Gravel Bed Tree Nursery

Volunteers planted more than two dozen seedlings in the new gravel bed tree nursery.

New to The Fairest Garden in 2023 is a gravel bed tree nursery, an irrigated raised bed filled with pea gravel where bare root trees are placed and cultivated for three to six months.  The purpose of the gravel bed is to increase the tree’s fibrous root system in preparation for planting at a later date.  

This system has been in use at commercial nurseries, municipalities and universities for more than 20 years. There are many communities throughout Minnesota that have built these types of gravel bed systems with great success.

Our bed is a visually appealing trapezoid shape of approximately 100 square feet that is designed to hold between 25-50 trees each year. 

The project is a collaboration between the Washington County Conservation District, Washington County Fair board, Minnesota Water stewards, Climate Action Corps (community forestry program) and the Washington County Master Gardener Volunteer Program Tree Squad.  The grant for this project was generously provided by North Woods and Waters of the St. Croix heritage area. 

Our tree nursery will serve as a demonstration and educational resource in addition to providing new trees throughout Washington County, including:

  • Washington County Fairgrounds, to replace diseased ash trees
  • Sunfish Lake City Park in Lake Elmo, a forest restoration effort through the Sally Manzara Interpretive Nature Center.

Gravel bed benefits

  • Savings: Gravel beds can save the community money through the utilization of bare root stock, which is typically 1/2 the price of containerized trees and 1/4 the price of balled and burlap trees.
  • Species Diversity: Gravel beds can help increase species diversity because there are typically more species available as bare root stock than as containerized or balled & burlapped stock. Greater species diversity can reduce a community’s vulnerability to insects and disease.
  • Flexible Planting Times: Gravel beds allow bare root stock obtained in the spring to be planted throughout the growing season and into the fall. Communities can plant less expensive trees when they have the time and resources.

More information about the benefits of gravel bed tree nurseries comes from the UMN Forestry Outreach & Research Nursery & Lab at:  (https://trees.umn.edu/outreach/gravel-beds)

Plant List

A American linden – tilia americana

B autumn blaze maple – acer x freemanii

C bur oak – quercus macrocarpa

D chestnut crabapple – malus domestica

E hackberry – celtis occidentalis

Garden Map

Map of the five species of trees in the gravel bed tree nursery at the washington county fairgrounds.

Photo Gallery

  • Building the frame for the gravel bed tree nursery at the Washington County Fairgrounds.
    First step: Building the frame, using AC2 4”x4” Critical Structure Cedar Tone Pressure Treated Timbers. The bed is a trapezoid shape with sides 10’ x8’ x11’ x12’ and 17.5” high giving 100 square feet of bed area. Rebar was added every 2 feet to the outside of the frame for structural support.
  • Gravel delivery day! Several cubic yards of gravel filled the bed.
    Gravel delivery day! Seven tons (4.6 cubic yards) of bulk river rock (3/8”) was used. The gravel depth is 15 inches, the recommended depth is between12-18”.
  • Master gardener volunteer Blair Johnson holds a group of seedlings
    Master Gardener Volunteer Blair Johnson holds 29 Bur Oak bare root trees that were 5-12” tall at the time of planting.
  • Four varieties of trees were selected to fill the gravel bed tree nursery: hackberry, chestnut crabapple, American linden, and autumn blaze maple.
    Sixty trees were planted, and five species were selected: hackberry, crabapple, maple, linden and bur oak (not pictured).
  • Each tree was nestled into the gravel bed, aligned next to an irrigation hose.
    Each tree was nestled into the gravel bed, aligned next to an irrigation hose.
  • Volunteers planted more than 2 dozen trees in the new gravel bed tree nursery.
    Volunteers planted 60 trees in the 100 square foot gravel bed. Once the trees develop a stronger root structure they will be transplanted.
  • The trees will spend their summer at the fairgrounds before being transplanted at their final home in the woods along the St Croix River watershed.
    The trees will spend their summer at the fairgrounds before being transplanted to their final homes within Washington County.