Beyond the Border 4: Maintaining Perennials to Last

This is the final post in a series I’ve been doing on how to design perennials and grasses in landscape settings. By landscape settings, I’m referring to non-garden sites, including public parks, commercial and institutional landscapes, or even residential sites larger than a single bed. Throughout this series, I’ve made the claim that herbaceous plants—the most dynamic and expressive plants a designer can use—ought to be used more often in our built landscapes.

My last post talked about how to select plants for these low maintenance sites. This post will focus on the single greatest reason people avoid using perennials and grasses: uncertainty about how they should be maintained. Almost every time I suggest using herbaceous plants in landscape settings, here’s what I hear: perennial plantings are fussy and high maintenance; clients don’t understand them and won’t take care of them; in a year from now, it will all be a weedy mess; use more shrubs or lawn.

It kills me. Some days I wonder if I will spend half my career battling the tyranny of low expectations.

The reason it kills me is because I know from experience how low maintenance perennials and grasses can actually be once established. I know that clients can have a lasting, beautiful, and sustainable planting in a fraction of the time it takes to maintain a lawn.

To understand how to maintain perennials and grasses, one must first understand a few basic concepts:

1. “Low Maintenance”: Those are perhaps the two most misunderstood words in the landscape industry. In today’s landscape industry, they are code words for “do nothing” or “I don’t have to care.” Landscape professionals promise this to clients, and clients expect this as a result. The low maintenance landscape is the holy grail of the industry. Plant breeders breed plants for fewer inputs, retail nurseries only keep inventory of proven plants, and contractors and designers stick close to their small palette of tried and true plants. It is a self-perpetuating cycle.

Of course, this is a mythology. Without maintenance, almost any designed landscape will fall apart. The cruel irony of maintenance is that to reap the benefits of a low maintenance landscape, one must first heavily maintain it until it is established.

2. “Once Established”: This is perhaps the most critical concept to developing a planting that lasts. An established plant is one that is fully rooted, adapted, and growing in the native soil. For perennials and grasses, the establishment period is typically two to three growing seasons from the time of installation. An established planting requires dramatically less water, less weeding, and less overall care than a new planting.

3. Client Buy-In: Without a doubt, the most important thing you can do is to come to make the owner aware of the maintenance before you plant. When I meet with clients, I describe in detail the weekly requirements of a new planting. I try to fit the landscape to what they can afford to maintain. But if you can invest them in the process, the results will be remarkable. Every good relationship I’ve had with a client, the landscape thrives. Every mediocre relationship produces mediocre landscapes.

Ok, what about the specifics? Getting plants to establishment requires three basic tasks: watering, weeding, and re-planting. Each of these concepts is relatively simple. The question is: how often and how much?

Watering

Plants need water. One would think this is a non-controversial statement, but more and more often, I find clients—particularly those interested in green design—surprised that they have to water. “Isn’t it drought tolerant?” “Isn’t watering wasteful?” Or my favorite: “Can’t you just specify me some plants that don’t need to be watered?”

Even drought tolerant plants need water. “Drought tolerant” is another phrase that makes me antsy. Like “low maintenance,” “drought tolerant” is code for I-don’t-need-to-ever-water-it. Though some plants like it dry, no plant likes drought. Even if a plant survives drought, they rarely thrive. Regular watering is a signal to a plant that it’s ok to grow and flower, whereas drought is a signal to cut back.

S. Aitken

By all means, choose plants adapted to your region’s average rainfall. But until the plant is established, count on regular watering, at least one inch of water a week, perhaps two during the heat of summer. Why? Typically, nursery plants are potted in a lightweight potting medium. In a nursery they get watered daily, and fertilized quite often. So when they are planted, they must adapt from growing in a soilless bark medium with heavy external inputs, to heavy soils with little external inputs. This is quite a transition. Watering allows the plant to make this transition. I also believe in fertilizing young plants during the early growing season with an organic, nitrogen-rich fertilizer. Do not fertilize during the heat of summer or during a prolonged dry-spell.

What about irrigation? I am a fan of any system that makes it easier to take care of a planting. Drip irrigation is the most efficient form, but pop-ups are often easier to maintain. If you decide not to irrigate, consider temporary irrigation. Just make sure that the plants get watered regularly until they are established.

Weeding

Newly disturbed soils must be weeded. The good thing about perennials and grasses is that they grow so quickly, often shading or crowding out weeds even within the first growing season. Plant spacing makes a difference in weed control. If the client can afford it, I try to space perennials and grasses 18” on center (average—this depends on the plant). Twenty-four inches on center works well for most landscape perennials, but this spacing will require more initial weeding. How much time should you budget for weeding? Roy Diblik, co-owner of Northwind Perennial Farm and author of the book Small Perennial Gardens: The Know Maintenance Approach. Diblik states that his gardens require an average of 15 to 20 minutes of maintenance every 10 to 14 days. That’s considerably less time than it takes to mow most lawns. Here’s my conversion rate for larger landscapes. For every quarter acre of planting, assume a three man crew for two hours at least three times a growing season. You can scale that ratio up or down depending upon the size of the landscape.

Re-Planting & Transplanting

Begonia grandis (foreground) did not come back in this garden, so the Hakonechloa was expanded to fill in the hole

This is the one that surprises most people. Successful planting installations require occasional re-plantings. I typically estimate that 5-10% of the total planting will need to be replanted after the first year. No matter how well you know your plants, no matter how well you studied the soil and the exposure, some replanting is typically necessary. This is most important one year after the initial installation. Some replanting at the second and third anniversaries will help ensure that lush, full plantings continue.

A Different Mindset

Maintenance is not a bad word. Maintenance is gardening, a personal investment into the landscape. The initial planting is just the beginning of the story, not the end of it.

This series is dedicated to the proposition that our built landscapes can be more than they currently are. Perennials and grasses are largely absent from our public, commercial, and—to a large extent—even our residential landscapes. These plants are the most dynamic, most ephemeral, and most expressive plants available. They have the ability to transform stiff public spaces into lush, living landscapes.

As a culture, we’ve learned to maintain ridiculous expanses of lawn. We’ve developed special machines that cost hundreds of dollars (mowers, edgers, trimmers) and expect that every landscape must have one. We expect these landscapes to be maintained every week or two during the growing season. When you think about it, we’ve chosen one of the highest maintenance landscapes possible—the lawn-- as our national landscape.

Don’t listen to the bush-pushers, those jaded contractors or city officials who tell you that shrubs and lawn are the only things that can be maintained. We can have richly layered tapestries of perennials and grasses as a part of our everyday landscapes. But it will require a different mindset. And it will require different maintenance approaches. But the end product is worth it.