What's Blooming: Cactus Garden
by Lauren Springer, Horticulturist, Gardens on Spring Creek
An unusual
planting at the Gardens is wowing visitors and attracting a myriad native bees
and other pollinators. To see what the buzz is about, and perhaps fall in love
with some intriguing plants that broaden horizons for gardening in Northern
Colorado, head to the Cactus Garden on the south side of the Undaunted Garden.
In this relatively
small, sloped space, traversed by a casual gravel path and graced by a large
pergola for shaded seating and viewing from its north side, several hundred
winter-hardy cacti are making themselves at home. The planting is one of the
largest public outdoor collections of cacti hardy to USDA Zone 5 in the world.
Unique in its attention to design, this specialty garden blends regionally
resonant rockwork and companion plants with the striking and prickly cacti stars
in thoughtfully artistic ways that also benefit the cacti horticulturally.
When I was
growing up, cacti were mostly the domain of eccentric collectors. Those of us
who were intrigued by nature as youngsters and collected rocks, shells, bugs
and the like often also found these oddly shaped, armed plants fascinating. At my first home in Northern Colorado, I grew
hardy cacti outdoors in the late 1980s and early 1990s. Passersby complained and wrote letters in the
town paper claiming they were unsightly, unfriendly and dangerous and that I needed
to remove them.
After a few years, I moved and took them all with me to my next home in the Foothills. A few of those original plants are now in the Undaunted Garden, as are many of their offspring. Things sure have changed – I’m back living near town and now have to worry about people stealing cacti from my home garden rather than demanding I remove them.
More and more people
are being won over by the architectural beauty of cacti, the luscious colors of
their showy flowers, their water thriftiness and ease of care. As demand rises,
the nursery trade has stepped up to produce an ever-expanding array of options.
However, most of the emphasis has been on growing and offering species with little
regard to winter hardiness because the North American cactus market is dominated
by highly populated areas where they can be grown outdoors such as California,
Arizona, and Florida. In colder and damper regions, these winter-tender cacti
are marketed as houseplants and / or movable container plants that can be moved
and sheltered from both extreme cold and too much moisture.
Winter-hardy
cacti have been the forgotten stepchildren of the cactus and succulent trend.
It has been slow going for those of us in the less populated, arid and cold
interior West wanting to grow these in our plantings, but fortunately, several
intrepid and talented plantspeople are propagating and selling hardy cacti mail-order
and wholesale to regional retail nurseries. Some of the plants in the Undaunted
Cactus Garden come from these great folks—the late David Salman of High Country Gardens,
Jeff Ottersberg of Wild Things and Kelly Grummons of coldhardycactus.com, to
name a few. I propagated other plants from garden- and wild-collected seed
(hedgehog, clustering or barrel species) and cuttings (Opuntia or prickly pear species) over a period of years—the plan
for Undaunted was born in 2012, but the site wasn’t ready until 2018. And some
come from my three-decade-old home garden collection. A few were collected from
the wild in “rescues” before an area was stripped and graded for development.
Perhaps the
most exciting part of having a public garden space devoted to these incredible
plants is to share the year-round beauty of cacti in a big way and inspire
people to plant them at home. They need full sun in our climate, preferably a southerly
or westerly slope for better drainage and a site that offers them some
protection from cold winter winds. If the soil is particularly heavy clay,
building a raised berm and incorporating about equal volume scoria (small-sized
pumice / lava rock) or expanded shale (used in many green roof projects) into
the soil will help prevent cold and wet conditions in winter and spring that
promote rotting.
Placing cacti
among rocks complements their forms and helps protect their roots from wide
temperature fluctuations and drying out quickly after rain. At the same time, rocks
reflect much-desired extra warmth onto plants’ tops when nestled close by. A
gravel mulch looks good and does the same things as individual larger rocks.
I’ve been observing cacti in nature most of my adult life and they often grow
in rocky, gravelly places, or even out of fractures in sheer stone, so it just looks
natural and best to me to incorporate rocks and gravel into a cactus planting.
The stone in
the Undaunted Cactus Garden was acquired from the Rock Garden in Fort Collins
and is a rhyolite from the Dakotas, an igneous rock, like basalt, that weathers
and breaks in columns of faceted “crystals”. In the wild you can see these
chunks littering a hillside below their mother caprock of hard rhyolite. I
aimed for this look, though the “caprock” in the garden is actually entirely different—the
similarly ruggedly angular and tawny seating blocks that were part of the
overall expansion hardscape installation are actually sandstone. Plantsman and
crevice garden expert Kenton Seth and I spent a hot, hard – but also fun and
rewarding – week moving, placing and setting ten tons of this rhyolite to
create the naturalistic look I was after.
Now it’s up to
the plants to settle in and mature. It is fun to watch the new garden knit
together and become a more cohesive visual and horticultural community. We may
lose a few of the marginally hardy species in an unusually cold winter or a sudden
extreme temperature drop during the shoulder seasons, but such is gardening. There
are more seedlings and cuttings in the wings. From the busy hum of pollinators among
the vibrant rainbow of bloom in May and June to the quiet architecture of
snow-dusted spines and hummocks in winter, hardy cacti are a joy to experience
in any month. They are natural living and growing art, all year round.