Establishing urban tree canopy using planting stock other than traditional balled & burlapped (B&B) and containerized nursery stock is of increasing interest in the City of Saint Paul. Seedlings are an available option. However, seedlings are vulnerable to animal browse. Placing tree tubes around seedlings can protect them from browse, as well as act like a greenhouse to create a microclimate to maximize growth. An open hillside at the new Trout Brook Nature Preserve presents itself as an excellent opportunity to monitor the effects of different tube types, tube colors, and tube heights on bur oak growth, establishment and survivability. Preliminary studies like this date back to the 1990s.
In May, 2014, one hundred and forty-four bur oak (Quercus macrocarpa) seedlings were planted into a completely randomized, two way factorial design. The seedlings were two years old at planting, and were grown in air pruning propagation trays at the University of Minnesota. Six different types of grow tubes of different heights and brands are being used in the study. Three different types of soil amendments were used at planting. Data collection, beginning in fall 2014 will consist of the following variables: mortality - years 1, 3 and 5, tree height - years 1, 3 and 5, stem taper - year 5, stem caliper year 5. After the initial five year period, data will be collected at five year intervals and will consist of the same variables collected during the first five years.