Published in the Contra
Costa Times on
If Trees Could Talk: Interview With a Birch Contra Costa Master Gardener
Interviewer:
It isn’t every day that I interview a birch tree, so please be patient with me.
It occurred to me that lots of people in
Birch:
If you’re talking about the geographical distribution of the Betulaceae family, of which I am a member, it is
vast. We are about sixty species and widely scattered throughout the
northern hemisphere, from the
Interviewer:
This is a huge area!
Birch:
That’s right. Did you know that we are the most common native tree in
Interviewer:
And where else in the world are birch found?
Birch:
You will find members of my family in the
Interviewer:
In other words, you’re saying that you were carted here by people who wanted
you nearby, for whatever reason.
Birch:
I suspect that along with our practical uses, we filled a sentimental gap for
certain immigrants from those lands I just mentioned. When they traveled
to start a new life, they knew they wouldn’t return to their original home so
they brought something dear to them to remind them of home. That’s one of
the ways plants expand their territory.
Interviewer:
What are some of those practical uses you refer to?
Birch:
Birch is ‘bhurga’ in ancient Sanscrit,
and that means a tree whose bark is used for writing on. Our timber is
also used for boatbuilding and roofing, so we are also at the root of the Sanscrit word, ‘beorgan’, which
means to protect or shelter.
Interviewer: Canoes were made from birch
by American Indians, weren’t they?
Birch:
Yes, that would be the Canoe or Paper birch (Betula papyracea) whose wood was
used as a skin for canoes. Mostly, our tough and straightgrained wood is used for humble purposes, such as
thread bobbins, broom handles, cradles, and herring-barrel staves.
Interviewer:
Your bark has many useful purposes, I believe.
Birch:
Yes, oil from our bark has antifungal properties so the people in
Interviewer:
Can parts of you be used for medicinal purposes?
Birch:
Different peoples use our leaves, sap, and bark to treat a variety of common
illnesses. So you see, we have been useful to mankind
for millennia. Ever hear of the word ‘birching’?
Interviewer:
Not since I was a kid.
Birch:
When a child was delinquent, a leafless bundle of birch twigs was tied together
and the child’s bottom was duly whipped. That’s no longer done nowadays.
Interviewer:
Let’s get back to…Tell us what sort of climate and soil requirements birches
have. That’s something our readers would want to know, especially if they
are considering planting one, two, or three birches in their yard.
Birch:
Site characteristics for birch can vary a great deal. We can live in soil
that is slightly acidic to very acidic, completely neutral, slightly
alkaline to very alkaline. It just depends on which birch you want to
plant where. If the soil is at all acidic, you will find that many birch will do well. Examples are Yellow birch (Betula alleghaniensis),
Heritage river birch (Betula nigra ‘Heritage’), Streamside birch (Betula occidentalis),
our friend the Canoe or Paper birch, Youngii European
birch (Betula pendula
‘Youngii’), Gray birch (Betula
populifolia), and Downy birch to name a
few. Those of us who thrive in soil that is alkaline are Jacquemont birch (Betula
jacquemontii) also known as the white-barked
Himalayan birch, Monarch birch (Betula maximowicziana), River birch (Betula
nigra), and European white birch (Betula pendula).
Interviewer:
Are there birch that like either acidic or alkaline soil?
Birch:
Yes, they are the Japanese white birch (Betula
playtphylla japonica), Weeping birch ‘Dalecarlica’ (Betula pendula varieties), and Pyramidal white birch (Betula pendula ‘fastigata’). By the way, don’t let all those Latin
names put you off, they are there to help you when you are at the nursery
looking at birch trees or reading catalogues. We tend to all look alike
to the untrained eye! For the most part, birch do
well in soil that is either clay, sand or loam. As far as sun exposure is
concerned, we are happy in full sun or partial shade. Jacquemont,
River , Streamside, Canoe (Paper) and Weeping birches
can even tolerate full shade.
Interviewer:
What about water? Are there xeric birches?
Birch:
The most important characteristic of birch is that they do not tolerate
drought. Remember this because drought is death to us. Our roots
must be surrounded by wet or moist, well-drained soil. Most of us are riparian,
which means that we like life along streams or riverbeds. Drought puts
stress on us, weakens us and leaves us vulnerable to attack by pests, such as
the bronze birch borer and birch leafminers.
When we are well watered, we can tolerate up to 60% leaf damage by the leafminers!
Interviewer:
No offense, but I’ve heard birch described as ‘buggy’.
Birch:
When we become unhealthy, usually due to drought stress or when we are pruned
in the spring, which is the wrong time of year for that, we become easy prey to
the bronze birch borer. In
Interviewer:
What damage does it cause?
Birch:
Certain wasps produce larvae that feed between the upper and lower layers of
our leaves. What you see are leaves with blotchy or irregular
mines. The larvae are actually inside the leaf, voraciously tunneling
through. Our affected foliage turns brown, wilts, and drops prematurely.
Interviewer:
How can this pest be controlled?
Birch:
The best thing to do is to plant birch cultivars which are less susceptible
to leafminer attack—Black birch, monarch birch, river
birch or yellow birch, for example. These are fairly resistant to leafminers and birch borers. There are also cultural
and chemical controls which help manage birch pests.
Interviewer:
I didn’t realize that pests could be such a serious problem for birch. If
my irrigation philosophy were one of laissez-faire, or no watering program
except for rain, I wouldn’t plant a birch. Your species is too high
maintenance!
Birch:
Homeowners nowadays have elaborate irrigation systems, so with lots of water,
we can survive. Of course, what happens when the property is sold and the new
owner doesn’t know birch are not drought
tolerant? We suffer, and frankly, when we are stressed, we don’t look
good. I think the beauty of our bark and leaves and our shape is the
reason people want us near them. Let’s face it, we are beautiful year
round. It’s hard to be modest. We also tend to create a whole
universe around us.
Interviewer:
If you were planted in a frequently irrigated lawn, would you be happy?
Birch:
There again, there is a problem. Lawn and birch are both thirsty and lawn
drinks more than its share of water, since its roots are shallower than
ours. And, all that water can be expensive. Rather than select
birch for their yards and gardens, homeowners in this area should opt for trees
which can survive on their own.
Interviewer:
It seems strange for a birch to talk about other trees… But, go ahead.
Birch:
That was my intention from the very start. People living in
Interviewer:
Yes, I know what you mean. I’ve planted the wrong tree in the wrong place
before. I suppose I was excited about planting my first tree.
Impulsively, I went with a mental picture of what I wanted and didn’t research
the needs of the tree and the particulars of the site. After I realized I
had made a mistake, I felt guilty for years. Then I moved away, and still
feel guilty.
Birch:
You aren’t alone in this. Let’s talk now about what trees grow well in
Interviewer:
I’ll make sure the trees are listed at the end of our interview. I feel
we’ve gotten to know you today, any last words to our readers?
Birch:
There is a lot to know about trees and their requirements, soil, which is alive, and horticultural practices that can help control
pests. No one can know all of it. An excellent resource for that
kind of information is the
Partial list of trees for
Acacia (Acacia sp.)
Arbutus (Arbutus unedo)
Ash (Fraxinus
sp.)
Australian Willow, Wilga
(Geijera parviflora)
California Buckeye (Aesculus
californica)
California Pepper Tree
(Schinus molle)
Chaste Tree (Vitex agnus-castus)
Chinese Flame Tree (Koelreuteria
bipinnata)
Goldenrain Tree (Koelreuteria paniculata)
Chinese Hackberry (Celtis
sinensis)
Chinese Pistache (Pistacia chinensis)
Chinese Tallow Tree (Sapium sebiferum)
Citrus (Citrus sp.)
Crabapple (Malus sp.)
Crape myrtle (Lagerstroemia indica)
Deodor Cedar (Cedrus deodara)
Eucalyptus (Eucalyptus sp.)
Fruitless Mulberry (Morus
alba ‘Fruitless’)
Goldenchain Tree
(Laburnum)
Hawthorn (Crataegus sp.)
Japanese Maple (Acer palmatum)
Locust (Robinia
sp.)
Loquat (Eriobotrya
japonica)
Bronze Loquat (eriobotrya
deflexa)
Magnolia (Magnolia sp.)
Maidenhair Tree (Ginkgo biloba)
Mayten Tree (Maytenus boaria)
Oak (Quercus
sp.)
Olive (Olea europaea)
Pear, Flowering (Pyrus
calleryana)
Pine (Pinus
sp.)
Pomegranate (Punica granatum)
Silk Oak (Grevillea robusta)
Silk Tree (Albizia julibrissin)
Sumac, African (Rhus
lancea)
Sweet Bay, Grecian Laurel (Laurus
nobilis)
Sweet Gum, (Liquidambar sp.)
Variegated Box Elder (Acer negundo
‘Variegatum’)
Sources:
Pests of Landscape Trees and Shrubs: An
Integrated
http://selectree.calpoly.edu (see
below)
Reimer, Jeffrey L. and W.
Mark. “SelecTree: A Tree Selection Guide.” http://selectree.calpoly.edu/
(
http://www.treesforlife.org.uk