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Asian dogwood ( Cornus kousa )

"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.

Cornus kousa tree in Rock Alpine Garden

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!

]Engelmann's cactus ( Opuntia engelmannii )

"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!

Bull Bay ( Magnolia grandiflora )

"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?)

Dragon Arum (Dracunculus vulgaris)

"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!

Texas Agave (Agave havardiana)

"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!

Drakensberg gladiolus ( Gladiolus saundersii )

"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.

Giant Sequoia ( Sequoiadendron ) in south Metro area

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.

Crevice garden

"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.

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!

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Pushing limits...

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