The Plant Man column
for publication week of 10/12/03 - 10/18/03

The Plant Man
by Steve Jones
www.landsteward.com

Groundcover: good or bad for your trees?

One of the subjects I get asked about quite frequently is groundcover. More
specifically, many people want to know the pros and cons of planting ground
cover around trees.

One of the main reasons that you might consider planting groundcover is that
lawn grass generally doesn't do well in the shady area around a tree trunk,
leaving you with bare or sparsely covered patches that aren't very
attractive.

What could possibly be wrong, then, with planting groundcover around your
trees?

Well, for a start, imagine yourself as a tree. You can't exactly go
walkabout in search of food and water. You must rely on the moisture and
nutrients that you can suck through your roots. You probably wouldn't
welcome the presence of an aggressive rival for that sustenance; especially
a rival that moves into your space and rapidly makes itself at home all over
your roots.

Furthermore – and remember, you're still imagining that you're the tree at
this point – some zealous landscaper is likely to come by and start thinning
out your "guest" groundcover, but in so doing can also tear up your delicate
little root extensions that have become tangled up with the groundcover's
roots. Ouch!

So if you were to ask a tree, it would probably say, "Don't plant anything
beneath my drip zone." But that's a big area, consisting of the circle on
the ground directly beneath the circumference of the tree's canopy. You can
probably find landscapers who would agree with the tree, but I'm not one of
them. I believe that thoughtful planting of groundcover near or around trees
can be very attractive without too much risk of hurting the trees.

Of course the main "pro" for planting groundcover is that it is very
effective in adding some green (often, all year ‘round) and, unlike a lawn,
doesn't require mowing or very much attention at all. Additionally, some
groundcover plants can be effective deer deterrents which you might consider
to be a nice bonus!

There are a number of groundcovers that I particularly like, and I shall
discuss a couple of my suggestions here in the next "Plant Man" column. If
you can't wait that long and need some advice, Send me an e-mail at
which is exactly what this reader did:

QUESTION: "I bought a tree / bush from a local landscaper who didn't know
much about this plant. It is called "Senna corymbosa", also known as
"Flowering Senna". I am trying to find out how much sunshine the plant needs
each day: morning sun or all day? Can you also tell me if it is a tree or a
bush and how big it will get? If you could please let me know the answers to
these questions I would appreciate it!" – Evelyn Adams

ANSWER: That is a tough one but here is some information that might help.

The sennas are a group of plants that vary greatly in size, but their
flowers all look the same: they are yellow with five petals. We have a small
tree-sized one called Argentine senna (Cassia corymbosa or Senna corymbosa).
A native of Argentina, Brazil and Uruguay, other names for this plant are
common tree senna, yellow senna, yellow cassia, flowery senna and Argentine
wild sensitive plant (although the leaves never react like those of true
sensitive plants).

Once again, I had no luck with germinating the seeds so I bought a small
plant. It grew rapidly, acquiring three main trunks and a height of about 7
feet. The tree is quite attractive, with dark, finely grained bark, long
slender leaves, and bright yellow flowers in the early summer.

Afterwards, it produces plenty of seed pods, but these are often infested
with insect larvae. Two years ago, several of the top branches died during
the winter. This was followed by an entire trunk dying during a period of
heavy rains which lasted almost a month in the early summer. Part of the
tree
continued to look just fine, but I had to prune off quite a number of
branches as they succumbed. Two healthy trunks with a reduced number of
branches survived through last summer but this past winter, one of the
trunks died. The remaining trunk has a small group of branches which are
still healthy. (Note: In my e-mailed response, I was also able to give
Evelyn some information about caring for her senna tree and an idea of how
large it might grow.)

Evelyn wrote back to say, "You are a lifesaver! I appreciate all the
information that you gave me. You provided more information than I ever
thought I would receive. Just wanted to thank you again for your helpful and
descriptive information." I'm glad I was able to help you, Evelyn!

The Plant Man is here to help. Send your questions about trees, shrubs and
landscaping to and for resources and additional
information, including archived columns, visit www.landsteward.org where you
can also subscribe to Steve's free e-mailed newsletter.

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