You Won't Believe These Crazy Rhododendron Roots

Sometimes, plants survive in spite of our treating them poorly. Like this Rhododendron.

I was asked recently to do what I could to save a roughly 20-year-old Rhododendron, which had grown to about 5 feet. It stood atop a site where a heating oil storage tank had to be removed, so the Rhododendron had to come out before the backhoe arrived. I hate to see beautiful, mature shrubs destroyed, so I gladly took on this project.

The challenges of removing a Rhododendron planted 20 years ago

With the help of two other men, we dug around the shrub with shovels to loosen the roots. In every previous rehab of rhododendrons and azaleas this size, I’ve had no problems simply digging them out and transplanting them elsewhere. Unlike deep-rooting shrubs such as yews, rhododendrons’ and azaleas’ roots mostly run relatively close to the surface, usually within the top 12 inches of soil. They also have a vertical root structure from the center of the shrub which plunges the same depth or deeper, but which is fairly easy to free.

Poor-quality clay soil can act like concrete

Within the first three inches of digging, we discovered that the rhododendron was surrounded by what appeared to be construction backfill – hard clay mixed with lots of small stones and rocks. And when I say hard, I mean concrete-like. The soil was compacted like none I’d ever seen and was impenetrable with shovels. We worked at it for 2 hours, but the shrubs wouldn’t move and we made little progress.

Granted, our clay soil here in Pennsylvania can pose a challenge when planting or transplanting trees or shrubs. Once you get down below the top six or eight inches of soil, you’ll sometimes encounter red clay as hard and dense as brick.

High-quality clay soil feeds a plant for many years

The thing about clay soil is that it’s very fertile. It can feed plants for many years if the plants’ roots can penetrate it. That’s why it’s imperative that organic matter like compost and sometimes peat moss is mixed regularly into garden beds built on clay. The organic material separates the clay molecules, creating fissures that roots and water can penetrate. And of course, compost replaces nutrients the plant has used.

What happens when a plant is planted incorrectly

When a shrub is dropped into a hole dug in dense clay, and the same clay is backfilled into the hole, the roots may struggle to find water and nutrients after a few seasons. If the clay is very dense, the roots may only grow in a circular manner within the clay bowl they were planted in because it’s impossible for them to move beyond it.

Adding to the problem is when the plant is fertilized heavily season after season. This restricts root growth because the plant doesn’t need to find nutrients beyond the hole it’s planted in. Hence, the roots never develop beyond the hole, and just keep wrapping around themselves and growing within the clay bowl.

Once the plant exhausts the nutrition within the surrounding clay and fertilizing schedules change or are eliminated, the plant suffers enormous stress and may die. That’s why when planting trees, arborvitae, rhododendrons, or any perennial, organic amendments and soil conditioning are the difference between a plant just surviving or thriving.

But back to the job at hand.

A backhoe succeeded where we failed.

Eventually, we gave up trying to dig out the rhododendron by hand – if 3 grown men can’t dig out 1 plant, it probably can’t be done without machinery. Fortunately, a skilled backhoe operator removed both plants intact and with a minimum of damage.

When I looked at the mountain of clay the backhoe excavated, I couldn’t spot a single worm, beetle, or any insect whatsoever – not one. And that is a terrible sign. It tells me that the soil is virtually lifeless or at least the soil food web was completely inactive. This was probably the result of the dense clay soil being treated with chemicals for years and zero soil amendments, which also explained the soil compaction.

The roots of the rhododendron were encased in a cement-like ball of clay. I went to work on the clay around the roots with a handheld cultivator and freed up all the root area possible. What I found was startling.

Freeing the rhododendron roots from the clay

The roots of the rhododendron had barely penetrated vertically. The plant adapted to its condition by creating a thick carpet of fine roots across the top 3-4 inches of soil. The roots literally overlapped themselves – when they reached a few inches past the shrub’s drip line, they started back in the direction they came from, growing over the top of the other roots. This added to the plant’s problems, as the overlapping roots created a tangle so dense that little water or anything else could penetrate it. Undoubtedly, this rhododendron was surviving completely on the topmost surface roots.

After I freed as much root mass as possible, we dug new holes, and the shrubs were planted back in their original positions. Compost was added to the soil surface around the root area and the damaged parts of the plant were then pruned out. So far, the shrubs are doing fine and will hopefully survive many more years with proper care.

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