Mulch Zones for Three Kinds of Garden

By Kenton Seth:

Above: Cactus and desert plants are archetypical of the gravel zone. PHOTOS: Kenton Seth

The Lazy Greedy Gardeners says...

THERE ARE ONLY THREE KINDS OF GARDEN

An insatiable lust for plants, and enough gardens to contain them, led me down the unintentional path of having numerous gardens across Colorado. It’s my job, literally, to maintain them. Year after year of certain tasks –chopping down dry grasses in spring, pulling weeds – and a growing resentment of myself for not allotting enough time to do it all, became a spicy environment of mild stress that forced me to figure it out. It compelled me to design gardens that are more sane to maintain. There is a dark side to “low-maintenance” gardening in that it enables less interaction with nature. I believe in maintenance that is good exercise but not back-breaking, and not so pivotal that a garden plummets to disaster when a timely chore isn’t done. I also believe in work that has traction and is not needlessly hard. What if each of us could garden another thousand square feet with the energy we use now? Would our medians and verges be gardens, too? Would it allow us higher quality moments than breezing through it in our effort to get it all done?

Above: Under trees is great use of a woodchip and chop-and-drop area where plants completely hide the organic mulch. This garden has not had any twigs, leaves, or other plant debris removed in over ten years, absorbing every inch of it since then.

What I’ve landed upon is a dogma of categorizing space by what sort of plants and mulch are in it. Three essential types of planted space have arisen and solidified, and their edges can figuratively and literally blur into one another. But at their hearts, they have an essential spirit of seasonality and the relationship of the plant to the space that is unique to that category. I think of them as the mineral, organic, and living-mulch categories. I also find that each category tends to have its special suite of patterns, plants, and spirit. I want to present the essential personality of each: best use, biggest strengths, biggest weaknesses, and the natural system and biome embodied therein. After all, these categories were designed by nature.

Mineral Mulch (Desert)

The gravel top-dressed garden is the backbone of classic Colorado xeriscapes and best home to so many of our favorite plants like those from PlantSelect. It is perhaps the most “gardeny” of the categories, lending itself to the addition, subtraction, and shepherding of new plants. Generally, there is a little or a lot of space between plants, which allows the best exposition of individual plant forms, their silhouettes, their textures. Rock Alpine Gardens as well as Crevice Gardens fit this category.

When plants are trimmed or weeds pulled, these wastes are removed in an effort to keep the soil lean and low in organic matter. Thus, the mineral zone is not as appropriate under trees or shrubs. Their continual leaf-drop is at odds with the spirit of the mineral mulch garden.

The “armored surface” of the gravel garden is ideal for leaf-blower sweeping. Ironically, gravel or breeze paths are essentially maintained just the same: weeded and swept clean. The gravel surface also tends to promote seedlings of flowers and weeds alike, making this the most weed-intensive of the categories. An effective prince of a gravel garden rules with a hoop hoe in 1/2" or finer gravel, so he can scuffle out dandelions and tumbleweed seedlings with the ease of vacuuming, leaving desirable seedlings of plants who are at home enough to make a family. A larger-sized gravel makes digging and weeding a greater burden.

The world knows this category as Beth Chatto’s “Gravel Garden,” a niche celebrated in the Mediterranean garden books by Olivier Filiipi, who tells us that here, soil improvement comes down to decompaction rather than compost. This category is also beautifully expressed by the gravel garden in Philadelphia’s Chanticleer Garden. A mineral mulched garden is the domestic archetype of the world’s naturally rocky places, deserts, and arid steppes, all of which have low-fertility soils. And it is also where we grow plants from those ends of the earth.

Organic (Forest)

This zone often starts mulched in woodchips or bark and, at its best, when mature enjoys such dense vegetation that the purchased mulch is hardly visible and not needing replacement when it decomposes. The enterprising gardener will allow it to be mulched by its own plants with the “chop-and-drop” routine. It can start with compost being tilled in deeply, or with the patient topdressing and no-till approach. I’ve noticed that in areas recently converted to chop-and-drop, these will be slower to decompose in the first year or two, but I presume that the developing soil biome must be responsible for its rapid and seemingly magical disappearance in later years. This of course entirely depends on not using weed fabric. A new area can employ cardboard or paper weed barrier under woodchips to great effect, which will decompose on its own after its job of smothering the perennial weeds or turf roots is done. A generous 3-4" seems to be the right depth.

Organically mulched gardens favor strong herbaceous plants, shrubs, and trees, which, after all, create the mulch and resulting soil. Some vegetable garden systems fit this category. I first learned this concept from Denver’s Jim Borland, whose pruning system amused me initially. He prunes off a branch, then cuts it up into 2" sections that fall right to the ground. This seemed like extra work until I realized that it completely offsets the need for gathering, reducing, hauling away, or composting and, ironically, wheel-barrowing that organic material right back to the garden as compost or woodmulch. Why not just keep all organic matter instead of working so hard to throw it away and later buy and apply compost and bagged mulch.

A shrub garden with organic mulch is the lowest maintenance category of all, creating its own weed-fighting team between the mulch and the plants, and foregoing colorful, fitful herbaceous plants for permanent woody shrubs. Extremely xeric plants usually don’t like it - cactus, desert penstemons, and eriogonums – because they rot in all that organic matter. This category replicates the shrubby, leafy flora of alluvial river valleys, forest, and chaparral, and is home to mushrooms, worms, falling leaves, and perhaps a tow-hee scratching for lunch.

Living Mulch (Prairie)

Some living mulch gardens are new and novel, like meadow gardens, but one old example already surrounds us: turf. It can start with or without organic amendments and rarely involves an applied mulch. It’s often grown from seed, plugs, or, of course, rolls of sod. Establishing a meadow from seed can be the best or worst experience: a near effortless creation of a garden by throwing handfulls to the wind, or a terribly awkward era of separating weed from flower seedlings on your knees. The soil is simply covered in live plants; a vegetable garden with cover crops fits this category. It lends itself to broad-sweeping maintenance as you essentially “prune” your lawn with a mower, or cut a meadow down with a trimmer. It treats the whole area the same. This category reminds us of pasture, hayfields, and systems that have long involved the human hand or the role of fire and grazers. As a garden, it offers the best food supply for wildlife, pollinators and larval hosts, made up of herbaceous plants which, having bloomed, create a lot of dead material. It’s a biomass factory and soil builder.

An extension of Jim’s chop-and drop, I have learned a technique called “sectioning” for tall grasses: cutting them down from the top a few inches at a time, leaving a fine mulch of shorter sections on the ground. It’s like a giant manual version of the mulching mower, letting all that bulky dead material lie remarkably flat. Anecdotally we find that smaller pieces (2-4") rather than larger (4-12") are less apt to blow away, especially if some stubble of the plant is left up.

If it isn’t turf, this might be our least understood garden system in current American gardening tradition, being the easiest or worst to maintain, depending on the gardener’s knowledge. Its style is the wildest, giving you the least control aesthetically and practically. It’s the least formal. Plant species come and go and interact intimately and mysteriously. It is an exciting vanguard because it is not only the best way to have an in-vogue pollinator garden, but it also might be the most natural manifestation of what we should think of as “xeriscape” on the front range of Colorado.

Nature offers glorious inspiration and homelands of garden flowers in the steppe regions of the earth, from the South American pampas to the Turkish yayla (highlands), to our very own North American tallgrass and shortgrass prairies. I first saw an avalanche-driven ecology In the Caucasus that can inspire home gardeners: heavy winter snow slides down the hills flattening the prior year’s dead plant material and excluding anything woody. Its melt fuels very short spring bulbs, which emerge from this flattened blanket to start the successively taller and taller growth of flowers throughout the season, ending with tall golden summer Liliuwm, architectural towering fall umbellifers, and a party of tall Asters. The forces charged to cut it down are buffalo, blizzards, and fire.

When you do the work of buffalo or an avalanche in your yard, an area dominated by tall summer-blooming grasses and prairie plants becomes shockingly short when cut back in spring, like a fresh cut hayfield, or a close-shorn sheep. It’s startling and no one finds its glamourous. But that “ugly’ moment quickly becomes a fantastic stage for the triumphant entry of a well-timed expansive bulb display. In the foothills, Pulstatilla patens and sand lilies are nature’s actors for this. An award goes to the gardener who cleverly times their meadow-cutting precisely with the emergence of bulbs from the ground. Veteran-level meadow gardeners may cut down one part of the meadow, like the warm season grasses, much later (when earlier-cut parts of the meadow have already sprung up in green) so that there is never a moment when the whole meadow is totally flat.

Above, a new landscape zoned with modern artsy borders between the gravel, blue gramma, and woodchip zones. Below: The same landscape a couple years later, filling into itself.

Leveraging the strength of the team

Certain patches of earth just fit a certain category: a wet spot will continually attract moisture-loving weeds; a dry windy spot might beg for cacti; a tree-shaded area will fight a gravel garden with its great drop of autumn leaves every year.

Being aware of and being deliberate about these zones has helped me narrow in on a sane maintenance scheme with minimal tools, since I am so often sleeping in my plant and tool-filled truck bed while traveling. Just shears, a blower, and a hoe do about 90% of the work. I’m excited that powerful electric trimmers now exist to quietly cut down a meadow on-site and leave the trimmings to decompose. Doing an extra pass with the shears over a meadow may seem like extra work, but it totally eliminates the work of tarping, bagging and hauling away trimmings while creating a weed supressing mulch that favors existing deep-rooted perennials.

I also like to leverage the strengths of each zone in combination with one another. A rock garden backed by a shrub garden means that its own topography will resist buildup of puddles of autumn leaves or debris. Anything it doesn’t shed on its own I can easily blow into the neighboring organic-mulch zone to enrich that soil and keep the rock garden soil lean. Aesthetically, each zone will have a different peak season so a combination can keep a year-round show going continuously. When we chop down the dry meadow garden in spring, the rock garden is no longer hidden; its sculptural agaves and sunlight-catching cactus spines glow without nearby distractions of gaudy, tall forbs that dominate the meadow later in summer.

We are incredibly lucky to live in Colorado where the biomes that inspire each category exist naturally. Most states have geology and climate that favor just one. For us, it is not hard to make small modifications to the soil and surface of our yards so we can forever enjoy a botanical and spiritual taste of the desert, forest, and prairie in our own suburban homesteads.

Kenton J. Seth is a hands-on garden designer based in Fruita, CO. His small nursery supplies plants for his native gardens, meadows, and crevice gardens. (His book on crevice gardens is due out June 2022.) He writes about quirky plant stuff at kentonjseth.blogspot.com. See his work at Paintbrushgardens.com