Hill Gardens of Maine - Tree Roots Get It All!

Click on "Teddy" for Fred's Amazing Journey Back In Time

Answers to your gardening questions

Five-part article series on flower-drying starts here

Eight-part article series on vegetable gardening starts here

Asian Lily Beetles

A new scourge in New England ornamental and veggie gardens.

Japanese Beetles

They can be controlled...but not the way you think.

An effective Deer Fence!

Only three feet tall...and no deer has ever jumped over it!

Why won't my flowers grow? (Tree Roots!)
by Fred Davis, Hill Gardens, Palermo, Maine (To view other articles, click Archives)

Welcome through Fred’s Garden Gate! Here’s a question that’s popped up at least a half-dozen times this season: “I’ve got a really nice spot; I’ve spent loads of money on what I thought were healthy plants; I fertilize and water until I’m nearly blue in the face. Yet, after all that, they hardly even survive, let alone bloom and get as big as they’re supposed to. And now I can barely get a shovel in the ground. What in the world is wrong?”

Questions like this usually send me into my “Sherlock Holmes” mode and I ask a series of questions to try to get a fair picture of what’s going on. Eventually, using that tack, solutions to the puzzle quickly fall into place. Most of the time. Sometimes, as in the case of one of the six, I felt the need to actually eye-ball the garden...at which point the cause popped out and almost hit me in the nose.

Picture this: nicely designed and arranged planting along the driveway to a two or three year old new home. Perfect light exposure for the perennial varieties planted. Neatly trimmed trees and shrubs nearby and mixed in with the perennials. Well maintained. She’d originally spaded bags of peatmoss and store-bought compost into what the contractor left behind as fill. It should have worked perfectly.

Problems like hers are more common than you might expect. And the problem in five out of six was roots. Not from the flowers and small shrubs, but from the trees. Here’s the deal: trees are greedy; they get really hungry and thirsty. Dramatically improve the soil around and nearby, and their feeder roots swoop in to grab all they can...elbowing everything else out of the way in the process. They can do that in a single season!

Worse: four of the six gardens were almost completely surrounded by compacted driveway gravel, patio paving stones or buildings. Trees are smart enough to know that it’s more advantageous to focus all their food-gathering efforts on improved soil instead of packed gravel and concrete. Path of least resistance sort of thing. And they do that with dizzying speed and proficiency.

So, the end result: feeder roots to support nearby trees created a tight and suffocating mat so dense that it would’ve taken someone with raw, bull-headed determination and extraordinary strength to drive a spade more than an inch or two into the soil. Healthy trees; sorely malnourished and shriveled up flowers.

Masses of feeder roots from nearby trees overwhelm a hosta crown. Click photo to enlarge.

Unfortunately, there wasn’t much to be done with those four “island” or “peninsula” gardens short of taking a chain saw to most of the trees. Not an option. Neither was enough root-pruning to have any real impact since most of the surrounding trees had all their feeder roots inside the bed border. Root-pruning, in those cases, would mean eventual tree death. All that could be done was to be more aggressive with the watering and feeding, or abandon the garden altogether.

One shovelful of tree feeder roots...
a single season worth of growth! Click photo to enlarge.

Of the remaining two gardens, the problem with one was soil compaction from lack of cultivation, weed competition, grossly unhealthy soil pH (powerfully acidic...since it had never been tested or limed) and, because of accompanying stress, sap-sucking insect infestation. I recommended that he enroll in the next Master Gardener class through the Extension.

The sixth troubled garden, fortunately, had enough space around it so that judicious root-pruning could be accomplished without seriously challenging tree health. In this case, once the job was done, all returned to near-normal.

Tree feeder-root-pruning is relatively simple: get someone to grind or file a rough-sharp edge on your shovel, then slice straight down as deep as possible all the way around the flower (or vegetable) garden—safe as long as you don’t sever more than about a fourth of the tree’s feeders. Do that once every season immediately after spring cleanup and just before annual feeding and liming, and once-struggling plants will likely take off and make you jump back.

Our Local Weather

Find your State and County Cooperative Extension Office

Which Maine Hardiness Zone Do I Live In? (.pdf)