Poorly Transplanted Spruce Trees

November-December 2010

“HI JEN, HERE IS A PHOTO of a blue spruce where the needles are turning brown and dropping on the inner branches.”

“Dear Jen, I have a newly planted blue spruce and the needles are turning yellow, brown and falling off.”

“Hello Jen, Please provide some assistance with a potential problem with our Colorado spruce… early needle drop on internal old growth.”

Now I haven’t crunched the numbers, but I’d be willing to bet that nearly a third of the calls I get about troubled trees in the landscape pertain to Colorado spruce (Picea pungens). Most horticultural references describe Colorado spruce to be hardy, fairly drought tolerant (once established) and adaptable to a wide variety of soils but preferring rich, moist soil. I have seen this species growing in the nursery on a wide variety of soils types and soil pHs. It seems to do quite well on clay loams, especially where the fields are tile drained. It can also thrive on sandy loams that have organic matter in them. In the nursery, these trees are grown from young transplants with a full root system and they are managed to support optimum plant growth.

So why is it that we have so much trouble transplanting them out in the landscape? Well, first of all they are one of the top-selling conifers in the industry so the probability of encountering them is that much greater. But it’s also about the way we handle and plant them; there are a lot of factors that can affect transplanting success. The tree can be desiccated by wind and high temperatures during shipping and at the job site. If the tree is planted too deep and/or mulched too heavily, the lower stem is constantly wet and it rots, leading to decline and death in 2-5 years. If the tree is planted too high, the root ball may dry out and the tree is more susceptible to blow over. If the twine is not removed from the lower stem at the time of planting, the tree will be girdled and die within a few years. Sadly, this happens more often than you would think.

The planting site may not be prepared adequately and the hole may not be wide enough to accommodate rapid root growth into the surrounding soil. This is especially important on sites with heavy clay loam. Even the foot and machinery traffic we generate when preparing the planting site can lead to significant soil compaction around the hole. Roots will have a difficult time growing out into the heavy clay and may be forced to circle around and around inside the soil in the original transplant hole.

Some landscapers say that a tree grown on a clay soil at the nursery will have an easier time transplanting into a clay-loam landscape. But if the soil surrounding the root ball is heavy clay with poor drainage, that tree will likely still struggle to establish its root system out into that soil. By widening and amending the planting hole to accommodate a more gradual change to the original landscape soil, the tree can establish itself more quickly and develop anchoring roots that are so important to long term survival. Mixing in soil amendments like sand and sometimes even bark will help improve drainage of heavy clay soils. Roots of groundcover-type plants, such as deeply-rooted grasses will also help create channels where water and air can move through the heavy soil. Some landscapers are using liquid fertilizer soil injection systems to artificially create channels in heavy clay soils around struggling trees.

It probably wouldn’t surprise you to find out that transplanting into heavy clay or compacted soil with poor drainage is the most common factor linking these sad tree stories together. Heavy, poorly draining soils can hold too much water – and not enough air. Roots need air and without it, they will die. By digging out a hole to plant a tree, you disrupt the natural channels for air and water. Any water that falls on the ground will follow the path of least resistance; it will travel right into that tree pit. Without adequate soil drainage, the tree pit will quickly fill up with water and the water will sit there. When you remember how much rain we have had in 2008, 2009 and 2010, you can imagine how poor soil drainage might explain some of our transplanting issues. Then when you find out that the homeowner has been irrigating for 45 minutes every other day, you might actually cringe.

The other factor in play here is insufficient root system in the root ball. When a spruce tree is grown in a field nursery, it is transplanted about 2-3 times during its production cycle. In addition, the tree undergoes root pruning in the field at least every other year. These two practices encourage more fibrous roots to grow in the soil nearest the tree, the soil that will be harvested as the root ball. These two practices can mean the difference between life and death in the landscape. The greater percentage of roots in the root ball will provide more resources to help the tree overcome the stress of transplanting. When you are purchasing field grown trees, you may want to inquire about transplanting and root pruning practices. As with most things, you get what you pay for. A field grown tree that has never been transplanted or root pruned is going to have a tougher time establishing in the landscape.

Contact Information

This column is written by Jen Llewellyn, Ontario Ministry of Agriculture and Food and Rural Affairs (OMAFRA) Nursery Crops Specialist

Email any questions you have directly to Jen and we'll publish her response.

P: 519-824-4120 ext. 52671 • F: 519-767-0755

OMAF website: http://www.omafra.gov.on.ca/scripts/english/crops/agriphone/index.asp

Nursery Landscape Agriphone: 1-888-290-4441

Our mission is to enhance and promote the care and benefit of trees for present and future generations in Ontario through education, research and awareness.