Brian E. Jackson

Assistant Professor, Ornamental Horticulture

Research Publications Substrates Lab Links
 
 

In the past 5 years, over 30 species of woody shrubs and trees have been grown in pine tree substrate.  Additional fertilizer is required for most species (2-4 additional pounds per cubic yard) to have comparable growth to plants grown in a traditional pine bark substrate.  More information concerning fertilizer requirements can be found in the publications on this site. Click on the images to see a larger view.

woody plants

woody plants

woody plants

woody plants

woody plants woody plants

Long term (2 years) production of shrubs in 5-gallon containers and trees in 15-gallon containers has also been conducted.  Even during the long-term production, no significant shrinkage of the rootballs occurred with the 100% pine tree substrate.  Based on out research, it is shown the pine tree substrate does not decompose (shrink) any more than pine bark during long-term production. Yes, the wood is decomposing, but the plant root growth (often better in wood substrates than in pine bark) fills the voids created by the slowly decomposing wood particles, and prevents significant shrinkage. 

woody plants woody plants
woody plants woody plants

During our growth trials over the past 5 years, we also conducted studies to test how plants grew when stepped-up from small containers to larger containers with pine tree substrate.  Arborvitae liners were grown in 1 gallon containers in pine tree substrate or pine bark.  These 1 gallons were stepped up to 3-gallons and then the following year to 15-gallons.  After growing in the 15-gallon containers the plants were planted in the landscape for further post-transplant evaluations.  No growth differences were seen been plants grown in pine tree substrate or pine bark. 

Root Ball

The rootballs of several plants from 3-gallon containers. These photos show the healthy root systems and the intact rootballs of plants grown in both pine tree substrate and/or pine bark.

Root balls

The picture below on the left is pine tree substrate that was removed from a container that was on an outdoor nursery pad under irrigation (with fertilizer) for 2 years.  You can see that the color has changed (from yellow to dark brown) compared to the fresh wood substrate on the right, but the wood particles are still visible and the substrate still has physical properties suitable for plant growth.

aged substrate fresh substrate