't seem to be any obvious way of telling how old they are. I vaguely suspect that the structures are not ancient (multiple centuries or millennia old), or if they are ancient they received ongoing maintenance and reconstruction. The cairns look like they would be fairly fragile over the long term in a heavily wooded environment such as has existed for most of the past thousand years in southern New England; sooner or later they would have an oak grow up inside them and break them apart, or a three-foot diameter chestnut trunk would fall on them, or frost and ice would push the stones out of place. In the absence of human intervention, the structures would have a half-life, and if I had to guess I would put that half-life at much closer to 100 years than to 1,000 years. But for now at least, that is only a guess, and there seems to be a good amount of real mystery surrounding the lithic sites of Connecticut.

Carnivorous Plant Show

Nepenthes edwardsiana at the New England Carnivorous Plant Society Show.

The New England Carnivorous Plant Society held its annual show this past weekend, and as usual the membership displayed and sold a fantastic array of plants. Attendance was excellent, as well, with something around 1500 visitors on Saturday alone. The show took place at Tower Hill Botanical Garden in Massachusetts, Worcester County Horticultural Society's immaculately maintained complex in the Worcester suburbs. In earlier phases of the NECPS's existence, the show was held at Roger Williams Park in Providence (and one time at the University of Rhode Island), but the event has become a popular autumn tradition at Tower Hill over the past couple of years.

Visitors to the carnivorous plant show, Saturday Morning.

The American Pitcher Plant (Sarracenia) table was packed solid with plants.

Emmi K's comprehensive collection of the bladderworts (Utricularia) of New England. Emmi and some friends travel around to swamps and bogs in the summer, collecting bladderwort specimens, then use the plants to create an educational display.

A big pot of a giant Venus' Flytrap cultivar, Dionaea muscipula 'B52'. The name B52 apparently derives from a label code in Henning Von Schmeling's flytrap breeding program, and has nothing to do with the bomber (or the band).

The very rare and almost shrub-like South American pitcher plant Heliamphora tatei.

Another "Sun Pitcher" species that is almost never seen in cultivation, Heliamphora sarracenioides.

An art installation made of woven saplings on the Tower Hill grounds: "Wild Rumpus" by Patrick Dougherty.

The Great American Eclipse of 2017

Total solar eclipse, August 21, 2017, from Greer, SC.

Various circumstances came together this week, so that I was able to drive south and stay in the Asheville, NC area, within easy striking distance of the path of totality through South Carolina for Monday's solar eclipse. I headed to Greer, SC, where there was an eclipse viewing event in the city park.

Some of the crowds at Greer City Park.

Traffic getting down to the Carolinas from the Northeast on Sunday was pretty heavy, though a couple of hours added onto a 15 hour drive wasn't a huge deal. On the state roads to Greer Monday morning, there were quite a few cars heading into the path of totality, but things moved along and there wasn't too much trouble finding parking. The parks department had some entertainment going and was handing out eclipse guides and solar viewing glasses. The area near the food trucks and such was crowded, with lawn chairs and picnic blankets packed into every patch of shade, so I headed for another section of the park that was pretty lightly populated.

My cheesy projection system.

In addition to the solar glasses, I had some pinhole viewers, which worked but made kind of small, pale images. I also jury-rigged a projector with binoculars tied with string to a tripod, which made nice, bright images that included smaller details like sunspots that were invisible with the glasses, but which was unstable and needed a lot of fiddling to keep working. I should have put in more preparation: if the binoculars were firmly affixed to the tripod and there was a shade blocking the sun around the lenses, it would have been much more useful.

Getting darker, near the bandstand. I think the camera didn't really know what to do with the exposure at this point.

There were scattered clouds around in the morning, but as the eclipse progressed they got thinner and finally pretty much disappeared for the main event. This is a fortunate effect of the weakening of solar heating of the air, causing atmospheric convection to dissipate, as the moon blocks more and more light.

A photo through solar glasses, with some thin remaining clouds over the sun.

During the darker phases of the three hours of the eclipse, the air temperature noticeably cooled. It was quite a pleasant change from what had started out as a hot, steamy morning with scorching sun. People starting moving out from under the trees and out onto the open lawns.

Crescent images of the sun under a tree.

One of the well-known eclipse lighting effects is that splotches of sunlight under trees take on the shape of the crescent sun. Actually, dappled light under trees always includes images of the sun focused by diffraction between leaves, but these are normally round and unchanging, and go generally unnoticed as just part of the way the natural world always looks. Especially as totality is getting near, shadows get weirdly sharp, and include little crescent shapes along their edges.

Clouds disperse and the parks lights flicker on as totality gets close.

About 15 minutes on either side of totality, it was dark enough that street lights came on. Animal life started reacting, too, and some kind of loud nocturnal insect (a southern katydid?) started singing from the trees.

The sky is getting dark and a crow flies overhead.

Birds were affected as well. In particular, I noticed crows flying singly and in small groups, all on the same course, the way they normally do in the evening when they are heading to their roost. In the final seconds before totality, the "shadow bands" effect was visible on the sidewalk, with stripes of light and dark rapidly running across the landscape

The park at totality, with sunset-like light all around the horizon.

Totality itself was as amazing as promised. One astronomer I caught on NPR on the drive down said something to the effect of "seeing a 99% eclipse is like taking a family trip 99% of the way to Disney Land," and I'd guess that's probably about right. The million-degree plasma of the corona is sort of a ghostly grey-blue-violet that doesn't really occur elsewhere, and even pro photographs don't do it justice, let alone my quick snapshot at the top of the post. That contrasts with the outline of the moon, which looks, at least in comparison, to be an absolute dead black. Some other celestial objects were theoretically visible at totality, but the only one that I noticed was a blue point, almost within the corona, that was apparently the star Regulus. Venus must have been easily visible, but I wasn't aware of it because I was focused so intently on the eclipse. Totality lasted about 1.5 minutes in Greer, but it seemed like it was over in about 10 seconds to me. The big show finished with a supremely brilliant "diamond ring" effect as a tiny point of the sun's surface reappeared.

The shadow bands had started up again when I turned away from the sun, with the bands running in a different direction than they had been moving before totality. I waited around Greer for a bit after the eclipse, while people cleared out, but there was still a certain amount of traffic even on the back roads returning to North Carolina. That evening I thought to check out the traffic function on Google Maps, and there was an obvious wave of traffic jams spreading out on the highways from the midline of the eclipse, all across the country.

A wild ginger, probably Asarum arifolium.

I hung around the foothills of the Smokey Mountains for another couple of days, and did get a chance to get out into the woods a bit. In steep, damp ravines I saw some interesting smooth-leaved wild gingers, not the familiar Asarum virginicum.

Kudzu, Pueraria montana, the vine that ate the South.

I flew back north on Wednesday, and there were still others traveling who had been in the area eclipse-watching, carrying tripods and talking about the wonders of totality. The lines at the smallish Spartanburg airport were probably considerably longer than they normally are in the middle of the week, but I got through security with time to spare and was back in Connecticut in time for dinner.

Minor Natural Disasters: Summer '17

Accumulating hail, the day after the storm. Horsebarn Hill, Storrs, Ct, June 28, 2017.

Things have been just a tiny bit apocalyptic here in northeastern Connecticut this summer. Last Tuesday there were some impressive thunderstorms around in the evening, and even a bit of hail on and off for about 10 minutes at my house. The hail was pea-sized, and it all melted about as quickly as it fell, which is pretty typical for this part of the country, where even that level of thunderstorm severity is uncommon. The next morning, though, I discovered that the storm hit much harder around the UConn campus. 

The biggest hailstone I could find, about 2 cm in diameter. The top half has melted off, so the internal layering is visible.

 Along the roads approaching campus, I started to see piles of hail that had survived a fairly warm summer night. There were plenty of dime-sized hailstones and even a few nickel-sized specimens. In some shady spots, the frozen piles persisted until lunchtime. I've never seen a storm like that in the East, though I have experienced comparable accumulating hail events in New Mexico and Wyoming.

Yellow Pitcher Plants (Sarracenia flava) outdoors at the UConn greenhouses were moderately shredded.

The storm was bad enough to cause noticeable damage around UConn, where the worst hail occurred. The vegetation was generally a bit torn and bruised, and there was a layer of shredded leaf fragments under some trees, though everything still looked pretty green from a distance. There wasn't any structural damage to buildings around campus, as far as I could tell, though I suspect that the storm was pretty close to the severity that would have dented car roofs and broken glass at the greenhouse.

Gypsy Moth-defoliated trees in Gurleyville, Mansfield, Ct, June 2017.

Eastern Connecticut has been the site of another, slower but more ecologically serious, tree-damaging phenomenon this year: the worst Gypsy Moth outbreak since the 1980s. The caterpillars have been incredibly numerous this year, after a couple of years of increasing Gypsy Moth populations and a very mild winter, and there are large areas of woods that have been defoliated to the point where they look like what you'd expect in April, before the trees have leafed out. 

Hundreds of Gypsy Moth caterpillars on a Pin Oak in Woodstock, Ct. Most have been killed by disease.

Fortunately, there are signs that the current outbreak is just about finished. Gypsy Moths tend to come and go in cycles, becoming problematic for a time, but then virtually disappearing for a decade or more as various diseases and parasites catch up to them. The past few weeks I've been noticing more and more mushy, dead caterpillars on tree trunks; these are probably victims of a fungus, Entomophaga maimaiga. Some Gypsy Moths do seem to be surviving and are entering their pupal stage now, but with any luck the trees will leaf out again soon and the moths will not be able to return in significant numbers in 2018, or for many years to come. 

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.

--
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

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.

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.

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.

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.