Kathy Zuzek, University of Minnesota Extension Educator
Spring is here bringing planting season. Early spring between the time that the ground thaws but before bud break is one of two optimal times during the year for planting bare-root trees and shrubs.
What is a bare-root plant?http://www.youtube.com/watch?v=LLYI6MVJqsg
Advantages and Disadvantages of Bare-Root Plants
Bare-root stock offer several advantages:
- Bare-root plants are usually ½ to 2/3 of the cost of containerized or balled & burlapped plants because bare-root plants are easier to handle, store, and ship.
- Longer root lengths are possible on bare-root plants since weight of the soilless root ball is minimal.
- The entire root system of a bare-root plant can be inspected so deformed, circling, and broken roots can be detected and corrected or removed.
- Appropriate planting depth is easy to gauge because the root system is visible.
- Because there is no soil around the root zone, there is none of the dramatic change in soil interface between the rootball and native soil that can hinder plant establishment.
There are also disadvantages to planting bare-root trees and shrubs:
- The range of plant sizes and plant types in bare-root plants is smaller. Bare-root trees are usually a 2" caliper or less, because larger sizes do not transplant well as bare-root plants. Caliper is the diameter of a tree stem, measured 6" above the ground. If that stem diameter at 6" above the ground is greater than 4", move up the stem another 6" and measure the diameter at 12" above the ground for your caliper measurement. Evergreens are not sold as bare-root plants unless they are very small seedlings.
- Bare-root plants should be dormant when planted so there are seasonal restraints to planting.
- Early spring between the time that the ground thaws but before bud break is one time to plant bare-root plants. Autumn is a second good time to plant bare-root stock. Soil temperatures and moisture levels encourage active root growth at these times of year and lower air temperatures and dormant crowns help to minimize transplant shock.
- Careful handling of bare-root stock is important. The exposed root system cannot be allowed to dry out during handling, transporting, or planting.
How to Plant Bare-Root Woody Plants
Keep the roots moist and protected from wind and sun. If you can't plant immediately, place the plant in a cool, shaded, sheltered location and cover the roots with moist straw, hay, damp burlap, or loose moist soil.
Bare-root plants lose up to 95% of their roots when they are undercut and removed from a nursery. After transplanting it is hard for this reduced root system to absorb enough water to meet the needs of the plant. Until the root system grows and reestablishes to its normal size, a newly planted tree or shrub often experiences transplant shock, which is primarily drought stress. You should plant and care for your bare-root plant in a way that provides the optimal environment for root growth and replacement during the first few years after transplanting.
Optimal planting and care include:
- A planting hole only as deep as your root system's height. This prevents settling and all of the stresses caused by deep planting.
- A planting hole at least 2-3 times as wide as the root ball that allows for rapid root growth through the backfill soil before hitting growth-slowing compacted soil outside of the hole.
- A planting hole with sides that slope towards the base of the hole. The majority of a woody plant's roots grow in the top foot of soil and a planting hole with sloping sides encourages new roots to grow horizontally and towards surface soils.
- A planting hole backfilled with the original soil. Adding amendments to improve soil quality doesn't help and sometimes hurts by causing poor water drainage in the planting hole. Your time is better spent digging a wider planting hole than amending soil.
- Adequate watering until the plant replaces missing roots. Water is usually the most limiting factor affecting plant growth after transplanting. Because your bare-root plant has lost the majority of its root system, it relies heavily on water in the root ball through the first growing season. For a bare-root tree with a caliper of 2" or less that is planted on a well-drained site, apply 1 to 1 1/2 gallons of water per inch of stem caliper daily during the first week after planting, then every other day for 1-2 months , and weekly after that until the plant is established.
Establishment Tips for Bare-Root Woody PlantsHow long does it take for a bare-root tree to become reestablished? That depends on genetics, environmental factors, and tree size. A good rule of thumb for Minnesota though is to assume that it will take 1 ½ years of time for each inch of stem caliper. So a 1" caliper tree will replaces its roots in 1 ½ years while a 2" caliper tree will take 3 years.
- A 3" layer of organic mulch instead of turf under the canopy of your tree or shrub. Organic mulch eliminates the competition for water and nutrients that sets up between roots of grass and woody plants, suppresses weeds, retains soil moisture, buffers soil temperatures, protects stems from mechanical injury, and adds organic matter to the soil. Make sure that your mulch is pulled back a few inches from stems to eliminate direct contact.
- No pruning except to eliminate problems and to ensure good branch structure. Remove diseased, dead, broken, crowded, and crossing or rubbing branches or to encourage a central leader, to eliminate narrow branch crotches with included bark, or to remove basal sprouts on trees. Leaving as much of the crown intact as possible maximizes photosynthate production that can be used to promote root and trunk diameter growth.
- No quick-release nitrogen fertilizers in the planting hole. Direct contact between quick-release fertilizer and roots will burn the roots. Slow-release and organic fertilizers can be incorporated into the backfill soil. See the trees, shrubs, and fruits section of http://www.extension.umn.edu/distribution/horticulture/DG1731.html for more information.
- Staking if your new tree is densely-crowned and planted on sites with lots of wind exposure. Attach stakes with flexible web belting or any other strips of wide, soft, but strong materials low on the tree trunk. This will prevent movement of the lower trunk and the root system, but allow for movement and resulting strengthening in the top of the tree. Staking may be necessary for 1-3 years while roots are growing and beginning to stabilize the tree. Check the attachment points of the webbing or strips on the stem every 3 to 6 months and loosen if necessary. For more information see: http://www.forestry.umn.edu/extension/urban_com/StakeandGuyBestMaterialsandTechniques.html. We are sorry, this link is no longer available.
- Trunk protection for smooth-barked species such as crabapples, lindens, and maple will prevent injury from sunscald. Apply paper tree wraps or white wraps made from synthetic material from the bottom up in an overlapping pattern until the first major branch is reached. The wrap can be secured with duct tape or expandable plastic tape. Apply tree wraps in late October or early November and remove in March or early April.