Can cultivars be considered native plants?

One of the questions that arise in discussing native plants is the question of whether ornamental cultivars (e.g., ‘October golory’ red maple) can or should be considered ‘native’.  In short, my answer is ‘No.’

Here’s my rationale on this.  First, when we think about natives we need to put political boundaries out of minds and think about ecosystems. Political boundaries – a ‘Michigan native’ or ‘an Oregon native’ – are meaningless in a biological context.  What’s important is what ecosystem the plant occurs in naturally.  In addition to taking an ecological approach to defining natives we also need to consider its seed source or geographic origin.  Why is it important to consider seed origin or ‘provenance’?  Species that occur over broad geographic areas or even across relatively small areas with diverse environments can show tremendous amounts of intra-species variation.   Sticking with red maple as an example, we know that red maples from the southern end of the range are different from the northern end of the range.   How are they different? Lots of ways; growth rate, frost hardiness, drought tolerance, date of bud break and bud set.  Provenances can even vary in insect and disease resistance.

 


Native range of red maple

If we’re dealing with an ornamental cultivar, do we know the original seed source or provenance?   Sometimes yes, sometimes no, sometimes maybe.  Think for a minute how most ornamental cultivars come to be.  Some are developed through intentional crosses in breeding programs.  The breeder may or may not know the geographic origins of the plants with which they are working.  Or they may produce interspecfic hybrids of species that would not cross in nature.  Some cultivars are identified by chance selection; an alert plantsperson finds a tree with an interesting trait (great fall color) in the woods or at an arboretum.  They collect scion wood, propagate the trees and try them out to see if they are true to type.  If the original find was in a native woodlot and the plantsperson kept some records, we may know the seed source.  If the tree was discovered in a secondary location, such as an arboretum, it may not be possible to know the origin.

 

So, if a breeder works with trees of known origin or a plantsperson develops a cultivar from a chance find in a known location AND the plants are planted back in a similar ecosystem in that geographic area, we can consider them native, right?  As Lee Corso would say, “Not so fast, my friend.”  We still need to consider that matter of propagation.  Most tree and shrub cultivars are partly or entirely clonal.  Cultivars that are produced from rooting cuttings; for example, many arborvitae, are entirely clonal.  Cultivars that are produced by grafting, like most shade trees, are clonal from the graft union up.  The absolute genetic uniformity that comes from clonal material is great for maintaining the ornamental trait of interest but does next to nothing to promote genetic diversity within the species.  From my ultra-conservative, highly forestry-centric perspective, the only way to consider a plant truly native, it needs to be propagated from seed and planted in an ecosystem in the geographic region from which it evolved.  Few, if any, cultivars can meet that test.

Lamb’s Ears Revisited

A bit more on my recent travels to the big floriculture conference in Columbus, Ohio.  I always try to make it out to the Chadwick Arboretum & Learning Gardens, on the campus of THE Ohio State University. There are several components, including trials, a large arboretum, and several small gardens.  My favorite is the Steven Still Perennial Garden. It’s a lovely mixed garden, designed by Adrian Bloom (Blooms of Bressingham), and was installed in ONE DAY by their garden volunteers – 2005, I think.

Watching it grow has been fun. I noted [ with pleasure] that they’ve already had to start cutting back and removing some things. This makes me feel better because I am The Queen of Planting Too Close

A few highlights:

I thought of y’all when I saw
this…remember our conversation about Stachys the other day? Here’s a
new one on me: Stachys byzantina ‘Silky Fleece’.   What teeny, tiny
little leaves! And seemed to be limiting itself to a small area on the
edge of the border. Introduced in 2006 by German seedmeisters Jelitto
Perennial Seeds. They missed the boat on naming it…could have all kind
of fun with ‘Little Lamb’ or even ‘Mary’s Little Lamb’ as the director
for their North American office is Mary Vaananen. Heh.



My foot is just in there for scale – I’m really not that inept a
photographer
.

 

A gorgeous flock of Rhus typhina ‘Tiger Eyes’.  Hardy to Zone 4, the foliage is golden in summer, blazing apricot in fall, a wonderful shrub accent in any garden… What? Hang on a sec.

Correction:
That’s Rhus typhina ‘Bailtiger’ PP16,185. Trade name is First Editions® Tiger Eyes® Cutleaf Staghorn Sumac. Well, that took all the fun out of it.

Moving on…



Belamcanda chinensis – Blackberry or Leopard
Lily.  A tough cookie, this midseason bloomer takes drought and even
reseeds a little bit in my home garden. The pods burst open to
reveal a cluster of seeds that look exactly like a blackberry. These
weren’t quite that far along, but in between flowering and seed setting, they
do something else interesting..



The petals twist up into these hilarious
little bundles. I have no idea why or what for. Just kind of neat
.

All for now!

The Other Lamb’s Ears

I’m assuming even you tree people (aka other
Garden Professors) are familiar with the soft, silvery leaves of Stachys
byzantina
or Lamb’s Ear (variously Lamb Ears and Lamb’s Ears).  Not to
disparage S. byzantina, but in our part of the world it looks like a
pile of wet dryer lint in the winter; and can become similarly
disfigured during a hot, wet summer.  Spring brings bright,
pet-able new ears, followed by woolly flower spikes that could serve as
Q-tips for Shrek. Runs/reseeds like a banshee in my home garden.
As
Dr. Allan Armitage notes, “We’ve been lamb-eared to death.”

But there are several other species of
garden-worthy Stachys, one of which is garnering lots of attention in
our campus garden at the moment. Behold, Stachys officinalis ‘Hummelo’ – Wood Betony or Alpine
Betony.

Also sold under S.
officinalis
and S. densiflora. Most nurseries seemed to have settled on
S. monieri
, but that specific epithet does not appear in the ITIS
(Integrated Taxonomic Information Systems) database. Armitage lists it as a cultivar
of S. officinalis and then has S. monieri as a separate species.

Regardless of pedigree, ‘Hummelo’ is a terrific perennial.
Clumps of glossy green scallop-edged foliage are topped with
spikes of rosy-lavender flowers throughout the summer. Heat- and
cold-tolerant; it’s hardy from Zones 4 to 8. Full sun or part shade,
drought tolerant, deer resistant…what’s not to like?

Back to the ubiquitous version of lamb’s ear…we
have a superior selection of S. byzantina with the fabulous cultivar
name of ‘Countess Helene von Stein’. Rarely flowers, and has bigger, tougher leaves that hang in there regardless of humidity. Very effective
when barked at students with a Teutonic accent: “Countess Helene von
Shtein! You vill learn dis plahnt!”  You may find this in
the U.S. under the comparatively boring ‘Big Ears’.

What’s old is new again

While the Emerald Ash Borer (EAB) continues to expand in the upper Midwest (see http://www.emeraldashborer.info/files/MultiState_EABpos.pdf  for a current infestation map), EAB is old news here in Michigan, especially in the southeastern part of the state.  Efforts to restore urban and community forest canopy lost to EAB will continue, however, for the foreseeable future. In 2003 we established an Ash Alternative Arboretum MSU Tollgate Education Center in Novi, MI – which is near ‘Ground Zero’ for the EAB infestation in North America.

 

The planting offers some insights into selecting alternative landscape trees to replace ashes.  A couple of elm cultivars, in particular, have emerged as shining stars in the demonstration planting that includes five specimens of 37 different species and varieties.  All trees were planted as 1½”-2” bareroot liners by Tollgate volunteers.  Tollgate farm manager Roy Prentice has overseen the maintenance of the planting.

 


Accolade elm (Ulmus japonica × wilsoniana ‘Morton’)  Compared to most of the other selections planted in the arboretum at Tollgate, Accolade elm looks like a man among boys.  Growth of these trees has been outstanding – the trunks of the trees have grown fast enough that they have split off their plastic rabbit guards (see photo).  Like Triumph elm, Accolade elm has dark green glossy leaves and develops into a large tree.  Although elms are often thought of ‘ugly ducklings’, both Triumph and Accolade are quickly developing well-formed vase-like crowns.

 


Triumph elm (Ulmus ‘Morton Glossy’) has also done very well at the Tollgate planting.  This elm develops a vase-like crown with age and has dark green, glossy leaves.  A large tree to 55’.

 

The elms are part of series of elm cultivars that have been developed with high tolerance of Dutch elm disease.  Most of the new elms are hybrid crosses with Asian and European elm species, though selections of American elm that are tolerant of Dutch elm disease are also available in the nursery trade.  The irony in all of this, of course, is that native American elms were devastated by another introduced exotic pest, Dutch elm disease.  As elm trees were rapidly lost during the 1950’s, 60’s, and 70’s, ash trees became a popular replacement due to their ease of transplanting, growth rate, broad site tolerance and pest resistance (yet another irony).  Now we’re promoting elms to replace ashes.

 


Street scene before and after Dutch Elm Disease.  Photo: theprincetonelm.com

The moral of the Dutch Elm Disease and Emerald Ash Borer stories is that it’s critical to avoid over-reliance on one species or even one genus – even a native one.  In Michigan some of our urban and community forests are over 50% maple.  As global trade increases and the potential for destructive pests to hitch-hike around the world rises, the best hedge against catastrophic tree loss is to plant a broad and diverse array of adapted trees.

Blue Spruce Blues

One of the roles I’ve evolved into over the past decade as an extension specialist at MSU is that of ‘the Conifer Guy’.  Conifers are great and fascinating plants.  The oldest trees in the world are conifers, the largest trees in the world are conifers, and some of the most interesting (at least to me) landscape plants are conifers.  Unfortunately, for a variety of reasons, in the Upper Midwest we have gravitated to Colorado blue spruce more than just about any other conifer.  Part of this over-reliance on blue spruce in the landscape is driven by production (see, Linda, I’m not always an apologist for nurseries).  Growers want to grow what they know and what’s easy to grow.  As a nursery tree, blue spruce is a reliable performer that is well adapted to a relatively wide range of site conditions.  Of course, growers also want to grow what they can sell, and there always seems to be a steady demand for blue spruce.  In many neighborhoods it appears that there is an ordinance that every other tree has to be a blue spruce.  So what’s the issue?  In the Great Lakes region, blue spruce often look pretty good when young.  However, as trees age they become susceptible to several major pests, especially cytospora canker and gall adelgid.  So all those shapely blue Christmas trees that were planted 10 or 15 years ago are now a bunch of ratty-looking messes.  So what’s the solution for blue spruce burn-out?  Clearly landscapers and homeowners need to think beyond blue spruce and look for a greater variety of choices.  Here are three to consider.

– Serbian spruce Picea omorika  Whenever I’m asked to suggest a conifer, Serbian spruce is usually one of the first trees in the conversation.  While the color may not be as striking as a blue spruce, Serbian spruce still has impressive needles in its own right – bi-color with dark green on the upper side and silver below.  Adding to Serbian’s charm is its graceful weeping habit.

– Swiss stone pine Pinus cembra The late, great conifer expert Chub Harper used to remark, “I never met a cembra I didn’t like.”  Chub’s fondness for Swiss stone pine was well founded.  Here is an understated, consistent landscape performer.  Few pests, dark green needles and stately upright form.

– Korean fir Abies koreana  It would be a stretch to consider Korean fir an alternative to blue spruce.  While Korean fir is more broadly adapted than many of its pantywaist cousins in the genus Abies, it will still do best on the Holy Grail of moist, well-drained slightly acidic soils.  Nevertheless, Korean is tougher than the average fir and is a conifer with some character and worth a shot.  Korean firs are often heavy cone producers, which can add an interesting element of color.