Viburnum Revisited
Family: Caprifoliaceae (Honeysuckle family)
although some
place viburnums in the Adoxaceae family, with Sambucus
Genus: Viburnum
containing more than 150 species
In
January 2005 I resolved to reflect from time to time on
plants featured
in past columns. Recently I had reason to revisit
a 2000 column about Viburnum davidii, and in this month’s
column I report the results. Such as they are….
 Plants can be very confusing. Actually, the plants themselves
are neither confusing nor confused; but sometimes the information
about them can be both.
Let’s say a question comes in to the Master Gardener
office about Viburnum davidii and berries: I want
to plant Viburnum davidii, and I want to make sure I get those
metallic
blue berries. I’ve read that I need a male plant and
a female plant. How do I tell the difference?
Whoa. Searching for information to answer this question properly
can make any Master Gardener dizzy. Without a botanist on staff
who specializes in the sex life of viburnums, coming up with
the correct answer can be tricky.
 The short answer
is, With most plants, you can’t tell
the difference between a male plant and a female plant, unless
it’s in flower. Even then, you need pictures to know
for sure which flower is which. This doesn’t help the
caller very much, because they want to buy their viburnums
this weekend and this time of year, they’re not in flower.
So to be of service, the conscientious Master Gardener goes
searching for more information.
My Plant of the Month column from 2000 is no help at all,
because on this topic I offer just one single line: Remember
that plants of both sexes are required for berry production. Most reference books written for the layman and recommended
for use by MGs don’t address the issue of “male” and “female” at
all where viburnums are concerned. They merely describe flowers
and berries and required growing conditions. A few offer
some details: The American Horticultural Society’s
Encyclopedia of Garden Plants remarks about V. davidii: “If
plants of both sexes are grown, female plants bear decorative,
metallic blue fruits.” Taylor’s says this: “Plant
2 or more shrubs to increase berry set.” Well, okay.
That makes sense, does it not? But we still don’t know
male from female, do we? All we know at this point is that
if we plant two of these evergreen viburnums, we have a 50
percent chance in each case of hitting the jackpot. But since
the odds are per plant, we can still end up with all males,
or more males than females.
Then we find this,
from Virginia Cooperative Extension (specifically from Virginia
Tech’s department of environmental horticulture): “Roses
and viburnums are examples of perfect flowered plants. This
means that each individual flower has both male and female
parts; stamens, which produce pollen, and a pistil, which contains
the ovary(ies) which will produce the seed and hence the fruit.
This makes self-fertilization possible.” Wow. That means
the gardener doesn’t have to worry about which plant
is male and which plant is female. Each plant is both!
Problem solved?
Well, not quite. Here’s what Oregon
State University’s landscape guide to shrubs has to say
about V. davidii: “Broadleaf evergreen shrub, 3-5 ft
(1-1.5 m), forms low, compact mounds. Leaves opposite, simple,
thick, leathery, dark blue-green, narrowly, oval or slightly
obovate, 5-15 cm long, 2.5-6.5 cm wide, conspicuously 3-veined,
petioles usually less than 2.5 cm. Pink flower buds, in spring
dull white flowers in 5-8 cm wide clusters appear. Small, 6
mm, oval, bright blue fruit held on red pedicels. Need
both male and female plants to obtain fruit.” The emphasis,
dear reader, is added by me.
So we’re back where we started, right? Well, maybe not.
In our search we’ve learned the difference between perfect
flowers and imperfect flowers. It has nothing to do with good
looks or pest resistance or anything else of that sort. No,
perfect flowers have both male parts and female parts. There
are two kinds of perfect flowers: one in which both parts do
their part, so to speak; and one in which one or another of
the two parts is infertile. Then we have imperfect flowers,
which has either male or female parts, but not both; and whichever
is there, is fertile.
 We’ve also learned the terms monoecious (separate male
flowers and female flowers on the same plant) and dioecious (flowers of only one sex on each plant). OSU literature tells
us that monoecious and dioecious plants have only imperfect
flowers. Aha! Logic (according to OSU) then dictates that all
flowers on both monoecious and dioecious plants have either
male or female parts, but not both, and whichever is there,
is fertile. Then we read the description by Virginia Tech’s
College of Natural Resources of V. ellipticum as monoecious,
with perfect flowers. Arrgh!
This is where our heads start to spin, our office hours are
up, and we leave the question about berries and V. davidii for
the MGs on the next shift so they can have a go at it. Or we
give it to Al. Who may (or may not) pass it to Craig.
My conclusion?
Questions coming in may be challenging. Our search for the
correct
answer may leave us more confused. We
have access to experts who can help (remember the MG mantra: “I
don’t know but I’ll find out.”) It’s
better to pass the question along to a more experienced authority
than to give the wrong answer. And sometimes it‘s very
hard to be sure what the right answer is.
 But often a short
answer will do, so long as it’s not
misleading. That may be all the client needs. In this case,
we can try something like: “You know, there’s a
great deal of conflicting information about this and I can’t
quite sort it out. But what I can say is, you can’t tell
the difference between a male and a female plant unless they
have flowers or fruit. If you must plant right away and no
flowers or fruit can be seen, plant several and take your chances,
if you’d like. But remember, it’s a gamble. The
surest way is to take a cutting from a plant you know is a
male or a female because the person who grows it knows for
sure. This cutting will be a “clone” of the parent
plant and will have the same sex. Or, you can check the tag
carefully. Many plants are sold “unsexed”: that
means you can’t be sure which is which. But some growers
are now producing clones and they are marked accordingly. Chances
are good the tags are correct.”
You see? This entire
column might’ve been only one paragraph
long.
All photos in this article courtesy of Oregon Landscape Plant
Database http://oregonstate.edu/dept/ldplants/index.htm |
