The Ascocentrum genus is a relatively small group of about
10 species that hails from the Asian tropics—yet from a collector's
point of view, these are extremely important plants. Ascocentrum plants are closely related to Vandas and easily hybridize with these orchids. The resulting Ascocentrum x Vanda cross is known as Ascocenda, or Ascda. The Ascocenda
plants offer the very best of both their parents: they are compact
monopodial plants that can easily be grown indoors; they have the same
outrageously awesome growth habit; and they boast the jewel-like flowers
of the Vandas. If you have any interest in growing hanging monopodial orchids, my advice is to start with an Ascocenda. Once you've mastered these plants, you can move up to the much larger Vanda plants.
Taxonomy and Structure:
Ascocentrum are in the Vandeae tribe and Sarcanthinae subtribe of orchids. They are close related to Vandas and Renantheras and easily hybridize with these plants. Ascocentrum are monopodial orchids, like Phalaenopsis, meaning they lack pseudobulbs and grow from a single stem, with their roots emerging from the bottom of the growing stem. Ascocentrum
have strap-like leaves that emerge alternating left and right. Their
roots emerge from the bottom of the stem, but sometimes roots will
emerge from between leaves and wander into the open air. Over time,
older plants will branch, sending out alternate stems, and gradually
increasing the plant's overall size. Propagation by division is possible
by removing side stems, providing they have at least two healthy roots
established.
Light:
Like Vandas, Ascocentrum
thrive in strong, bright light. They can be acclimated to direct
sunlight, and in areas where they are grown outside, can sometimes be
seen in nearly full morning sunlight. Plants that are receiving enough
light have light green leaves with red mottling on the leaves. Leaves
that are dark green or a lack of flowering typically indicate inadequate
light. In northern latitudes, the winter is particularly challenging
when it comes to light. Growers in these areas might need to supplement
with an HID light. In the summer, your Ascocentrum might appreciate being hung in a tree outside.
Water:
As with all orchids, the amount and frequency of watering depends on the growing habit. Ascocentrum
orchids can be grown in pots, in a very fast-draining orchid mixture,
or they are particularly well suited to basket culture. Many growers who
have greenhouses grow Vandaceous orchids in open slatted baskets with
no growing medium and the roots hanging free in the open air. In
general, Ascocentrum have fairly high water requirements. Hanging plants should be watered or misted daily. To correctly water a hanging Ascocentrum,
give it a good soaking, then let it dry for two or three minutes and
water it again. The roots should turn green or silvery as the plant
absorbs water. Providing adequate humidity is also important: a minimum
of 60% is necessary for healthy growth, but more is better. There is no
upper tolerance—these orchids are well suited to 90% humidity, providing
there is a strong airflow. A healthy plant should remain cloaked with
leaves all the way to the bottom of the stem. If the plant starts
dropping leaves, the most likely culprit is lack of water or improper
feeding.
Fertilizer:
Ascocentrum are
heavy feeders. Fertilize weekly with a 1/2 strength orchid fertilizer.
Plants that are properly fertilized will retain their leaves and bloom
much more vigorously.
Temperature:
Ascocentrum
are warm-house orchids that prefer temperatures above about 65˚F. They
can tolerate lower temperatures, but a prolonged exposure to colder
temperatures will have a profound effect on the plant's growth and
flowering. Exposure to any temperatures below 50˚F can cause delayed
flowering for up to a year.
Blooming:
The plants typically flower in the late winter or early spring, although my Ascocenda
hybrids have been known to throw flower spikes throughout the year. The
plants flower from an upright inflorescence that is covered with small,
perfectly shaped flowers. Ascocendas follow this same pattern: an upright inflorescence that looks like a cone of flowers. True Ascocentrum flowers are often red, scarlet or deep orange, depending on the species.
Potting and Media:
Ascocentrum and the closely related Asocendas
really do best as mounted plants. Most growers prefer growing them in
open slatted baskets, wiring the plants into place until the roots have
had a chance to work their way through the basket and firmly hold the
plant in place. As they plants grow, they sometimes need additional
support to prevent tipping over; this can be provided by wiring the main
stem loosely to the basket support. Plants grown in this way will
eventually develop a hanging curtain of white roots. People who are
unfamiliar with orchids are always enchanted by the sight of a beautiful
orchid seemingly growing in mid-air (not knowing, of course, that you
water it daily!). Baskets can be made from cedar or plastic. You can
also grow these plants in containers, but it is absolutely essential
that you use a very fast draining mix and allow the plants to completely
dry between watering. Despite their extremely high water requirements,
dampness is the enemy of these beautiful plants. The roots must be
allowed to completely dry out.
Grower's Tips:
Ascocentrum and indeed all Vandaceous orchids are not really beginniner's plant. They require more maintanence than your average Phalaenopsis,
including sometimes daily watering and rather more extreme growing
conditions (high humidity, high temperatures, very bright light).
Additionally, I've found that growing them well requires some patience
in the beginning—there is a natural balance between watering, humidity,
temperature, air flow, and light that is optimal. It's hard to say
exactly what this is, because every growing situation differs a little
bit. To some degree, it's just a matter of feeling it out, learning to
recognize this sweet spot by instinct as much as anything else. But
don't let me discourage you: there's a reason this plants win so many
awards, a reason that people literally build additions onto their homes
to keep Vandaceous orchids. They are exotic and beautiful and
tempermental, and they reward your efforts with sublime displays of
blooms.
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