A photograph and written entry by Tamara Bonnemaison today. She scribes:

During a morning with frost a few weeks ago, the silvery-tipped leaves of this Saxifraga paniculata stood out among the many other beautiful specimens in UBC Botanical Garden's Alpine Garden. Daniel has been patiently teaching me to use the BPotD camera, and despite my best efforts, I was not quite able to capture the glow of the morning sun playing across the surface of the saxifrage's rosettes. This photo comes fairly close; for the rest, you'll need to use your imagination.

Saxifraga paniculata, also known as lime-encrusted saxifrage and white-alpine saxifrage, is a circumboreal species that is found in calcareous boreal, subalpine, and alpine habitats in North America, Europe, Scandinavia, Iceland, and Greenland. This species' common name is a result of lime-secreting pores on the leaf edges, which give the toothed leaves a silvery or 'encrusted' appearance. What I had at first thought to be the work of a particularly hard frost was actually the combination of frost and secreted lime, both of which contributed to making this plant literally glow against the shaded ground.

Encrusted saxifrage is a stoloniferous perennial that is extremely hardy. Its stiff, leathery leaves form 3cm tall rosettes that close as they become desiccated, with the outer leaves acting as an evaporative and solar shield for the younger leaves in the centre of the rosette. During times of extreme drought, these outer leaves dry out completely, but the plant itself is protected and survives. The species is also able to survive a short growing season and long periods of cold-induced photoinhibition (meaning that it is so cold that very little photosynthetic activity can occur). On top of having to survive extreme cold, drought, and insolation, Saxifraga paniculata must contend with an irregular supply of pollinators. However, it can both reproduce vegetatively through its stolons and self-pollinate.

The perfect flowers of lime-encrusted saxifrage are quite beautiful. I came across this species at the wrong time of year to capture the white, five petaled flowers, but thankfully these have been amply photographed by others. The Acta Plantorum website has many photos that show the curious purple-dotted white petals, as well as some images of lime-encrusted saxifrage growing in its alpine habitat.

Again, scribed by Taisha. She writes:

Frost and crisp air have greeted me the past few mornings when starting my commute to UBC, two signs in these early days of December that the holidays are approaching. Around the city, empty lots are being turned into temporary sites for Christmas tree sales, lights are being strung up, and wreaths are being hung upon doors. In the spirit of the holidays, I've chosen to write an entry on Viscum album, or European mistletoe! The images of this species are courtesy of stevieiriswattii!@Flickr, who uploaded them to the Botany Photo of the Day Flickr Pool (image 1 | image 2).

Viscum album, a member of the sandalwood family, is a hemi-parasitic evergreen shrub. Hemi-parasites are plants that receive additional nutrients via a haustorial attachment to a host, but are also able to photosynthesize. In the case of mistletoe, their parasitism can lower the host tree's vigour, induce premature mortality, reduce the quality of wood, or induce water stress. As a species, Viscum album is able to infect a large number of host plants. There are five or six subspecies of Viscum album recognized, differing in part by host specificity. For example, Viscum album subsp. abietis (shown today) is a parasite on Abies (fir) species (in today's case, silver fir or Abies alba). Similarly, Viscum album subsp. austriacum parasitizes Pinus (pine) species and rarely Larix (larch) or Picea (spruce) species. Other subspecies parasitize flowering trees or different conifers.

European mistletoe is dioecious and insect-pollinated. The flowers are yellowish to green and inconspicuous. The fleshy white berries ripen through the early winter in Europe, and are bird-dispersed from late winter to spring. Birds do eat the berries, but digestion is not necessary for seed germination. Instead of eating the berries, birds will sometimes disperse the fruit by dropping the berry in flight or while on the tree. The mucilaginous viscin on the outside of the berry allows it to stick to the bark of the tree, where it will eventually germinate and infect (see Kahle-Zuber, D. 2008. Biology and evolution of the European mistletoe (Viscum album). (PDF) Doctoral dissertation, ETH Zurich, No. 18080.

Mistletoe appears extensively in mythology and folklore. To the ancient druids of Britain, mistletoe was a symbol of magical powers and medicinal properties. From Norse legend, Balder (a Norse god and the son of goddess, Frigga), was killed by mistletoe. However, his life was later restored and Frigga, in her joy, said that anyone who passed under mistletoe should receive a kiss. This custom remains today, with kisses being shared under the mistletoe which is commonly used as a Christmas decoration. Where this truly originates, I'm uncertain, although it is known to have been part of Christmas customs since at least the seventeenth century.

If you live in Vancouver, and are looking to decorate for the holidays, the Friends of the Garden are selling hand-made wreaths at the Shop in the Garden until December 23, 2013, or until quantities last!