This is the fourth (and final) installment of the annual cycle of
bonsai care tips I have prepared. The others - fall, winter, and
spring - can be found in our archives.
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Caring for Your Bonsai Over the Long, Hot Summer

Ahh, Summertime . . . and the livin' is easy.

But wait. You've got all those bonsai to take care of. The
bonsai are growin', and the bugs keep eatin' -- while you
desperately plan for that hard-earned, two-week vacation. Whew!
Maybe the livin's really not that easy.

So, what to do . . . ?

Let's start with the bonsai are growin' . . . which leads us
directly to managing that new growth to keep your trees under
control.

Pinching and pruning -- Candles are lengthening on your pines.
New growth on your junipers is a bright green. Your maples are
getting leggy and if you don't get busy, the internodes will be
two inches apart. Your Chinese elms look like that Kia Pet you
had when you were 10 years old.

Since you did most of your major seasonal shaping when you
repotted in the spring, summer chores in the pinching and pruning
department are aimed at refinement of the basic shape. But, be
sure you rotate your trees a quarter turn every week to balance
the light reaching various parts of the canopy, or your tree's
shape may turn out to be "lopsided style".

You've probably already pinched new growth from your
conifers at least once in spring. Early summer is the time to
get rid of unwanted buds around the tips of the branches, leaving
only the buds that guide growth to where you want it. Rapidly
growing species will be putting out new growth almost as fast as
you can keep up with it. Using your thumb and forefinger, twist
off the new clumps of needles you don't want. Be sure to get rid
of buds that form beneath a twig.

Many of your broadleaved trees desperately will need a
general haircut. Generally, you will let perhaps one or two
pairs of new leaves remain on each branch -- except where you
might want a branch to extend. In late June (and again in
mid-to-late July if you have a long growing season) you might
think about complete defoliation of your mature broadleaved trees
that are growing strongly (NOT those that were repotted this
spring) to help develop smaller leaves and, incidentally,
improved ramification. Defoliation seems to work best with trees
whose leaves have longish petioles (stems). Leave at least half
of the petiole attached to the tree.

Early summer is also when you do some fairly hard pruning on
Satsuki azaleas and other spring-blooming bonsai.

You will get no vacation in THIS part of summertime.

Fertilizing -- It seems a bit strange while you're busy taking
OFF new growth to think of fertilizing your trees on any kind of
a schedule. (That's why I NEVER fertilize my lawn; it just needs
mowing that much more often.) But a tree's growth takes energy
and regular application of fertilizer to our relatively sterile
bonsai soils helps your tree meet its energy needs.

For most trees, a more-or-less balanced (in terms of
nitrogen, phosphorous, and potassium -- NPK) fertilizer will be
satisfactory. Newly potted or young trees that you're still
growing on probably would appreciate a weekly application.
Established trees will be just as happy with an every-2- weeks
application, and your oldest trees can get along with a dose of
nutrients once a month. Some growers recommend less N as summer
comes to an end, especially for flowering trees. I'm not at all
sure that it matters, so long as there is plenty of P and K
available for the tree to use.

Micronutrients -- zinc, magnesium, manganese, iron, and
others -- are necessary minerals for healthy trees. Your
most-used fertilizer should contain a full range of
micronutrients. In late summer, you might begin to supplement
your fertilize with a bit of Epsom salts (about one teaspoon per
gallon) for an extra shot of magnesium.

Fertilize at label strength; there's no need to go half
strength as many books recommend, but do not over fertilize.
Organic fertilizers, such as fish emulsion, blood meal, or bone
meal, tend to stick around on our mostly inorganic soils a bit
longer. However, most organic fertilizers lack a full complement
of micronutrients. An increasing number of growers are using
timed-release fertilizers mixed into the soil at spring
repotting, then scattered over the soil surface once or twice
during the summer. I prefer a bit more control over when my
trees get their doses of nutrients, but it probably doesn't
matter. Growers tend to make fertilization more mysterious than
it is.

Watering and the Trials of Summer Heat -- It gets hot in the
summer. The sun is high and it beats down upon your bonsai
tables. The combination of wind, sun and fast growth sucks
moisture from your bonsai pots. Some trees -- Japanese maples
are the most notorious -- can suffer severe leaf scorch from hot
sun and wind.

This means you MUST keep a close eye on your trees. With
almost no exceptions, barring a rainy day, your trees will need
to be watered at LEAST once a day. Shohin and mame bonsai may
need water 2-3 times a day in the hottest, driest part of mid and
late summer. But only a close watch over, and intimate knowledge
of, your trees' needs will determine your watering schedule.

I use an automatic watering system that goes on once a day
in late afternoon. In the morning, I use a misting attachment on
my hose and give individual trees a good soaking if they need it.

Some trees -- Wisteria and bald cypress come to mind --
thrive in a shallow pan of water during the hottest parts of
summer. A few drops of vegetable oil in the pan keep the
mosquito population in check.

On the other hand, some trees like to dry out -- such as
Texas ebony and other arid-land acacia relatives. If you have a
summer rainy season that sometimes can be difficult.
Bougainvillea and juniper are somewhere in between and must be
watched carefully so they don't get TOO dry. I do not include
any of these trees in my normal automatic watering cycle.

Shade -- provided by "big" trees, a lathe screen, or shade
cloth -- may be necessary for some species of tree. In North
America's deep south and the arid southwest it will be a
requirement for ALL trees. Summer sun beating down on
dark-colored pots and dark soil can raise soil temperatures --
especially in moist soil -- to dangerous levels. Pots can
actually become too hot to touch for any length of time. Many of
your trees will appreciate being moved into larger-than-normal
(for display purposes) pots for the dog days of summer. While
moss can help keep a pot cool, summer heat and moisture often
causes it to "melt" from mold and bacteria. So-called sun-loving
trees almost always will do better with sun in the first half of
the day and a bit of shade in the afternoon.

Some growers wrap pots in aluminum foil to reflect sunlight
and heat. This can be dazzling on a sunny day. It also makes
watering more difficult.

Repotting -- Summer is NOT the time to repot most trees. True
tropicals may be an exception. Trees such as buttonwood and some
of the Ficus species prefer to be repotted during the hottest
period of the year -- or so I'm told. Consult an expert on
tropical plants before you repot anything in July or August.

There always is the odd emergency repot -- after root rot,
or following a squirrel's depredations. Do it quickly. Disturb
as few roots as possible (being certain that all rotten roots are
removed), move the tree to the ground or a slightly larger pot,
keep it in the shade for the remainder of the summer, and water
sparingly.

In warmer areas, trees often go into a late-summer dormancy
around mid August to early September. Trees CAN be repotted
during this narrow window of time, but it still is dangerous
because of the summer heat. Repotted trees should stay in the
shade for the remainder of the growing season. It is always best
to wait to report in late winter or early spring.

Weeding -- Weeds are the mostly a problem of early summer. Pull
them as soon as you see them. Weeds are yet another reason to
examine each tree and pot at least once every day. "Weedlets"
are more easily removed than a weed whose roots have permeated
the pot and intertwined with the tree's roots. Large weeds steal
nutrients and water from the tree.

Keep moss trimmed and in most species of tree, away from
tree trunks. Moss can help keep roots moist. It also can rot
the bark on some trees if allowed to accumulate. It also can
block the penetration of water and fertilizer to the soil, so wet
the moss thoroughly before you fertilize.

Wiring - In summer, keep a close eye on trees that are wired.
Especially in early summer, trees are growing rapidly and wire
can dig into the bark almost overnight. Azalea are wired in
early summer. Other trees may be wired in mid to late summer
after most of the spring pinching is done.

Pests -- In early summer, the overwintering critters are
busiest -- including a few caterpillars (webworm, etc.) White
fly, scale and aphid begin to show up early in the warm season,
but reach their peak after July. These last pests bring on the
related nuisances, honeydew and sooty mold. Wipe both off
leaves.

Stink bugs can appear almost anywhere at any time in the
summer, but they are hit-and-run sucking pests and seldom cause
much damage on bonsai. Later in summer, azalea caterpillars,
army worms, tent caterpillars, and inch worms will be munching on
many leaves. Don't automatically massacre caterpillars. They
turn into moths and butterflies which are very important
pollinators. Move them somewhere else. (EXCEPTIONS: army worms,
tent caterpillars, azalea caterpillars.) Slugs can be a problem
if tables and display areas are continuously wet. The Japanese
beetle is a problem in some areas. In the south, the tiny
shotgun beetle is about the only beetle that bothers bonsai.

(How do you know what is chewing on your leaves? You have
caterpillars if the munching starts at the leaf edge and moves
inward; you have beetles or slugs if there are holes in the
leaves.)

There are "good bugs." Lady beetles, praying mantis,
assassin bugs, any beetle with large grasping pincers, and others
are one of your best defenses against insects on your trees.
Other bugs are neutral. Centipedes and millipedes are no problem
to trees; neither are pill and sowbugs. Earthworms also won't
hurt trees, but seem to appear in organic bonsai soil by
spontaneous generation. Worm casts can cause clogging of soil
if worms are abundant. Submerge your pot in water up to the soil
surface for a few hours to rid the soil of earth worms. Toss the
worms into your garden

Soaps and summer oils can control most sucking insects. (If
you use an oil spray, keep trees out of the sun for several days,
and do not use soaps on maples!) Pyrethrum sprays work on just
about everything, but spray in late evening. Most pests eat at
night and an evening spray is less likely to affect bees and
other pollinators. A jet of water helps with aphids, spider
mites, and whiteflies. Use yellow sticky traps for whiteflies.
A saucer of beer (please use LITE beer) works on slugs and
snails. Use pesticides ONLY when you are severely infested! And
know your bugs. Many good bugs resemble bad bugs.

Leaf spots and other plant diseases -- In the heat and
humidity of late summer, expect to see odd spots appear on the
leaves of your trees. Almost none of these will be fatal to
otherwise healthy trees. However, if you grow apples, pears,
firethorn (Pyracantha) and junipers, you may discover an
infection of cedar apple rust. There is no spray that will
eliminate (or even control) this in the summer. Remove and
destroy (burn or toss in the garbage) infected leaves on the
apples and pears. Remove and destroy any of the jelly-like
growths that may appear on your junipers. A copper fungicide
applied in the early spring MAY help prevent infection next
summer. But don't bet on it.

Pear, Chinese Quince, and Pyracantha also may get a
bacterial black spot on their leaves. Again, remove and destroy
the leaves. Again, a copper spray MAY help. But picking and
destroying the infected leaves is the best approach.

By September, leaves are simply getting old. Just as we
elderly people get "liver spots" on our hands, tree leaves become
blotched and worn out looking. You (and they) just have to live
with it. In warmer areas of the country, most Japanese maple
leaves look as if they've been through a war by late September.
They should still turn color in the fall.

To be able to identify the pests and diseases that might
affect your trees, you should own the "Ortho Home Gardener's
Problem Solver." It is available as a book and as a CD for your
computer. Southern Living Magazine also has its excellent
"Garden Problem Solver." Sunset Magazine has the smaller,
cheaper, and less comprehensive "Garden Pests and Diseases" which
is useful. Check also with your state forestry department.

Caring for deadwood -- Summertime is the best time to apply lime
sulfur for that weathered look on pines. junipers, other
conifers, and the few broadleaved trees that are suited for
whitened deadwood.

And Finally, Vacations -- You should consider an automatic
watering system. It goes against most recommendations I've seen,
but I recommend battery-operated timers. BUY BATTERIES JUST
BEFORE YOU LEAVE FOR VACATION and your trees will not be harmed
by those common summer power outages and spikes that can
"re-program" (read: ZAP!) a timer connected to your home wiring.

Another option is to plant your trees in the ground --
either pot and all or after lifting them from their pots. Put
them in the ground in light shade. Your trees then will have the
entire reservoir of the ground to work with. Again, however, an
automatic watering system (perhaps for your lawn, set for perhaps
every third day) is helpful.

Friends and family also can water your trees while you are
gone. However, long experience indicates there is a certain lack
of reliability in even close friends and family if they are not
bonsai growers themselves -- or at least dedicated gardeners.
Someone from your bonsai club may have a summer "business" set up
to care for members' trees. Ask. And, you might find a local
nursery that will take care of your trees -- for a fee.

In late summer, it's time to start thinking about how you're
going to over winter your tender trees. See the first article in
this series. It and the others are in our archives.

Jim Lewis

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