Tall perennials can add height and drama to your border without demanding lots of water.

A prime garden spot for tall perennials is the back of the flowerbed, an area that is often neglected.  Perhaps gardeners who shop for plants exclusively in the spring are easily seduced by the flowering groundcovers of the season and ignore the perennials that do not reach their full height or flowering potential until later in the summer. Or maybe gardeners who begin planning their flowering borders from the front wind up squeezed for space at the back.  Some homeowners might even be a little bit frightened of tall perennials.  Will the plant overwhelm the flowerbed? What will that tall plant do to the water bill?

Fortunately, there are a variety of tall perennial plants that use little water and deserve a place of honor in the garden.  Whether planted in their traditional place at the back of the border or placed as a focal point among smaller plants, the following waterwise tall perennials make delightful additions to any garden.

For early season flower, giant kale (Crambe cordifolia) is a winner.  Like baby's breath on steroids, sprays of small white flowers spring up a majestic 4 to 5 feet above the plant's large, leathery foliage in early summer.  This drought tolerant, sun-lover looks lovely alongside shrub roses, peonies, or other early-blooming, large-flowered plants.

Shrub mallow (Lavatera thuringiaca) is an elegant, long-flowering perennial that reaches a height and a width of 4 to 6 feet.  Shrub mallow 'Barnsley' has soft pink flowers with darker rose eyes, reminiscent of hollyhocks.  "Burgundy Wine" features vivid fuchsia flowers. From early July to mid- fall, the flowers sway in the breeze on their long arching branches. With full or partial sun and a moderate amount of water, this airy shrub grows quickly enough to give even the newest garden a feeling of maturity. In spring, shrub mallow should be cut back to about six inches above the ground to promote new growth.

Another tall perennial that should be cut down to about six inches in the spring is Russian Sage or Perovskia atriplicifolia.  After its spring trim, the plant bounces right back and soon becomes an aromatic shrub of about 4 feet high and wide.  Despite being native to Afghanistan, the delicate wands of hazy blue flowers have become a signature of the late summer western garden.

Globe thistle (Echinops) provides a much sturdier looking blue accent in the garden. Unusual spherical flowers crown this 4-foot upright plant in late July and August.  The steel blue, spiked globes bring to mind medieval weaponry and attract pollinators in droves.

False sunflower, or Heliopsis 'Summer Sun,' is a tough, low-maintenance plant with modest watering requirements that makes a cheerful exclamation point in the summer garden.  This upright, sun-loving plant boasts school bus yellow, semi-double blooms from the end of June through August.  The bright blooms are the perfect complement to golden daylilies or coreopsis and contrast beautifully with plants that have burgundy foliage.

For the brave gardener, the perennial sunflower Maximilian (Helianthus maximiliani) makes a big, bright splash of yellow in the border. Although the lemon yellow flowers of Maximilian are small compared to annual sunflowers, they make a bold statement.  The blooms cover the enormous 7-foot tall plant from the end of summer into the fall.  Maximilian will require some upkeep as the plant does produce an impressive number of seedlings.

Bronze fennel (Foeniculum vulgare 'Purpureum') is a 5-foot tall plant with dark ferny foliage that looks great with yellow flowers like heliopsis or helianthus. The fennel itself puts out inconspicuous flat yellow blooms in July, which gardeners should be sure to deadhead before the flowers produce seed.  All parts of the plant are edible from the fennel seeds (an essential ingredient on the spice rack) to the licorice-flavored root. Caution should be taken when working with the plant, as some people can experience skin discoloration when working with the plant in sun.

Prince's Plume (Stanleya pinnata), a striking plant native to the Four Corners region, produces glistening yellow foot long spikes of flower in June.  Prince's Plume likes dry, well-drained soils and can reach a height of 4 feet in our area.

For a touch of sky blue in the garden try Pitcher Sage (Salvia azurea). The arching stems of this unusual, 4 foot tall sage plant is topped with clusters of brilliant blue flowers from July to September and thrives with low to moderate water.

Perennials of different heights are essential for making a flower garden interesting.  With just a little water and plenty of room to grow, tall perennials can be the standout stars in any border.

Q: How can I keep squirrels out of my yard?

A: One way to help keep unwanted squirrels out of your yard is to make it unpleasant for them to be there.  This can be done by not providing food for them such as uneaten pet food or birdseed or store food in metal containers. Dogs are also a good deterrent.

Q:  Deer keep getting into my yard and eating my shrubs.  What can I do?

A: Deer like most animals are creatures of habit.  Making the once pleasant experience into an unpleasant one can help break the habit of deer eating your shrubs.  Try leaving your dog outside over night. Just the smell of the dog can be a deterrent.  Or have your sprinklers go off when they are feeding. Another way is to plant shrubs that are less desirable to deer around the border of your yard.  A few of those are Virginia creeper, daffodils, gaillardia and potentilla.

Q: My house has big windows.  What can I do to keep birds from flying into them?

A: You can try putting up a sheer curtain. This will keep the birds from flying into the window but won't block your view.  Another way is to install an artificial predator by the window.  You can purchase an owl or even a snake at local nurseries and garden centers.  Finally, try putting up flashy ornaments by your windows.  These ornaments will reflect the sun and scare the birds away.

Avoid using plastic weed barrier material under rock or fiber mulch. It prevents oxygen and water from reaching the roots and creates anaerobic conditions. This can cause root rot, leading to plant death.

To help manage mosquitoes around the home eliminate standing water, repair or replace loose screens and reduce unnecessary lighting to make yards less attractive to insects.

Fall webworm is a tent-making caterpillar currently developing on chokecherries and cottonwoods. Bacillus thuringiensis (Bt) can be an effective and selective control for the insect but since the insect must ingest the Bt, it must be applied before the insect covers the leaves. Carbaryl is another effective chemical control of fall webworm.

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:  June 27, 2003