Fraxinus americana 'Autumn Purple' (White Ash)</p> "Disaster in slow motion" is a phrase that has been applied to many phenomena including global warming, the collapse of biodiversity, chronic drought...and most recently it's been appled to the Emerald Ash Borer (Agrilus planipennis</em>: henceforward referred to as "EAB") a green beetle from East Asia that was introduced accidentally in wood pallets in Detroit fifteen years ago. Since that time it has infested billions of ash trees in twelve states. The cost for removing dead ash from the urban forests of America is already climbing into the millions for even small cities, and the concomitant issues: thinning of the urban canopy, storm water abatement, air quality--these costs are hidden but real. No wonder when EAB was confirmed in Boulder only twelve weeks ago, arborists and decision makers across Colorado practically panicked. Ashes comprise around 15% of the trees in Colorado's cities: the cost for removing and replacing these trees over a short period of time is truly astronomical and daunting.</p> On Tuesday of this week, several of our staff joined hundreds of arborists from across the state and beyond at a daylong Emerald Ash Borer Management Seminar sponsored by Denver Parks and Recreation, the State Forest Service and Davey Tree. Several local authorities as well as those from some of the first areas affected by EAB gave very informative presentations that helped dispel some of the panic and provide some clear options. Several points that emerged were that because of Colorado's compartmentalization into different river drainages, the progress of the insect will likewise be compartmentalized. Since enough cities are separated by open space where ashes are not present, the progress may likewise be slower. A multiplicity of factors are showing that there are viable options for preserving many ashes with timely insecticidal treatments, and that a coordinated effort could preserve many ashes for a long time--rather along the lines of the strategy pursued with American elms--many fine specimens of which are still standing throughout our region despite the fungal infestation that destroyed nearly all of the elms in parts of the East.</p> Although there are compelling ecological and economic reasons to deplore this latest threat to our horticultural legacy--I came out of the meeting somewhat heartened by knowing so many professionals and decision makers cared, and that there were some practical strategies that will mitigate if not forestall this impending "disaster in slow motion". This link to a paper by Dr. Daniel Herms, Professor at Ohio State University at Wooster</a>, gives a good summary of the methods that will likely be used to preserve many--alhough by no means all--of the tens of thousands of ashes that grace Denver and the Front Range.</p> Ashes to ashes--but not yet quite to dust!</p>
Young Siberian larch (Larix sibirica</em>)</p> You have probably walked by this willowy sapling many times--although I suspect if it were not in fall color, you would have walked by it barely noticing it! There is another specimen or two of Siberian larch at the Gardens. This one is west of the Western moongate just outside PlantAsia. If you're a tree fancier, you might linger for a moment and think, "A larch from Siberia--I suppose there are larches there." As botanic gardens mature they often focus more and more on recondite research issues, or more global conservation concerns almost forgetting what most people expect. Visitors who come are usually curious about plants. How wonderful it would be if they would realize that the modest specimen at the Gardens often represents a major plant where it comes from. So it is with this larch which covers literally millions of acres across the breadth of Asia.</p> Enormous mature larch in the Altai Mountains</p> Here you can see what heights Siberian larch is capable of attaining in the wild! I was very fortunate to have had Plant Select underwrite a trip that Mike Bone and I took to Central Asia in 2009. One of the many highlights was seeing thousands of enormous Siberian larch everywhere in both Kazakhstan and Mongolia. Unlike our native tamaracks in both New England and the Pacific Northwest and Alaska, their Siberian cousins often grew on steep, sunny slopes rather than wet streamsides and bogs. They formed open forests all the way to dry treeline, but could be found also isolated on surprisingly dry areas in the higher steppe, growing among sparse grasses and sage. This specimen was enormous.</p> ! Siberial larch alongside explorers</p> Here you can see Mike Bone on the right with our guide Vladimir Kolbintsev, leaning on that same giant tree. I doubt I will be around to see the saplings planted at Denver BotanicGardens attain half this size and girth--but it would be fun to do so!</p> Rugged larch on the Austrian road</p> When we finally reached the summit of what they call the "Austrian Road" in the Kazakhstan Altai (built by Austrian prisoners of war) we saw a rugged tree in the distance we decided to investigate...</p> Giant Siberian larch on summit of pass</p> We could scarcely believe our eyes as we approached--this one had even greater girth, and the most rugged habit. We could see the highest peak in Siberia (Mt. Belukha) from the pass. Not far away (near the very heart of Asia, equidistant from Indian, Arctic, Atlantic and Pacific oceans), this area experiences unbelievable cold in the winter, and the winds on this alpine summit must be hurricane in force for months on end. And yet here it grew, almost solitary, as picturesque as an ancient oak in Windsor Great Park.</p> Larch cones</p> The needles are so fine and soft, the cones are so delicate that they belie what must be ironclad toughness in the tree itself. I have always felt that larches would be a wonderful addition to Denver's parks and streetscapes because of their airy look and toughness. Siberian larch I fancy would be the best choice, although I know of almost no commercial sources. Unfortunately, our local landscape contractors aren't familiar with larches. I know of several instances where larches have been removed in winter because it was supposed that they have died when their needles fell. It would take quite a campaign to educate our local populace about them. But I think it's worth doing!</p> Larch cones</p> Another glimpse of the nearly golden cones in the late summer. Makes you want to look inside them!</p> Our larch near PlantAsia</p> We end where we began, with our still very modest larch. Seeing the venerable specimens in Kazakhstan, one can appreciate how these might one day grow to be massive and imposing. More to the point, perhaps, one is humbled to realize that every one of the tens and thousands of accessions of plants at Denver Botanic Gardens has a compelling story much like this one. The world of plants is infinite!</p>
Asian dogwood (Cornus kousa</em>)</p> "Asian dogwood? Surely photographed in Oregon, or perhaps New Jersey?" Nope--taken at Denver Botanic Gardens last June. There are several specimens--this one in the Rock Alpine Garden, but also at Waring House that reliably bloom late every spring.</p> Cornus kousa</em> tree in Rock Alpine Garden</p> You are not apt to find many dogwoods elsewhere in Denver--but staff at the Gardens are fond of "pushing the limits" and trying plants that are generally considered marginal, or unsuited to our windy, steppe climate. Time and again we succeed!</p> ]Engelmann's cactus (Opuntia engelmannii</em>)</p> "Surely this picture was taken in Arizona? Mexico?"--a big bushy prickily pear loaded with fruit?Taken at the Watersmart garden where this clump is easily a yard high and twice that across!</p> Bull Bay (Magnolia grandiflora</em>)</p> "This tropical looking magnolia must have been photographed in Mississippi? Or California? Surely these evergreen magnolias can't possibly be hardy in Denver?": there is, in fact, a comparatively huge specimen in the courtyard of a public school in Jefferson County--but you can find several of these all around Denver Botanic Gardens. This one bloomed beautifully in July in the Victorian Secret Garden (it would have been nice to have one of those models nearby to pose with it?)</p> Dragon Arum (Dracunculus vulgaris)</p> "This huge-flowered black aroid must be from some Subtropical country? Turkey perhaps?" No, Virginia--the black arum in the Rock Alpine Garden where this is self-sowing. Here it is very hardy indeed and seems to love growing in Colorado. You won't want to linger around these clumps when they're in bloom, however: the smell is pretty strong!</p> Texas Agave (Agave havardiana)</p> "And this huge Century Plant? It must be from the Davis Mountains of Texas?" That may be where the seed came from originally, but this hefty specimen--over a yard across--is in the Watersmart Garden in front of the Conservatory--and may well bloom in a year or two!</p> Drakensberg gladiolus (Gladiolus saundersii</em>)</p> "And this African Gladiolus--are you telling me this is hardy too?" Coming as it does from the highest Drakensberg it should not be surprised that this beautiful gladiolus is root hardy in Colorado--despite its exotic looks.</p> Giant Sequoia (Sequoiadendron</em>) in south Metro area</p> Not many Denverites would believe that there are giant sequoias around the city: Denver Botanic Gardens is not the only entity that "pushes the limits" around here--lots of private gardeners do too. Here a number of the staff who are keen on trees recently visited what may be the largest in the immediate Metro area, although the State Champion is in Grand Junction. We have a whole grove of these in the Gates Garden that are approaching this one in size. Despite many sub-zero winters, these seem to show no winter damage.</p> Crevice garden</p> "Surely this picture was taken on Mt. Evans? Such a natural outcrop has to be in the hills, right?" Wrong again--this is one of a half dozen wonderful crevice gardens that have been built in the Rock Alpine Garden and Children's Gardens the last two years which are one of the best ways of growing tricky alpine plants.</p> All these exotic plants and garden styles are examples of how gardeners seek to "push limits" and grow what they perhaps shouldn't try to. Of course, a Botanic Garden is the logical place to do this experimentation since we have the room and knowledgeable staff to study up on plant needs.These exotic plants offer a great contrast to the more extensive collections of native and adapted xeric plants we are so famous for showcasing. Nevertheless, time and again we have been shocked at how well "marginal" plants perform--sometimes better than "tough" natives! Almost three decades ago staff planted Hesperaloe parviflora on the site of what was to become the Watersmart Garden: I remember scoffing as I walked by "Surely this plant from southern Texas doens't have a hope here"...within a few years it proved its mettle, and now there are thousands thriving all over the Metro area--all because we pushed some limits at the Gardens! </p> </p>
Scott Skogerboe and mystery maple...</p> Everyone should have a hero. Scott Skogerboe has always been one of mine: Head of propagation at Fort Collins Nursery Wholesale</a>, he and his boss, Gary Epstein have been the force behind most of the woody plant introductions of Plant Select</a>. Here he is standing in front of...well...you shall have to wait and see (I have my crafty ways of making you read all the way to the bottom of my blog posting!)....</p> Amur maple at Box Store</p> This is NOT the same maple as the one with Scott above--this is an Amur Maple (Acer ginnala</em>) I photographed today (October 20) on West Colfax in front of a Box Store which I am NOT</em> endorsing (although I confess I did</strong> by 50 of awesome plants while I was there...). As the name suggests, Amur maples originate in the Amur river region of East Asia, the river that separates Manchuria from Siberia. No wonder the tree is so cold hardy! But that area is also Maritime--and the soils are podzoils: generally acid, more like the soils of our upper Midwest and New England. So of course, Amur maples in Denver are frequently chlorotic, and usually not recommended by horticulturists "in the know". No one bothered to tell the landscape architects, who filled the vast parking lot of this box store with them--and each and every one of them are blazing in DIFFERENT colors, and looking mighty healthy!</p> A whole ROW of frickin' amurs</p> Here you can see bits and pieces of a half dozen Amur maples in blazing color---looked like a regular conflagration! Each was robust, and each a very different shade of flaming red and orange (and some yellow and one or two green--this picture doesn't show them quite right--I'll show some closeups to better demonstrate a wonderful quality that is being increasingly denied people: namely, the wonderful biodiversity and variability that comes with seed grown plants.</p> Yellow-orange Amur</p> Although most of these maples were an unalloyed scarlet-vermilion, one was more orange-yellow in tint...</p> Green leafed Amur</p> Right alongside all the red ones, one had barely begun to turn and was still mostly green</p> Bright vermilion Amur Maple</p> But of the several dozen Amur maples around the parking lot, most were this flagrant, bracing, wonderful red color that we all love so much in the species. I have seen dozens of Amur maples all around Denver looking this good--there are some massive ones near Denver Botanic Gardens (and I have a pretty awesome specimen in my own garden too--hee hee)...but for every stunning Amur maple, there are usually a few gnarly, miserable things that look awful year around and hardly color up in fall. I have a hunch some of these are simply inferior plants, and others are probably growing in particularly bad sites with more alkaline soils, perhaps, or other environmental problems...Here, you should generate a drum roll and have the summon the cavalry with trumpets! Woo hooo!</p> Acer tataricum</em> at Fort Collins Nursery Wholesale</p> Last Friday, while visiting Scott at Fort Collins Nursery Wholesale, I espied a furiously red small tree in the distance--the same one pictured at the beginning of this posting with Scott standing in front. This is a superb, red-fall coloring Tatarian Maple--a sib to the Plant Select Introduction, Acer tataricum</em> Hot WingsTM</a>. I have observed around town that Hot Wings Maple has been quite reliable about turning a wonderful reddish purple color in most sites. And since it is a selection of Acer tataricum, it will thrive in far more alkaline pedocal soils ("Tatarian" refers to "Tatary"--the archaic term used for "Turkestan", the designation for the portions of Czarist Russia in Central Asia--namely contemporary Kazakhstan, Kirghistan, Uzbekistan and the smaller neighboring "stans" that are now mostly independent states, but formerly parts of Russia and the Soviet Union. Mike Bone and I found Acer tataricum</em> several times in Kazakhstan--many of them with the bright red samaras much like the Plant Select clone...</p> And here's the rub--you can go to almost any nursery in Colorado (in fact around the United States, Canada and Europe as well) and find Hot Wings in several convenient sizes--which you can purchase and plant in your garden and get not only spectacular fall color, but a shapely small tree the rest of the year which has brilliant red fruits for much of the summer--which look as bright and dazzling as flowers for an extended period: it is apt to thrive for you on acid or alkaline soils, and once established in Colorado thrives with almost no supplemental irrigation: what's not to love?</p> One of the great ironies of Colorado horticulture is that the ultimate seedsman (Scott Skogerboe) has also developed a number of clonal plants that will one day greatly outnumber the millions of seedlings he has grown in streetscapes and gardens around the world. Such are the ironies of our crazy modern world.</p> A piece of me wishes we could have developed a seed strain of red-winged maples so we could enjoy the wonderful biodiversity that thrilled me earlier today at Home Depot as I wandered through the Amur maples (imagining what they must look like in their native habitat right now, with the last few Siberian Tigers slinking through them nearby)--wait! What was that orange flash I caught out of the corner of my eye!? For a brief second I felt like Derzu Uzala</a> (you must rent this dazzling Kurosawa classic if you've not seen it yet) and a moist Siberian breeze caressed my cheek.</p>
Random sampling of Burr Oak Leaves</p> Our spring may have been the worst I can ever remember, but fall is shaping up to be extraordinary. Yesterday, towards the end of the amazing Pumpkin Festival at Chatfield I found myself wandering through the extensive windbreaks, most of which were planted twenty or more years ago by my friend Chris Hartung, who now runs an amazing nursery in Canyon City</a> with his wife, Tammy. It would be fun to walk the windbreaks with Chris and hear his stories: the trees have grown surprisingly well despite no irrigation, abundant bunnies, deer, elk and you name it in the way of herbivores. Even the "slow growing oaks" are getting some size despite the lack of irrigation! Burr Oaks (Quercus macrocarpa</em>) do not color brilliantly as most trees do in Denver: but they make up in rugged charm and wonderful leaf shape and acorn what they may lack in brilliance! Just look at the amazing variabillity in leaf color and shape in this very random sampling!</p> Burr Oaks at Chatfield</p> Denver Botanic Gardens at Chatfield is truly stunning: although the plant collections are still modest (the Visitor Center Garden--designed by Lauren and Scott Ogden, is world class, however, and large nevertheless), what makes a visit to Chatfield so gratifying right now are the wonderful vistas! The Rockies looming all along the West, the gently rolling countryside: it is our Secret Garden (although the tens of thousands of people coming to pick their pumpkins yesterday must have had an inkling! There were record crowds this year!)</p> Windrow of Burr Oaks: each one different!</p> It's great fun to stroll the windrows: every plant looks different. Some have already lost all their leaves, a few are still bright green. I wonder where the acorns were collected for these: are they from the Midwest? Or did Chris find a source from the wonderful Burrs that grow around Devil's Tower in Wyoming. On a recent visit to Gillette in early spring a few years ago, my hosts drove me up to the Devil's Tower and we walked around it (clockwise--the way you should walk around mountains of course!). This is the Westernmost colony of the tree in the northern Plains, and they were almost exactly intermediate between Gambel's and Midwestern Burr in character--some even stooling like a Gambels. The ones at Chatfield look more treeform (although still only fifteen or twenty feet tall at the max). I planted two burr oaks at my house about the same time Chris planted these and my Burrs are enormous now--one has to be over 30' tall and almost as wide and starting to take on the rugged adult form: three or four times the size and girth of these specimens: such is the power of irrigation!</p> Burr oak acorn</p> There were not a lot of acorns (the trees are yet young) and the ones I found were much smaller than the golf ball sized burr oak acorns I used to marvel at as a child in the park next to my house: those more than justified the common name "mossy cup" or "overcup oak".</p> An example of variability</p> This shows how variable the trees are: the one on the right was still mostly green, the one on the left is all brown and in the distance the burr oak is totally naked. All in proximity with what must be very comparable soil and exposure. Go figure!</p> Sprig of oak</p> For tree lovers, oaks and pines have a special resonance. If you've ever been lucky enough to see the massive burr oaks throughout the Midwest--all the way to the East Coast actually. Although I associate them especially with the magnificent oak savannahs around the Great Lakes and the rolling hills of the upper MIdwest. From a distance the white oak (Quercus alba) and burr oak look somewhat similar--but closeup the leaves and acorns are immediately distinguishable. Right now the handful of white oaks in Denver are a blazing, furious scarlet color (well worth their own blog!)--but even despite their superior fall color, it's the burr oak one finds here and there throughout our fair city. I believe the State Champion is just west of Cheesman Park--a massive creature that fills all the neighbors yards with leaves...(I know one of those neighbors and she's not to crazy about that tree)...</p> What sets this oak apart from many of Denver's street trees is its obvious drought tolerance. Chatfield's vast strings of windbreaks (so lovingly planted and cared for by Chris for years) are coming into their own: they make Chatfield a friendlier, more inviting place.. and they are teaching us a lot about the adaptability and variability of plants we should be planting more: the survivors!</p>
</p> Allium</em> 'Millenium'</p> Diane Reavis, one of our long time Plant Select committee members, observed that "we don't do a lot with the summer Alliums at Denver Botanic Gardens" as the committee strolled through the Gardens the other day. That got me thinking: I used to grow lots of Allium ramosum</em> in the Rock Alpine Garden, and I know there are some wonderful forms of Allium cepa</em> that bloom right about now. But with the notable exception of this spectacular clump of Allium</em> 'Millenium' in the middle of the Water-Smart garden, we really don't have very many right now.</p> Since this has been an area of great hybridization in Europe and the East, I have a hunch our staff will incorporate far more in coming years. You can probably guess what year Mark McDonough--who hybridized this showy beast--introduced it in? It has Allium glaucum</em> ancestry, and probably some A. ramosum</em> as well. I love the way it contrasts with the Devil's Shoestrings behind it (Nolina lindheimeri</em>).</p> </p> Allium senescens</em> v. glaucum</em></p> Here is one of the parents growing in my private garden. It was taken a few years ago this is only now starting to bud up and won't be in full bloom for several weeks. These form dense tufts of swirly foliage that look like a vortex, decorative in its own right. Thrives in almost any sunny, well drained spot. I've even had it over-winter in containers!</p> </p> Allium cernuum</em></p> One of the best late onions, however, is our native nodding onion, which you might encounter almost anywhere in our mountains below treeline. In fact, it grows pretty much across the United States from coast to coast. It is enormously variable in habit, size and flower color. It's worth trying this from various populations--you will find quite a bit of variation. This one was photographed in the Rock Alpine Garden.</p>
