Wow!  You have just seen one of nature's most beautiful creations - a rock garden in the mountains filled with alpine plants snuggled up against ancient rocks. The plants, huddled behind rock and in cracks and crevices, are so exquisite and tiny that you feel compelled to take a closer look.

These plants, growing wild in the mountains, are some of our loveliest garden plants.  The term “alpine” usually means plants growing above timberline.  Now it is used loosely and includes many low-growing plants that may be grown successfully in rock gardens at lower altitudes.  Rock gardens are an attractive and efficient way of eliminating some areas of unnecessary turf and decreasing water use. Growing these fascinating, intricate plants in our own yards can be very appealing and addicting.

Rock garden plants all require well-drained soil.  Most of them also like full sun although some will tolerate part shade. Rock garden plants should be small varieties with low growing or mounding, cushion forming habits.  Many would not survive in our everyday perennial flower beds.  Ground covers, bulbs, herbs, succulents, dwarf evergreens, small shrubs and grasses all can be grown in the rock garden.   Aggressive growers such as Snow-in summer (Cerastium tomentosum) should not be planted as the rocks and delicate alpines would soon be overgrown.  From the unusual Fameflower (Talinum okanoganense) and common Hens and chicks (Sempervivum tectorum) to easily-grown Sedum ‘Cape Blanco’ and difficult Alpine forget-me-not (Eritrichium nanum), gardeners of any level of expertise will be gratified and challenged by the number of rock garden plants available.

The size and physical characteristics of your property sometime determine the site of the rock garden.  If you are so fortunate to have rock outcrops just under the surface of the soil, then nearly all that has to be done is some excavation and possible soil amendment. Small valleys or gullies, areas of slope and banks are also suitable.  Lacking these natural features, any of them can be constructed with creative placement of soil and rock.

The goal is to make your rock garden look like nature created it, only in miniature.  Visit the nearby foothills and mountains for ideas on rock formations.  The Denver Botanic Garden has a wonderful alpine garden, as does the Yampa River Botanic Park in Steamboat Springs.  Some of your friends or neighbors may have rock gardens that can give you ideas.

The rock garden should receive mostly sun and be located where it will have the most natural appearance and yet fit in with the rest of your landscape.  A slope has the best drainage.  Even a flat area can become a raised outcrop with large irregular rock tilted up to give the impression that there is a larger formation underground.  Dry streambeds and rock terraces with flat area and pockets for planting both make good rock gardens.

Stone that is native to our area is less expensive and more readily available.  It is best to use rock from one general geologic type rather than to mix types.  Rock that is weathered or has lichen is wonderful.  Avoid newly quarried or cut rock.  You want the rock garden to look old and eroded.

*  The size of the rock should be in proportion to the size of the garden.  Even a smaller garden should have a few large rocks.

*  Combine two moderate size rocks of similar shape to give the impression of one large rock.  Plant in the crevice that is formed.

*  If using stratified rock, rock should be placed with the lines of strata in one direction and at the same angle to form terraces.  The terraces can be different sizes, with some more shallow.

*  Tilt rocks back into the slope slightly to allow water to run back into the roots of the plants.

*  If the garden is very large, add a path for ease of maintenance and viewing.

*  For stability and naturalness, set rock into the ground so that one-third to two-thirds of the rock is buried.  The soil must be tamped down firmly around the rocks to prevent air pockets.

*  Rocks should be placed irregularly and sized irregularly to achieve the natural look.

*  Think about starting small and leave room for expansion later.

*  Fall is a good time for construction.  It is cooler.  The rocks can settle during the winter.  You will have time to look at the formation and make changes before spring.  It is best to plant in spring.

Well-draining soil is important for the rock garden. Winter wetness is the #1 killer of rock garden plants.  If your soil is not the type favored by these plants, you must amend the soil with compost to make it well drained. Water should not sit on top of the soil but drain through after watering. Heavy clay should be replaced by a well-draining soil. An all-purpose soil mix is one part compost, one part coarse sand or 3/8-inch gravel and one part good quality, seed-free topsoil. The soil mix should be used to a depth of at least one foot in every spot you plan to place a plant.  Alpine plants naturally grow in nutrient-poor soil and no additional fertilizer is generally necessary, as it will make the growth spindly.   When you choose your plants, make sure that their cultural needs are compatible with your rock garden.

The entire surface of a rock garden should be covered with mulch of small crushed stone; 3/8 to 1/2-inch is best.  This will help slow evaporation, help keep the soil cool and keep soil from splashing on the plants. Many rock garden plants can literally be smothered by wood mulch.  The rock garden should be given about one inch of water weekly to encourage deep root systems.

No two rock gardens are ever alike.  There is no right or wrong way to construct your garden.  It will be a garden suited to your tastes.  Your only regret may be that you didn't make it larger.

Q:  There are warts all over the undersides of my hackberry leaves.  What is this and will it kill my tree?

A:   This is called hackberry nipplegall.  It is the result of a small insect called a hackberry nipplegall psyllid.  These psyllids overwinter in protected areas as adults and lay eggs in early spring on the undersides of the new leaves.  The young nymphs begin to feed and as they do, raised swellings are produced which ultimately turn into the “warts” or galls with the little insects inside. In late summer, adult psyllids emerge from these galls. This condition is pretty harmless to the health of the tree and the psyllids are a favorite of several bird species.

Q:  I received two beautiful Amaryllis plants for Christmas—both with several huge blooms.  I cut off the flowers when they were finished and then leaves came out.  I’ve had them in a bright southwest window and have been watering them. The leaves look great and are about 18-25 inches long.  Is it too late to get them to re-bloom for Christmas?

A:  Ideally plants should be planted outdoors in May, but try it now!  In a protected location with bright filtered light, dig a hole and plant pot and all with top at soil level. Use a water-soluble fertilizer (10-60-10) or similar, every two weeks.  Continue watering to keep soil moist but never soggy.  In mid-September bring the pots and bulbs indoors, cut leaves off 1” above top of bulb and place in a cool (50-60 degrees F cool temperature is important), dark location for six to eight weeks. DO NOT WATER.

In the last week of November, after this rest period, repot bulbs in fresh potting mix with top half of bulbs exposed. Water well and set in a sunny, (55-65 degrees F cool is again important) location.  Don’t water again until green growth appears.  When stalks grow to six inches, begin to water the plants.  If they fail to flower, just maintain them as foliage plants as you did this year, and start the process in May next year.  Good Luck!

Q:  Quite a few of the leaves on my honeylocust tree are kind of shriveled with yellowish stipple-like spots on the leaves.  Some leaves are even turning yellow.  What is causing this?

A:  This condition was likely caused in the spring by an insect called a honeylocust plant bug that feeds on tender new buds and leaves.  Although there is only one generation per year, which occurs in the spring, there can be significant damage and controls can greatly benefit the tree.  Vigorous hosing of foliage can be effective as well as control from several insecticides, labeled for use on honeylocust plant bugs.  Timing of application at the earliest emergence of insects—usually by mid-May—is necessary for maximum benefit.  There are some other insects which can cause damage to honeylocusts.  If you are unsure, bring a sample into the Larimer County Cooperative Extension Office for identification.

Gladiolus thrips (Thrips simplex) are tiny insects that damage leaves and can prevent flower production in gladiolus, iris and daylilies.  Thrips cause scarring injuries, dying foliage, flecking and distortion of flowers by puncturing the cells and removing plant sap.  A vigorous jet of water can kill exposed thrips.  During the growing season they can also be controlled with a systemic insecticide.

Corn is usually ready to pick 21 days after the silks appear.

Take photos of your garden to help you remember what was blooming at different times during the summer.  Shoot your pictures in early morning or just before dusk for the best light.  Avoid bright, mid – day sun.  In January you can use the photos to decide what plants should be moved or divided or added to the compost pile and what you should purchase from all those catalogs that are showing up in your mailbox.

A successful butterfly garden should include plants for the entire life cycle of the butterfly.  Eggs are laid on host plants and those plants are eaten by the caterpillars.  The adult moths then feed on nectar plants.  Butterflies also need shelter from wind, a source of water and rocks to bask in the sun.  For more information, see Fact sheet 5.504 - Attracting Butterflies to Your Garden.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  July 30, 2003