... hedges of juniper and other shrubs, vertical mulch,
dividing, edging, mowing
Tip of the week:
Vertical mulching can cure hard packed soil. It creates vital
pathways for air and moisture to reach roots. Fall is a good time
to employ this technique.
Many holes about three inches in diameter are drilled into
ground beneath a tree's branches. Compost and slow release
fertilizer may be placed in the holes so each contains an airy,
rich moisture-retentive mix where roots can grow. Microorganisms
that establish there move laterally from the holes into surrounding
soil, gradually loosening the spaces between.
In this issue:
Think succession for success on wooded lot: Basics
for creating a natural, wooded area.
Native juniper best for a hedge in sun
Twiggy, fast deciduous shrubs for hedge
in part shade.
Vertical mulching frees trees from
hard packed soil.
Dig and divide any time after summer heat
Good time now to re-cut trenched bed
Proper mowing height and tips for
various lawn grasses.
High time to seed and plant, or cut back
tomatoes and other veg.
Wooded lot design basics
I am trying
to naturalize a side yard that was wooded, but the builder used as
a parking lot for his trucks while building our house. We've
planted some evergreens and deciduous trees, but want to fill in
between them with woodland type plants. The soil is very dry and
rocky. Any suggestions? Would hemlock or bayberry
(Myrica) work well there? - D.C. -
Plant choices for a wooded lot are right up our alley. We're
surrounded right now by materials we use in teaching about native
trees, shrubs, woodland wildflowers and their settings. That's
because we're preparing our parts of a Natural Gardening and
the Wooded Lot workshop (check our calendar for these workshops or
contact us to invite us to present these sessions
for your group).
Here are excerpts and distillations from that workshop.
You're smart to make woody plants your first priority. To
preserve the health of existing desirable trees or add or remove
trees and shrubs from a wooded lot, take your cues from succession.
That's the natural process that Nature follows to create, age and
change a woods.
You can learn more about succession in the books Woodland
Stewardship: A Practical Guide for Midwestern Homeowners (by
Baughman, Alm, Reed, Eiber and Blinn, University of Minnesota
Extension) and The Forests of Michigan
(http://www.press.umich.edu:80/titleDetailDesc.do?id=12017) (by D.
Dickman and L. Leefers, University of Michigan Press) or under
"Forests are an ever-changing ecosystem" in Attracting Woodland Wildlife: A
Copying from natural succession, we let the first woody plants
on a site improve the soil for later species. If those pioneers
grow well, they convert minerals, air and water into organic
matter, that falls on and enriches the soil.
Soil condition is critical, and
Compacted soil is hard on the gardener who wants to plant there
but even harder on tree roots in that soil. Roots cannot get enough
oxygen or water through the densely packed pores in a squashed
soil. So consider hiring a tree care firm to loosen the soil via
Plot great paths
Next, map out paths and places for visiting humans and wildlife
to rest and enjoy that little woods. Think about what you will do
when you walk there and your angles of sight as you look in that
direction or approach from your home. Create entrances and
invitation, suspense and surprise with the placement of your paths
and sitting areas, and flow of your paths.
If walks in the woods soothe you, be sure to create paths
through your own wooded lot. It doesn't matter if the lot isn't big
enough to have a path that goes on and on as it might in a large
woods. Give your paths twists and eye-catching features that
recreate the feel of the big woods. Use photos like this of natural
woodlands as your guide.
Mulch, and more mulch, naturally
Mulch the paths heavily, right away. Keep deep mulch away from
tree trunks but add it liberally over your travel routes. That
helps prevent additional compaction from foot traffic. It also
provides a places that nurture and spread important soil-building
organisms -- everything we don't like to name plus worms,
beneficial fungi and more. If you add mulch now you will find that
even as early as next spring the soil under the path and several
inches to a foot out on either side will be looser and easier to
dig. The effect continues outward, season by season.
Let fallen leaves lay on the floor of your little woods, and
spread more as you get them when neighbors rake this fall. Hold a
leaf layer in place with sticks laid on top if the area is very
windy and you're concerned about leaves blowing back to your
Choose new plants for their best features
Then check the qualifications of plants you' might add. That
means looking into leaf characteristics, as you've probably done to
discover the featheriness of evergreen hemlock (Tsuga
canadensis) or that brush-past fragrance of bayberry
(Myrica pensylvanica). Think, too, about color in the
fall, bloom and berries, mature height and spread, and growth
Right: Serviceberry (Amelanchier canadensis) is an
understory tree with spring bloom fragrance, coppery fall color,
and pretty berries that are great eating if you can beat the birds
to the harvest. Serviceberries taste like raspberries with the
texture of blueberries.
In answer to the hemlock or bayberry question, look into
something about each plant that's vital to creating an easy,
pleasingly natural woodland. That's the plant community to which
your potential additions belong.
What's grown there naturally is a clue about what to
Hemlock's normal associates are sugar maple, beech, yellow
birch, white pine, arborvitae, rhododendron and fir. Bayberry often
occurs naturally with sandcherry, chokeberry (Aronia
species), scrub oak and sweet fern (Comptonia peregrina)
in dry soils, and elderberry (Sambucus species), hazel
alder (Alnus rugosa) and hardhack spirea (Spiraea
tomentosa) in wetter spots. If any of these plants are there
already and doing well you have a first indication that the new
addition might thrive in that soil type and exposure.
Perhaps more importantly, you can expect naturally associated
plants to help each other. They live compatibly, drawing from
different nutrient banks rather than competing and each one fosters
soil microbes that are beneficial to other plants in the
Much of the information you need for putting native plant
communities together is in Native Trees, Shrubs and Vines for
Urban and Rural America by Gary Hightshoe (1988, Van Nostrand
Reinhold Books). Although the book's out of print, secondhand
copies are worth seeking. It's a measure of the value of this
book's information that used copies may fetch a higher price than
they did new.
You can also find some of this kind of information by searching
under the plant's scientific name at plants.usda.gov/java/ for North American
natives, and Missouri Botanical Garden's plant finder
for landscape plants both native and foreign.
Wait to add smaller plants such as woodland wildflowers after
your upper- and middle story plants are selected and placed. Then,
choose them as you did woody species, for their fit with the
community and appeal to your senses. At this step you can use
Perennials and Their Garden Habitats (by Richard Hansen
and Freidrich Stahl, Timber Press), the websites listed above, and
wildflower guides such as Michigan Wildflowers in Color
(by Harry C. Lund, Thunder Bay Press).
When you've completed your woody plant work you can write again
or post questions on our Forum.
Hedging for privacy
Right: Virginia juniper or eastern red cedar (Juniperus
virginiana) occurs naturally in windy, open areas such as along
Interstate Highways. Named varieties like 'Spartan' (at right) make
good hedges in sunny, windy spots. Before you plant them, consider
the fact that they are the winter-time host for diseases of
crabapple and hawthorn called cedar-apple rust
and cedar-hawthorn rust. So if crabapples or hawthorns are on a
site, avoid planting Virginia juniper nearby or use its
rust-resistant varieties such as 'Burkii' or
A coworker asked me to recommend an evergreen tree for
his yard. It's on the edge of his property and his neighbors are
close, so he wants an evergreen for privacy. The spot gets full sun
and is very windy during the winter.
He originally had fraser firs but they suffered a lot of
windburn. He also has a couple black spruces, which also got some
winter damage. He is willing to 'baby' the black spruces with a
wind screen and Wilt-pruf for a couple winters if they will be okay
once established (he doesn't want this to be an annual
requirement). Any ideas for a tree I can recommend? - M.G.N.
Isn't it rewarding to be a resource to others? We gardeners do
make a difference.
Given a sunny site and a hankering for evergreens, we
always put Virginia junipers (Juniperus virginiana) on the
top of the list. There are varieties such as 'Manhattan Blue'
and 'Emerald Sentinel' that are wonderful in terms of color and
form, plus most members of this native North American species have
great wind tolerance and respectably fast growth.
If the planting site has some combination
of shade and wind we suggest a tall hedge of twiggy deciduous
plants. That's more sensible than wasting money and time pampering
evergreens. It also eliminates the burden of living with an
imperfectly-suited species, in which we still must face occasional
plant replacement no matter how old and well established the hedge.
Snowmound spirea (old-fashioned Spiraea x Vanhouttei) at 8
feet tall, privet at 10-15 feet and burning bush are all
candidates. They're twiggy enough to be visual barriers even in
winter, amenable to pruning and tolerant of tough growing
conditions including wind.
Allow burning bushes
(Euonymus alatus) to grow into a hedge without pruning and
they will form a wall 8 to 12 feet tall. They are not only a good
privacy screen during the growing season but twiggy enough to block
at least some prying eyes even as the shrubs lose the last of their
leaves and stand bare in winter. Note: Burning
bush has invasive tendencies and has become a problem in some
areas including some New England States. There are native
alternatives, such as chokeberry (the unfortunately named but
beautiful Aronia species).
care: vertical mulching
Vertical mulching is a process that creates vital pathways for
air and moisture to enter the soil and reach plant roots.
Typically, holes about three inches in diameter are drilled into
the ground beneath a tree's branches, creating a grid of holes 12
to 18 inches deep and 18 to 24 inches apart. Compost or sand along
with slow release fertilizer may be placed in the holes so each
contains an airy, rich moisture-retentive mix where roots can grow.
Microorganisms that establish there move laterally from the holes
into surrounding soil, gradually loosening the spaces between.
Fracture the soil with air pressure
Sometimes, compressed air is forced into each hole, in place of
or after adding the back-fill mixture. A stream of air forces the
soil to fracture outward from the hole.
Trees often react to airification as if they have been
fertilized, even if no fertilizer was used. This is because their
roots have gained the benefit of more air and water.
If compost and/or fertilizer was poured into the hole, the air
stream pushes water- and nutrient-bearing organic matter into the
gaps. Then, soil animals move more quickly into the adjacent
Certified arborists can do this for your
Look up tree care firms in an area phone book or arborists
certified through the International Society of Arboriculture
(www.isa-arbor.com). Ask about vertical mulching. Some use
compressed air to clear away soil without drilling, in the form of
an air spade (http://www.youtube.com/watch?v=WTIobRz_2TU) or
air knife (http://www.rhizosphere.co.uk/AirKnife.htm).
Steven spent time in the field with ISA-certified arborist
Bernie Car, who was using an air knife to loosen compacted soil. We
were impressed with Car's work and his ability to explain its why's
and how's. We're also impressed by the wealth of information about
soil and loosening techniques on his company's website http://treeandshrubcare.info/.
Right: Bernie Car, an arborist from Organic Air
(Norwalk, Ohio), uses an air knife to penetrate compacted ground 30
inches deep and then force in air to fracture the soil in all
directions from that hole.
This week in our gardens
Grow with us! This week we will:
Dig and divide
Start digging and dividing perennials that have outgrown their
bounds or have become crowded and sparser of bloom than they once
were. The soil is so receptive when it's warmer than the air for
some portion of each 24 hour period. Even better when at this time
of year that temperature differential exists plus the
soil's charged with rainwater, too. Both conditions are common
in late summer, after the nighttime heat breaks. Then, transplants
"take" like magic.
Cut- or clean up edges on
Re-cut and clear out all the trenched edges between flower beds
and adjacent lawns. Once the nights cool in late summer and rains
begin, lawn grows ferociously and can infiltrate a flower bed or
groundcover across portions of that trench that filled during
summer with moisture-holding material or soil. Spending 30 minutes
edging now can save us an hour of weed extraction next April when
we might be dealing with lawn grass grown two feet into the
Avoid drowning plants now
that late summer rain's come
Empty all the cache pots and saucers under our containers after
a rain, so roots at the bottom of the container won't rot.
stop the lawn-scalpers!
Argh! to the lawn mowing crews who have not had enough to do all
this dry summer from mowing lawns too short as it begins to grow
again. Lawn height should be:
- 2-1/2 to 3 inches tall in spring or fall and 3 to 3-1/2 inches
in summer if it's bluegrass or tall fescue (Iowa State University
Extension tells the straight story on mowing)
- • 2 to 4 inches tall if it's that sturdy buffalo grass used in some Great Plains
- • 1/2 to 3/4 inches tall if it's creeping bentgrass. (Many
Midwesterners hate this stuff as "the invader you can't get rid
of!" but it does have its uses -- which is why it's included
on mowing charts such as this from University of
- • 3/4 to 1 inch tall during spring, summer and fall on what you
find in many Southern yards, a bermudagrass lawn. Mow that bermudagrass up to
1/2 inch taller December through February.
These are the heights each type of grass needs to be healthy and
shade out weed seedlings that try to take hold in open spots. These
also usually have the effect of producing the very best bare-foot
(Take note, J.W., you can print this out and give it to your son
who asked for lawn mowing guidance. Say it's not only height that
matters but that he not take more than 1/3 of the leaf surface off
at any one mowing. So during fall and spring when grass grows
faster, it needs more frequent mowing.).
One other basic mowing guide:
Keep your blades sharp. Mow often and let clips fall to
decompose, rather than mowing infrequently so that clips fall in
clumps to smother remaining grass.
Green thumbs up...
...to people who accurately read the first dewy morning in late
summer as the sign that nighttime heat has broken. (Hereabouts, it
happened just over a week ago, right on schedule in the third week
of August ). The best thing ever is if we jump on that indicator
and begin right away to sow seeds, plant, divide, transplant,
and then receive the greatest blessing a gardener can
receive -- a rainy follow-up. It does often happen at this time of
...to expecting much if you cut back warm season vegetables like
tomatoes, pepper or squash now. The plant will need about three
weeks to form new shoots and flowers. Even if you have that much
time before temperatures will drop below the plant's comfort zone,
and even if those new flowers do set fruit, the remaining growing
season may not be long enough for that fruit to ripen.
Below: Oh the sprawl of it all! At summer's end a tomato,
squash or bean plant may crowd nearby plants that are in the
process of ripening fruit. Or the sprawling past-prime plant may be
shading neighboring cool-season crops just coming into their own.
It's best to remove the offending galoof. Then in the freed-up
space, plant cool-season crops that can come on during fall.
Broccoli, spinach, lettuce and peas are all possibilities.
First published 8-25-07