De-Topiary bushes

Question

The prior owner of my house liked to trim the bushes with straight sides, or make them into gently rounded rectangles. I have some azaleas, a beautiful Sasanqua Camellia, and some others I've yet to identify.

To call his work "topiary" would be an exaggeration, but I'm not sure what else to call it. Well groomed bushes maybe.

In any case, I'd like to see whether I can trim these over time to look more natural. To be a controlled size, but to keep their native, natural shapes.

I'm looking for advice on how to approach this beyond "look at pictures." How do I learn how to properly prune with shape in mind? There are a ton of videos and resources out there about how to prune properly. But none that I've found that approach the plant in a more clinical, educational way, while looking at the characteristics of the plant itself. What I've found is more about the general mechanics.

Answer 1

I'm currently 1 year into a similar project with a long forsythia hedge. I like these guides from This Old House and University of Maryland for the mechanics of pruning, and I usually find shaping inspiration from looking at wild plants on walks or reading bonsai aesthetics and style type literature (when I am shaping, instead of aiming for 'natural').

I'm sure you've seen with your bushes, whenever one is cut it encourages branches to grow below the cut. After a few iterations of trimming to the same point the plant ends up far too dense.

Even if you had the space to just stop trimming and let it grow unmolested over the tangle of old growth, the tangle of old growth inhibits air and sunlight to the plant's detriment.

What I have been doing with my forsythia is systemically thinning the bush every year to remove the old, highly branched sticks and allow new, unbranched, 'natural' branches to replace them. I do not want to remove any more than 1/3 of the plant in a year for its health, so this is a 3 year project. I think the azalea in your picture would especially benefit from this.

To help illustrate the goal, here is a forsythia that has never been trimmed. The branches originate near the bottom, are long, and rarely branch. Totally au naturel.

Here is a forsythia that has been trimmed many times, but not lately. Several passes of trimming it to shape left it unnaturally dense and branching, and the lack of recent trimming let long vines grow out, but only from the boundaries that were once trimmed. The bottom of the plant is too shaded for it to grow out from near the roots, in a 'natural' way.

Answer 2

I agree with Ecnerwal. If you do not trim these plants they will assume their natural shape over time. As to what the best shape is for these plants I have to resort to a favorite but unsatisfactory adage of "It depends". The key factors are:

• hardiness zone
• any microclimate factors
• soil type
• pests and diseases
• the maintenance in terms of pruning, weeding, top dressing that you do
• snow load and annual rain cycle

All of these factors influence how a plant grows and recovers from weather events.

For example, I see a boxwood planted next to your house in picture number three. This plant is commonly used for topiary but this one does not appear to have been shaped to any great extent.

Where I live boxwood is a chancy venture as our winters include whipsaw temperature changes from -30 deg C to +10 Deg C in a day along with the possibility of freezing rain. You don't see tall boxwoods, they don't last long enough. It is better to place them in an area with deep soil with lots of organic matter protected from cold dry north winds and windblown snow drifts.

In Europe I see boxwood pruned into geometric shapes, cats, people and more. They don't have the same problems.

As far as educational assistance my advice is the same: "It depends". The Manual of woody landscape plants by Michael Dirr is one of the finest books describing shrubs in the United States by an extremely well qualified author. However, despite the depth of knowledge, this book is written for the Illinois region. You can derive value if you are a few zones warmer or colder but indications of height, shape and habit are not always reliable outside of those zones.

For example, the buttonbush, Cephalanthus occidentalis, is described as "growing 3' to 6' high, occasionally 10' to 15' shrub (southern part of range)". The specimen I planted in USDA zone 4 was 3' tall for a few years and now easily reaches 16' in what is supposed to be the northern end of its range.

My recommendation for you is to use local knowledge. Drive around and see who is growing what, go to the local nurseries (not Home Depot and their like). Ask them what grows well and how to grow.