Xeriscape Perennials That Withstand Colorado

“The quality of mercy is not strained

It droppeth as the gentle rain from heaven.” Shakespeare

It was great to have a long cool spring with plenty of moisture, but since it followed the very hot temperatures and drought of 2002, it really felt like a merciful blessing. Now instead of dying trees and brown lawns, the streams are gushing, the reservoirs brimming, the wildflowers are extravagant and the birds are joyfully singing. Those plants and gardens that survived 2002 have never looked better. We’ll take it.

But like the poet Ghalib exclaimed, “No Paradise can cure a man like you, knowing as you do, the after-taste of all sweetness.” And so, though we can celebrate the glory of this generous season, we who have been scorched and burned by the drought and shocked by water restrictions, look back to what did well last year. And we look forward to planning and planting for tougher times. July showed us just how fast Colorado can turn from cool and moist into very hot and very dry.

In August of 2002, during the worst drought in a hundred years, I took an inventory of the plants that looked good in our display gardens at Harlequin’s Gardens. In this case “looked good” does not mean, in full bloom or as photogenic as the cover of “Fine Gardening”; it means the plants looked healthy, vigorous and attractive.

In this article, I will limit the list and discussion to the perennials in our Xeriscape Rock Garden which was watered only five times in 2002. This garden, it is important to note, is located on the east side of the house and so is mostly protected from the late afternoon sun and the strong, drying west winds. The soil is very lean and gravelly with little or no clay to help hold moisture, and has been amended and top-dressed occasionally with compost

Your gardening conditions may differ from ours, but I believe that even without scientific validity, our list of established plants that looked good in August of 2002, will help you to get to know some plants that can succeed in very dry Colorado conditions with very limited watering. This might be an excellent time to start a file of lists of successful plants growing in very dry conditions: collect these from your own experience, your neighbors, from nature, from native gardens at Denver Botanic Gardens etc.

Here are descriptions of a few of the Stars of the Drought:

  1. Moonshine Yarrow is not a viciously spreading millefolium yarrow. It is a is a hybrid between Achillea taygetea and A. clypeolata, with beautiful ferny silver-blue foliage and heads of soft sulfur yellow flowers. It grows 24—30″ high and 18—24″ wide and blooms in late spring and summer. The flowers are attractive even as they dry. It has survived many years of droughty conditions in my garden, and it can live at elevations up to 9000′. Another variety of similar size and habit is ‘Anthea’ with primrose yellow flowers fading to cream. It is said not to rot out as can happen supposedly with ‘Moonshine’. I am now growing ‘Anthea’ on the scorching west side of my house where it seems to be quite happy.
  2. Calylophus serrulatus, Prairie Sundrops, is a native of Boulder County and in fact, I got my plants originally from a volunteer that appeared by my duck pen. It is a little sub-shrub 8—15″ high and wider, that could easily be overlooked in early spring, but by late spring when it is in bloom, it is a delight. Its four-petaled evening primrose-like flowers are profuse and continue for a long season. It can be long-lived and even self-seeds where it gets some moisture. I shear it after blooming to keep it tidy and to save its strength.
  3. Geranium sanguineum is called Bloody Cranesbill because of its brilliant red fall color and its beak-like seed capsule. This is a hardy geranium, coming originally from Europe and northern Turkey, and seems very well adapted to Colorado. The leaves are small and deeply dissected into 3-toed lobes. The flowers are usually a purple-magenta, 1—1½” in diameter, and can be very long blooming, especially if dead headed. The plant form can be highly variable, from 8—to 24″ high and from 16—to 36″ wide. The flowers vary with the varieties: ‘Album’ is a beautiful pure white, “Dwarf Purple” is a darker magenta, ‘New Hampshire’ is rose-pink; variety striatum is blush pink with deep pink veins. Five selections are growing in my xeriscape rock garden, some in part shade and some in full sun.
  4. Helianthemum nummularia is a tribe of sunroses. They come in many colors and grow 6—12″ high as small woody-stemmed shrublets. The foliage can be glossy green or even blue-gray, and is mostly evergreen. The plants are tap-rooted and tolerate drought well. They prosper in loose, alkaline soil and often self-seed to make multi-colored patches. This more than compensates for the fact that individuals may not be long-lived. The yellow and white varieties may be the toughest and most enduring, but there are some other very attractive and successful varieties: ‘Dazzler’ is a good red, ‘Ben More’ is deep orange, ‘Wisely Pink’ has pink flowers against blue-gray leaves, and there are many more. Shearing the spent flowers can prolong the life of the plant and encourage it to rebloom.
  5. Ruschia pulvinaris is sometimes called “Shrubby Ice Plant”, but in my xeriscape garden, it has proved to be much more drought and heat tolerant than most of the ice plants (Delospermas). Ruschia is a woody groundcover 3″ high that slowly spreads to 12″ wide. It does well in lean, well-drained soil, but it may take dry clay as well. Thick, succulent bluish gray leaves make a dense groundcover, and the fuschia-pink, daisy-like flowers are a half-inch in diameter, blooming late spring and early summer. Some books say “hardy to zone 6″, but Ruschia seems to be doing well in the Denver-Boulder area. We are growing a similar variety, Ruschia putterellii, that has been flourishing for six years. It may be even hardier and tougher and looks great, draping over our rock wall.

Sometimes it seems like our lives and our well being hang in a very delicate balance. This year abundant crops and lush gardens, next year? It could be like 2002. Gardening ties us to the earth and to her seasons and cycles. We gardeners, like everything else in the garden, must learn to adapt and be prepared for changing conditions. And so we try and we test; we watch and we learn. Cultivating Nature is such great fun, isn’t it?