How to Build Rock Gardens

  • 01 of 10

    Rock Gardens for Small Spaces

    Image of a large, colorful rock garden in Maine, USA.
    This large, colorful rock garden in Maine, USA makes quite a statement in the landscape. David Beaulieu

    Some homeowners design rock gardens to exploit rocky slopes in their yards. Others, like me, import rocks into yards that are flat and rockless; we need stronger backs, but the effort is well worth it.

    Another consideration that can influence the design of rock gardens is space. I am allotting but a small space for my rock garden. In larger spaces, the goal is often to create sprawling, naturalistic rock gardens. But given my space restrictions, I'm contenting myself with what amounts to a...MORE round raised bed made of select rocks. This design fits neatly into the nook I have chosen for it. My small rock garden won't be in the way when I mow my lawn, nor will it require much maintenance.

    Yet a third design consideration is color. I have a collection of attractive red sandstone pieces; they will provide the structure for my rock garden. In turn, this choice will influence my plant selection. I want a color scheme that will work well with the red sandstone. I would like some plants with a hint of red in them, but also some plants displaying silver, yellow and white.

    The sandstone with which I'm working is hardly the most durable of materials. Indeed, many of the pieces are crumbly, well on their way to becoming soil! But beauty was my goal, not longevity.

    Rock gardens normally achieve some elevation above the surrounding ground. In this case, that means laying a first course of rocks and soil, then building upon it. In Step 2 I lay the first course.

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  • 02 of 10

    The First Course of the Raised-Bed Rock Garden

    Picture of the base or first course of a rock garden.
    The base of the rock garden: a circle of stones filled with soil. David Beaulieu

    For this rock-garden project, I'm claiming a patch of ground covered with grass. I could dig up the grass before beginning but decided on an easier way: laying down a layer of newspapers and shoveling dirt on top of them to hold them down.

    The layer of newspapers will eventually smother the grass, which will then begin to decompose. But even before decomposition takes place, I've accomplished my first task for the current project: furnishing a clean slate upon which to work.

    If you have an...MORE area already cleared, you can skip the task of laying newspapers and proceed to the following task, which is to lay the first course of stones and soil.

    Again, my rock garden is essentially just a round stone raised bed, so I begin its construction by laying out a circle of rocks as the perimeter for my base. The diameter of my base is about 4'. None of my rocks is larger than 12" in any dimension, so they aren't too tough to manipulate.

    With the circle of stones in place, it's time to fill it with soil. Rock gardens, as a rule, are composed of plants that require a soil with good drainage, and I'll select plants that conform to the rule. I have a sandy soil on hand for use in my project, thus meeting this requirement. If, on the other hand, you have a clayey soil, you'll have to add sand to it to promote better drainage. I'm also adding some compost to my soil. Once shoveled into place, walk on the soil to pack it down.

    In Step 3, I'll build on this first course.

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  • 03 of 10

    The Second Course of the Raised-Bed Rock Garden

    The second course of a raised-bed rock garden is shown in this photo. The plants come next.
    The second layer of the rock garden: a circle within a circle. David Beaulieu

    The second course of the raised bed rock garden is simply a smaller version of the first. That is, the diameter of the stone perimeter that you lay on top of the first layer will be smaller, forming a circle within a circle.

    I used my heaviest stones for the first course. For the second course, I did reserve some large rocks, but it was the prettiest rocks, in particular, that I laid aside. That's because the rocks of the second course will show up more, being closer to the eye.

    With the two...MORE layers constructed, we're ready to turn to plant selection in Step 4.

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  • 04 of 10

    Selecting Plants for Rock Gardens: Pay Attention to Growing Requirements

    Spurges are good plants for rock gardens. Some supply red stems for a color scheme.
    Spurge (middle plant) supplies red stems and yellow flowers for my color scheme. David Beaulieu

    As mentioned in Step 1, my selection of plants for rock gardens will be driven by color scheme. But the use of color schemes in landscaping projects differs markedly from their use in, say, painting, in at least one important respect. And that is that plants, as living things, have growing requirements to take into consideration. So adherence to color schemes in landscaping can never be as single-minded as it can be in the art world.

    We have already looked at one growing requirement: drainage. I...MORE want specimens for my rock garden that will grow best when water percolates readily through their soil. It would be a mistake to add a plant that prefers wet soil to this mix, no matter how much it does for my color scheme. Only plants with similar growing requirements should be grouped together unless you're willing to sacrifice longevity for temporary "good looks."

    Besides drainage, other considerations are light requirements and amount of water needed. I want plants that will thrive in full sun, making them compatible both with each other and with the spot I chose for my rock garden. I would also prefer drought-resistant plants, although, as I'll point out later, I did make an exception for one particularly handsome specimen, which I'll treat as an annual plant.

    I'm also seeking some variation in plant height and leaf texture.

    To summarize, before going to the nursery to shop for rock-garden plants, I've established certain criteria. My rock-garden plants should:

    • fit into the desired color scheme
    • prefer good drainage
    • prefer a sunny area
    • exhibit some variation in height and texture

    In my separate article on rock garden plants, I present a wide array of choices for your plantings. But in Step 5 I reveal my plant selection for this particular project, after adding one more criterion to this list.

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  • 05 of 10

    More on Plant Selection for Rock Gardens

    Plant selection for rock gardens includes snow-in-summer.
    White flowers will soon sit atop the silver foliage of snow-in-summer plant. David Beaulieu

    It is tempting when shopping at the nursery to select a wide variety of plants. Resist this temptation! Succumbing to it will lead to a hodge-podge, rather than a unified look. For the sake of your design, stick to a theme. In my case, I need to stick to the color scheme I mentioned. Also, too many different kinds of plants will make the space look too busy; two different plants of each desired color is plenty for my space. Repetition of the same plant-type promotes unity.

    Here's how I...MORE achieved a unified look with my plant selection. I bought:

    1. 6 pots of Scotch moss
    2. 1 yellow daffodil
    3. 3 pots of wood spurge
    4. 3 pots of hens and chicks
    5. 3 pots of snow-in-summer
    6. 1 lamb's ear plant
    7. 3 pots of candytuft

    I have acquired specimens of some of these plants in sufficient numbers to achieve unity through repetition. As the years go by and the daffodil and lamb's ear grow larger, I'll divide them. If I decide that they clutter up my rock garden too much, I'll transplant them to somewhere else in the yard.

    Most of these plants were chosen with an eye to meeting the criteria already established, both in terms of growing requirements and design. Each plant I selected helps me achieve my design objectives -- and on more than one level. I not only had a color scheme in mind but was also seeking variation in plant size and leaf texture.

    I'll discuss the latter in greater detail in Step 6, as I present my plant selection.

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  • 06 of 10

    The Color Scheme for the Rock Garden

    I chose Scotch moss to help me with the color scheme of my rock garden.
    I chose Scotch moss for the hint of yellow it offers. David Beaulieu

    Here's a closer look at the plants I selected -- and why:

    • Scotch moss (Sagina subulata 'Aurea') gives me a short plant with a touch of yellow.
    • Daffodil (Narcissus) offers more yellow. This particular daffodil is a miniature, suitable for rock gardens.
    • Wood spurge (Euphorbia amygdaloides 'Purpurea') provides yellow (its blooms) and red (its stems). It's a taller plant than the rest, giving the composition some depth.
    • Offering more red is the foliage of low-growing hens and...MORE chicks (Sempervivum tectorum).
    • Low-growing snow-in-summer (Cerastium tomentosum) gives me silver (its foliage) and, later, white (its blooms).
    • The taller lamb's ear (Stachys byzantina) offers more silver foliage.
    • My most striking white at present is provided by the flowers of candytuft (Iberis sempervirens 'Purity').

    I focus on foliage in my rock garden design. Flowers come and go but foliage serves as a backbone for a composition. Even so, this rock garden will look nicer in spring and early summer, when the plants are in bloom, than it will in late summer. That's a compromise I made. If I insist on colorful blooms throughout the summer, I can easily add the annual, portulaca, to the mix.

    I made another compromise: with the Scotch moss, which is not drought-tolerant (one generally selects drought-tolerant specimens for rock gardens). This was a case where I sacrificed longevity for temporary "good looks." This plant (suited to planting zones 4-9) bears small white flowers, but it is grown mainly for the solid carpet of yellowish-green that it provides. Grow it in full sun to part shade. It is very much like Irish moss, except that the latter is a deep green color.

    The only plant in my rock garden grown more for its flower than its foliage is the daffodil. The relatively coarse textures of the lamb's ear, wood spurge and hens and chicks contrast well with the other plants, all of which have a more delicate foliage.

    In Step 7 we begin planting.

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  • 07 of 10

    Planting the Rock Garden

    Planting rock gardens means planning. I made the triangle of white candytufts anchor mine.
    The "triangle" of white candytufts anchors the planting. David Beaulieu

    When I laid my second course of stones for my rock garden, I made the circle small enough that plenty of room for planting was left over around the perimeter of the first layer. A little bit more planting space is available on top of the second layer itself.

    So where do you begin planting? And with which plants? I find it useful for such a project to plant in 3s - 3 of the same plant, that is. The white blooms of the candytuft will be one of my rock garden's most striking features early on,...MORE so I decided to plant the 3 candytufts first, using a garden trowel to dig my holes.

    The result (see photo above) is a triangle that anchors the composition. As you can see, I've already begun planting some of the other plants. In Step 8, I proceed to install the rest of my plants, radiating out from each point in the triangle.

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  • 08 of 10

    Rock Gardening Techniques: Inserting Additional Rocks

    Rock gardening techniques include proper placement. Picture: red rock being inserted.
    The light red rock was inserted just after the hens and chicks was planted. David Beaulieu

    As you plant, add more rocks. Since this is a rock garden, the look I'm after is a mass of rocks with plants popping out between the cracks. But if all the rocks were laid at once, they'd be in the way of the plantings.

    So instead, additional rocks (mainly small ones) are inserted as the planting proceeds. Install a plant somewhere first, then create the "cracks" around it afterward. It's a lot easier to change your mind and move a rock to another position than it is to dig up...MORE plants and replant them somewhere else.

    There's a delicate balance to pursue between the planting and the rock installation, but your goal ultimately is to cover as much of the surface as possible with rocks and plants. The process is rather like putting together a jigsaw puzzle -- except that you determine how the puzzle turns out.

    Once you've covered the entire surface of the rock garden with plants and rocks, it's time to mulch, the subject of Step 9.

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  • 09 of 10

    Mulch for Rock Gardens

    Picture showing sandstone mulch for my rock garden.
    A sandstone mulch works well in my rock garden. David Beaulieu

    Mulching can present a dilemma for the novice in rock gardening. On the one hand, you want to suppress weeds in the rock garden, but, on the other hand, the widely used bark mulches would look out of place in rock gardens. So what do you use for a mulch?

    The answer is stone. But not just any stone. Strive for a stone mulch whose color will fit with the color of your main rocks -- in my case, red. Fortunately, I had a range of sandstone rock at my disposal, from the large rocks that formed my...MORE circles to smaller stones to pebbles! The latter will make the perfect mulch for me. If I hadn't had such a supply on hand, I could have bought some red stone mulch from a local nursery (although the color wouldn't have been as perfect a match as I achieved).

    With the mulch in place, it's time to show you what the final version of the rock garden looks like, in Step 10.

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  • 10 of 10

    Photo of the Final Version of the Rock Garden

    Photo of the completed rock garden.
    Photo of the completed rock garden. David Beaulieu

    The photo above shows the rock garden in its final form.