Delosperma floribundum</em> 'Starburst'</p> There have been a veritable flood of hardy ice plants on the market in recent years, to the point where we have forgotten about some of the worthy old timers. This happens to be a twenty year anniversary for the time when I first saw and collected this delightful morsel on the windy steppe near Springfontein, just a bit west of the Drakensberg mountains of South Africa. It was growing in sparse grassland that was terribly reminiscent of Colorado. This picture is a particularly robust specimen in cultivation--but the wild ones were almost as flashy. This was one of the second wave of hardy ice plants that were championed by Plant Select,</a> and which certainly helped propel that worthy program.</p> The commonest query I get in recent years when the subject of hardy ice plants comes up is, "Aren't you afraid these will become weeds?" I can well imagine how a surgeon must feel when asked, "Aren't you afraid the patient will die on the table?" Of course, there is a remote possibility that any plant grown out of "context" (although humans have impacted practically every square centimeter of the earth so that I wonder if there really is a "natural," non-human context any more, truth be said...) and I invariably respond that Carpobrotus edulis</em> (the weedy Californian ice plant in question) is a massive plant comparitively speaking, and the ecology of California coasts and shortgrass prairie in Colorado are not one and the same. Well... guess what I found across the street from my very own house? My charming South African waif has flown the coop!</p> Delosperma floribundum</em> "escaped"!</p> As I pull out my car from the garage, and drive a few hundred feet down my street, on the unkempt prairie to the west of me I've been noticing some pinkish-purplish flashes. What could these possibly be? I finally stopped the car and wandered out and Lo! and behold, a dozen or so Delosperma floribundum</em> had naturalized in the weedy grassland. Horrors! What have I done?</p> Delosperma floribundum</em> ESCAPED!</p> Here you can see that all the plants are growing within a few feet of a weed barrier and a mulched bed that was where the original plants were planted a year or so ago (and which have summarily died). I am curious if the demise of the parent plant was due to the richer soil, or the pathogens engendered by the bark mulch. The lesson here, of course, is that Delosperma floribundum</em> is a grassland plant that prefers to grow in sparse shortgrass prairie, in a harsh pedocal soil to the fluffy garden pedalfer mulched with bark chips. This speaks volumes about our horticultural practices. We strive to grow plants from more humid climates that need more acid, humusy soils (pedalfers), while Plant Select and others are introducing plants from semi-arid regions that do much better in our alkaline, native mineral soils (pedocals). Crazy, no?</p> At Denver Botanic Gardens Waring House</p> Of course, a few self sown seedlings a few feet from the parent plant does not a rampageous weed make (although the exotic plant haters are loth to make any distinctions). Here you can see that Delosperma floribundum</em> has produced a random seedling on occasion in the past, such as this charming plantlet I photographed ten years or more ago growing in a low wall along the street in front of the Waring House. A number of the species ice plants have shown a willingness to seed--although rarely to the point of being a serious garden menace. I suspect a goodly number of our garden plants (including natives) can self sow enough to lead to a fastidious gardener avoiding them. I'm thinking of Red Valerian (Centranthus ruber</em>) , Knautia macedonica</em>, Perovskia, black-eyed-Susan (Rudbeckia triloba</em>) and a throng of other garden classics that have been proscribed from this or that local garden because of their profuse spreading. They are pesky plants in the wrong spot, perhaps, but hardly obnoxious weeds.</p> Obviously I shall be watching these Delosperma</em> over the years to see how much more (and if) they spread in the vant field. Meanwhile, I marvel that twenty years after first seeing these they've come home to roost, so to speak. If not home, across the way!</p>
Hydrangea quercifolia</em></p> This time of year I am amazed to see spectacular mounds of Hydrangea</em> 'Annabelle' glowing around the metro area. That is one cultivar that has certainly made its mark, although one doesn't see quite as many of them as you would in a more humid part of the country. I've noticed a few other sorts here and there--including small plants of the blue species (I think the jury is still out on these when it comes to our climate however.). There is one particularly striking hydrangea that has really proven its mettle for many, many years at Denver Botanic Gardens. The Oakleaf Hydrangea (according to the USDA)</a> is restricted to just the eight southeastern-most states, and yet the plants shown above have persisted in a dense stand of English Ivy alongside Denver Botanic Gardens' Waring House for nearly 30 years.</p> Blossoms of the typical wild form</p> The common wild form has long, graceful flowers that form a bit of a cone shape up to a foot long. Like others in the genus, the fresh flowers are white, but age a lovely soft green. If you cut them and hang them in a cool dry spot, they can make wonderful dry flowers for the winter too!</p> Hydrangea quercifolia</em> 'Snowflake'</p> Growing alongside the typical form is a more compact flowered and smaller leaved cultivar that looks a bit more like the Eurasian species. It seems to have fared just as well over the decades, and makes for a nice contrast. All forms of this wonderful shrub turn glorious orange and pink in the fall, reminiscent of their native cousin Jamesia americana,</em> that grows everywhere in our mountains (the only member of the family that does).</p> Both cultivars together</p> Here you can see both cultivars growing alongside one another more clearly. Surely, if they can grow well in this most challenging spot, nearly swamped with thirsty ivy, imagine what it might do in a well prepared spot in your garden with some compost and TLC? We have another handful of cultivars of this wonderful plant elsewhere on our grounds--but not enough! Come to think of it, I have a perfect spot in my garden for one... I better go out and get it before you beat me to the punch!</p>
Winecups in Watersmart Garden</p> Strolling around York Street gardens this time of year, you are apt to see a bright rose red plant that resembles a geranium in many gardens. It is apt to be winecups (Callirhoe involucrata</em>), a favorite of many staff and keen gardeners in the area. Not a geranium at all, this is in the Mallow family, and another common name is "Poppy Mallow", although it's no more a poppy than it is a geranium. It is a native plant found sparingly on the Great Plains east of Denver, more commonly in the Midwestern prairies. It is a stellar garden plant that will survive with no supplemental irrigation once established...I see it occasionally as I drive around Denver--but not nearly enough!</p> Winecups in Highlands</p> Here is an amazing planting I found yesterday in Highlands neighborhood--easily ten feet across, completely filling one of those triangular hellstrip corners that are so often weed infested and neglected-looking (making neighborhoods look like slums). Here is a great alternative--a rock, a bit of Russian sage (Perovskia</em>) and an exuberant mass of winecups blooming for months on end--all with no supplemental water!</p> A closer look</p> This mass is growing in part shade--and the mound is almost two feet tallk, as opposed to the first picture in this series taken at Denver Botanic Gardens, in full sun--well less than a foot tall. It does need some room to ramble--but almost everyone has a spot where this can flourish.</p> Callirhoe involucrata v. tenuissima</em> Not everyone likes the hot magenta of the typical form of this species: there is a lighter, more pink form of winecups that is found originally in Mexico--sometimes classed as var. tenuissima. It does have even more finely divided foliage and a neater habit and the flowers often have a striking white eye--here seen growing in the Rock Alpine Garden as it transitions to the Gates Garden in the west. I am especially fond of this form, first introduced to cultivation by Yucca-do a few decades ago.</p> Closeup of tenuissima</em>.</p> You can see if you compare this with the next that var. tenuissima</em> is quite different in effect. Come to think of it, I think I need both in my garden! And I wish we'd see it a lot more everywhere in town: one of the toughest and most beautiful native perennials!</p> Closeup of var. involucrata</em></p> Here is a closeup of the typical form for comparison with the one above--both are really stunning! For sale in better Garden Centers (forget the Box Stores when it comes to native plants)..can be planted any time--just make sure it doesn't dry out in the height of the summer until established!</p>
Purple Mountain sun daisy at City and County Building</p> For over a decade the Master Gardeners of Denver and I maintained a low water garden</a> in front of the City and County Building in the Civic Center of Denver. It was with mixed feelings that I saw this replaced a few years ago with a much simpler, and rather classic garden design. A few days ago, as I drove past, I was startled to see a familiar flash of rosy purple pink: Surely that's not "Purple Mountain Sun Daisy?" I stopped and sure enough, Osteospermum barberiae</em> 'Purple Mountain'--one of the first hardy ice plants to be promoted in U.S. horticulture--was making quite a show. This was introduced to horticulture by Plant Select in 1998</a>--and has gained a steady following across the country over the interim.</p> Closeup of Purple Mountain</p> If you are not familiar with this plant, take a closer look. Photographs have a hard time capturing the distinctive and unique color--somewhere between hot pink and rich purple violet. The color is fantastic, and everyone loves it. There is a slightly darker ring around the disk flowers that make it even more alluring, and it does change hue every so slightly over the days that it opens. The reverse of the ray flowers is a silky bronze color--important because the flowers close at night or in dark weather. And while it blooms most enthusiastically from late April to mid June, there are scattered flowers on this lovely plant all summer long. Did I mention it has leathery, dark green evergreen leaves?</p> Purple Mountain bedded out</p> I take more than a little pride that the park's staff and designers have chosen such a prominent spot to showcase a plant that was debuted at Denver Botanic Gardens in 1991 (a few years later High Country Gardens began to sell this from germplasm they obtained from us). And now I see it popping up here and there around town.</p> Bank planting of Purple Mountain</p> I took this picture of a mass planting at a bank a few blocks from Denver Botanic Gardens a couple years ago--I noticed it's still going strong and blooming spectacularly this year again...</p> I've seen wonderful plantings in Pueblo and Vail--two utterly different environments: the plant obviously has a wide latitude of cultural tolerance. I have friends who have grown it in Massachusetts and California. Truth be said, it does seem sensitive to fungal or bacterial damage in some gardens. If you've had trouble with 'Purple Mountain', do try Osteospermum</em> AVALANCHE (see below).</p> Osteospermum AVALANCHE in the Mordecai Children's Garden</p> If you have never visited the Children's Garden at Denver Botanic Gardens (thinking it was only for kids), do not pass go, do not collect $200 Monopoly dollars--get yourself down there pronto! You will find amazing spreads not only of this gorgeous South African, but of all manner of wonderful montane and alpine plants that thrive in theCildren's Garden's green roof soil mix.</p> Denver Botanic Gardens can be proud indeed to have debuted such an important and uncanny group of perennials. The annual Osteospermums are well and good--but these hardy sorts make plush groundcovers, and bloom for months on end. Perhaps you should include a few in your garden? Who doesn't need a little Purple Mountain majesty above one's fruited plains!</p>
