Plant of the week for May 16th-23rd, 2010: Houstonia caerulea
After a bit of an end-of-the-year moratorium, here's another entry. And even though late spring is one of the most glorious times of year, with the wild apples blessing the air with their sweet fragrance, and the violets and dandelions blooming in the meadows, I'm going to be focusing on a more subtle beauty, one which only made itself known to me this spring. I am referring to...
Azure Bluet, Houstonia caerulea
Synonyms: "Quaker Bonnets", "Quaker Ladies", "Bright Eyes", Hedyotis caerulea
Range and Habitat: The USDA website lists H. caerulea as ranging through all states and provinces east of the Mississippi and south of the boreal forest proper, plus also Missouri, Arkansas, and Louisiana. There are also, apparently, related species that extend out into the Dakotas. Bluets grow among low grasses in moist, sun-speckled forest openings and in wet meadows. They prefer mildly acidic soils, especially those rich in organic matter. So well do they coexist with grasses that they will even take root in lawns, if the lawn has not been ruined by over-mowing and the excessive application of herbicide and harsh fertilizers.
Native? Y/N: Y Indeed, according to Wikipedia, the genus Houstonia exists only in North America, save as it has been planted elsewhere by enthusiastic gardeners.
Plant ID: Bluet may be known by its pale dainty flowers1, which are sky-blue to white in color with an almost glowing yellow center. There are four petals per flower, which is in total perhaps 1/6th of an inch across. The flowers grow on stalks 3-6" tall. There is only one flower per stalk, but the stalks grow in dense clusters2, making a splash of cheery blue against the forest floor. They have flowered almost continuously since the end of April, and supposedly they will continue to do so 'till the middle of June.
The plant has a clump of leaves growing in a small rosette at the base of its stem, plus a few other even smaller ones climbing along the stem at widely-spaced intervals. The fruit is a tiny green capsule which forms after flowering has ended at the tail end of Spring.
Ecology: According to the Ladybird Johnson Wildflower Center, the azure bluet becomes more common as one moves east through its range. This makes sense, given that soil moisture and acidity also tend to increase going east from Old Muddy. Bluet is quite vulnerable to summer droughts, which kill off the above-ground portions of the plant. But it is a perennial, and its roots remain to give new life next spring. Plus, if the spring has been a sufficiently wet one,
the bluets will already have set seed by the time that drought hits3.
Based on the pattern of coloration of H. caerulea's flowers, I would guess that it is pollinated by bees, especially the many solitary digger bees of the American forest.
Uses and Horticulture: As far as I can tell, the only real use that the bluet has for human-kind is in our admiration of its charm and beauty. It produces no medicinal, chemical, structural, or nutritive products. But its flowers are sufficient to attract the attention of gardeners, and so Alfred Pink, in his comprehensive, if dull, Gardening for the Million, includes a note in praise of H. caerulea. The common recommendation for the plant is to grow it in a rock garden, nestled between large stones. As it self-sows, just a few seeds planted in a well-drained, well-watered nook can, in a few years, form one of the charming clumps seen above. The Ladybird Johnson Center also notes that they can be grown successfully in lawns, as well, to make a charming addition to the sometimes monotonous green of turf grasses. The Center adds, though, that if it is to be a permanent addition to the lawn, one should desist in mowing until the bluets have set seed in June. While this runs quite contrary to the American obsession for perennially close-cropped and uniform lawns, it is in harmony with the more sensible dictates of beauty, ecology, and sound gardening.
Taxonomy: As mentioned above, it seems that the entire genus of Houstonia (some 20-25 species) is exclusive to North America. The synonym Hedyotis caerulea is, according to all sources, obsolete. The old genus Hedyotis was polyphyletic and has since been broken up. Houstonia is placed within the Rubiaceae, the madder4 family, whose most famous member is the coffee bush, Coffea. Other culturally important madder family members are the anti-malarial quinine tree Cinchona and the madder Rubia tinctorum, whose root is the traditional source of the dye to which it gives its name.
Paleontological evidence indicates that the Rubiaceae first appeared in Australasia and North America at the very beginning of the Tertiary. From which of these locations the family originated it is impossible to tell until more and older fossils are discovered.
Discovering more and older fossils since 1986,
--mark
1 Photo courtesy of Wikipedia.
2 Photo courtesy of Delaware Wildflowers and David G. Smith.
3 Most of the above information was provided by the Sunlight Gardens website, who offer bluets (seeds? whole plants?) for sale.
4 Image courtesy of Botanical.com
Azure Bluet, Houstonia caerulea
Synonyms: "Quaker Bonnets", "Quaker Ladies", "Bright Eyes", Hedyotis caerulea
Range and Habitat: The USDA website lists H. caerulea as ranging through all states and provinces east of the Mississippi and south of the boreal forest proper, plus also Missouri, Arkansas, and Louisiana. There are also, apparently, related species that extend out into the Dakotas. Bluets grow among low grasses in moist, sun-speckled forest openings and in wet meadows. They prefer mildly acidic soils, especially those rich in organic matter. So well do they coexist with grasses that they will even take root in lawns, if the lawn has not been ruined by over-mowing and the excessive application of herbicide and harsh fertilizers.
Native? Y/N: Y Indeed, according to Wikipedia, the genus Houstonia exists only in North America, save as it has been planted elsewhere by enthusiastic gardeners.
Plant ID: Bluet may be known by its pale dainty flowers1, which are sky-blue to white in color with an almost glowing yellow center. There are four petals per flower, which is in total perhaps 1/6th of an inch across. The flowers grow on stalks 3-6" tall. There is only one flower per stalk, but the stalks grow in dense clusters2, making a splash of cheery blue against the forest floor. They have flowered almost continuously since the end of April, and supposedly they will continue to do so 'till the middle of June.
The plant has a clump of leaves growing in a small rosette at the base of its stem, plus a few other even smaller ones climbing along the stem at widely-spaced intervals. The fruit is a tiny green capsule which forms after flowering has ended at the tail end of Spring.
Ecology: According to the Ladybird Johnson Wildflower Center, the azure bluet becomes more common as one moves east through its range. This makes sense, given that soil moisture and acidity also tend to increase going east from Old Muddy. Bluet is quite vulnerable to summer droughts, which kill off the above-ground portions of the plant. But it is a perennial, and its roots remain to give new life next spring. Plus, if the spring has been a sufficiently wet one,
the bluets will already have set seed by the time that drought hits3.
Based on the pattern of coloration of H. caerulea's flowers, I would guess that it is pollinated by bees, especially the many solitary digger bees of the American forest.
Uses and Horticulture: As far as I can tell, the only real use that the bluet has for human-kind is in our admiration of its charm and beauty. It produces no medicinal, chemical, structural, or nutritive products. But its flowers are sufficient to attract the attention of gardeners, and so Alfred Pink, in his comprehensive, if dull, Gardening for the Million, includes a note in praise of H. caerulea. The common recommendation for the plant is to grow it in a rock garden, nestled between large stones. As it self-sows, just a few seeds planted in a well-drained, well-watered nook can, in a few years, form one of the charming clumps seen above. The Ladybird Johnson Center also notes that they can be grown successfully in lawns, as well, to make a charming addition to the sometimes monotonous green of turf grasses. The Center adds, though, that if it is to be a permanent addition to the lawn, one should desist in mowing until the bluets have set seed in June. While this runs quite contrary to the American obsession for perennially close-cropped and uniform lawns, it is in harmony with the more sensible dictates of beauty, ecology, and sound gardening.
Taxonomy: As mentioned above, it seems that the entire genus of Houstonia (some 20-25 species) is exclusive to North America. The synonym Hedyotis caerulea is, according to all sources, obsolete. The old genus Hedyotis was polyphyletic and has since been broken up. Houstonia is placed within the Rubiaceae, the madder4 family, whose most famous member is the coffee bush, Coffea. Other culturally important madder family members are the anti-malarial quinine tree Cinchona and the madder Rubia tinctorum, whose root is the traditional source of the dye to which it gives its name.
Paleontological evidence indicates that the Rubiaceae first appeared in Australasia and North America at the very beginning of the Tertiary. From which of these locations the family originated it is impossible to tell until more and older fossils are discovered.
Discovering more and older fossils since 1986,
--mark
1 Photo courtesy of Wikipedia.
2 Photo courtesy of Delaware Wildflowers and David G. Smith.
3 Most of the above information was provided by the Sunlight Gardens website, who offer bluets (seeds? whole plants?) for sale.
4 Image courtesy of Botanical.com