What is the best way to plant shadblow bushes in clay conditions?


I recently purchased two shadblow bushes (Amelanchier canadensis). We have very heavy marine clay on our property. I often amend with lots of compost/rich soil, but recently I am hearing more and more about how too much compost can create conditions where the roots just stay in the soil-rich area. Approximately how much compost/rich soil would you put into the planting hole? In the summer, the marine clay becomes like cement. 


Jonathan Foster, Special Project Assistant

Shadblows are beautiful plants.

This is a bit of a tricky situation. You are absolutely right that, with or without compost amendment, plants that haven’t evolved for seriously compacted soil conditions will tend to keep their roots inside the more hospitable area. I reached out to Brad Libby, superintendent of grounds at UMaine in Orono and someone with a lot of experience with Amelanchier. He is of the opinion that the shadblows might tolerate being planted where you are describing, but they won’t thrive and may be susceptible to pests or pathogens because they aren’t established as well. Shadblow is a reasonably tough plant, but compact soil is a challenge.

Since you’ve already purchased the plants, we see two or three possibilities for you. One is to hire a landscaping company to build a berm large enough for the two specimens, though this is a larger operation than you may be looking for and would require some heavy machinery. Two, you could plant them in very large containers or in constructed raised beds. Though this would limit their spread and overall growth, it would give them more soil room to work with. They would also need more protection from cold weather during establishment, since above ground growing conditions freeze faster than in-ground. And last, you could excavate a larger portion of the yard than the standard planting hole for tree transplants and fill it with native soil before planting.

Just for reference, I will include links to our UMaine Bulletin on Tree Planting, as well as our UMaine fact sheet on Amelanchier canadensis.

I’m sorry not to have an easier answer for you, but I wish you happy gardening, regardless. Good luck!