Gentiana autumnalis, the pine barren gentian, is a lovely autumn to early winter flowering wildflower of the eastern coastal plain. It is native to moist, open pine woods from southern New Jersey to Georgia. In North Carolina, I have seen it blooming in longleaf pine savannna in Croatan National Forest. Like many of the plants in that ecosystem, it is dependent on fire. When fire is suppressed, growth of woody shrubs and deciduous trees soon chokes out the gentians, along with the orchids and carnivorous plants that grow in the same habitat.
My plant was purchased from the North Carolina Botanical Garden seven or eight years ago. I grow it in a mix of sand and peat in an 8″ (20 cm) diameter plastic pot sitting in a saucer of rain water. I give the plant very little fertilizer, and it blooms reliably in early November.
This week, I traveled to San Diego, California for a scientific conference. It was my first trip to San Diego–my first trip to anywhere in California, actually–so it was exciting to see a new part of the country. Even the flower beds around my hotel and the convention center were full of new and interesting things.
The meeting didn’t leave much time for sightseeing, but I managed to slip away one morning and take a bus up to Balboa Park, which houses the San Diego Zoo and a variety of gardens. I considered just wandering around the free areas of the park but eventually decided that I couldn’t miss the world famous zoo. That turned out to be the correct choice. In addition to being an amazing collection of endangered species (the zoo is famous for its captive breeding successes), the grounds are also a very fine botanical garden. The weather was cool, so the animals were active, and there were hardly any visitors. I had a good long visit with the pandas (red and giant), koalas, Tasmanian devils, komodo dragon, giant tortoises, okapis, elephants, jaguars, and many other animals, but I took more pictures of the plants.
Today being Saturday, here are six things that caught my eye in San Diego–garden related, of course.
1. Flowering trees.
November is clearly not the best time of year for blooming trees, but nevertheless, I saw some beautiful tropical and subtropical flowers.
2. Bird of Paradise flowers
Strelitzia reginae (bird of paradise) and Strelitzia nicolai (white bird of paradise) were growing (and blooming) all over town. S. reginae is my wife’s favorite flower, so when we were first married I tried growing some from seed. After fifteen years, I managed to get a only single flower from an enormous clump that took up a lot of real estate in the greenhouse, so I gave up. Clearly, flowering is not a problem when they are grown outside in San Diego.
3. The Botanical Building
The Botanical Building is a Balboa Park landmark that was originally built for the 1915-1916 Panama-California Exposition. Before seeing it, I had assumed it was some sort of greenhouse or conservatory, but there is no glass involved. Instead, the Botanical Building is a giant lathe house, built of wooden strips that provide the perfect amount of shade and wind protection for palms, tree ferns, and other tropical/subtropical understory plants.
4. Australian plants
Callistemon ‘Woodlanders Hardy’ and one or two eucalyptus are the only Australian plants I know of that can be grown in North Carolina, and even those are marginal outside of the coastal plain. The climate of southern California is more similar to parts of Australia, so I wasn’t surprised to see a wider variety of plants from Down Under.
5. African and Malagasy plants
The zoo has a really impressive collection of succulents from Madagascar and southern Africa.
6. Hawaiian plants
I suppose the climate of Hawaii, particularly on the drier leeward side of the islands, must be not entirely unlike that of coastal San Diego County.
For more Six on Saturday, click over to The Propagator, where you will find his Six and links to other participants.
Autumn in the mountains of North Carolina is all about apples, but here in the piedmont, autumn means persimmons. I sometimes forage for the little native persimmons (Diospyros virginiana) that grow wild in the local woods, but collecting them requires perfect timing. Pick them too soon–before they are completely ripe and soft–and they are unbelievably astringent. Wait just a little too long, and they all vanish. Piles of scat filled with hard, flat seeds indicate where they all go. Raccoons and opossums like persimmons just as much as I do.
Because they are harvested when mushy, American persimmons are better used for cooking than for eating out of hand. We use them in soft persimmon cookies and rich persimmon pudding. If I’m going to eat a fresh persimmon, I much prefer Diospyros kaki ‘Fuyu’, a non-astringent variety of the Asian persimmon. The fruit of our little ‘Fuyu’ tree can be eaten when hard and crisp like an apple. It can also be left to soften for cooking, although it never develops the complexity of flavor of the little wild persimmons.
D. kaki ‘Fuyu’ has been a carefree garden plant thus far. No insect pests have bothered the leaves or fruit. Squirrels, raccoons, and opossums don’t seem to be attracted to the fruit, either, unlike our blackberries and figs, which often disappear a couple of days before I think they’re ready to harvest. Fruit is produced without pollination, and although the non-pollinated persimmons have a tendency to abort, those that do ripen are generally seedless. Occasional seedy persimmons might indicate cross-pollination by a male D. virginiana tree growing at the edge of my garden.
Even in years when very few fruits make it to maturity, the tree ends the growing season with a spectacular show of flaming orange foliage.
Here are some more plants on their way to my greenhouse for the winter. I previously photographed some of my Pachypodium plants and gave cultural suggestions in Six on Saturday #3. Those photos, taken in July of last year, showed leafy plants. Here in October, most of my pachypodiums have already shed their leaves and are dormant. Flower buds will start to emerge in late winter to early spring, and fresh new leaves will follow.
All of the species shown here are from Madagascar
1. Pachypodium eburneum
Pachypodium eburneum is a very compact species with strongly compressed branches and relatively short inflorescences. In that sense, it is somewhat like a less extreme version of P. brevicaule. While P. brevicaule has soft spines, however, the thick spines of P. eburneum are hard and sharp. Very old P. eburneum have a lumpy, irregular form, but this plant (eleven years old, grown from seed) is still nicely symmetrical. The flowers of P. eburneum are white or pale yellow.
2. Pachypodium rosulatum var. gracilius
Pachypodium rosulatum is a very variable species that some botanists (and many horticulturalists) split into a complex of several closely related species. Here, I’ll follow Dylan Burge  in considering this and the following plants to be variants of one species.
P. rosulatum gracilus is distinguished by its dense, very fine spines. It generally has a bottle-shaped or globular trunk. Flowers are small and bright yellow. This is a seventeen-year old plant, grown from seed.
3. Pachypodium rosulatum (near Tôlanaro)
This P. rosulatum variant, which appears to be undescribed, supposedly comes from the vicinity of Tôlanaro (Ft. Dauphin) in southern Madagascar. It has large yellow flowers and very sharp spines that are stronger than those of var. gracilius. This plant was purchased as a small artificially propagated seedling in 2008.
4. Pachypodium rosulatum var. makayense
Like Pachypodum rosulatum var. bicolor, P. rosulatum var. makayense has bicolored yellow and white flowers. At least under greenhouse conditions, var. makayense seems to be more compact than var. bicolor. It is also more difficult to grow, and I have lost a number of seedlings to root rot. This plant is eleven years old, grown from seed.
5. Pachypodium rosulatum var. cactipes
Pachypodium rosulatum var cactipes has fine, acicular spines, rather like those of var. gracilus, but in var. cactipes they are more widely spaced on long branches. The plant shown above was purchased as a small seedling from Arid Lands in 1999. It has the longest flowering season of any of my pachypodiums, producing yellow flowers successively over more than a month in mid to late spring.
The plant shown below also seems to be var. cactipes. It is the “super branching form” sold for many year by Highland Succulents in Ohio. I bought this plant in 2000.
6. Pachypodium windsorii
Pachypodum windsorii has bright red flowers in the spring. The plant above, a 1997 purchase from Glasshouse Works nursery, is the parent of the seedling below. Shortly after germination, I deliberately damaged the apical meristem of this seedling, and it responded by branching. Usually pachypodiums branch after flowering for the first time, and the trunk is expanded only below the first branch. In this seedling, each of the four basal branches is developing a swollen base, giving it the appearance of four plants fused together. I think it will make a really nice specimen in ten or fifteen years.
The nights have started cooling off, so it is time move my tropical plants back into the greenhouse before we have our first frost. I thought I’d snap some pictures of a few interesting specimens before I put them away for the winter.
At first glance Adenia globosa looks distinctly alien–definitely more so than the hybrid Paphiopedilums that they invariably seemed to use as stand-ins for alien flora on old Star Trek The Next Generation episodes. When examined more closely, however, its anatomy starts to make sense. Adenia is a genus in the Passifloraceae, the passion flower family, and like our native Passiflora incarnata (maypop), many Adenia species are leafy vines with tendrils that help them to climb other plants. A. globosa has evolved in the arid savannas of east Africa, so its features reflect that history.
The base of the plant is swollen into a more or less globular trunk to store water.
With no need to climb other plants, the stems are rigidly erect or arching, and the tendrils have been modified into stout thorns to protect the plant (and its stored water) from herbivores. New stems have a single, tiny leaf under each thorn. The leaves soon fall, so the majority of photosynthesis is carried out by the stems, which are less subject to water loss than large leaves would be.
Old stems develop a glaucous coating that probably serves to further protect them from sunburn and water loss.
A. globosa seems reasonably easy to maintain, given warm temperatures, bright light, and very well drained potting media, but growth is very slow. My plant has just about doubled in size over the past seventeen years. Some succulents (e.g. Pachypodium) develop the best form and character when underpotted, but Adenia seem to grow fastest when somewhat overpotted. Some growers have had good luck using large tubs or raised beds to get plants to the desired size before moving them to smaller display pots, but great care must be taken not to over-water when using large pots.
A. globosa is dioecious, so separate male and female plants are required for seed production. My plant has never flowered, so even if I had a second specimen, seeds would be entirely hypothetical. Cuttings will root relatively easily and slooooowly produce a swollen trunk. Patience is definitely required for all aspects of A. globosa cultivation.