Plectranthus: Coleus’ Cousin

February 18, 2002 - 15:47

Textured, colorful foliage and a nice habit makeTextured, colorful foliage and a nice habit make plectranthus one of the best new plants for mixed containers.<

With all the well-deserved attention that coleus hybrids are
receiving for their landscape and interiorscape performance, it seems like a good time to take a look at some of the closer relatives of coleus that have the same strong characteristics and solid performance.

As with coleus, plectranthus are fast-crop annuals; salable
almost as soon as they are rooted and tolerant of a variety of production
conditions. As the primary interest is foliage, plants can remain in good
condition on retail shelves for longer periods of time. Use plectranthus as you
would coleus, although since leaf colors aren’t as vivid, plectranthus
will sell best as accent crops, foliage filler and mixed container materials.
With the flowering types of plectranthus, schedule to make the most of the season
and use for color and as value-added hanging baskets. In spring 2000,
plectranthus was one of the plants of focus at the University of Florida trials
and showcased at the annual May field day.

Plectranthus are like coleus and salvia, members of the mint
family, with rapid growth, aromatic foliage and a variety of shapes and sizes.
Like coleus, these plants will do well in the irrigated landscape, container
gardens and indoor situations as long as light levels are high. In fact, many
of the best known plectranthus are for the indoor market. Most plectranthus are
used for foliage interest and have insignificant flowers, with a few notable
exceptions.

With all the interest in new crops, groups of plectranthus
are coming onto the market with profuse and very attractive flowers and green,
aromatic foliage. The flowering plectranthus group is predominantly from South
Africa, where they are used as bedding and flowering hedge material. While the
flowering mechanism is still being worked out, they appear to flower best in
late summer as nights cool and day length begins to shorten, which in north
Florida, is around October first. Timing schedules for the flowering
plectranthus are still a bit sketchy, but the industry should be able to get a
winter/spring flowering crop and perhaps another in the late summer and fall.

Suggested Varieties

The best-known flowering form in our industry is ‘Mona
Lavender’ from Ball Floraplant. This plant has a great form for
containers and hanging baskets. Mona forms a low mound, requires a pinch in
production to get the best shape and flowers profusely from
all nodes. While Mona has deservedly the best recognition of the flowering
types, there are many other notable varieties. Some other forms currently in
southern region trade include plectranthus ecklonii, which reaches a height of
4-5 feet and flowers with a rich, blue-purple, 6-inch spike from all terminals,
and plectranthus ecklonii ‘Erma’, a pink flowered form. Both plants
are annuals, even in north Florida, but add strong color to the fall landscape.
They can tolerate full sun, but foliage is best when some protection from
strong sun is provided. As a side note, the “fragrance” of the
foliage is probably a bit of an exaggeration; stench might be more accurate. We
nicknamed these plants “Smelly Dog Plant”, as the foliage odor was
pretty close that of a wet dog. However, this name actually stimulated interest
in the plant; it was one of the most popular plants in the Milton trials.

Foliage types of plectranthus vary a lot in growth habit and
form but are predominantly colored in shades of green, gray-green to silver and
white, the most common of these forms being plectranthus amboinicus —
Cuban Oregano. While this is not a “true” oregano, the foliage is
highly aromatic, and the leaves are generally white edged with green centers.
Growth habit for Cuban Oregano is loosely upright or mounding, reaching a
height of 24 inches in the landscape. This plant will sport back to a solid
green form, so propagators need to keep an Á eye on stock plants as the
green form is much more vigorous than the variegated form. Allan Armitage, and
the University of Georgia, released ‘Athens Gem’, a tri-color
variegation that is quite nice. Try using Cuban Oregano in mixed containers for
sturdy summer foliage color, as an annual in the landscape and pared with herbs
(although few cooks use it twice…).

A close companion to Cuban Oregano is plectranthus forsteri
‘albo-marginatus’, Forster’s plectranthus. This is also a
green-white variegated form but with larger leaves, a more upright growth habit
and a more refined look to the plant. Leaves are corrugated olive green with a
clean white border. Plants rarely flower and have a better growth habit in the
landscape than Cuban oregano.

Plectranthus argentatus  is a strong, upright, solid gray species. This is a horsy
large plant with matt silver foliage, similar to ‘Dusty Miller’,
though not as bright a gray. The plant lends itself to landscape use very
nicely in much the same way as Dusty Miller but with larger and faster growing.
In mixed containers, this plant will take over if you don’t use vigorous
plants in the mix with it.

For hanging basket culture, there are quite a few
plectranthus to choose from and all of these work equally well in mixed
containers. Most of these plants flower sporadically in late summer, but they
hold onto their leaves, so flowering is a good thing in this case, unlike
coleus.

Plectranthus australis (verticillatus), Swedish Ivy, is an
old standard houseplant and hanging basket plant that has literally been
hanging around for years — and for good reasons; it holds up well with
the average consumer’s care or lack thereof. Consider working this plant
into your hanging basket and mixed container schedules; it is fast, has glossy
green leaves, takes shade and always looks good. This is definitely one to
avoid full hot sun, as the leaves will scorch.

Plectranthus oertendahlii, Creeping Coleus, and plectranthus
fruticosus are two plectranthus with purple-toned foliage. In the industry,
these two plants are often confused with one another and sold synonymously.
However, P. oertendahlii is a smaller leaved plant with prominent silver veins
on a purple-green leaf, and P. fruticosus has larger leaves and a more general
purple tone overall. Both are strong hanging basket plants and add purple tones
to mixed containers.

Plectranthus madagascariensis, Variegated Mint Leaf, is
another old time plant making a come back because it takes bright light, grows
fast and easy, and has an arching, creeping growth habit that works in both
baskets and mixed containers. Green leaves reach up to 1 inch in diameter with
clear white margins, and the plant will grow to 3 feet in diameter in a season.
It is a strong performer in the southern landscape as well as in containers.
Unlike many of the other plectranthus, which can be gangly without a pinch,
this plant has a good, dense growth habit and looks good all the time.

The variety of textures, colors and forms available to
growers make plectranthus a crop we should all consider adding this spring.

 

Why Weeds?

In our industry, things are changing very quickly as
floriculture adjusts to becoming a commodity to the American consumer.
It’s really only beginning — we have a long way to go. In my view,
the future of the greenhouse business looks a lot like the history of the
American farmer, but nurseries have an advantage. We watched what happened to
the small farmer; we know what is needed to make the transition; and we have
excellent examples of successful small farmers around us today. So as we face
the same forces shaping our industry, we can avoid a lot of the pitfalls that
the small farmer faced.

This stuff has all been written before. Increasing market
pressures will force the formation of major nurseries; these
mega-nurseries’ sole purpose will be to supply the demand for flowers at
the retail level. As these large corporations grow, the small local nurseries
are going to need to change as well. Small nurseries are going to need to
develop specialized products and services that separate them from the mega-nursery.
If they fail to do this, they will disappear because, to the consumer, they
will become invisible. Quality won’t be enough to save the small nursery;
it wasn’t enough to save the small farmer. The average consumer
can’t tell the difference between an average and a superior
product…unless you are there to tell them the difference.

Don’t get the wrong impression; the formation of
mega-nurseries isn’t evil; it is a fact of life for our industry, as is
the development of the big box garden center. This is our future, it is the
cost of becoming something Americans feel is a necessary part of life. Imagine
how the corner market felt when the first supermarket came along —
probably a bit like the smaller nursery feels today. The message is change; the
medium is plant materials and services, and the whole thing is progress whether
it seems like it right now or not.

So why a column on a bunch of weird crops that have small
market share? Because they offer something different; they give smaller
operations an edge in the market, and honestly, because I love these plants.
While all these giant operations are forming and learning how to control big
markets, there is a lot of money to be made by personalizing what you do. I
think a conservative adoption of new crops is a good first step in
differentiating your nursery from your competition. It’s only a step
though, because you’ll need to know how to use these plants, how to
present them differently and how to provide services that augment your original
crops.

So this column is here to promote new crops. Not all of them
will work for you, but some will, and by carrying them as part of your crop
mix, perhaps you’ll attract a few new customers. New crops are always a
complicating factor in nursery production. They cause problems; they sometimes
fail; but every production nursery should develop a crop experiment program,
because it keeps you thinking about change. Also, getting new crops out in the
press raises the awareness of our industry’s plant breeders.

This column will also promote the new markets that are
always coming along and offer ideas to nurserymen looking for niche markets. So
I hope you enjoy this concept column, and I’ll try to make something
productive out of my 15 minutes of fame by giving you some ideas — some
reminders — that there’s always something new coming down the
pipes. If there’s a group of plants you’d like to hear more about,
please contact me, and I’ll work on getting some of the basics out to
you.

About The Author

Richard Schoellhorn is associate professor of horticulture at the University of Florida, Gainesville, Fla. He can be reached by phone at (352) 392-1831 or by E-mail at rksch@ufl.edu.

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