Dimorphorchis lowii

Meet Dimorphorchis lowii. This has to be one of the strangest, and not to mention rarest, orchids in our collection. Look closely and you will see that the basal flowers are structurally different from the rest of the flowers on the inflorescence.

The basal one or two flowers are yellow with small purple spots. They are also strongly fragrant.

The remaining 20 or so flowers are ivory overlaid with large red-purple blotches. They have no fragrance.

This is an example of dimorphism in flowers, hence the name, Dimorphorchis. However, this is an unusual type of floral dimorphism, because both floral forms appear fertile and capable of self fertilization.

A better known type of floral dimorphism is sexual dimorphism, in which male and female flowers are produced that are structurally different. In Catasetum, for example, male and female flowers can be produced by the same plant, but are usually produced at different times, a temporal barrier to self pollination that increases the likelihood of cross pollination and genetic recombination. (Male Catasetum flowers are pictured above, female flowers below)

So, what's up with Dimorphorchis? Why are there two floral forms?

If successful outcrossing is a rare event in nature, for example if plants occur at low density, then there might be selection for a floral form that is readily selfed.

Possibly the plant attracts two different pollinator species, one species that arrives early for the fragrance, doesn't linger, flies long distances, and has a high success rate of outcrossing, creating fewer capsules but stronger offspring. Maybe a crowd of secondary pollinators arrive late to the party and stick around long enough to ensure that the remainder of the flowers are self pollinated. Without field studies, it's just speculation.

I'm currently waiting to see if the selfing I did on our plant last week was successful. It would be lovely to be able to distribute some seedlings from this plant.

Another Fantastic Bucket Orchid

Our magnificent Coryanthes bruchmülleri has been flowering regularly since it reached maturity last summer. C. bruchmülleri is the Goliath of the genus, with flowers four to five inches in diameter.

Coryanthes bruchmülleri grows in lowland wet forests near the border of Colombia and Venezuela. In the wild, Coryanthes are typically found growing in ants' nests in a mutualistic relationship with the ants. It's not uncommon to read that Coryanthes are difficult to cultivate, perhaps lacking something provided in nature by the ants. In our greenhouses, without ants, they are no more difficult than any other member of the Stanhopeinae, provided you can exclude the slugs and bush snails that consume the roots and new shoots. Our tactics: frequent repotting, applications of diatomaceous earth, and eliminating the source of new introductions -principally orchids from Hawaii. I'm happy to report that we've got a capsule gestating on one of our plants. It will be terrific to get this fantastic species in production.

Now opening: Coryanthes macrantha

We've produced a bumper crop of Coryanthes seedlings that are now reaching flowering size. Coryanthes, with their provocative morphology and intense fragrances are simply the best teaching tool ever for introducing students (or anyone!) to orchid pollination concepts, and Euglossine bee pollination in particular. But, since the flowers only last about three days, a large number of plants are needed for a continuous display.

We are very fortunate to have a mircro prop lab to allow us to produce orchid seedlings. Coryanthes are somewhat weedy in the sense that they reproduce rapidly. They have a very short capsule maturation (60 days), produce copious quantities of seed and robust, fast growing, fast flowering seedlings.

After they outgrow the plug stage, our Coryanthes seedlings grow best on vertical mount, rather than in a pot or basket. Tree fern slabs have worked well for us, but last year, in an attempt to wean ourselves from our tree fern dependency, we tried a new slab material: coarse filter media, borrowed from our aquarium colleagues.

Filter media isn't a good choice for every orchid, but the Coryanthes love it. Within a couple of months, their roots completely fill the interior spaces of the slab.

We are super excited to have more of these fascinating orchids on display for you to see. Look for them this year in the Orchid Display House!

Where are all the labels?

Lycomormium squalidum

One of the most frequent comments on our visitor survey is 'Why aren't all of your plants labeled?' I totally get this. After all, an important function of plant collections in a botanical garden is to serve as a reference. But labeling all plants with a 3x4" sign can be problematic. For example, in the Orchid Center, many of our epiphytic orchids are permanently installed in trees. It's tricky trying to attach signs to a tree. In addition, many orchids are tiny -smaller than their label. And, finally, one has to consider the questionable aesthetic appeal of a bed orchids thickly planted with tombstone-like labels. For all of these reasons, very few of the orchids in the FOC have the big black metal labels that are standard issue in outdoor gardens.

To find out the name of one of the orchids in our permanent collection, you'll have to look a bit closer for the data card, one of which is pictured above. In most cases the data card is wired to the pot, or, if the orchid is in the ground, wired to stake. The data card will tell you the genus, species, accession number, source and nativity for that particular plant. In addition, many of our plants have a handwritten white vinyl label, which gives us a place for additional notes.

And remember, you can always ask one of us! Sarah, Derek and I are always happy to answer your questions.

A Summer Tour

Good morning! Ready for an early walk through the Fuqua Orchid Center? Those of you who are buckling under the summer heat can head straight to the High Elevation House to cool off. Everyone else, follow me. As we enter the Orchid Atrium you can see our wonderful new collection of Italian terracotta containers, donated this spring by Hill Street Warehouse. (Thank you, Hill Street!) As a centerpiece for the tall pots I chose some magnificent Grammatophyllum 'Broga Tiger' with 4' spikes of leopard-spotted flowers. Their soft olive hue is nicely complemented by the arching pink Phalaenopsis. On the trellis in the background, Wilsonara Space Mine 'Red Rendezvous'.

In the Orchid Display House, hybrid cattleyas appear under a bower of dainty Oncidium phymatochilum flowers.

Above the Reflection Pond are hybrid Vanda orchids. The indigo hybrids must be the most photographed of all of our orchids. The vandas, at least, are loving the summer suana that is Atlanta.

Be sure to stop and linger over the ultra sweet fragrance of Encyclia cordigera.

A closer look at Encyclia cordigera reveals a skirt-like lip of rich magenta. Notice, also the plum colored ribbons that are the petals and sepals. They look like they've been curled with a pair of scissors. We grow our plants bright and dry in a warm greenhouse. E. cordigera grows as an epiphyte at low elevations, often in dry scrubby habitats, in Mexico and Central America.

Another plant thriving and flowering in summer is Phalaenpsis bellina. The flowers are well-known for their delicious fragrance -like a summer smoothie with citrus and vanilla. Welcome, summer!
And don't forget, if you can't make it early, we are open until 9:30 every Thursday night through September for Cocktails in the Garden.

Early Summer

May and June are two of my favorite months in the Orchid Center. It's a photographer's paradise. Because we're inside a greenhouse, the 'golden hour' for photography, in which light assumes that uniquely warm and glowy quality, tends to occur only in certain corners at certain times of year when the early morning sun is unobstructed. Nevertheless, the light is almost always soft and diffuse and completely camera-ready.

Polycycnis muscifera

Some of our wonderful Polycycnis species are flowering this month. Polycycnis is a genus of Euglossine bee pollinated orchids in the Stanhopeinae native to Central and South America. The flowers are small and delicate with a graceful arching column (reminiscent of Cycnoches, with whom they share a name derived from the Latin root cycnis, meaning swan). All the Polycycnis species have labella that are to some degree hairy. I'm amazed that any insect would regard the extraordinary velcro lip of Polycycnis muscifera (above) an enticing landing platform. Those long hairs must act as a flag to attract the bee's attention to the landing field.

Like other Euglossine bee pollinated orchids, Polycycnis offers fragrance compounds as a reward to male Euglossine bees. The bee lands on the lip and starts scratching near the base in order to obtain the fragrance volatiles. The weight of the bee pulls the flower down. When the bee starts hovering to transfer the fragrance to his hind legs, the flower's sticky viscidium disc, which you can see above in profile projecting like a tab from the club-like column, attaches to the bee's thorax.

Polycycnis are not at all common in cultivation, so be sure to stop by and catch ours in flower!

Anguloa cliftonii

The most elegant Tulip Orchid in our collection is Anguloa cliftonii. The lovely curvature of the lateral sepals make it instantly recognizable. Just visible between the pale yellow sepals are two red-marbled petals that are a shade lighter in color.

Not only is it one of the loveliest anguloas, it's also one of the heftiest. A mature plant can produce a pair of leaves that are two feet long atop a five inch pseudobulb. As you can see, the new shoot on our plant gives promise of massive growth later in the season.