Planting Edmonds is a column written by and for local gardeners

Just about anyone with pruners can make a plant look nice today. But how will it grow after those cuts — will it grow back weird, aggressive or break the natural form?

Students in the Edmonds College Horticulture Program combine classroom learning with practical, hands-on training. Pruning, a class offered every winter quarter and occasionally in summers, dives into the way plants grow and how pruning can impact that growth.

The class covers techniques for maintaining healthy and beautiful plants, melding art and science. Students get practical experience pruning all kinds of plants in gardens around the region — at private home gardens, public parks and botanical gardens.

Rhody Ridge Arboretum in Bothell has been a teaching site for Edmonds College students for a number of years. Two pruning classes each winter bring their classes here for full four-hour sessions.

During the class in these photos, Keith Kelley from Kelley Garden Service demonstrated pruning techniques for these older bushes. He is very active in helping to preserve the giant collection in the Arboretum.

The pruning students pruned in nine “stations” over the four-hour class. Most of the stations were rhododendrons, but they all had different needs. Some students were able to remove a higher “dose” (or percent of leaf volume removed) from plants because the plants were more vigorous and could handle that without injury.

Other plants needed just a light cleanup, removing dead wood and only a couple branches. Removing more than is needed can mean the plant may not recover. Or it could mean the plant will put a lot of energy into new growth that is growing straight up, breaking from the desired form. A light touch is important on valuable older shrubs. 

Another project is to prune off branches that brush against the ground. That can be a way to reduce the damage caused by root weevil.

Plants have individual needs, just like people or pets. Even within the same species, they’ll have different needs — and different goals based on their location.

Learning the fundamentals

Horticulture students at Edmonds College can specialize in landscape design, greenhouse and nursery management, sustainable landscape management or urban agriculture. Across all disciplines, horticulture students learn the foundations of horticultural science — how plants grow, how to identify them and soil science, as well as pests and diseases.

Pruning students learn fundamentals that they can transfer across different types of plants: mounding shrubs, cane-growing shrubs, trees, conifers and vines. There are a few plants that are in virtually every garden around here, and rhododendrons are high on that list.

Students coming out of our program are almost certainly going to be pruning a rhododendron in a client’s garden, in their own or in their parents’. Rhodies are forgiving plants, but you do have to use a thoughtful approach to make sure you’re enhancing their natural branching pattern. We work at Rhody Ridge near the end of the quarter, because we want the students to have a little more experience before tackling such a precious collection of old plants.

It might seem odd to prune the rhododendrons now just as they are about to bloom. Partly this is when our class takes place, but really it isn’t bad for the rhododendrons to prune them now (in late winter/early spring).

The main reason you might wait is because you want to preserve flower buds, but if you’re pruning mindfully and only taking a little off, you’ll still have lots of flowers in spring. Some plants genuinely don’t do well if you prune them in winter, whether because they can get fungal infections more readily, or because it causes awkward regrowth. Happily, that isn’t the case with these plants.

One of my goals as an instructor is to get students to think about not just how the plant will look when we’re done pruning today but about how this will look in three months or three years. Plants respond in specific and consistent ways to pruning cuts. In class, we talk about the science of what’s going on at the cellular level, how plants grow, how they compartmentalize wounds, where we’re likely to see new branches emerge and what the plant will look like.

The students learn to think it through and execute a vision that will preserve the beauty of eachplant’s branching structure.

About Rhody Ridge

Maintaining a garden like Rhody Ridge requires a long vision. Many of the plants here have been in the ground since 1954, when Fir and Merlin Butler started their home garden on this site. Fir and Merlin were big rhododendron fans and were involved in the local horticulture scene. They wanted to create a garden that felt like a forest. Planted on a hillside, the garden does provide a real hike for nature lovers.

The Arboretum relies on volunteers and contractors to maintain its 11 acres, having no regular staff. Diana Riley and her husband Patrick have been the longtime volunteer stewards of the park and the Rhody Ridge Foundation. The partnership with Edmonds College is a great help in maintaining the plants and benefits the students as well – it isn’t every day they get to prune mature rhododendrons.

After 70-some years, many of the original rhododendrons have gotten quite large! Some are spreading into pathways or crowding other plants. This provides a great learning ground for our Edmonds College students to get hands-on experience pruning rhododendrons and other shrubs.

Rhody Ridge isn’t just a practice site for pruning; other classes also come here. I bring my Plant ID classes here in spring and fall. It’s a beautiful and peaceful setting, with a surprisingly large collection of different plants for such a tucked-away location. Students always love coming here — it feels homey and comfortable like your own private garden but it’s also big enough that you can meander and get a little lost if you want.

We have one of the best regions to grow Rhododendrons in the world. You can find short, tall, evergreen, deciduous, plants with big and small leaves, and flowers in all colors (except maybe true blue — but some of the purples are a close approximation!)

Rhody Ridge Arboretum will be coming into its peak floral display in the next month, so now is a great time to go visit. The Arboretum is at 17427 Clover Road in Bothell. It is free and open daily from 7 a.m. to dusk.

Cynthia Welte is a horticulture professor at Edmonds College. She has worked in horticulture for over 25 years, in nurseries, as a horticulturist in public gardens and in botanical garden administration. She teaches, is on the board of the Northwest Horticultural Society, leads tours at the Arboretum, and gardens at her home in Beacon Hill, Seattle.