Rocky Mountain High Part 2-Horseshoe Mountain

A couple of days after arriving in Denver, I and several staff from the Denver Botanic Gardens were walking a long winding trail up Horseshoe Mountain.  To reach the mountain we drove west into the Rockymountains (which are visible from Denver), then cut southwest, I think, across a large flat plateau area with cows and much grassland before reaching the mountain base.  The base had lots of conifers and some forest wildflowers, but we parked at the transition zone where the conifers end and the only woody plants are some Salix bushes and potentilla species.  We soon passed that zone and entered the true alpine zone, where a veritable feast of flowers awaited.  Thanks to good rains and a late season, the flowers were at peak.  I was astonished at the diversity, we just don't  have this kind of floral diversity out east.  In the pics above, we see first the mountain itself, with its distinctive horseshoe marking. Next is a shot of two hemiparasitic plants, a pinkish purple Pedicularis, possibly P. sudetica var. scopulorum.  Alongside grows one of the numerous Castillejas, C.occidentalis flaunts its large creamy bracts.  Third is the agave like rosette, though far less menacing, of Frasera speciosa, a strange member of the Gentianaceae that must grow for many years before erupting into a final fountain of greenish white flowers, setting masses of seed, then expiring.  In the fourth photo the diminuitive Gentiana prostrata opens its tiny flowers only when the sun is shining.  It surprised me just how tiny and fragile in appearance this gentian was. Also rather small is Lewisia pygmaea, with its succulent quill like leaves and pink to whitish flowers. An odd Apiaceae, the yellow Alpine Parsley, Oreoxis alpina, shows its delicate divided foliage and petite bright yellow flower umbels.  A grey leaved Senecio, possibly S. canus, was one of many species of this genus that I saw.  I was struck by how many of them looked just like Senecio species in the mountains and grasslands of South Africa, this one reminds me a bit of Senecio coronatus, a grassland species from eastern South Africa.  Truth is the senecios of the Rockies are hard to differentiate, because there are so many of them and they apparently hybridize.  Lovely things, though!  Microseris aurantiaca is the closest thing to an orange dandelion that I have seen, and even its seeds look an awful lot like Taraxacum to me.  Some true native yellow Taraxacum grow there also, in addition to the ubiquitous T. officinale.  The purple spires of Phacelia sericea were quite common scattered here and there across the low vegetation.  Finally a dwarf wallflower, Erysimum capitatum (or asperum, the true name of this alpine variant apparently is controversial) looked like a bouquet of yellow flowers just the right size for a fairie or perhaps a Leprauchan.  So incredible is the wealth of wildflowers on this mountain I feel compelled to follow up shortly with another post showing yet more wildflowers from this beautiful and botanically rich location.

Rocky Mountain High, Part 1

 Any true plantsman or woman will find a chance to learn more about gardening and plants in places other than where they live an exciting adventure.  I got just such an opportunity to go to Denver in early August and stay for a little over a week as a guest of Panayoti Kelaidis, world reknowned horticulturalist and plant explorer.  I gave two talks, one on Pelargoniums and another on South African Plants for American Gardens, to the local chapters of the North American Rock Garden Society and the Cactus and Succulent Society of America, and toured several outstanding gardens, hiked up flower filled mountains, and got to hang out at the Denver Botanic Garden and meet many of the enthusiastic and knowledgable horticulturalists that make it a must visit place for anyone going to Denver. I found it so thrilling to interact with like minded plant lovers, to "shop talk" about our respective gardening experiences and to see and experience gardens and plants in a climate that can be downright bizarre at times from my eastern American perspective. I learned enough and took enough photos to provide material for the several blog posts I intend to produce as a result of my amazing experiences in Denver.

For starters, the photos above show some real horticultural treats from the incredible home gardens of Mike Kintgen, who is in charge of the justly famous rock garden at the DBG.  We arrived one morning to view his gardens, and despite the daytime heat and the fact that Denver gardens are generally not at their prime in August (like many other places, may/June tends to be a more floriferous time), there was no lack of really nice things to see.  A vigorous Monardella macrantha with screaming red flowers by itself would have sufficed to make the visit worth it, as this rare southern California native creates a spectacular mat of brilliant flowers which beckon hummingbirds to come closer to the ground that they probably would prefer. It is one of many plants that no one suspected should be able to handle Denver's cold and very volatile winter weather, but evidently it does so just fine.  It also grows in the DBG rock garden and even in one of the planters along a walkway in front of the greenhouses, as well as in some other gardens in the area. Next one of the delospermas that seem to love Denver's high light intensity, low humidity, and generally drier winters than what we experience in the eastern states.  It is Delosperma dyeri "Red Mountain".  Soon to be released (by Plant Select, a partnership of DBG and local nurseries) as "Firespinner" is a somewhat similar species that blooms earlier and it will be a wonderful addition to the growing list of hardy mesembs or "ice plants" in the USA. If you see it get it! It is a selection of a species from a very cold area of the eastern Cape in South Africa, in fact I understand that it will not flower in places like Cape Town where the winters aren't cold enough. It most closely resemble D. dyeri, but the foliage is different and the plant grows into a larger mat. Next, a western phlox, P. nana, blooms as floriferously as our eastern mat forming ones do much earlier in the season. The yellow mat forming Zinnia grandiflora was everywhere in better Denver gardens, and so different than the commonly seen annual ones.  It is a perennial blooming machine, and is very resistant to the highly localized but insane hail storms that can randomly devastate broad leaved taller plants in the area. Gardeners worldwide obsess about weather, but I learned that no place has more changable weather than Denver.  The hail storm stories I heard from several people were legendary. Apparently its a matter of unluck as to when one strikes as they cover relatively small areas and generally some years go by between really bad ones.  But when a bad one hits, nurseries can be devastated to the point of going out of business (unless they have great insurance), gardens are denuded of foliage and flowers on many taller plants while some smaller ones are just pulverized into mush, woody plants are injured and killed from foliar loss and even bark stripping, and houses end up with roof tiles stripped as well.  Still many native plants like this zinnia are adapted to cope with such events, and with their narrow leaves and ability to bend rather than oppose the hail, they suffer less damage than broad leaved plants like hostas or annual zinnias would.

Centaurea rothrockii (closely related to and perhaps a variant of or conspecific with C. americana) is another wildflower native to certain areas of the southwest, but the only one I saw in the local gardens was the superb specimen in Mike's garden.  It was huge, over four feet tall, with enormous white flowers.  Apparently it grows as a biennial or short lived perennial, but when it flowers it is absolutely majestic. 

All over the Denver area, and in every garden I visited, foliage in various shades of grey, silver, and blue green accentuate the visual aspects of the landscape. Silvery and grey leaved plants seem to love the abundant sunshine and they contibute much interest to gardens.  Several cacti, such as various opuntias, pediocactus, echinocereus, and others are winter hardy and do very well in Denver, where excess winter moisture is less of a threat than in the eastern states.  In the last photo such plants combine beautifully in Mike's home rock garden. 

Searching for a Silene

When I was a teenager, I remember walking deep into the woods to find out what those pink blobs of color I saw each May on the rocks above the highway were. I climbed a small wooded slope from the side opposite the highway until I reached a cliff which had a fence running down it, parallel to the New York StateThroughway which was straight below the cliff edge. The fence had an occasional hole in it, so I could access the cliff edge, though I never went too far, I didn't (and still don't) like heights nor danger. Some rocky slopes were inside the fence at the top of the wooded slope, and these too sported the bright pink Silene caroliniana var pennsylvanica that I had seen from the highway before. One time after part of the adjacent slope was denuded of trees when someone decided to build some apartment buildings below. That following spring the plants grew in abundance, sporting flowers in various shades of pink from light to dark. I imagine they liked the increased sunlight.

Many years later I remembered speaking with the wildflower curator when I worked at the NYBG, and told her that I saw these plants, but could find no mention of them in a field guide covering all the native plants the NYC area by the Brooklyn Botanic Garden. She had heard of the plant in the area, and told me it was considered rare in NY, and that the BBG field guide probably didn't realize that it was still extant in NY (I think a later edition added it in).

So finally one decent Sunday morning this past May I went out to the location where I remembered seeing the silene growing. I parked my car in the parking lot below the slope (despite the signs warning not to do so, the restaurant there was undergoing renovation) and hiked up the slope. There was more poison ivy and smilax than I remembered, but I carried on until I reached the cliff. It took me a while, but I spied some pink flowers in the short grass among the rocks, and found a few plants inside the fence, far fewer are there now than when I was a kid. I also found two fence openings, and a more robust population on the cliff margins outside the fence. It was past prime blooming time, but I was able to photograph some flowers and also gathered some stems with maturing seedpods and a few basal shoots for rooting. More seeds than I expected were produced by the ripening pods in the next few days at home, and the basal cuttings are still green so hopefully they are rooting.

Silene caroliniana var pennsylvanica is not a rare plant in general, but it is rare and localized in New York. I had no idea of that when I was a teenager, and would try and transplant plants to my small garden where they would die after a couple of seasons or so. It appears that they have a very specific habitat preference; very well drained acidic soil among large boulders, preferably in tight cracks, and with good sun exposure. This plant does not tolerate larger competion well, its immediate neighbors are grasses, Hypoxis hirsuta, Corydalis sempervirens, and some sort of small blue flowered annual linaria-looking thing. The soils it grows in must dry severely during summer droughts. It is opportunistic, spreading and/or growing more vigorously when nearby trees that cast shade on some plants are removed (in nature by fire), but fading out again as succession proceeds and the canopy closes again. The most secure plants are those on the cliff edge and and the cracks below it on the vertical side facing the NYS throughway--the latter are impossible for any human or animal to access. However development has occured nearby on the slope leading up to the cliff, it is a very developed area of lower Westchester county anyway. Not far north of there, also on cliffs overlooking NYS 87, is another colony I have observed from my car window, but a huge development of a mall and apartments appeared there in the last couple of years after the entire hilltop was cleared. Plants there can now only persist on the cliff face itself. So in both colonies the silene is only safe so long as the cliffs themselves are not dynamited during road widening or more development. However the silene's potential for expansion into nearby woodlands after fire or other successional event is nonexistant due to habitat destruction. Its long term future is also bleak since small limited populations separated by development from each other are more vunerable to extinction in general. I am not optimistic for its long term survival locally, in another generation the area it grows in will be indistiguishable from NY City.

Silene caroliniana in both of its varieties is a suitable plant for a rock garden, it being a natural chasmophyte after all. It is quite striking when in full bloom and has the potential to increase rapidly via means of the numerous seeds produced. I will start some seeds next year to try on the slope garden at school, in addition to what plants may result from the basal cuttings I took.