How to Evaluate Existing Landscape Plants
- nvilu7
- 2 days ago
- 10 min read
Do They Stay or Go?
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In Anchor and Foundation Plants Part 1 and Part 2, I covered how to create a low-maintenance foundation planting from scratch.
I’ve known many homeowners that simply assume that the landscaping they’ve inherited is either untouchable, or that it all has to go.
Neither is true.
It’s your house, your yard, and your choice.
In this post, I’ll cover how to evaluate your home’s current landscaping, how to work with existing landscape plants, and how to decide what stays and what goes.
Step 1. What Kind of Plant is This?
Before you build a landscaping plan, identify the plants that are already growing in your yard.
The easiest way to identify the plants in your yard is to use a plant identification app. There are many available, and some are free. These apps work by analyzing a plant’s leaves, flowers, bark, or fruit, and matching them to a plant in the app’s botanical database.
Depending on the app, you’ll at minimum get the plant’s common name and genus, which you can use to Google more information if the app doesn't provide it.
If you bought your home during the growing season, you can identify your plants immediately. If you’ve moved in when your yard is dormant, you can start the process with the evergreen plants in your yard.
A friend bought a 50-year-old home in an established Portland neighborhood in the depths of winter. One of the home’s selling points was the professionally-designed garden that surrounded the house—which was tough to imagine in January.
When the snow melted, before she started planting, she began exploring her yard.
“There’s a lot planted already,” she told me. “I’m going to wait and see what’s here before I start digging.”
When Spring arrived, her yard came to life, rolling out display after beautiful display of flowers and foliage that lasted through the Fall.
She didn’t change a thing. Instead, she got her green thumb on via a vegetable garden she planted in the back yard.
In contrast, I first saw my house in mid-June, at the height of the growing season, the existing landscape plants included:
an over-pruned japonica blocking a front window,
two boxwoods and some ornamental grasses dying due to their placement in full shade,
seven invasive chinese elms threatening the house’s foundation,
a hawthorn tree in the process of pulling down utility lines,
a horse chestnut tree lifting up the garage floor, and
five-foot mounds of invasive English ivy.
And that was just the front yard.
I decided to remove everything and start from scratch. You can read about how that process started here and here.
Whether you get your plant facts from an app, or another resource, here’s what you need to know to make an informed decision about whether a plant should stay or go:
Plant name
Life cycle (annual, biennial, perennial)
Habit (the plant’s shape, form, and structure, for example, shrub or tree)
Whether the plant is woody or herbaceous
Light and moisture requirements
Preferred soil
Current height and width
Mature height and width
Life span
Plant health (if the app provides it or if you have eyes)
Once you’ve identified your legacy plants, you can start thinking about what to do next.
Step 2. How is This Plant Doing?
Before you build your landscaping plan, assess your plants’ current health, maturity, size, and habit.
Plant Health
The most obvious signs that your plant is sick are leaves that are yellowing, wilting, or dropping. Sick plants can also have structural damage, including drooping stems and stunted growth. Signs of plant pests included damaged leaves, sap or webbing deposits, or visible bugs on stems or leaves.
Determine why the plant is sick and treat the problem immediately to avoid infesting or infecting neighboring plants. I recently had an earwig army attack my dahlias, chewing incessantly on their leaves and flowers. I usually avoid chemical warfare, but the problem got so bad that I (reluctantly) sprayed with Sevin. Problem solved. Dahlias saved.
In many cases a sick plant may have been pruned too aggressively or lack adequate water and fertilizer. If that’s the case, time, TLC, and a pruning ban will bring it back to health. It may take a season or two to see results, but if you like the plant and its placement, you’ll eliminate the need to buy a replacement—and a lot of digging.
A sick plant may just be down to inadequate or too much light. In this scenario, saving the plant means moving it to a more suitable location. In his late sixties, my dad replanted a 5-year-old pear tree that was failing due to a lack of sunlight after a nearby stand of rhododendrons went through a 2-year aggressive growth spurt. It took him a full weekend of digging.
My mom was aghast. But both the pear tree and my dad survived, and the pear tree bore fruit the following season.
If the plants are healthy but you still want them gone, and they are relatively easy to remove, check with your neighbors, friends, or family to see if anyone wants them before you remove them. I once scored six mature peony bushes with deep magenta blooms from a neighbor (he didn’t like them but was otherwise sane) that became a mainstay in my spring cutting garden.
Plant Maturity, Size, and Placement
Once you’ve identified the plants in your yard, it’s easy to determine their age. Simply measure their height and width at the height of the plant’s growing season and compare that with the information you’ve gathered about the plant.
If the plant is a herbaceous perennial and is at its full height and width, it’s three years old or older. If the plant is a woody perennial or shrub, it may take more than three years for the plant to fully mature. Check the internet for specifics.
Why is a plant’s age important? On average, herbaceous perennials can live anywhere from 3 to 20 years. Some perennials, like hydrangeas, can live for up to 50 years; peonies can live up to 100 years. Knowing how long your plant is expected to live may influence whether or not you want to preserve it where it is, move it, or remove it.
Size comes into play depending on where the plant is located in your yard.
Is it intended to be an anchor or foundation plant?
Given its mature height and width, does its current placement in your yard complement your home?
Does it (or will it) block a window or a sight line to your front door?
Does it highlight—or obscure—an architectural feature of your home?
Does it complement the other landscape plants in your front yard?
For more about how anchor and foundation plants can complement and enhance your home, read this post.
Plant Habit
Plant habit is the overall three-dimensional shape of the plant—for example, round, columnar, weeping, and spreading. Do you like the plant’s shape? Does the shape complement the plants around it? Does the shape complement your home and your outdoor living spaces?
I once rented a house that had creeping juniper in the back yard. It was mature, well-established, and so vigorous that it had covered virtually every inch of that back yard, limiting outdoor lounging to the very small patio area. The owner was very proud of it—but I was completely creeped out by a yard covered with dense mats of scaley blue-green foliage.
Step 3. What Plants Am I Willing to Live With?
This is where gardening gets personal.
Now that you’ve identified the plants in your yard, and assessed their health, you can figure out whether or not the plant stays—or goes.
In this step, use Step 2’s criteria with a slightly different spin to tell you whether keeping the plant is worth it—for you.
Plant Health
If your plant is sick, how much time and effort are you willing to expend to make it well?
Is it just planted where it has little to no chance to thrive? If that’s the case, do you have a location in your yard where the plant will do better? Like my dad, are you willing to take the time and energy to dig a new hole, dig the plant up, and move it to a better location?
Finally, if you do restore the plant to full health, will it stay healthy where it’s planted? Is it a plant prima donna, with high maintenance requirements? Are you willing to put the time and effort in to keep it healthy?
Plant Maturity, Size, and Placement
Approximately how old is your plant? Based on its typical lifespan, how many years can you expect the plant to live? Can you count on it being in your landscape for the foreseeable future?
Is the plant at full size? If not, when will it get to full size? Will the plant at its mature size work where it’s planted? Will it complement or obscure your home’s architectural features? Will it block doorways or sight lines? Will it work and play well with the plants around it—or the plants you’d like to plant around it?
In other words, will it earn its keep at mature size, or turn into a troublemaker? Young plants look cute in the pot, but they can turn into behemoths at maturity.
Plant Habit
Do you like your plant’s natural shape? Is its shape appropriate for its location? Does it complement the plants around it? Would your landscape benefit if the plant was carefully pruned?
Some landscape plants, like boxwood, Japanese holly, yew, privet, and some spruces, do very well when carefully pruned. They can provide a structured counterpoint to more freeform plants like hydrangeas, ornamental grasses, and perennials like yarrow and black-eyed susan.
What you need to decide is if you’re willing to commit to regular pruning, or hiring someone to do it.
Do You Like the Plant?
If you’re on the fence about whether or not to keep a plant, ask this:
Do I like this plant enough to care for it for a decade or more?
If the answer is “no”, you know what to do.
The one plant “keeper” in the yard of my most recent home was a single, confused liriope planted in a random spot in my back yard.
I tried to save it by planting it in a raised hydrangea bed, but it didn’t make it, despite my best efforts.
I’m still a little sad about that.
Step 4. Build a Plan Around Your ‘Keeper’ Plants
Once you’ve decided what plants to keep and have removed the rest, you can build a planting plan.
As described in this post, draw two diagrams of your home and the area you want to landscape—one top-down and one at ground level.
Mark the location and mature size dimensions of your “keeper” plants, then plan your landscape garden around them (see this post for the steps).
Place new plants at least 12” away from existing plants’ trunks or centers to help avoid damaging existing plant root systems when you plant.
Planting Around Existing Landscape Plants
Having killed many existing landscape plants by digging too enthusiastically, I’m including some technical detail here to help you avoid Plant Assassin status.
Removing an Old Plant and Planting a New One in its Place
When removing a plant, remove as many of the large and thick roots belonging to the old plant as possible to give your new plant a fighting chance. If the soil is matted with fine root hairs from the old plant, it’s fine to break up that soil and reuse it—the root hairs will break down and feed the soil.
Prepare a large enough hole to accommodate the root ball of the new plant so it fits easily in the hole without hitting old roots. I usually dig out enough space to give the new plant’s root ball two or three extra inches of soil all around.
If you’ve pulled out a very large plant, give the soil a few days to settle before planning anything new.
When you plant the new plant, add some compost to the soil as a welcome-to-the-neighborhood gift.
If the plant you’re replacing is an invasive tree, woody shrub, or thick vine, and you don’t want to deal with it growing back, take extra precautions when removing the original plant. Cut the plant down first, leaving a few inches of the trunk or center stem, then immediately apply a chemical stump killer to the exposed trunk or stem according to the directions on the container. Avoid getting stump killer on the plants you want to keep.
Before buying the stump killer, check its label to make sure it's effective against the plant you want to kill.
After applying the stump killer, you’ll need to wait until the plant is fully dead. Stump killer takes 4 to 12 weeks to kill and soften the wood, and 6 to 12 months to fully break down the stump. Take it from someone who skipped this step—the wait is worth it.
Protect the Roots of Plants You’re Keeping
When digging a hole for a new plants near existing plants, stay least 12” away from existing plants’ main trunk or center. Carefully dig with a hand trowel instead of a spade or shovel to avoid accidently cutting through existing roots. If you encounter roots of existing plants that are larger than 1 1/2” wide, move your new hole over a few inches to avoid destroying the existing roots.
Replacing a Plant in a Grouping
If you removed a sick plant that’s one of a pair or part of a plant grouping, and want to replace that plant, figure out first why the original plant became sick before you potentially send another plant to its death.
While managing the condo property, one of our prized (and absurdly expensive) Hinoki cypress trees bit the dust. After doing some research, I figured out that it had literally drowned due to a misconfigured gutter. After the gutter was fixed, we were able to safely replant.
Once you’re confident that a new plant will do well in the same spot as the old one, your chances of planting success are better with a younger plant.
Older plants have larger root systems that are more prone to transplant shock; if the plant has been in a pot for a long time, the roots may struggle to grow outward. Older plants also recover slower than new plants.
Older plants also cost more.
If you plant a younger plant, it will grow more quickly and catch up with the established plant’s size sooner than you think.
Save the Plants That Work for You and Your Home
Don't evaluate plants by what they are today. Evaluate them by what they'll become—and whether they help you build the garden you actually want.
You don’t have to save every plant in your inherited landscape.
You don’t have to remove every plant, either.
It’s your house, your yard, and your choice.
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