[CANUFNET] Medians

[Ian Wilson]

Thanks Alison, and others who've responded.
 
FYI, here's some of the species we've tried.  We are Zone 6a / 5b so
we've got a few more options:
 
1)  Red oak - seems to be one of the best overall for salt tolerance and
tree health
2)  London plane - good tolerance to the harsh median conditions,
however they will suffer bud dieback due to salt spray in the winter,
mostly on the lower branches, which causes witch's brooms on the lower
part of the tree.
3)  Norway maple - excellent salt tolerance but they suffer bad leaf
scorch in late summer
4)  Austrian pine - does pretty well, but we have to trim them up for
sightlines
5)  We've tried black locust ("purple robe" variety) but this particular
variety is NOT doing well, mostly because it is so weak-wooded and
breaks apart
6)  Callery pear - a recent trial but seems to be doing ok so far, and
the Chanticleer variety is more upright
7)  Armstrong maple - seems to be doing ok in areas with lower speeds
(not as much salt)
8)  Honeylocust - also seems to do quite well, we have some mature
specimens on our highway medians
 
In terms of shrubs, we've used junipers and some varieties of Rosa
rugosa successfully.  In the winter they look pretty bleak and the roses
tend to catch the garbage, unfortunately
 
Ian

	-----Original Message-----
	From: canufnet-bounces at list.web.net
[mailto:canufnet-bounces at list.web.net] On Behalf Of Alison Bond
	Sent: Thursday, March 26, 2009 6:27 PM
	To: Canadian Urban Forest Network
	Subject: Re: [CANUFNET] Medians
	
	
	Ian,
	
	In Collingwood (zone 5a...in southern Ontario's snowbelt) we
find that perennials tolerate snow better than shrubs as they don't get
crushed.  We've tried Rosa rugosa, False Spirea, and Gro Low Fragrant
Sumac with no luck.  Karl Foerster Feather Reed Grass has been extremely
successful in a 1m median (irrigated) and curbside planting beds (not
irrigated.)  It is cut once a year in the early spring (cool season
grass that greens up early) so we have the benefit of the grass in the
fall/winter.
	
	As for trees, we had moderate luck with honeylocust in a 1m x 1m
x 1m tree vault (the road engineers designed the vaults and we came in
afterwards to 'green things up.'  Covering the canopies with burlap over
winter (not an easy job) improved the survival rate.  The ones that
survived their first year seem to be doing (relatively) well 4 years
later.
	
	Inspired by the Quebec City Urban Forestry Conference tours, we
recently tried planting one of the Dutch Elm Disease resistant elm
cultivars in a boulevard (zone 4.)  After the first winter there was
100% survival for the elms and serviceberry (A. canadensis), if you can
believe it.  Honeylocust was third.  Red oak (native to the area) did
terribly.  We don't know if it was stock from a warmer seed zone or if
the red oak is just not able to tolerate that much salt and snow (trees
were often buried in 2m snowbanks.)  Anyway, I'd try the elm in in a
median if I were planting trees.
	
	Finally, I've noticed that if trees are tall enough to have some
of the canopy above the salt spray, they seem to pull through.  We
planted four freemani maples in a boulevard.  As you may know, they grow
almost too fast and the stock at planting was very tall.  The lower
canopy was killed off by the salt but the rest of the canopy seems to be
doing OK...again about 4 years later.  
	
	Alison
	
	Alison Bond OALA CSLA
	Landscape Architect and Certified Arborist
	Envision-Tatham
	
	
	On Mon, Mar 23, 2009 at 4:48 PM, Ian Wilson <IWilson at kelowna.ca>
wrote:
	

		I'm looking for information on low-maintenance plant
materials and landscaping designs for road or highway medians that have
"stood the test of time".  I just got a copy of the new "Planning the
Urban Forest" book and saw a photo of an interesting median planting in
Urbana, Illinois utilizing native plants, which got me thinking about
what other cities might be using for medians.
		 
		The City of Kelowna has been developing more medians in
recent years.  We've tried a variety of different designs and plant
materials.  Medians seem to be among the most difficult growing sites in
terms of maintenance and plant health.  Here's some of the challenges
that we have had:
		 
		1)  Getting enough soil volume for trees and plants,
particularly in narrower medians
		2)  Salt spray due to winter road maintenance in our
climate.  Some trees suffer bud dieback due to salt spray.  Others might
suffer soil toxicity once the salts get too high.  One of the best trees
we've found so far seems to be red oak.
		3)  Sand accumulations in the planting bed.  Even if you
have a nicely mulched bed, after a year or two it all ends up looking
like a bed of sand.
		4)  Worker safety in order to maintain median plant
materials and remove garbage and maintain irrigation etc.
		5)  Landscaping medians on highways with higher speeds -
the additional wind and salt spray etc seems to be particularly hard on
plants when the traffic speeds are higher.
		 
		We have several different designs that we have tried,
depending on situation.  We're starting to move towards a couple of
different designs, one is more of a xeriscape design with trees in a
large planting bed and xeriscape plant ground covers (where we have the
space).  Where speeds are higher and sand and salt accumulation is an
issue we're trying more hardscape with trees in "pits" and hard
surfacing, but unless we use Silva cells or something similar we run
into the challenge of limited soil volumes.
		 
		Anybody have some good designs or ideas that they'd like
to share?
		 
		thanks, Ian
		 
		
		Ian Wilson, RPF, Certified Arborist
		Park Services Manager
		City of Kelowna
		Park Services
		Civic Operations
		1359 KLO road,
		Kelowna, BC  V1W 3N8
		iwilson at kelowna.ca
		Phone: (250) 469-8842
		Fax:  (250) 862-3335
		 
		 
		 
		 


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