Watering Newly Planted Trees And Shrubs | UMN Extension

How much to water

• When watering newly planted trees, apply 1-1.5 gallons per inch of stem caliper at each watering (see table).
• When watering newly planted shrubs, apply a volume of water that is one-quarter to one-third of the volume of the container that the shrub was purchased in.
• As roots grow and spread, water volume will need to be increased.

Where to water

• Apply water directly over the root zone.
• Be sure to keep the backfill soil in the planting hole moist. This encourages the roots to expand beyond the root ball into the backfill soil.
• Tree roots grow approximately 18 inches per year in Minnesota, so expand the watering area accordingly.
• Create a water reservoir by making a circular mound of soil 3 to 4 inches high around the plant at the edge of the root zone.
• Use a slow trickle of water to fill the reservoir to allow water to slowly infiltrate into and around the root zone.
  • Consider using a Treegator® bag, which holds 14-15 gallons of water and releases a slow trickle of water over 5-9 hours.

Mulching trees and shrubs maximizes water uptake

When trees and shrubs are planted into turf, competition for nutrients, water, and space occurs below ground. Turf often outcompetes woody plant roots because its dense, fibrous root system prevents trees and shrubs from producing new roots for water and nutrient uptake in the top few inches of soil. As a result, woody plant establishment and growth are slower in areas with turf above the roots than in properly mulched areas.

To optimize root production, water uptake, and establishment of newly planted trees and shrubs:

1. Eliminate turf and weeds from the base of the plant out to several feet beyond the drip line.
2. Apply a 3-inch layer of organic mulch around newly planted trees and shrubs in a circle that extends several feet beyond the tree or shrub drip line.
3. Leave the root flare bare, and be sure mulch does not come into contact with the trunk.

Mulching around newly planted trees and shrubs with organic materials (wood chips, pine needles, etc.) has several advantages over bare soil cultivation.

Mulch:

• Decreases water evaporation from soil.
• Serves as a sponge that reduces runoff around plants growing in heavy clay soils or on sloped sites.
• Helps control weed growth.
• Insulates soil and buffers extreme summer and winter soil temperatures.
• Reduces soil compaction from mowing equipment.
• Prevents damage to stems and trunks by lawn mowers and string trimmers.
• Improves soil health by increasing microbial activity, nutrient- and water-holding capacity, soil pore spaces, and air penetration as it decomposes.

Don’t add more than a 3-inch layer of mulch. Deep mulch applications may:

• Prevent movement of rain or irrigation water into the root zone of newly planted trees and shrubs. This can result in roots drying out.
• Lead to new root growth in the mulch that often results in forming stem-girdling roots.
• Reduce oxygen levels around roots and cause root suffocation.
• Keep poorly drained soils too wet, which favors root rot development.