Back to Basics: Planting Trees & Shrubs

Get Creative in the Garden with Bryn — By on February 1, 2009 11:49 AM

How hard could it be to plant a tree?  Don’t you just dig a hole and drop it in?  Well, judging from the number of poorly planted trees I see everywhere, it must be harder than most people realize.  Actually, I wouldn’t describe it as difficult at all-it just takes a little forethought and understanding about how trees grow.
 
First, before you dig that hole, before you even bring a tree home, observe your site.  Note how much sun you get and at what time of day (afternoon sun is hotter than morning sun).  How fast does the soil drain?  Is it frequently wet?  What type of soil do you have-sand, clay, silt, loam?  Is there anything that may create a microclimate (an area with slightly different conditions than the surrounding area)-a west wall that radiates heat, a dryer vent that periodically produces warm moist air, an AC unit that creates a drying breeze, etc?  How much space do you have?  Remember that your plant will grow (it’s amazing how often this is forgotten).  Are there overhead wires?  Neighboring plants or pathways?  In addition to the site restrictions, you may want to add functional or aesthetic requirements.  Do you want shade? Flowers? Edible fruits or nuts? Fall colors?
 
Armed with this knowledge, you are now ready to choose your new tree.  There are a number of resources to assist with this.  If you don’t have any books of your own, try the local library.  A local arboretum or garden may also have a reference library you can use, as well as knowledgeable staff to ask.  Your local Cooperative Extension may be able to help or they should be able to put you in touch with a Master Gardeners group.  Your favorite nursery may have knowledgeable staff and the plants themselves should have tags with basic information.  There are also a number of websites that may be of help.  Try the search programs on the websites for The Missouri Botanical Garden, the Ladybird Johnson Wildflower Center, the Arbor Day Foundation, and the Urban Forest Ecosystem Institute as a starting point.  You may be able to find a list of recommended trees for your state or region online, as well.  One word of caution: don’t use a catalog or other piece of marketing as your only source of information.  While they can be helpful, they probably won’t give you the whole picture.  Remember, putting the right plant in the right place is half the battle.
 
Assume you were struck with the urge to plant a tree in the middle of winter.  Can you do that?  Well, if your ground hasn’t frozen solid and you can actually find a tree to plant at this time of year, you might be able to get away with it.  However, the best time to plant is in the spring or fall.  In the temperate parts of the world, these are times of moderate temperatures and plentiful rainfall.  I would be inclined to say fall is the best time to plant because soil temperature lags behind air temperature.  This will encourage root growth but discourage top growth-just what you want in a newly planted tree.  (Besides, nurseries tend to have sales in the fall because they don’t want to have to overwinter their stock!)  Planting in the summer can be stressful because of both the heat and lack of rain.  Why fight it?
 
Now that you’ve picked your tree, found a nice healthy one with a good form (need help? try here, here or here), and gotten it home, you are now ready to dig that hole.  The hole should be no deeper than the height of the soil around the roots and two times wider.  Find the root flare on the tree.  This is the point where the trunk flares out to form the roots.  If you have a balled and burlapped (B&B) tree, the root flare will likely be visible as soon as you remove the burlap at the top of the root ball, because the tree was field-grown and just recently dug.  If you have a container-grown tree, the root flare may unfortunately be below the soil line, as the tree was likely repotted in larger containers a number of time before you bought it.  If you can’t see the root flare, remove soil until you find it.  The root flare gives you the true planting depth for your tree.  Think about it: roots are designed to be below the soil and the trunk is designed to be above ground.  Placing the trunk below ground is just as likely to cause harm as leaving the root above ground.
 
Now, to place the tree in the hole:  If you have a container-grown tree, pull gently but firmly on the trunk while holding the container to remove it from the pot.  If this doesn’t work, tip the tree on its side and apply pressure to the sides of the pot, rolling it to access all sides, and then try pulling it out again.  Container-grown trees frequently have visible roots that have been circling just inside of the pot.  Gently tease them loose.  If you don’t, they will remain stuck in that position.  As the roots grow, they will literally choke the tree and eventually kill it.  You want to encourage them to grow out into the new surrounding soil.  If you have a B&B tree, place the whole thing in the hole.  If the burlap is biodegradable, remove the top 1/3 of burlap and twine.  The rest can remain to give some support to the root ball while you are planting-it will eventually disintegrate.  The same is true if the tree is in a wire basket-just remove the top third.  If the “burlap” is actually a plastic mesh or some other non-biodegradable material, you must remove it all.  B&B trees shouldn’t have circling roots to worry about because they were likely recently dug.
 
With the tree in the hole, double check to make sure that the root flare is just above the finished soil line.  Make sure the tree isn’t leaning-this may be easiest to do if you have a partner who can step back and look as you hold or make adjustments.  (If the branches have been tied up, cut them free first.)  Also make sure that the tree is rotated how you want it.  Now start filling the hole up again with the soil you originally removed.  It was once believed that you should add fertilizer and “good” soil as you fill in the hole, but it was discovered that frequently the new growth on the roots would want to stay in this rich area and wouldn’t spread out into the existing soil.  Firmly press down on the soil as you backfill to remove large pockets of air.  (Some air below ground is necessary, too much is not good.)  Make sure that you haven’t mounded up soil against the trunk.
 
Build a small berm (mound of soil) just past the edge of the hole to help hold water all around the tree (or on the downhill side if you are on a slope).  Cover the whole area with 2-4″ of mulch.  I sometimes add a thin layer of compost on top of the soil before adding the mulch.  Watering will slowly percolate the nutrients from the compost down into the soil.  Make sure the mulch is not touching the trunk.  Burying the root flare in mulch is similar to burying it in soil-it allows pests shelter from which to attack the trunk and also creates a moist environment which may lead to fungal problems.  Please, please don’t build “mulch volcanoes”-large mounds of mulch with a tree erupting out of the middle.  I know you see them everywhere, but they were built by landscaping crews whose only training was to copy what they see around them.  These trees unfortunately tend to be short-lived. 
 
Finally, deeply water the entire excavated area.  The tree will need about 10 gallons of water weekly for the entire first growing season.  Since it takes a while for this much water to soak in, the simplest way to manage this is to buy a Treegator® irrigation bag (those green bags you sometimes see on new trees) or similar product.  You can also create your own by drilling small holes near the bottom of a 5 gallon bucket.
 
Staking used to be recommended for all new trees.  Now it is only recommended if the tree is located in a particularly windy area or if the tree might need some protection (say near a playfield or to protect it from car doors or carts).  If you do stake the tree, allow some freedom of movement-it will cause a stronger trunk and root system to be created.  Also remember to use wide, soft material against the trunk.  Wires will quickly cut into the trunk.  Remember to remove the stakes and ties within one year.  If you don’t, the tie may girdle or otherwise permanently damage the tree.
 
Another planting recommendation, which has since been revised, relates to pruning.  It used to be recommended that pruning be done at planting time under the belief that you have just removed and/or stressed some of the tree’s roots and therefore you should proportionally remove leaves and branches.  It has since been learned that the more leaves a tree has, the more energy it can produce and the faster it can recover.  The only pruning that should be done at the time of planting is to remove any broken branches or suckers.  Corrective or aesthetic pruning can wait until the tree has been in the ground for a year and become established.
 
Note:  All of these comments can be applied to planting shrubs as well as trees.
 
Happy gardening!
 
Bryn Richard is a licensed landscape architect with a strong interest in sustainable design.  She can be reached at Bryn@BlueTrillium.net and welcomes your questions and suggestions for further articles.

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