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Botany Photo of the Day
In science, beauty. In beauty, science. Daily.

Jul 3, 2015: Solanum pyracanthos

Solanum pyracanthos

Don McClane (aka Don McClane@Flickr) took this beautiful photo at Botanica Gardens in Wichita, Kansas. Solanum pyracanthos is native to Madagascar and is a member of the genus that includes tomatoes, potatoes and eggplants. I wouldn't try to eat the small fruits without a good indication of their edibility, however, as many members of the Solanum are poisonous (at least when raw).

Solanum is one of largest genera of flowering plants, with about 1500 species distributed across all continents except for Antarctica. Solanum pyracanthos is a member of the subgenus Leptostemonum, or spiny solanums. Members of Leptostemonum usually have prickles, long tapering anthers, and star-shaped trichomes (hairs). There are 76 native spiny solanum taxa in Africa and Madagascar. Until recently, their identification and phylogeny were unclear. In 2012, Vorontsova et. al. published African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle. This study represents the first research focused on the evolutionary history of the spiny solanums in Africa and Madagascar. Vorontsova et. al.'s analysis confirmed that the Old World Leptostemonum is a monophyletic group (clade) - meaning that all members of the group evolved from one common ancestor. Within the old world spiny solanums, the authors tentatively place Solanum pyracanthos in a clade composed of all of the Madagascar species of Solanum, even though these species are morphologically dissimilar.

Solanum pyracanthos, also known by the common name of porcupine tomato, is a cold-intolerant shrub that reaches a height of 1-2 meters. Its stems and leaves are covered with prickly orange spines that are purple at the base. Some gardeners grow porcupine tomato for the novelty of its pinnately-lobed leaves and bright spines, but growing this species takes a bit of effort. In warm climates, Solanum pyracanthos can be quite weedy and gardeners are advised to remove the fruits. However, in temperate climates, it must be coddled in much the same way as tomatoes do.

The purple, star-shaped flowers of Solanum pyracanthos have connivent anthers (the anthers are touching but not joined). Their anthers are also described as poricidal; the dry pollen is only accessible through a small opening at the tip of the tube-like anther. Such flowers (labeled Solanum-type, irrespective of the genus) are pollinated through buzz-pollination, or sonication, in which the bee must vibrate its wings and muscles in order to knock out the pollen. This intense vibration generates forces of up to 30 G! Sonicating bees make a characteristic sound, captured beautifully in a video posted on the Leonard Lab website. I can recall hearing the sound of bees sonicating many times, but I didn't know what I was hearing until seeing (and hearing) this video. Interestingly, not all bees sonicate--honeybees are not good pollinators of most Solanums, which is why commercial greenhouses typically pollinate their tomato crops by hand or with bumblebees.

Jun 30, 2015: Carex utriculata

Carex utriculata

Today's photo features a stand of Carex utriculata, photographed by Matt Lavin (aka Matt Lavin@Flickr). This strikes me as an uncommonly beautiful image of the common beaked sedge.

I have had a fondness for sedges ever since I took one of my first ecology classes, when my fiery Scottish professor taught me, in a thick, R-rolling brogue, that "Rrrrushes are rrrround, and sedges have edges!" I have no idea what else I was meant to learn in that class, yet his words popped into my head, loud and clear, when I spotted this lovely photo of Carex utriculata. Carex is the foremost genus in the sedge family, and sedges are easily recognized by their triangular (edged) flowering stems. The last part of the mnemonic, which I imagine my professor left out because it is not nearly as catchy as the rest, is that "grasses have knees". The knees of grasses are the joint-like nodes found along their round, hollow stems.

While differentiating between rushes, sedges, and grasses is relatively easy, identifying sedges to the species level is much more difficult. Carex species are numerous (estimated to be about 2000), flowering parts are tiny, and sometimes both the inflorescence and the fruit are required for a positive identification. Thankfully, a number of excellent sources are available to those who want to invest the time in learning sedge identification. For eastern North Americans, Morton Arboretum's Applied Field Identification of Sedges and Rushes (PDF) provides excellent information along with basic keys and species data. Sedge enthusiasts should consult printed field guides for their regions; good examples include the Field Guide to the Sedges of the Pacific Northwest and An Illustrated Guide to Common Grasses, Sedges and Rushes of New Zealand.

The Morton Arboretum identification guide notes that Carex utriculata is a member of a group of wetland sedges termed the "bottlebrush and bladder sedges". The perigynium, or bottle-shaped bract surrounding each female flower, is an important identifier for the bladder sedges. Carex utriculata's perigynia appear inflated and papery-brown. This characteristic provides the name for the species (an utricle is a leather bag or bottle). Carex utriculata is found in a variety of open wetlands throughout Canada and the northern USA. Plants grow in tufts or dense clumps. Carex utriculata is often referred to by the synonym Carex rostrata var. utriculata.

Jun 29, 2015: Eriogonum kennedyi var. alpigenum

Eriogonum kennedyi var. alpigenum

Thank you to today's photographer, Mojave Wildflowers@Flickr. This is such a beautiful photograph of Eriogonum kennedyi var. alpigenum, and the detail on the bee is stunning. Notice the pollen grains scattered across the bee's foreleg, for example.

Eriogonum kennedyi var. alpigenum is one of five varieties of Kennedy's buckwheat. This variety, commonly called San Gorgonio wild buckwheat, is found in subalpine to alpine areas of the San Gabriel and San Bernardino Mountains in California. It is differentiated from other varieties of Eriogonum kennedyi primarily by its range, but also by its scapes (.3-2cm), leaf blade (2-4 x .7-1.5mm), and involucres (1.5-2mm).

The broader species, Eriogonum kennedyi, has a cushion-forming habit. Of the five varieties, four are endemic to California with the fifth occurring in western central Nevada in addition to California. Like other species of Eriogonum, Eriogonum kennedyi is important to native bees and butterflies (the species is a host for many butterfly species including the Mormon metalmark (Apodemia mormo), bramble hairstreak (Callophrys perplexa), and Comstock's hairstreak (Callophryssheridanii comstocki)). Kennedy's buckwheat has 1cm long green leaves that are coated in brown to pink or white tomentose (matted hairs), giving the leaves a woolly, light appearance. In July to August, plants of Eriogonum kennedyi send up .4-15cm tall scapes bearing heads of delicate pink and white flowers. In late summer, the fruit on the scapes are dry, brown achenes.

Jun 26, 2015: Lilium humboldtii

Lilium humboldtii

I have chosen many brown or green photos lately, and I realized that Botany Photo of the Day needed some colour! Sandy Steinman (aka Sandy Steinman@Flickr) came to my rescue with this stunning photo of a Lilium humboldtii flower. I am not sure where this photo was taken, but Sandy includes it in a group of "Bay Nature" photos, so I deduce that it was taken somewhere in the Bay Area of California.

Humboldt's lily is a magnificent lily that grows to a height of 2.5 meters. It is endemic to California, growing in oak canyons and under ponderosa pines (the Wikipedia entry also claims its range extends to Baja California, Mexico). The purplish bulbs send up leaves in 2 to 8 whorls, with each whorl containing 3-16 weakly oblanceolate leaves. The inflorescence is a raceme (that is, the flowers are arranged around a central axis) that bears up to 40 large, pendent, leopard-printed flowers. The two subspecies of Lilium humboldtii can be distinguished by their range and flower colour: Subspecies humboltii is found in the foothills of the Sierra Nevada, and has orange sepals and petals with magenta spots. Subspecies ocellatum is found in southern California and possibly Baja California, and has yellow or light orange sepals and petals with red to magenta spots.

Lilium humboldtii was named after Alexander von Humboldt, a Prussian polymath who achieved great fame in the 19th century. Humboldt, who for a time served as a French diplomat, also wrote the five-volume Cosmos, a comprehensive work covering all of geography and the natural sciences. During his expedition to Latin America, he laid the foundations of physical geography with his concept of "isothermal lines". Alexander von Humboldt continues to be celebrated today; the book Alexander von Humboldt: a metabiography, was published in 2008, and the blog Humboldtian Tales provides an entertaining glimpse into some of Humboldt's many interests and accomplishments. Lilium humboldtii was named in commemoration of Alexander von Humboldt's 100th birthday (see Gardener's Chronicle, 728).

Jun 25, 2015: Sarcococca confusa

Sarcococca confusa

This photo of Sarcococca confusa comes via the late James Gaither (aka J.G. in S.F.@Flickr). This species has a long bloom time in winter (in climates where it can grow), and the berries persist through much of the rest of the year. One of the nicest qualities of Sarcococca confusa is that it nearly always provides displays of either flowers or fruit--a quality which is expressed in today's photo of the fruit ripening alongside swelling flower buds.

Sarcococca confusa is an evergreen shrub species to 2 meters tall that is widely cultivated for its glossy evergreen foliage and intense honey-scented flowers (these give the species its common name, sweet box). It has been widely cultivated since the early 20th century--possibly from seeds collected by Wilson in China--but is not known from the wild. Blooming in mid-winter, the flowers are crowded into short clusters of typically three male flowers (though infrequently 1-2) and one to three female flowers. The bird-ingested fruits are glossy black berries that ripen by late summer. For images of the flowers and fruit, see this wonderful digital botanical illustration of Sarcococca confusa, by Niki Simpson.

Sweet box is an easy plant species to grow in all but the harshest climates. It will tolerate nearly any soil and level of sunlight, and can even be planted in dry shade such as under a dense tree canopy. It grows quickly, tolerates regular pruning, and unlike most of the other Sarcococca species, does not sucker. In addition, Sarcococca confusa can be used as an alternative to boxwoods (Buxus species), which, in UK and North American cultivation, are being affected by boxwood blight, a fungus that causes defoliation and death of boxwood plants. Unlike Buxus, however, Sarcococca cannot be pruned into complicated topiary. Basic shapes, such as rounded or square forms, are achievable. Sweet box should be pruned shortly after flowering, which will force the growth of new stems that will flower the following winter.

Jun 24, 2015: Photinia x fraseri 'Red Robin'

Photinia x fraseri 'Red Robin'

Today's photo features the bright red new leaves of Photinia x fraseri 'Red Robin', taken by Katy Wrathall (aka smilylibrarian@Flickr) in England.

Photinias are popular ornamental shrubs, and within the genus, Photinia x fraseri 'Red Robin' is the most famous. A hybrid, it combines the size (up to about 5 meters) of Photinia serratifolia (Chinese photinia ) with the general appearance and red young leaves of Photinia glabra (Japanese photinia). It is thought that the first Photinia x fraseri arose as a chance seedling at the Fraser Nurseries in Birmingham, Alabama. 'Red Robin' has particularly red, shiny young foliage, and has received the Award of Garden Merit from the Royal Horticultural Society. It is often used as a hedge species, and can be clipped into a formal hedge or allowed to maintain its bushy form. Photinia x fraseri was commonly used in the American south, but since the 1980s, southern specimens have been under attack by a fungus, entomosporium leaf spot. Sadly, due to this fungus, Photinia x fraseri is not nearly as common in American south landscapes as it once was.

Photinia x fraseri 'Red Robin' has leaves that emerge red, then slowly turn to a dark, glossy green. The red colour is the result of a common plant pigment, anthocyanin, that is present in new Photinia growth. According to an article in Plant Science (Oren-Shamir, 2009), the presence of anthocyanin in plants is fairly common, and it may be acting as a sunscreen and antioxidant for the young, tender leaves. As new Photinia leaves mature and develop protective, light-reflecting waxes, they no longer need the protection of the anthocyanin. The pigment is then diluted and broken down, to the point where there is no detectable amount left in mature leaves. The shiny quality of mature leaves not only negates the need for red pigment, it also leads to the name for this genus: photeinos means 'shiny' in Greek.

Jun 23, 2015: Citrus trifoliata

Citrus trifoliata

Do not worry -- Botany Photo of the Day has not decided to change its content to science fiction! Today's photo may look like a creative writer's vision of unexplored planets, but it in fact shows the fruit and thorny branches of Citrus trifoliata. Thank you to Universal Pops (David)@Flickr for this incredible photo.

The fruit of Citrus trifoliata may look like an orange (the common name for this species is trifoliate orange), but it certainly doesn't taste like one. The fruits are edible, but are intensely sour and bitter, and are best used for adding pectin to jams that feature tastier fruit. A Citrus trifoliata lemonade recipe advises to "take a barrel of water, a barrel of sugar and add one sour fruit" (UofA Division of Agriculture). Some sources do not consider this species to be a member of Citrus. Many botanists use the synonym Poncirus trifoliata (L.) Raf., considering trifoliate orange to instead be the closest relative to the genus Citrus (and the only species in Poncirus). For this article, I will stick to Linnaeus' original name, as this is the one accepted by The Plant List.

Whether you think trifoliate orange is a Citrus or not, this species is undeniably important to the lemons and oranges that we love to eat. Citrus trifoliata (pdf) makes an excellent rootstock for other Citrus species. It is very cold hardy (withstanding temperatures well below freezing), so other Citrus species grafted onto the rootstock can produce trees with tasty fruit that survive in cold climates. Arguably, the most significant advantage of a Citrus trifoliata rootstock is that it confers resistance to the citrus tristeza virus, the most economically-damaging Citrus disease. Trifoliate orange also hybridizes freely with other citrus, and has been used to make numerous crosses including: citremons (with lemons), citranges (with sweet oranges) , and citrumquats (with kumquats).

Aside from Citrus trifoliata's contribution to our morning orange juice, it is also an interesting ornamental species. Its young green branches are dense and bear stout, 5cm-long stipular spines. The overall effect of the plant's habit is that it can be considered an evergreen for aesthetic purposes, though it is actually deciduous. Trifoliate orange can be pruned into an impenetrable hedge or low boxwood-type wall. The twisted-stemmed cultivar 'Flying Dragon' makes an unusual specimen tree. The young shoots of Citrus trifoliata are stiff and have a triangular cross-section, and the leaves are trifoliate (composed of three leaflets), shiny and dark green. They turn a buttery yellow before dropping in the autumn. The flowers are white with pink stamens, hermaphroditic, and have a typical, citrus smell. These give way to globose (round) fruit that measure 3-5 cm in diameter. Technically, the Citrus trifoliata fruit is a modified berry termed a hesperidium, which has a tough leathery rind encasing a fleshy interior composed of separated sections.

Note: Citrus trifoliata is naturalized in the American southeast, and forms dense thickets that are impenetrable and displace native species. Planting trifoliate orange in these areas is not advised.

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