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>
Each summer college students from across the country descend on Denver Botanic Gardens to participate in our summer horticulture internship program. And even though there’s still snow on the ground, we’re already booking the fieldtrips and tours for the program. Designed to help students explore career opportunities in public horticulture, the program immerses students in most every aspect of public horticulture and provides the hands-on experience that employers value. In addition to educational activities and hands-on gardening, each intern is mentored by one of our professional horticulturists on an independent project. As usual this year’s list of projects covers a wide range of interests. This summer at the Gardens, interns will be:</p> Documenting our Quercus collection with photographs, measurements and herbarium specimens</li> Developing educational classes for community gardeners</li> Learning about maintenance of a Japanese style garden using native plants and learning about bonsai</li> Mapping and documenting plants in new and existing gardens for our plant database</li> Helping develop a seed herbarium</li> Helping measure and conserve water in mixed ornamental plantings</li> Developing and conducting horticultural therapy programs</li> Learning about and working in our CSA (community supporting agriculture) program at Denver Botanic Gardens at Chatfield</li> </ul> The program consistently receives positive ratings from the interns who participate. "I had an amazing experience here that exceeded expectations.” </em> - Aaron from the University of Nebraska "The summer flew by because I was having fun and I learned a lot thanks to the amazing mentors and the field trips that were provided for us.” </em> - Jacob from the University of Missouri at Columbia</p> Though I may be a bit biased, I think that the program we have planned for the summer of 2011 is equally good if not better than last year. For horticulture students, the February 15th application deadline is fast approaching. Click here for more information about the internship program.</a></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>
It isn't often that I linger at work until after the sun sets. Tonight is an exception. This evening, our Victoria cruziana</em> plants (also known by the common name of Santa Cruz Waterilies) are coming into full bloom in the Monet Pool. As I sit on a bench beside the pond, the heady pineapple scent of a first night's Victoria</em> blossom drifts my way. The creamy white petals are visible between the bronze tinged sepals and soon the bloom will open fully . . . although they say that a watched pot never boils and I am beginning to think that the same principle may apply to night-blooming lilies. </p> </p> Native to slow-moving water in the Amazon River basin of South America, the genus Victoria</em> consists of two species: cruziana </em>and amazonica</em>. V. cruziana </em>is the hardier of the two and therefore easier to grow in Denver's climate. This plant showcases large platter-like leaves with leaf rims that can reach a height of 4-6". The underside of each leaf consists of an impressive network of thick veins that allows for air to be trapped under the leaf, giving it the ability to hold a good deal of weight... an advantage that hasn't escaped the notice of birds hunting for fish or other prey in the waters below. Sharp thorns line the underside of each leaf and stem: an effective form of protection against would be predators, along with well-meaning horticulturists attempting to fertilize the plants!</p> </p> The impressive features of the plants don't end with the leaves, which brings me back to the point of my evening. The plants bloom at night, with each bloom lasting only two nights. </p> </p> The first night's bloom opens a pure, creamy white and smells strongly of pineapple. This fragrance, combined with the bright color that makes the flower more visible in the darkness, are lures intended to draw scarab beetles which pollinate the plant in its native habitat. The bloom also heats up (a horticultural phenomenon known as thermogenesis), which helps to spread the pollinator-attracting scent.</p> As the first evening comes to an end, the first night's bloom will slowly close, trapping the beetles inside. It will reopen the following evening but with one noticeable change. The flower will transition from a female bloom to a male pollen-producing bloom that is pink in color. As the beetles emerge from this second evening's bloom, now covered in pollen, they will once again be drawn to the luminescent glow of a first night's flower, thereby pollinating the plants. </p> It is now 8:30 p.m. at the Gardens. The crickets are serenading me as the twinkle of lights in the trees towering above the Monet Deck are reflected in the dark water. And low and behold, the petals of a first night bloom are beginning to slowly open. </p> </p> The Victoria cruziana</em> plants at the Gardens will continue to produce blooms throughout the summer months. First night blooms often stay open throughout the early morning hours. Also on display in the Four Towers Pool are Victoria </em>'Longwood Hybrid' plants (a cross between the two species) which should also be coming into flower soon. The Gardens are open from 9 am to 9 pm daily unless otherwise noted on our website.</p>
Birds and Bees' hotel</p> One of the things that struck me on my recent visits to Europe were that every botanic garden I visited seemed to have a structure designed to attract beneficial insects--a sort of "Bug Hotel" or condominium complex. I took pictures of these at several botanic gardens, intending to show them to my colleagues to inspire them to do something similar. Wouldn't you know, Katy Wilcox (one of our outstanding propagation department staff) had unbeknownst to me gone out and done just that. And with typical flair, Denver's habitat is unusually stylish and beautiful: one of the large pedestals for sculptures left over from previous exhibitions had not had a sculpture designated this year, and rather than have it sitting empty and forlorn, Katy and her volunteers combined these wonderful containers with the minihabitats! Enchanting!</p> Beneficials condominiums at Wurzburg Botanic Gardens</p> One of the most extensive such "condos" was at Wurzburg's astonishing botanic garden (one of the finest I have ever visited)--the holes of different sizes in different media attract a wide spectrum of bees, beetles and other insects which help with pollination and increasing the biodiveristy of garden fauna (a good thing). and I find these quite intriguing...</p> Hamburg's elegant habitat hotel</p> Of course, the fantastic botanic garden in Hamburg, Germany HAD to have a particularly elegant structure--which looked so good I was tempted to move in. There is a whole movement in America to make our gardens more ecologically responsible and friendly to the little beasties (who can be spooky--but our very existence ultimately depends on their well being)...check out the Habitat Hero website</a> to learn more about this important movement. And maybe next year you can construct your own habitat hotel!</p>
The new mine structure at the Children's Garden</p> A great proportion of the visitors to our York St. gardens have never even visited the Children's garden: perhaps they're afraid they are over the height limit there? Or there is simply too much to see West of York Street that they can't imagine what might be there for the kiddies. Well, I can assure you that the Children's garden is full of plants you will not see at York Street proper, and is WELL worth the visit! For one thing, where else in Denver will you see a brand spanking new antique mine structure? This popped up just in the last few weeks--I think it's quite authentic looking and adds some local color!</p> Alpine meadow</p> Although there's lots for tots to see and do, the appeal to gardeners here is in the extraordinary numbers of plants that have filled the various beds--plants chosen for their cultural adaptability to challenging sites...a few weeks ago I counted over 40 species of penstemon alone, but there are all manner of wildflowers and grasses that weave a very authentic looking meadows that have filled this garden in very short order. The picture above captures the tufted, wonderful way the mats and mounds have woven to make a veritable tapestry of color in this garden. You will find dozens of plants blooming here each week--a constant kaleidoscope of interest..many of them seem to require or do best in the fluffy, eco-roof mix that is employed on top of green roof structures. Whatever the secret, do check out the gems that are here and no where else.</p> Inula rhizocephala </em>and tiny Ziziphora</em></p> Here is an example of a tiny gem from Central Asia blooming in one of several exquisite new crevice gardens that have cropped up in the Children's area as well: I guarantee you that you will find things you will not have seen before!</p> Campanula incurva</em></p> We have grown Campanula incurva</em> many times over the decades, but I don't think we have ever had such wonderful specimens. Although often short lived, these bloom for such a long time that they are worth every inch of garden space they occupy! This is a rare plant in Northern Greece where it grows wild--it shouldn't be rare in our gardens, however! It's a winner!</p> Pond at bottom of Children's garden</p> There is something amazing about this garden: you get wonderful views like this of the pond--which really does look like an alpine tarn...</p> Penstemon richardsonii v. dentatus</em></p> And at the other end of the spectrum you get wonderful vignettes everywhere you look: although most penstemons are finished, some are still very much in evidence: there are not one but two subspecies of P. richarsonii</em> from the Pacific Northwest: this glorious one blooms for months on end--a first rate garden plant. Not to be found West of York at the "regular" botanic gardens!</p> Stream with kids</p> The children in their namesake gardens are almost always splashing in the stream or digging next door in the "digging place": watching them is an added bonus on a visit here: they really love the hands on activities!</p> Alpine meadow</p> But for even the most seasoned visitor here, this garden is a whole new palette of plants combined in utterly unique ways: Here you can see the luscious clusters of Buckwheat flowers on the 'Shasta' selection of Eriogonum umbellatum</em>--it's been glorious for weeks. The purple mats behind are a creeping germander from Spain (Teucrium cossonii</em>) and the diffuse pink perennial next to it the other form of Penstemon richardsonii</em>--all of these unique to this garden.</p> I know that many of us on staff this garden has been a revelation: I never thought we would have so many hundreds of kinds of plants growing so well that have been a challenge in the "adult" areas of the garden. The children's garden has become for me an essential place to visit frequently--it's a new gem that should not be a secret to so many people!</p>
Yucca rostrata in Yuccarama</p> There are certain floral spectacles through the gardening year at Denver Botanic Gardens that are not to be missed: when the foxtail lilies (Eremurus</em>) are all in bloom early in June, for instance, or the Iris beds much of May and June... Well, right now we have the time of Yucca blossoming--and they are truly amazing any time of day--although they seem to glow with a special luminosity in the late afternoon. Yucca rostrata</em> may be primarily Mexican in distribution, but there are many robust and happy specimens blooming right now throughout the Gardens. I believe this my favorite!</p> Forest of tree yuccas</p> Ann Frazier, a volunteer, recently scanned this historical photo, showing the largest tree yuccas at the gardens a year or two after they were planted in the late 1990's. I blogged about these recently</a>...but it's worth revisiting these now that the flowering season is here...</p> Same yuccas taken today, July 2, 2013!</p> Do look back at the previous picture and see how dramatically these have grown in the last decade: I never cease to be amazed that Chihuahuan desert plants growing over 1000 kilometers south of here at lower elevations have the genetic tolerance to our severe winters! These have shown less frost damage than some of our native plants over that time! These were donated to us by Mountain States Nursery for testing and display, and I recall as Dan Johnson placed these thinking they would be the most expensive annuals we ever planted! I was wrong, obviously....By the way, the largest yucca in this planting is Yucca faxoniana</em>, and the more slender ones are Yucca thompsoniana</em>--both from the Chihuahuan desert in Texas and Mexico with roughly the same range as Yucca rostrata</em>.</p> Denver Botanic Gardens has a remarkable collection of many dozens of accessions of cold hardy yuccas that are located in many of our gardens. Now is a wonderful time to look at these--I have discussed a few of them in yet another one of my blogs you can find by clicking here.</a> And another one here</a>! As you might have guessed, I like yuccas! I end my little disquisition with a tribute to our ubiquitous, overlooked and sometimes maligned Yucca glauca</em>: Last May I drove through vast forests of this species in the Oklahoma panhandle and was dazzled by their heavy blossoming. Among the mostly creamy or ivory flower stalks were many that were stained quite deep pink. It was a dream of Claude Barr's to find a truly red yucca: I think these are well along the way to that goal! Alas, I was unable to collect that trip--so perhaps you can be the one to locate and introduce that holy grail?</p> Red stained Yucca glauca in Oklahoma panhandle</p>
This week we’ve taken a few minutes from our busy schedules to consider pollinators and all they do for us and our environment. An earlier post advocated creating a pollinator-friendly habitat around your home or acreage. Here at the Gardens we’ve taken on that challenge as well.</p> The basics for pollinator survival - food, water, shelter, and nesting sites - are all easy to provide in a well planned garden. The abundance of food available in the form of nectar and protein-rich pollen on our flowers draws pollinators to the Gardens. There is always something in bloom when pollinators are active, from crocuses in early spring through the last aster of autumn. Horticulturists refer to this as succession planting – planning and planting for continuous bloom. We also often arrange plants in groups or sweeps. This allows for efficient foraging by pollinators; minimal energy is expended flying from one flower to the next. </p> Many of our gardens at York Street feature or incorporate plants native to our region. This is especially important for attracting and nurturing native pollinators. Our Chatfield and Mount Goliath locations are rich in native foraging opportunities for these important pollinators as well.</p> The second basic need, water, is accessible in our water features, and droplets from early morning irrigation are handy for a quick sip.</p> Shelter from inclement weather, from hungry predators, and from inattentive gardeners is readily available for bees and other pollinators in the Gardens as well. An unmulched area of soil can be home to ground-nesting bees that build nest tunnels under ground. Wood-nesting bees can find a home in dead limbs. Since we tend to cut out most dead limbs, we offer an alternative, nest boxes made from hollow reeds or bamboo. These nest boxes are being mounted in protected locations around the garden. </p> To help protect pollinator species we limit the use of pesticides at the garden. Integrated pest management (IPM) practices are employed to control insect pests and weeds. Cultural practices, mechanical means, and biological controls are all exhausted before we turn to a chemical solution. If chemicals are used, the smallest amount necessary is applied and only in a very targeted manner. When possible chemicals are dispersed early on a cool, calm morning when pollinators are not yet active or before flowers have formed.</p> Thanks to pollinators we have berries for our breakfast smoothie, tomatoes for our favorite marinara recipe, and pumpkin for pies. And perhaps more importantly, at least in our particular setting, pollinators help our plants set seed that can be harvested, propagated, and returned to the gardens in the form of transplants or shared with other public gardens. Simple steps result in a pollinator-friendly garden and the benefits pollinators provide. We encourage homeowners to join us in welcoming pollinators to the garden.</p>
Pollinators provide critical ecosystem services. Pollinator research is important to better understand the relationships between pollinators and plants and to improve conservation and management of both plants and pollinators. Here at the Gardens we work with roughly 70 of Colorado’s most rare and imperiled plants through surveys, monitoring, and seed collection. While we are learning more about each of these species, there is a big gap in our knowledge about the pollinators of most of these species.</p> Our pollinator research provides valuable information about the plants we monitor and enables us to better conserve and manage these species. Recent work we have done includes pollinator observations of the Colorado hookless cactus (Sclerocactus glaucus</em>). One question we are interested in is whether or not roads are impacting the pollinator communities of this species. We have found that bees are the main pollinator of this species and so far we haven’t found a difference in pollinator diversity or visitation rates. In addition to gaining valuable information for management, our research also allows us to find some pretty cool organisms, including a tarantula hawk (Pepsis mildei</em>). We found this wasp as part of our monitoring of Brandegee’s buckwheat (Eriogonum brandegeei</em>) in Fremont County. This wasp stings its prey (a spider), lays a single egg on each subdued spider, and then the larval wasp eventually eats the spider. </p> In addition to learning about the pollinator community of the plants we study, we are also interested in understanding the impacts of changes in land use and climate on the pollinator communities and how that impacts the success of the plant communities. Expanded urbanization, recreation, and oil and gas development all impact the lands where our state’s rare plants occur. All of these have the potential to impact the pollinator communities. Some of our research aims at better understanding the current health of pollinator communities in the face of these land use changes. We also know that climate change has affected plants and animals around the world, including affecting not only survival but where and when activities occur. Changes in migration patterns and timing of migration and flowering can impact plant pollinator interactions, including mismatches in timing or location between the plants and animals. Researchers across the world continue to better understand pollinators and their relationships to plants to help further our basic understanding of the biology of these species and improve conservation and management.</p> A basic component of pollinator research involves pollinator observations. Pollinator observations can be quite time consuming and require a lot of patience as they involve sitting in one spot for long periods of time observing a small patch of flowers. They can also be a fantastic way to gain a better understanding and appreciation for the plants and animals in the community you are studying. It isn’t often in research that you get to sit and spend a day (or many days) in one spot. If you would like to see what pollinator observations are all about and you will be visiting the Gardens this week, come join members of the Research Department collect pollinator observations each morning at 10:30AM through Saturday.</p>
Floral decoration in front of restaurant We shall get to the gardens in a minute--but this is a glimpse of an not unusual scene in the old town of Gothenburg: a tad early for the summer annuals, a wonderful restaurant we dined at had this cluster of trees and perennials at their front door--pretty sophisticated for city folk! It is so strange to see Helleborus niger (or its hybrids) used as ornamentation. I hope they plant it in their garden soon... Christmas roses still blooming in May in the Old Garden at Gothenburg The Botanic Garden (Botaniska Tradgarden) has such allure that we almost didn't visit what must have been the original botanic garden in the heart of the old city: that would have been a mistake! This graceful old garden is a masterpiece of horticulture: lavish beds on all sides... and the spectacular conservatory in the grand Victorian era manner. This is a must see if you come to Gothenburg! We were too early to get inside the grand conservatory which only opened at 10AM--but the collections were extensive and made us wish we didn't have to leave so soon! Seasonal planter with bulbs and pansies</p> I suspect the giant containers outside the conservatory had only been planted a few weeks (judging by their contents)--the double Ranunculus made a bold contrast to the rich tapestry of grape hyacinths and pansies--I suspect in another month or two this will be swapped for summer annuals.</p> I've heard topiary described as a lifetime commitment: anyone who has pruned knows that pleached trees such as this represent decades of care. Exquisitely pruned wisteria in front of a building on the Gardens' grounds. We were a few weeks early for the wisteria--although I suspect in an "ordinary" year it would be out by now... Long bank covered with Bergenia ciliata from the Himalayas After crossing the channel in a ferry and a certain amount of wandering, we arrived later that same day at the Botanic Garden of Copenhaven--like Gothenburg, this represents a very old institution (they celebrated their 400th anniversary a few years ago)...and likewise situated in the heart of the city. One of the first things to greet us in the entrance was this spectacular stand of one of the loveliest Bergenia.... Closeup of Bergenia ciliata v. ciliata We grow this at Denver Botanic Gardens as well--and I was rather proud of our yard wide stand--but this had gnarly, ropy stems many yards long, with hundreds of flower stems! Impressive! The Conservatory at Copenhaven botanic garden with our host, Dr. Hans Hansen. Like Gothenburg, CBG has a spectacular Victorian-era conservatory that is in excellent repair, with wonderful ancillary greenhouses with beautiful collecitons of cacti, begonias, orchids and more. Hardy opuntias planted outside the conservatory There were some vigorous masses of hardy cacti outside the conservatory. Despite a fierce winter, they came through well. Although I did notice much more rust than they would get in our own dry climate.</p> </p> There is much more to convey about both these venerable European gardens (Copenhagen in particular has an immense rock garden full of treasures--the result of their long history of research in Greece due to Arne Strid's publishing several floras of Greece in the last century). Perhaps I can share some more later...but meanwhile, we are off to Germany where there are botanic gardens in every town it seems, and some of enormous scope and activity. It will be great fun to visit some of these as well. Each mile we drive further south there are more and more trees in flower and spring is exploding everywhere--as it finally is back home we hear! Time to go out there and sniff the flowers!</p>
