[CANUFNET] trees on high speed right-of-ways

[Ian Wilson]

Hi Martha,

 

We have some medians on Highway 97 in Kelowna, where the posted speeds
reach 80 km/hr (and many people drive 100 km/hr).  These were originally
planted in 1998.  At the time, the transportation engineers originally
objected to the trees in the centre median as possible hazards, however
our parks manager at the time pointed out that it would be preferable
for a vehicle to hit these trees rather than to drive into on-coming
traffic.

 

The medians are not very wide - they are only the width of a lane of
traffic (about 4.2 metres I think).  They have a slightly sloped brick
apron around the edges, with a planting strip in the middle, planted
with trees shrubs and irrigation.  If you have the space, I would
definitely recommend going wider because the narrow width causes some
issues with sand, salt, and worker safety.  We are now in the process of
renovating some of our highway medians to include safety curbs as you
mentioned, we are converting the spray irrigation to drip (spray
irrigation is higher maintenance and creates runoff onto the road), and
we are also going to construct a flat spot at the end of each median
where a maintenance vehicle can park.

 

Many of our medians have shrub roses which seem to do fine with the
salts and look good but they catch all the flying garbage.  We are
replacing the roses with more xeriscape type plants such as low growing
fescues.

 

We have found species selection to be quite challenging due to road
salts and constant wind due to traffic which seems to dry out the leaves
in the heat of summer.  Norway maple is quite tolerant of the salts but
suffers from leaf scorch in late summer.  Red oak and Austrian pine
generally do pretty well.  London plane does well except that the salt
spray tends to kill the buds on the lower portion of the tree and you
get a lot of 'witches brooms' forming.  We're going to try some elms.
Something really tough and weedy like "Tree of Heaven" might even be
worth trying if you can plant males that don't go to seed.

 

We were concerned that the London planes would get too large but because
of the very limited soil volume they have only reached about an 8 inch
caliper and now grow very slowly.  The good news is they require very
little pruning and don't create much of a hazard for vehicles that run
them over, but in the long term they may start to decline due to the
limited soil volume.  Theoretically they may be able to access some
additional native soils through the bottom of the planter but they are
probably poor quality and compacted.

 

Good luck,

 

Ian 

 

 

Ian Wilson, Park Services Manager

Civic Operations

 

TEL 250 469-8842 

FAX 250 862-3335

City of Kelowna 1359 KLO road, Kelowna, BC  V1W 3N8  kelowna.ca
<http://www.kelowna.ca> 

 

 

 

 

 

 

 

From: canufnet-bounces at list.web.net
[mailto:canufnet-bounces at list.web.net] On Behalf Of Barwinsky, Martha
Sent: Saturday, February 20, 2010 9:45 AM
To: canufnet at list.web.net
Subject: [CANUFNET] trees on high speed right-of-ways

 

I have some questions for city arborists/foresters related to trees in
centre medians in higher speed zones:

 

1. Does anyone have a situation with trees, especially mature trees,
currently growing on centre medians of higher speed right-of-ways i.e.
80 km/hr? If so, how do you manage this with transportation engineers,
i.e. that their view is the trees are a hazard to driver safety?

 

2. Are you planting in these centre medians provided that the median is
a certain width, safety curbs are constructed, and/or the trees are in
raised planters, etc - barring concerns with de-icing salt impact on
tree health? 

 

3. Do you have guidelines in place in cooperation with transportation in
that you do or do not plant trees in these centre medians?

 

Thanks in advance for your feedback!

 

 

Martha Barwinsky

City Forester

City of Winnipeg

105-1155 Pacific Ave

Winnipeg, MB R3E 3P1

ph: (204) 986-3701

fax: (204) 986-3860

 

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