This article is Sponsored in part by:
Best trees have wide base
At a conference one day, during a discussion about proper
planting depth for trees, we said we use the trunk flare as a
guide. That is, we know a tree's at the correct depth when we can
see that area where the trunk widens as it joins the roots.
"What about oaks?" One person asked. "Oaks don't have
flares."
Oaks certainly do have flare (at right, a red oak). If you have
an oak without a visible flare, one that looks like a stovepipe at
ground level, it's too deep. Start digging around that trunk to
lower the grade or lift and re-set the tree if it's a new
planting.
Train your gardener's eye to look for flare on all trees. There
may be exceptional species (palm trees, for instance), and flare
may be less pronounced when a tree is young, but there is indeed a
flare on every tree species we know that's likely to be in northern
landscapes.
See tree flares that are works of art and how the flare develops
in
What's Coming Up Issue #136.
How that oak became so big:
Tree planting basics
(You'll probably want more
photos...)
Summary of planting! For determining growth rate, there's
help in What's
Coming Up50.
Tree
planting steps
One: Dig a planting hole.
Two: Check planting depth by
locating the tree's root flare.
Three: Position the tree in the
hole.
Four: Fill the bottom third of the
hole.
Five: Remove all wrappings from the
top part of the ball.
Six: Finish filling the
hole.
Seven: Stake the tree only if
necessary.
Eight: Create a watering
well.
Nine: Mulch the tree's root zone.
Ten: Follow up with water for at
least a year.
One: Dig a planting
hole.
Dig a shallow, broad hole, only as deep as the root ball but
much wider.
("Okay I got it. Jump me to step
two.")
(Take me back to the list of
ten steps.)
Right: We measure the ball against our spade to figure how
deep and wide to dig. Always much wider than the ball, never
deeper.
The most important and numerous roots a tree grows are in the
top five- to fifteen inches of soil and grow horizontally, not
down. The faster a tree's roots can spread out of the original root
ball and regain their pre-transplant rate (elongating twelve to 24
inches per year), the more self sufficient the tree becomes and the
better its long term outlook. So remove competing weeds and loosen
the soil fifteen inches deep at least two feet beyond all sides of
the root ball.
Digging the hole, misconception number 1:
Don't believe that, "Soil should be loosened under as well
as around the root ball."
People thought root systems were mirror images of tree branches,
until researchers excavated and examined thousands of tree root
systems on behalf of organizations such as the International
Society of Arboriculture and the USDA's Forestry Service. What they
found is that very few roots grow down from the original root ball,
or from the lower third of the root ball. So loosening the soil
under a root ball is unnecessary.
Digging the hole, misconception number 2:
Don't believe that, "Subsoil must be loosened to improve
drainage."
Loosening the subsoil is only useful if you can break through to
free-draining layers. In that case, loosen subsoil everywhere
except where the ball will sit. If there is no better drainage to
be obtained directly below the tree, place a tile to drain the base
of a hole or trench the perimeter of the bottom of the planting
hole so the root ball will sit on a "tee" above any excess
water.
Avoid loosening below the ball so the tree will not settle below
grade. Read on, for why this is to be avoided..
Two: Check
planting depth by locating the tree's root flare.
The flare is where the roots spread from the trunk base.
If you cannot see the root flare at the top of the root ball or
pot, you may have to remove some soil from the top of the root
ball.
Right, we peeled back the burlap and removed almost 4
inches of extra soil that had been added over the roots and against
the trunk. No, it didn't hurt the tree to do this, it helped. We
can say that not only with the confidence we had on planting it 10
years ago, but the satisfaction we feel in seeing it today, large
and healthy.
Wadded burlap atop a root ball or extra soil at a pot's surface
may mislead you, so that you plant a tree too deep. Even a few
inches of extra soil over the roots can slow their growth and stunt
the tree, and any soil against the base of the trunk can slowly but
surely kill the tree.
("Okay I got it. Jump me to step
three.")
(Take me back to the list of
ten steps.)
Check planting depth, misconception:
Don't believe that, "Always plant a woody plant 'at the same
level it was growing in the pot.'"
This is no longer a safe guideline. Even if
there were not other reasons to peel back and remove burlap from a
root ball, it would be essential to do so to check for the root
flare. This may be the newest of the news in this article.
Too-deep planting has become an epidemic. For years, we blamed
this problem on those who planted trees, saying, "You set it too
deep, or let it settle!" We know now we were wrong in many cases. A
new horticultural term has been coined and joint committees of tree
producers, landscape architects and landscape contractors have
convened to address the primary problem, trees "harvested too
deep."
How a too-deep epidemic happens
Trees are planted too deep throughout the course of
production.
- At the seedling or grafted-liner stage, a six-inch sprig may be
planted a bit deep to hide the crook of the graft union or to
satisfy an untrained planter's notion that deeper planting will
make the tiny twig more stable.
- Then as it's moved from starter pot to larger containers or to
a field, or balled and burlapped from a field and placed in a
container for easy handling, it may be set an inch or more too deep
at each step.
- At the end of the process a tree may have several to many
inches of soil over its roots, burying the trunk. They have been
"harvested too deep."
Given the normal wide, shallow profile of a tree's roots,
too-deep production planting means that trees lose even more roots
than they should when dug from a field. (See diagram.) (Diagram's
not here yet! See "Sponsorship, above!)
Avoid buying "too deep"
In recognition of this disastrous situation, the most savvy tree
buyers now carry a metal skewer with them as they choose trees in a
nursery. The buyer inserts the skewer vertically into a root ball
to determine how much soil there is above that plant's big,
main-order flare roots. If the skewer penetrates to two inches
before hitting wood, that may be judged unfortunate but common and
correctable. If the skewer goes deeper before touching roots, the
buyer will reject the tree.
Three:
Position the tree in the hole.
Now recheck the depth of your planting hole. It should be no
deeper than the distance between the root flare and the bottom of
the root ball. If you were misled by a tree that was harvested
deep, add soil at the bottom of the hole and pack it firmly. Then
set the tree a bit high to allow for settling.
To straighten the tree, look at it from several angles. Correct
any lean by using a long-handled shovel to tip the ball, then pack
soil to maintain the new position.
("Okay I got it. Jump me to step
four.")
(Take me back to the list of
ten steps.)
Don't use the trunk as a lever to move a tree
A tree's limbs, trunk and roots are not designed to support the
weight of the soil in its root mass. Lifting a potted or B&B
tree by its trunk or branches or using them as a lever to
reposition a root ball can break roots within the ball and injure
the cambium where you gripped it. Damage may show right away or may
not be apparent until years later. So avoid it altogether. Lift a
tree by its root ball, never by the trunk.
Positioning for depth, misconception:
Don't believe that, "Trees should be planted high, to be
above wet soil and poor drainage."
It is true that in compacted urban soils a tree has a better
chance of survival if 1/3 of the root ball is above grade. But
where drainage is adequate the tree will grow better and live
longer if planted at ground level.
Don't let your tree be one of the increasing number that survive
a warranty period above grade only to die soon after of root loss
or toppling. Plant high only in poorly drained areas where you
cannot correct that situation. When you must plant high, create a
raised bed at least four feet wider in diameter than the tree's
root ball to insulate the exposed shoulders of the root ball and
provide a place for roots to grow.
Four: Fill the bottom
third of the hole.
Gently but firmly pack soil around the bottom third of the root
ball. This will keep the tree from shifting.
Five: Remove all
wrappings from the top part of the ball.
If the tree is balled and burlapped (B&B), cut and remove
all string, burlap and wire from around the trunk and top third of
the root ball. Use bolt cutters and heavy scissors.
Be careful not to damage the trunk or roots in the process of
removing cords, clipping wire or slicing burlap.
("Okay I got it. Jump me to step
six.")
(Take me back to the list of
ten steps.)
Several important reasons to "bare the ball:"
- First, drought is the primary cause of new tree failure and
exposed burlap acts as a wick, drying out the soil next to the root
ball.
- Second, encircling string and wire can girdle and kill the
trunk and roots. It may be easy to see how a tight circle can kill
a trunk but even a wide wire basket or burlap-cinching plastic cord
can kill the tree in time. Those losses are often worst, coming as
the tree finally fills its place in a landscape.
- Third, roots that bend when they meet burlap or wire, remain
bent and often become girdling roots. Wire and cloth openings that
are smaller than a fully grown flare root -- perhaps several inches
in diameter -- may admit young roots only to girdle them
later.
Remove all wrappings, misconception number 1:
Don't believe that, "We mustn't disturb the root
ball."
It is true that root balls may crumble if unwrapped and
manhandled, but it is a risk we must take to address the deep
harvesting problem. A Washington State DNR tree planting brochure
says it best, "Don't disturb the root ball is a myth. The truth is
most root balls need corrective pruning prior to planting."
Corrections may be removal of soil or pruning circling roots and
adventitious roots above the flare.
Remove all wrappings, misconception number 2:
Don't believe that: "It's not necessary. Burlap and cord
rots quickly and wire cages rust away."
Since burlap and twine rot quickly under irrigation in a
nursery, everyone figured they would act that same way in the
landscape. When wire cages came into use, it was assumed they would
rust. Tree planters embraced these notions, glad they could thus
avoid some steps in the planting process. Then they maintained that
position despite lacking research to support either claim. Time and
an overwhelming number of problems associated with decades-old
twine, long-lasting new-age burlap and cages have now overturned
both assumptions.
Above: We dig the hole wide enough to fit our arms around
the ball as we lower the tree into the hole and set it straight.
There also must be enough space to do what Janet's doing now --
reaching in alongside the rootball with wire cutters and knife to
remove the wire and the burlap that would otherwise impede root
spread.
Six:
Finish filling the hole.
Fill the remainder of the hole, adding soil a few inches at a
time and settling it with water to avoid large air pockets
("Okay I got it. Jump me to step seven.")
(Take me back to the list of
ten steps.)
Filling the hole, misconception number 1:
Don't believe that, "Get rid of the excavated soil and
replace it with good soil and peat."
This is not necessary. A tree will eventually outgrow any hole
you dig. The single most important amendment you can add to that
eventually huge root zone is air, by loosening the soil in an
expanding circle as the tree grows.
Not only unnecessary but root of later problems
Some studies revealed problems from amending the backfill. Roots
circled within the enriched soil rather than growing beyond the
edges of the planting hole, limiting the root system and creating
girdling roots. Soil amended with organic matter settled, exposing
the sides of the root ball and allowing roots there to dry out.
Based on these studies we are sometimes warned against amending the
backfill.
Some experts doubt the relevance of those test results.
Researchers contributing to the book, The Landscape Below
Ground explain, "Those studies on sandy agricultural soils
provide little insight into urban situations with compacted clayey
soils."
We add compost to backfill around trees in poor, hard packed
soil to keep that soil from settling back into an airless mass,
with excellent results.
Filling the hole, misconception number 2:
Don't believe that, "Add some fertilizer or rooting hormone
as you backfill."
Studies show no benefit to fertilization at planting and some
danger of encouraging shoot growth at the expense of root growth.
So fertilizer is not recommended until a tree has been in place for
a year. As for rooting hormones, vitamins and beneficial fungi,
although they have been around since the 1940's, the jury is still
out on whether they have any positive effect. Trees treated with
these products fail to show any significant positive response as
compared to untreated controls. So if you want to save a few
dollars, skip the B vitamin, microrrhizae and seaweed
solutions.
Seven:
Stake the tree only if necessary.
Well-grown trees with root balls that meet nursery standards do
not need any support in most home landscape situations. Studies
have shown that trees establish more quickly, develop a stronger
trunk and have better roots if they are not staked.
("Okay I got it. Jump me to step
eight.")
(Take me back to the list of
ten steps.)
Sometimes reason to stake for a year
However, you may decide to stake where reckless lawn mowing,
vandals or extreme winds are concerns. To ward off mowers and weed
whips, you might circle the tree with stakes. Deter vandals or
avoid wind damage by flanking the tree with stakes and using wide
strap-like material between stakes and the trunk to prevent extreme
movement. Remove stakes and ties after one year.
A new staking system for very windy or severely sloping sites is
put in place when the root ball has been unwrapped but before the
hole is filled. The ball itself is strapped with wide,
biodegradable belts that lap over its shoulders of and attach to
stakes driven into the bottom of the planting hole.
Stake the tree, misconception number 1:
Don't believe that, "Stakes should immobilize the
tree."
The editors of the 1957 Taylor Guide to Gardening had no idea of
the long-term consequences of their advice to "...stretch three
tight guy wires fastened to stakes..." to support a new tree.
Research has tied staking to a number of problems, starting with
the fact that a tree which could not sway as it grows develops a
weak trunk, prone to snapping as the tree matures.
Eight:
Create a watering well.
Use soil from outside the planting hole to construct a one inch
high levee around that spot. You should be able to pour a bucket of
water at the base of the tree and see it remain within the root
zone long enough to be absorbed into the ball and the soil around
it.
("Okay I got it. Jump me to step
nine.")
(Take me back to the list of
ten steps.)
Keeping the ball moist is the most important step in
establishing a new tree, but is more difficult to do than you may
imagine. The root ball has a greater density of roots and is often
of a different consistency than the surrounding soil, so it dries
out more quickly than the ground around it. A watering well insures
that the ball is wetted, rather than bypassed as water runs down
its slope to the surrounding soil.
Nine: Mulch the
tree's root zone.
Blanket the planting area with two to four inches of
biodegradable mulch, but leave the area within one or two inches of
the tree trunk bare of mulch.
("Okay I got it. Jump me to step
ten.")
(Take me back to the list of
ten steps.)
Mulch acts as a blanket to hold moisture, shield roots from
temperature extremes, and reduce competition from grass and weeds.
Research has shown that fine roots, those responsible for most of
the water uptake in trees, can be fifteen times more numerous under
mulch than in bare soil, and trees that are mulched may have twice
the leaf density of those in beds without mulch.
Mulch, misconception:
Don't believe that: "If some mulch is good, a lot is
better."
Volcano mulching is a killer. Mulch deeper than four inches may
reduce oxygen and moisture in the soil, stressing and killing
roots. Mulch that rests against the tree trunk, like excess soil,
causes the bark to decay and eventually kills the tree.
Ten: Follow up with
water for a full year.
Water whenever the soil in the root ball or the surrounding soil
feels warm and dry. Continue watering into the fall and resume
watering the next spring as soon as buds swell on trees in the
area.
In one good growing season, roots can reach out to cover an area
nine times as large as the original root ball. From that area the
tree can draw water to grow for two weeks, a great improvement over
the two day supply it had in the original root ball.
(Take me back to the list of ten
steps.)
Follow up with water, misconception:
Don't believe that: "It's enough to water once a
week."
Root balls filled with fine roots dry out far more quickly than
garden soil. Container-grown root masses dry even more rapidly than
B&B plants. For several weeks after planting, container grown
plants may need water every day and B&B plants every two to
three days. You decide when to water by feeling the soil in the
original root ball.
One last misconception:
Don't believe that, "Trees should be pruned at planting
time."
It was once standard to prune back hard at planting time to
'bring the tree's top into balance with the roots.' The 1961
Better Homes and Gardens New Garden Book prescribed "...in
addition to pruning out broken and damaged branches, prune out 1/3
of all top growth." This has been proven to be both unnecessary and
harmful.
Unnecessary, because for a field-grown, B&B tree there is no
way short of killing the tree to reduce its top as much as its
roots were cut. Field grown trees routinely leave 90% of their root
system in the field! As for a container grown plant, we know that
if we can keep its root system moist it may "take" without losing a
single leaf.
Some trees do lose limbs or leaves after planting, but
studies have shown we cannot predict which portions will be lost.
So prune sparingly at planting time, just to remove broken or
damaged branches. Then wait for the tree to show you what, if
anything, it must lose. Begin any other pruning only after the tree
has grown on site for a full year.
(Take me back to the list of ten steps.)
Where are
the all tree-planting photos and diagrams?
Sorry! See really needs
images, below. We will add more illustrations and merge
this page with other tree planting basics as we continue to post
articles from our archives. (As we type this, it's our second
update.) Until then please refer to articles on this topic that
we've illustrated and alread made available:
- Our magazine Trees, available on our
Market. Three articles cover tree planting basics, deciding
what size tree to buy, and planting-related issues from mulching to
staking and watering.
-
What's Coming Up issue #33 in which planting a tree in
memory of our dear friend, arborist Dan
Kurkowski, very appropriately yielded the best all-in-one photo of
proper tree planting ever.
- Or, forgive us, the text-only article above.
This article is Sponosered in part by:
Given a Sponsor's help, we could retrieve from file the rest of
the photos that support the text above, format them and assemble
the pieces here.
During the months since we launched this website, we've burned
the candle at three ends to write new articles, post from our
library, and keep up our gardening work that supports this. Yet
w
It's been almost one year. We still have 70% of the total
library left to post. And we're stretched to pay the bills for all
this.
Your Sponsorship could help keep this site going. When you
Sponsor you can specify what topics you'd like to see added, or
which of those we've already posted should carry your Sponsor
message.