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PLANTING TREES? DIG A 'BASIN,' NOT A PIT
In the weeks ahead many of you will be planting trees and shrubs in your yards. I have no way of knowing what percentage of tree problems are connected to improper planting method, but I suspect it's a high number.
It's particularly important that we eastern Carver County gardeners understand proper planting techniques, since our trees and shrubs often have to spend their lives growing in heavy clay soil.
I believe the number one tree-planting error many of us make is digging a deep, straight-sided hole without adequate diameter for the root ball. This approach generally results in roots that never penetrate the vertical walls of the hole and instead spend years growing in circles. These plants never develop the root structure to support vigorous growth. It's as though the roots had to spend their lives growing inside a hard-sided bucket.
Horticulturists at the University of Delaware recently completed a tree-planting study that redesigns the planting-hole recommendations to promote rapid root regeneration in the surrounding soil.
A planting hole, they suggest, should be dug three times the diameter of the root ball with sloping sides. This hole should have a backfill volume of up to 400% of root ball volume.
A sloped planting hole - shaped like a giant washbasin or bowl - redirects root tips up to the surface where more oxygen is available. The hole should not be dug any deeper than the depth of the root ball. The surface of the backfilled area should be covered permanently with 4-6 inches of wood chips or mulch.
The Delaware study also demonstrated that amendments to the back-filled soil (e.g., peat or other organic materials) do not improve tree growth or health. The only benefit of soil amendments, the study found, was in water uptake and retention after watering during dry periods. In other words, the hole can be refilled around the root ball with black loam soil or even clay soil, as long as it doesn't contain clumps.
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Someone asked me late in March if it's the right time for applying crabgrass preventive. The answer is NO! Crabgrass is a warm-season annual grass that grows best in the heat of mid-summer. Crabgrass over-winters as seed, comes up
about mid-May or later, and is killed by fall frosts. Best time for applying a pre-emergence weed killer is during the first two weeks of May.
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Contrary to popular opinion, spring is not the best time to fertilize lawns. A recent University of Minnesota study tracked the lawn maintenance practices of 21 homeowners. They found that homeowners applied the wrong amounts of fertilizers and at the wrong time of the year.
The two most important application times for lawn fertilizer are September and again in late October. A spring application is necessary only if nitrogen levels are below recommended levels.
The researchers also found that phosphorus - contained in many lawn fertilizer preparations - is not needed because adequate levels exist in most soils. Adding extra phosphorus when it's not needed creates the potential for runoff and can be detrimental to the environment.
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Here's some plant variety names to look for this spring when you're selecting plants. The 1998 All-American winners are impatiens 'Victorian Rose,' Swiss chard 'Bright Lights,' lemon basil 'Sweet Dani' and petunia 'Prism Sunshine.'
The Perennial Plant of the Year for 1998 is Echinacea purpurea 'Magnus' (purple coneflower). It boasts strong carmine color with wide flat (not reflexed) ray flowers. Purple coneflower is easy to grow and prefers full sun. It combines well with Liatris (gayfeather), Perovskia (Russian sage) and ornamental grasses such as feather reedgrass and little bluestem.
Top scorers in 1997 annual flower trials include:
Ageratum: 'Blue Hawaii'
Geranium: "Pink Orbit,' 'Red Elite,' and 'Violet Orbit'
Impatiens: 'Accent Deep Pink,' 'Accent Salmon,' 'Cajun Red,' and 'Victorian Rose'
Petunia: 'Celebrity Chiffon Morn,' 'Horizon Exp. Yellow' and 'Purple Wave'
Rudbeckia: 'Indian Summer'
Salvia 'Firecracker Red,' 'Red Vista,' 'Reference,' 'Salsa Scarlet,' 'Signum,' and 'Victoria Blue'
Zinnia: 'Star White,' 'Star Gold,' 'Star Orange,' and 'Crystal White.'
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PUTTING DOWN ROOTS:
A Delightful Blend of
Gardening Wisdom, Wit
and Whimsy
$10 + $2 for shipping
by Cliff Johnson |
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