Centennial Gardens

Denver Botanic Gardens
A Perspective On Rocky Mountain Horticulture
By Panayoti Kelaidis, Director Of Outreach

Gary Whittenbaugh, a great gardener from Iowa, likes to say that the only thing that separates his garden from the North Pole in winter are a few strands of barbed wire, and most of them are missing. Northern gardeners are full of weather lore: in fact, anyone who lives any distance from an ocean can share whoppers about how much the temperature dropped in a single day, just how cold it gets and how long it lasts. Conversely, it can get pretty darn hot in these parts as well.

Colorado may not look too northerly on U.S. maps, but a glance at any climate atlas will show that zone 3 takes a colossal dip from central Canada down the Rockies practically to Mexico. Altitude mimics the effects of latitude; for every 100 feet you climb in Colorado you effectively drive 50 miles northward. Mt. Evans at over 14,000 feet hovers only 45 miles from downtown Denver at a mere mile high. You can drive to the top of that mountain in little more than an hour, a climatic equivalent of driving 4,000 miles northward to the North Slope of Alaska. There are, in fact, a number of plants that grow in the Alaskan arctic and on the Colorado Rockies that are absent in between.

Colorado is not only subject to the continental effect of extreme temperature variation, it is subject to a more or less permanent state of drought. Precipitation falls sparingly through the calendar year, averaging less than 15" everywhere below 5,000 feet elevation. The "evapotranspiration index" everywhere in the West is astronomical; sunlight and thin air quickly evaporated any surface water so that there was not one naturally occurring body of standing water found on the plains or plateaus of Colorado prior to European settlement. This is the land of 10,000 dry lakebeds.

So great has been the influence of the great gardens of England and Japan that horticulturists have come to think that gardening is synonymous with the color green and the proximity of the ocean. What hope is there of growing a variety of plants in a climate where daily isotherms on a graph look like the path of a yoyo? Where temperatures climb above 100°F in the summer and drop repeatedly below 0°F in the winter?

	Denver Botanic Gardens conservatory at the York Street site

A visit to Denver Botanic Gardens can help dispel these fair weather myths. An astonishing range of plants is grown here at four very different sites. The Gardens comprise an urban extravaganza on York Street, with a Tropical Conservatory and over 45 intimate gardens. In downtown Denver, next to Elitch's, Centennial Gardens is a five-acre formal garden in the heart of the city. Denver Botanic Gardens at Chatfield is a vast suburban open space in Littleton with 750 acres of wetlands. Mt. Goliath is an alpine unit at almost 12,000’ elevation, filled with alpine wildflowers and 1,500-year-old bristlecone pines.

The York Street site encompasses the largest concentration of garden styles and plant collections, varying from greenhouse and conservatory structures housing many thousands of tropical plants, notably orchids, succulents and a recreated Equatorial rainforest, to the largest collections of alpine plants in North America. It also boasts the most extensive collections of native plants of the Intermountain and Rocky Mountain west.

One of the first gardens that greets you as you enter the York Street site is the O’Fallon Perennial Border. This vast mixed border is filled with hundred of lush herbaceous perennials and complementary shrub plantings. This tribute to the English tradition would not look out of place at a stately home near London, and in fact contains most of the traditional perennials found in any maritime climate border. With deep garden loam and frequent watering you can in fact grow most classic perennials superbly in northern gardens, as these borders prove most any day of the calendar year.

The Romantic Gardens to the south are a series of vast borders organized for artistic effect, with extravagant colorist combinations of bronze, deep purple, ochre, umber with flashes of scarlet in the Tuscan influenced Schlessman Plaza, and pastel overtones in the lavender and moonlight yellow Fragrance Garden. The Herb Garden next door has always set a standard for impeccable maintenance with trim knot gardens and careful curation and labeling as befits this hallowed expression of botanic garden art. Parterres are filled with seasonal drifts of annual color alternating with temporary bulb mass plantings.

The Woodland Mosaic Garden contains a large collection of classic woodland plants such as hostas, primroses, winter viburnums and impatiens in the summer months. The Ornamental Grass Garden represents one of the oldest such gardens designed for this purpose in America.

PlantAsia is a departure from most Asian gardens, which concentrate on the woody treasures of the Himalayas with a few woodland groundcovers. These are represented in the lush “Yin” portion of PlantAsia; large stands of Asiatic lilies, tree peonies, hardy bamboo and a wealth of primroses, jack in the pulpits and other herbaceous treasures proliferate beneath a fine collection of Asian maples and other unusual trees. But the “Yang” portion of this garden showcases the vast steppes of central Asia, which harbor a rich, drought tolerant and biodiverse sunloving flora: especially bulbs and cushion forming plants like veronicas and spikethrifts. In April this garden overflows with thousands of scarlet tulips.

	The Rock Alpine Garden

There are gardens designed for children, like the Children’s Secret Path, and especially the Birds and Bees Walk with brilliant beds of annuals interspersed among signage designed to teach children and adults about the enormous importance of pollinators not just for plants, but for the very survival of humanity.

The Western portion of the Gardens contains the most famous gardens that house the widest assortment of plants and habitats. The Rock Alpine Garden is only an acre in extent, but comprises over 700 tons of rock artistically placed, and thousands of wildflowers form the world’s high places. Something of interest can be found here almost any day of the year, and it is a centerpiece throughout much of the growing season for vibrant color, texture and interest.

The Plains Garden is a sensitive recreation of the natural habitat that occurred here before Denver was settled: a favorite of staff for the varied and subtle moods of blowing grass and tangled wildflowers. The Dryland Mesa next door is a showcase of the rich upland flora of the Southwest, with hundreds of cacti, agaves, yuccas and the fascinating shrubs and wildflowers that make the southwestern deserts of America a tourist destination for people worldwide. Sacred Earth celebrates the wealth of useful plants employed by the native peoples of the Four Corners area of the American Southwest: Pueblo, Hopi and Navajo tribes. Healers of these nations consecrated this garden and helped guide the design and plantings here to reflect the plants utilized by these cultures and the way they have been grown from time immemorial.

Wildflower Treasures contains more native collections planted in semi-formal borders surrounding an elegant flagstone patio filled with stone and stone-like containers. Each border reflects a floristic assemblage of natives grown in English border fashion but with minimal irrigation to show the artistic possibilities of gardening regionally. And the container plantings are perfect miniature vignettes of several dozen wild sites designed to precisely recreate with the native rock, gravel and plants a wide range of specific locations on mountain, plain and plateau throughout Colorado: a horticultural tour de force that fascinates visitors and staff alike.

Japanese Garden

The Japanese Garden lies just beyond this cluster of naturalistic gardens, offering a fascinating contrast with meticulously shaped trees and shrubs and a verdant naturalism that appeals to every visitor. From here a great number of eclectic gardens open up around the expansive water gardens filled with Victoria waterlilies and their hardy cousins: cutting gardens that brim with color through the growing season, a French Kitchen garden designed for beauty as well as the palate. The Drop Dead Red Border is a favorite with visitors, positively glowing through the summer with refulgent crimson, scarlet, deep orange and magenta color that can make the heart skip a beat. Dozens of visitors are usually found sitting in the dappled shade of giant hackberries in the Monet Cafe amid these glorious gardens and ponds, including the 3,000 square foot namesake garden designed to mimic and to honor the artist's great garden at Giverny.

The Victorian Secret Garden is a particular favorite of mine, filled with marginally hardy plants that thrive in this protected microclimate: evergreen southern magnolia, the giant Chilean Gunnera, several species of hardy palm tree and even a hardy banana are a few of the surprises in this garden. These have survived and thrived through many winters when temperatures dropped below 0°F here with little protection and just a bit of mulching.

On your way back to the entrance there is still the expansive and lush Rose Garden filled with complementary annuals and perennials as well as the lavish shrub roses. Long sweeps of more woodland plants glimmer beneath a canopy of a crabapple tree collection that blazes with pastel color in high spring.

Such is the magic possible in a continental climate: add water diligently and you can recreate the lush verdance of maritime climates. Take full advantage of your microclimates and you can overwinter a surprising range of subtropical plants. But concentrate on seeking out the best plants of the world's high, cold plateaus and mountains and you can have rock gardens, prairies and numerous herbaceous borders filled with colorful treasures that grow best where summers are hot and winters are cold. A visit to Denver Botanic Gardens might convince you that continental gardening is not just different, maybe it’s even better.

For more information, be sure to visit the Denver Botanic Gardens website at www.botanicgardens.org.

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