View Full Version : Dangerous Black Locust Trees!!!

06-18-2008, 11:38 PM
Had a run in with a few of these yesterday... I originally thought that they were Hawthorn trees... Now I know better.

http://farm4.static.flickr.com/3217/2592382564_098aeedc56.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
The leaves

This is the leaves of the Black Locust (Robinia pseudoacacia) tree. A non-native tree that is originally from the East Coast of the US. In spring, it has fragrant white or pink flowers. Which makes it attractive... Looks can be deceiving... It is generally concidered a weed, and it hides a nasty suprise in those leaves.

The flowers

The black locust tree, seen here in Tigard, is heaving this sidewalk. it was clearly not planted here intentionally, as it would lead to liability suits (and if not controlled soon, a rough ride).

http://farm4.static.flickr.com/3025/2592384172_790d070b6f.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
The sidewalk is being heaved up by the roots.

This is a typical branch, it could be hanging over a sidewalk, or a bike lane at face level. A cyclist, skateboarder, or other fast moving user of the sidewalk would be tempted to push it out of the way...

http://farm4.static.flickr.com/3133/2591547573_df4ab8f237.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
Imagine this is at face level, overhanging a sidewalk/bikelane.

more in part 2

06-18-2008, 11:39 PM
Before you push this out of the way at speed, let's see what lurks beneath those leaves...

http://farm4.static.flickr.com/3228/2591548697_3fe6ae916f.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
That was hiding under those leaves... YIKES!!!

Same branch, but the leaves have been removed.

Those spines are strong, and sharp, and cover new growth, such as the suckers that it sends out, and it likes to send out lots of those, typically at face level.

I've seen these trees completly block bike lanes in Portland Oregon (Remember the one on SW 4th Ave. near SW Grant St.? Who do you think killed it?).

http://farm4.static.flickr.com/3196/2591549715_1a1243c45c.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
Detail shot... Those Fuckers are SHARP!!!

Detail shot of the spines... set in pairs, at close intervals.

Catch one of these in the hand, and you've got a nasty splinter. Get one in the eye, and your going to have a REALLY BAD DAY!

http://farm4.static.flickr.com/3071/2592388356_2f8ed34aac.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
I got off easy... I've had worse.

These are the scratches I earned when I cut three young black locust trees down along the bike lane on N. Interstate Ave. yesterday. I've had worse, but I didn't think to photograph them.

Now you know what they are, and why you should know about them. Seek them out... then KILL THEM!!!

Not everybody out there in the bike lane can see them. I have a blind friend who uses bike lanes because they are mostly free of obstacles. The scars on his forehead and face are proof that branches of trees and thorns from blackberries and roses are still a problem. He is why I got active in cycling advocacy (what I do to help him, often helps me, and helps YOU too).

If my tone seems a bit angry, it's just that I got scratched up taking out those three trees yesterday, and someone three years ago could have got them as saplings.

http://farm4.static.flickr.com/3142/2588739121_f008aa33e8_o.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622)
Taken near "Fire on the Mountain"

Any Questions?

See Something? Do SOMETHING!

Ok... deep breath, let it all out

06-19-2008, 05:25 AM
Who is supposed to maintain those strips along the bike lane? I mean, it's not terribly convenient for a cyclist to have to haul off a locust tree by themselves. :mad: Do we have to rattle on the nearby property owner, or is it a PDOT thing?

06-19-2008, 05:36 AM
I just drop them then make sure that the remains are not in the bike lane or the sidewalk.

06-19-2008, 05:48 AM
That's the trouble with weeds. Often you drop them, they start anew . :mad: Black Locust spreads by underground shoots, so unless the tree is either killed via chemical warfare, or removed roots and all, it might survive to continue spreading.

(edit) From the Wisconsin Dept. of Natural Resources (http://dnr.wi.gov/invasives/fact/black_locust.htm);

Mechanical Control: Cutting black locust stimulates sprouting and clonal spread. For this reason, some suggest to avoid simply cutting the stems. Mowing and burning temporarily control spreading, but mowing seems to promote seed germination, and burning stimulates sprouting. Girdling is ineffective because it kills the stem but does not prevent sucker formation. Annual haying may be adequate to control first year seedlings and prevent spreading in prairie communities. Bulldozing may be an option on disturbed lands.

06-19-2008, 05:52 AM
That's the trouble with weeds. Often you drop them, they start anew . :mad: Black Locust spreads by underground shoots, so unless the tree is either killed via chemical warfare, or removed roots and all, it might survive to continue spreading.

I'm not above chemical warfare...

The nice thing about chemical warfare. It's more subtle and you get outta there quicker. ;)

Rubberside Down!

06-19-2008, 05:55 AM
In that case:

Chemical Control: The extensive root system of black locust spreads herbicides over large areas. Basal stem application is preferred for treatment because it is selective and easy to apply. The herbicide should be applied in a band at least 6 inches high all around the trunk approximately 12 inches from the ground. Triclopyr formulated for dilution in diesel fuel or mineral oil is currently the herbicide of choice for black locust. Both diesel fuel and mineral oil release volatile organic compounds into the immediate area. Although more expensive, mineral oil is potentially less toxic to neighboring organisms. The triclopyr/oil mixture may also be applied to a girdle cut at standing height or to cut stumps.

For small isolated plants or thick patches under 5 feet in height (such as those resulting from cutting or fire), fisamine ammonium can be applied as a foliar spray. Fisamine ammonium kills plants by inhibiting leaf bud growth and flower formation in the spring. Fisamine ammonium should be applied at the end of the growing season. In order to effectively curb regeneration, every branch or stem must be sprayed because missed stems will leaf out. Triclopyr mixed with water may also be used effectively as a foliar spray in the latter half of the growing season.

Glyphosate can be applied to foliage of actively growing trees using a hand sprayer (1-1.5% active ingredient solution). However, foliar glyphosate spray should not be applied in high quality natural areas because it is a nonselective herbicide. Black locust stems can be cut at the base with brush-cutters, chainsaws, or hand tools; stumps should be treated immediately with a 20% active ingredient solution of glyphosate. The treatment works best when applied in late summer, early fall, or during the dormant season.

06-19-2008, 06:16 AM
I got this off the Portland Trans website:

Call 503-823-7306
to make a nuisance complaint of a vegetation obstruction of a sidewalk, path, or street

Make sure they know it's a noxious weed, so that they'll consider removing it rather than just trimming it away from the lane. Worth a shot, anyway.

06-19-2008, 06:21 AM
Cool Beans! :cool:

Still, if only a few cyclists carried pruning shears, and cut them down as soon as they came up, eventully the plant will die.


Chilly Willy
06-19-2008, 10:54 AM
Locust trees are used in landscape design primarily because they grow quickly, although they usually die within 10-20 years after planting. You usually see them used in real estate speculation where someone is trying to make a quick buck and dump a property.

The varieties used in landscaping have been specifically bred to remove the thorns.

06-19-2008, 11:05 AM
Still, if only a few cyclists carried pruning shears, and cut them down as soon as they came up, eventully the plant will die.


No, wyeast's quote #5 from the Wisconsin Dept of Natural Resources contradicts that assumption, and there's probably good reason to believe it's true. Still for the short term where bike and pedestrian lanes and paths are concerned, it makes sense to cut stuff back.

06-25-2008, 12:41 AM
Biked into PDX tonight... I found that DAMNED black locust that I cut down on SW 4th Ave, near SW Grant St. was growing back. :mad:

http://farm4.static.flickr.com/3243/2609419153_f735180e51.jpg (http://www.flickr.com/photos/ufobike/sets/72157605692150622/show)

I cut it down again.

Last time, it was over 20 feet tall, and completly blocked the bikelane.

It put up a lot less of a fight this time.

See Something? DO SOMETHING!

09-08-2008, 10:43 AM
I decided to see how the black locusts on N. Interstate Ave. had faired since being cut down back in June... DAMN! They were nearly as big as before...

http://farm4.static.flickr.com/3078/2838434331_7ac69971ff.jpg (http://flickr.com/photos/ufobike/sets/72157605692150622/)

So, I cut them back again...

http://farm4.static.flickr.com/3263/2838435501_ec9c6ba51d.jpg (http://flickr.com/photos/ufobike/sets/72157605692150622/)

(cont. in part 2...)

09-08-2008, 10:46 AM
(cont. from part 1)

As I was heading out there, I noticed that there were at least two overgrowing the NB bike lane of N. Interstate Ave.

http://farm4.static.flickr.com/3238/2839272620_e0d590659e.jpg (http://flickr.com/photos/ufobike/2839272620)
Thorns hanging down at face level... how nice...

I didn't have my usual kit to be able to take these out, so I ask one of you to try tackling it.

Be Safe Out There!

(had to split this as it had too many images to keep in one post)