Saturday, August 3, 2013

Location, location, location...(some thoughts on zone denial etc.)

Alpine House, Kew in 2010
Kew is generally acknowledged as the greatest botanic garden on Planet Earth: its glorious history, unbelievable herbarium and vast grounds full of treasures will ensure that in perpetuity. I have always thought that the Alpine House at Kew (here shown in its current sleek manifestation) represents the institution's unique and vital plant collections, however, and others (not as rock gardeny as me) have agreed. It would take several thousand blogs to properly treat this treasure trove, but I'd like to examine a few plants here and their location (comparing these to Denver), which I think will help illuminate a few perplexing issues: plant hardiness, invasiveness and zonal denial chief among these...

Inside the alpine house
An overview of one of the many mini-gardens that fill the structure--each and every plant has a story to tell (most of these plants are grown in pots and swapped in and out at their peak show periods--maintaining a breathtaking show through the entire gardening year)...

Salvia daghestanica in the Kew Alpine House
One of the first plants I noticed on entering the Kew alpine house was this lovely specimen of a lovely Salvia first collected by Henrik Zetterlund in southern Russia which has become a beloved Plant Select star performer in Denver. Friends throughout Europe have told me that this wonderful salvia is essentially impossible to grow in a garden: below you can see how it performs in typical xeriscape conditions in Denver: location, location, location!

Salvia daghestanica in Denver

It produces a few more blossoms in our intensely sunny steppe climate as well you notice!

Puya cf. caerulea outside the alpine house
Look below

Closeup of the Puya blossom

 Before you start to feel as though Denver is more congenial for growing things than England, consider the puyas: Kew boasts several vast mounds of puyas growing unprotected at the fringes of their rock garden--this would almost certainly perish with the first hard frosts we experience in Denver (Kew is Zone 8--some years barely experiencing frost at all)...location, location, location.l

Boy, would I love to grow this Puya outdoors here: I guess we'll have to settle for agaves and yuccas (although I did see puyas growing very high indeed in the Andes once...)

Scarlet bugler penstemons (left) and Apache plume (far right)
I was amazed to see large masses of our native Penstemon barbatus (which usually grows in relatively dry parts of the American West) thriving in open beds at Kew--and not far from these a very handsome large specimen of Apache Plume (the white mound on the right of the picture): Fallugia paradoxa is even more xeric in its distribution: both of these seem to find Kew's location to be just fine, thank you. Go figure!

Myrtle spurge Euphobia myrsinites

One of the most surprising "treasures" I saw at Kew was this ancient, gnarly, bonsai-like spurge--a plant which is classed as a noxious weed in Colorado! I have seen this Euphorbia lovingly displayed at many European botanic gardens. Euphorbias present some fascinating issues I have discussed can a plant that is pestiferous in Denver be a treasured alpine house denizen in England? Location, location, location!

I am coining the term "charismatic nega-flora" for plants like this which have inspired a veritable witch-hunt like zeal while the much nastier (but less attractive) Euphorbia esula causes far more trouble in meadows and median strips around Denver (I have pictures to prove this contention). There is a contemptible streak of puritanism in the noxious weed movement that focuses unduly on plants with ornamental merit. If you are reincarnated as a weed--hope that you are homely and you are apt to escape the weed-mongers scythe altogether!

Teucrium chamaepitys in the rock garden at Kew
 Another shocker for me was seeing this rather charming yellow flowered ajuga featured prominently in the Kew rock garden: for me this is an almost uncontrollable weed I remove by the wheelbarrow load from my home gardens. I don't think it was much a problem in cooler England where this may not set as much seed..

Araucaria araucana
 It is entirely possible that seed from very lofty populations of monkey puzzle trees might be induced to survive in Denver--in an extremely protected microclimate perhaps. I have seen a healthy specimen at Willard Bay Gardens in Utah...but we are not apt to have immense, graceful and obviously very happy araucarias in our parks as they do in the lawns at Kew. Location, location, location!

Delosperma cooperi in a glasshouse at Kew
But Delosperma cooperi, grown by the tens of thousands across Denver in just about any soil or exposure, encrusted for months on end with a solid mat of rosy purple flowers was represented at the Royal Botanic Gardens by this rather halting individual in a glasshouse. Location, location, location!

(I like to have the last say!)...


  1. The Euphorbia is an interesting circumstance. I understand that for gardeners in Colorado on the Front Range waffle a bit over whether this spurge is worth all the ranting and raging, but here along the Wasatch Front in Utah, it is clear to just about everyone this is a serious problem in the spring. There are foothills bordering wilderness that are covered in chartreuse flowers every May as the spurge marches up the mountainside. Even the non-botanically inclined population at large sees that it is taking over everything. Despite regular articles in the paper and an aggressive eradication program mounted by the cities and the native plant society, we are losing this battle. I'm wary even to try Euphorbia rigida because it may cause trouble as well.

    As you say, location, location, location.

  2. I've not seen those sites you refer two along the Wasatch front (and don't deny that it's a problem). I agree that growing myrtle spurge in ex-urban settings is irresponsible and reprehensible. Denver is full of gardens that have beautiful stands of it, however, that pose no risk for the wild.

    The range of Myrtle Spurge is a tiny fraction of E. esula in America right now--the latter has severely degraded pasture across vast parts of the upper Midwest and Rockies. I believe that esula merits far more attention and eradication efforts--and would have received them if it were a tad more charismatic.

    Humans are far too swayed by beauty (for both good and ill)

  3. Panayoti, If it makes you feel any better ... incipient populations of Euphoria esula are removed from local preserves with follow up occurring for many years. The areas are then monitored annually to make sure reinvasion does not occur. Other top invaders are Melilotus officinalis, Melilotus albus, Phalaris arundinacea, Alliaria petiolata. All of these were not introduced for any horticultural merit. Indeed, certain invasive species were promoted and planted by conservation agencies not many years ago. These would include species like Rosa multiflora, Lonicera maackii, and Elaeagnus umbellata. The reason you think only ornamental plants that become invasive are targeted for control is because your perspective is that of a garden curator and not a natural area manager.


    Chicago Area

  4. I am very much aware that some government agencies are working hard on various "non-horticultural" weeds across the West--although Euphorbia esula does not seem to be one of them. I believe Melilotus is still being sown in some areas despite its nasty tendencies for us, and vast numbers of Eurasian grasses are still being sown in the west to "improve pasturage": Bromus tectorum, Bromus inermis, Convolvulus arvensis, various Cirsium and Centaurea spp. seem to get far less attention than they should--these are the real pests in the west. Instead, we hear mostloy about Russian olive, Tamarisk and myrtle spurge: I don't think that's my bias, I think it's a fact, and it stems from a strange and undeniable streak of anti-ornamental attitude in the fringe environmental movement in America, which I believe traces to America's being founded by religious zealots. You may argue with this--and I am not sure it is provable either way without a great deal of statistical analysis--but I have observed it so consistently in my long life I am confident one day it will be acknowledged.

  5. This is a good "heads up". I slammed on the brakes outside of Princeton, BC in June because of a mess of yellow flowers off the side of the highway. Climbing the hillside for a better look, I realized it was Euphorbia myrsinites; in semi-wilderness, at least 2000 feet from the nearest home. The last time I handled this plant, I burnt myself severely, so I made a note to yank it (and I will, next chance I get). Isn't it ironic that I'd probably have troubles spotting it right now in August under Centaurea diffusa?

  6. Okay, okay: youse guys have convinced me that my favorite little bête noire is a bête indeed...

    The sap alone is reason enough to eschew it!


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