Tuesday, August 11, 2015

Aponogeton madagascariensis Seeds

Looking down into a large aquatic tank with a pot of Aponogeton madagascariensis.
 Aponogeton madagascariensis, the Madagascar Lace Plant, is a submerged aquatic with naturally occurring holes in its leaf blades. The leaves are like window screen, with a network of veins and photosynthetic tissue, but with gaps in the leaf between the veins. Aquatic plants have more difficulty than terrestrial plants obtaining carbon dioxide, because gas diffusion is much slower in water than in air; the lacy leaves of A. madagascariensis probably are an adaptation to create more surface area for gas exchange.

Aponogeton madagascariensis inflorescence, late summer.
As is the case with many aquatic plants, A. madagacariensis sends its flowers above water for pollination. The flowers seem to be able to self-pollinate and if conditions are right give rise to clusters of small, green, horn-shaped fruits a few weeks later.

Aponogeton madagascariensis fruiting shoot shedding floating seeds.
When ripe, the fruits split open and release seeds. The seeds are a milky violet color and have a water-repelling waxy surface, enabling them to float and disperse away from their parent plant. After floating for a day or two, the seed coat becomes clear and water-logged, and splits open to release the green embryo inside, which sinks to the bottom. I've been gathering the seeds and putting them in submerged pots of sand and soil, and hope to get some germination and Lace Plant seedlings soon.

Saturday, July 4, 2015

Dicrocaulon humile

Dicrocaulon humile, J. Vlok collection from Rooiberg, north of  Vanrhynsdorp, W. Cape, S. Africa. Cultivated by Steven Hammer, Vista, Ca (early April 2011).
Dicrocaulon humile is a low-growing dwarf shrub, from the family Aizoaceae (ice plants), native to the arid Knersvlakte near the small town of Vanrhynsdorp in South Africa. Its highly succulent leaf pairs are fused into pea-like bodies, which are exposed and green only during the cooler months. This plant is very rarely cultivated, and as far as I know is represented in horticulture by a single clone derived from material collected at Rooiberg. There is a confusing abundance of hills and peaks in South Africa called "Rooiberg," but this one is the Red Mountain just northwest of Vanrhynsdorp. Dicrocaulon plants, like most mesembs, are self-infertile, so that the lonely D. humile of greenhouse collections does not set seed. However, cuttings taken early in the growing season in autumn root fairly easily, and the plant has been passed around among connoisseurs of such things to a limited extent.

Dicrocaulon humile in flower in cultivation in Connecticut, July 2015.
Dicrocaulon humile flowers right around the summer solstice, when the plants are otherwise dormant and brown. The flowers have subtle violet color, which doesn't show up very well in my photos, and a very strong sweet smell that I can detect from some distance. The odor is reminiscent of artificial grape soda. The blooms stay open day and night, but the fragrance is most pronounced during the heat of the day, suggesting pollination by bees or other daytime insects.

Dicrocaulon had long been considered part of a group of mesembs called the Mitrophyllum Group or Mitrophyllinae, consisting of about half a dozen minor genera with plants characterized by strict summer dormancy, heterophylly (producing different leaf shapes at different seasons, often with very distinct, compact summer resting leaves), and an epidermis with large, water-storing bladder cells. Recent evolutionary work (Klak et al. 2013. A phylogenetic hypothesis for the recently diversified Ruschieae) has split the former Mitrophyllum Group into two natural units that are only distantly related: the Dicrocaulon Clade comprising the genera Oophytum, Monilaria, Diplosoma and Dicrocaulon, which is basally diverging in the tribe Ruschieae, separate from a Mitrophyllum Clade consisting of Mitrophyllum and Meyerophytum, which originated more recently within the Ruschieae. The Dicrocaulon Clade plants have, in retrospect, exaggeratedly minute, shrivelled summer resting leaves that are quite different from the meaty oversummering bodies of the Mitrophyllum Clade genera.

Friday, June 19, 2015

Newport Flower Show 2015

Rosecliff Mansion, home of the Newport Flower Show.
 The Newport Flower Show is running this weekend. I was there yesterday helping out with some of the setup, and it looks like it will be another impressive summer show in a spectacular setting at Rosecliff, one of the gilded age Newport mansions that are now public museums.

 Entries for succulent plants didn't seem quite as numerous as they have been in some previous years, but there were still some nice specimens. This giant medusoid euphorbia, Euphorbia esculenta made the trip from Pennsylvania. It was one of a number of entries from the Hamilton collection; Mrs. Hamilton is a fixture at the major East Coast flower shows.

  One of the special classes for the show this year was "Little America," for miniature gardens with a theme related to famous locations in the USA. I particularly liked this succulent dish garden titled "Roswell," complete with crashed UFO, alien accident victim and scraps of tinfoil.

The path gets rough in spots in the southern half of the Newport Cliff Walk.
 After I finished up my duties inspecting succulent plant show entries, I headed out for a stroll on the famous Newport Cliff Walk. The northern parts of the walk are pretty well paved, but the southern portion, which I had never completed before because of construction closings, gets kind of hairy in spots.

Conglomerate boulders with a quartzite outcropping at right, at then end of Ruggles Ave.
 The geology of Newport is complex, and I haven't located a good guide for interested laypeople such as myself. The southern tip of the island is weathering-resistant granitic gneiss (in the photo below), which transitions to the north into a mess of ancient Precambrian and somewhat less ancient Carboniferous sedimentary and metamorphic rocks, including serpentine, slate, quartzite and conglomerate (pudding stone - photo above). The conglomerate, a fossilized mass of gravel and cobbles, might be glacial till from a "Snowball Earth" event in the late Precambrian, when most of the planet seems to have frozen, right to the equator. I don't know enough about such things to be certain, but Snowball Earth sediments do occur in southeastern Massachusetts and Rhode Island.

Plantago maritima at Land's End near the southern tip of Newport, RI.
One of only a handful of native New England succulent plants occurs at various points along the Cliff Walk: Plantago maritima, or Sea Plantain, is a nearly cosmopolitan inhabitant of harsh, salt-sprayed habitats. Sea Plantain has thick, water-storing leaves that are said to be edible, but quite salty; I can't imagine it would be a good idea to eat a whole salad of them.

Tuesday, June 2, 2015

Tillandsia usneioides Flowering

Tillandsia usneoides was in bloom in the UConn greenhouses the other week. The flowers are minute and greenish and easy to overlook, but do emit a slight sweet smell. "Spanish Moss" is indeed not a moss (nor is it from Spain), but a flowering plant in the pineapple family, the Bromeliaceae.

Greenhouse flowering of T. usneoides is unreliable; looking back, I don't see any records of Spanish Moss in flower at UConn since 2004. Intriguingly, the blooms this spring all seemed to be on the clumps of T. usneoides that I had left outside for a portion of last winter in an impromptu hardiness trial. The plants grow perfectly well, vegetatively, when kept in a tropical greenhouse year round, but it is possible that a cold vernalization period triggers flowering. I can't be sure that cold was responsible, though, since a number of other factors were different with the outdoor Spanish Moss. It spent the entire summer of 2014 outside, which means it received rain water rather than tap water, and probably less water and nutrients overall than the non-flowering greenhouse material. Maybe I'll try keeping some plants refrigerated next winter, and see if a cold period alone encourages blooming.

Friday, May 22, 2015


Myrciaria cauliflora fruits, or Jaboticaba.
 Myrciaria cauliflora (alternatively Plinia cauliflora; family Myrtaceae) is a small tropical tree with edible fruits, native to Brazil. Its species name is derived from the term "cauliflory," which describes trees which produce their flowers and fruits along their trunk and large branches, as opposed to at the ends of younger shoots. Cauliflory is mostly seen in tropical trees, although what function it might serve seems to be debatable. Possibly, flowers along trunks are more visible to pollinators (or fruits more accessible to animal dispersers) than they would be in the dense leafy canopy of the rainforest. There are no native cauliflorous trees in my area, but a little further south one shrub, the Redbud (Cercis canadensis), shows this condition to some extent.

Myrciaria in the UConn greenhouses, in about a 20 inch pot.
 Jaboticaba (sometimes spelled Jabuticaba) fruits are pretty tasty, with sweet, grape-flavored white pulp inside of rubbery, nearly black skins. The skins are a little bit tough, but also edible, with a slightly acrid flavor reminiscent of walnuts. In the greenhouse the flowers of Myrciaria self-pollinate, and set abundant fruit in spring without any special attention.