Wednesday, August 10, 2011

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?


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.


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.


  1. I agree and have been to Northwind many times over the years. I have a layered garden and it takes some time and mistakes to do it successfully. I pretty much have something taking over for plants that are finished blooming. Good article, hopefully it will convince some to try this approach.


  2. Thomas, thanks for another great post. This one is especially timely for me as I've just designed a landscape for the entrance and common areas of a condo association that consists mostly of perennials and grasses, (as well as some shrubs). Your point about client buy-in is SO true. In this case my contact is great and totally bought in, but I just need to make sure everyone else involved in the project is as well. We're going to phase it in over several seasons in order to spread out the costs, and the initial, more time consuming, maintenance. Fingers crossed that in a couple years we'll have one of those lush tapestries that you describe!

  3. Oooooh, lots of great quotables in this post, Thomas!

    "Some days I wonder if I will spend half my career battling the tyranny of low expectations." Love this! Not only does this apply to your profession but to mine as well (teaching).

    "Maintenance is gardening." Seems so obvious....but I never really thought of it that way.

    And then my favorite: "Don't listen to the bush-pushers." Heh-heh, classic.

    -- Mary

  4. Eileen,

    Glad to hear about your experiences. It does take quite a bit of tweaking at first to get it right, but once you get it going, it's remarkabaly stable.

    I'd love to see Northwind. I'm a big fan of Roy Diblik.

  5. Anonymous 1: Best of luck with that planting. I'm currently dealing with two or three really tough clients. I complain sometimes, but their input and investment into the design are making a huge difference in the final product. So far, they've done wonderful maintenance. That relationship makes such a difference in the final project. Happy planting!

    Anonymous 2: I can't take credit for the phrase "bush pusher." I heard it from another designer and thought it was hilarious. Because it's TRUE! I battle bush pushers all the time. Sigh. Thanks for commenting!

  6. I think I want to print a t-shirt that has a big X through the phrase "Bush Pushers." You should copyright that phrase!

  7. I would have been ecstatic to find a landscape designer who urged me to use lots of perennials when I was redoing my back garden. They ALL wanted to give me a combo of shrubs and grasses, no matter how strongly I told them I was an avid gardener. There are lots of perennials that I love, but I am not good at combining them, or creating the drifts that I've seen in lots of other gardens. Now I have beds with individual plants that I love, but that don't really work together as well as I would have liked, because I did the design myself.

  8. Alison,

    Ugh, that's frustrating. You probably know more about perennials than the designers you hired. Perhaps just mass the ones that are doing well in larger groups. Like 12-30. Or even 50. It may give your perennials more legibility and cohesion. Sounds like you did a nice design.

  9. Thomas, I was just at Northwind a weekend ago and picked up another of their Amsonia Northwind Select (not on the market). They say it is a better variety than the others, we'll see! I did a post a couple of months back titled Northwind Perennial Farm, you might enjoy looking at their property.


  10. It was a May 31st post on Northwind.

  11. this collection of design are super and very nice post. new design are very good. all collections are pretty good..and all the best for your future designs..

  12. I spend most of my gardening time on maintenance - and I've spent a lot of my gardening time in this very hot summer making sure that my plants have adequate water. But I notice that hired landscaping maintenance crews hurry through with a mower and a trimmer. Irrigation is inadequate and/or inappropriate and soon even the bushes that have been pushed are dead.

  13. Ginny,

    It has been a brutal summer here. The heat, drought, and humidity make gardening tough. My first year garden looks like he'll now. Lots of work to do this fall.

  14. This is an EXCELLENT post. I'm going to have to go back and read the others in the series, but I know I'm going to be coming back to this. It's refreshing to see these concepts expressed so clearly and concisely--maintenance, watering, drought tolerance, getting plants established, all of it. It's not something you see very often.

  15. Many thanks, Andrew. Maintenance does make all the difference. It is worthy of more discussion. Thomas

  16. Thought-provoking as ever!

    I live and garden in Northern Califirnia, where we literally don't get a single drop of rain all summer. Our hills turn A beautiful golden hue, but that doesn't stop people from wanting gardens that look like they're in Connecticut.

    In addition to maintenance, I think context is very important. I don't think people ask "why" a plant is in their garden, nearly enough. And, yes, I believe that "because I love it" is a valid reason, much of the time. "I dunno," however is not.

  17. Lisa,

    Thanks for the comment. You make a really interesting point about context. I've become a rather myopic East Coaster and forget how different it is in different parts of the country. David, from Desert Dweller, gardens in the desert which makes every argument I make totally irrelevant. Context not only matters, it is everything.

  18. Such a great post. Thanks for talking about these 2 specific things… low-maintenance and drought-tolerant. I have to deal with this in my design practice all the time. People just don't want to do ANY work in their gardens.

    I'm THIS close to not taking clients who say they want a design for low-maintenance. And I ALWAYS tell a prospective client there is no such thing as NO maintenance… also NO watering. And if they think low means no, well, let's get that straight before we sign the contract.

    And MY single reason for not including very many perennials in my designs is that clients are adamant about having LOW-maintenance, and when they hear that, in general, perennials require significantly more maintenance (and often more water), they say NO PERENNIALS. Sigh…

    I also advise my clients to expect 2-3 full years of babying their new plants (including feeding, watering, primping and weeding) before they can expect any semblance of low-maintenance or drought-tolerance.

    So clients, expect WAY more work for the first 2-3 years than you ever thought would be possible… then you can relax a bit.

    Thanks again for the great post.

  19. Thank you for mentioning the Great Dixter in one of your posts. Having just visited it in June (it was my favorite English garden!!!!! sigh!!!!) your mention of Christopher Lloyd's books prompted me to order two of them. Enjoying both very much. - Marty

  20. This series of posts is detailed yet relatable info. for an amateur and even novice like me. I also appreciate that you don’t gloss over the inherent trial and error part of the process.
    I am inspired, really, thank you!

  21. Marry me? Or at the very least, move into my neighborhood so the two of us can start converting. Brilliant on every point. This is going up on my garden coaching site.

  22. I think you are exactly right about the amount of time a 75-100% perennial 1/4 acre property requires. I maintain several such properties and this is how I schedule them. Also very good point about how tilling begets some new weeds to be plucked, and also about the close planting. This was a very persuasive argument for ending the resistance to diverse yards/gardens.

  23. I think you are exactly right about the amount of time a 75-100% perennial 1/4 acre property requires. I maintain several such properties and this is how I schedule them. Also very good point about how tilling begets some new weeds to be plucked, and also about the close planting. This was a very persuasive argument for ending the resistance to diverse yards/gardens.

  24. Great post! Proper landscaping calls for maintenance and your article clearly explains good maintenance tips and processes. As what my friend at Landscaping Columbia SC said, with proper landscaping, right kind of plants will be selected and planted in their optimal growing location, outdoor living spaces are functional and aesthetically pleasing.


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