Removing Invasive Plants from Stanley Park

   Vancouver, British Columbia, Canada

Home   English Ivy   Blackberry  Lamium, Periwinkle, Laurel   Bindweed, Knotweed   Obstruction   

Knotweed and Bindweed


Knotweed - results unknown

Knotweeds (Polygonum spp.) are an economically important problem because they can grow through concrete, streets, and foundations. They grow an extensive thick root system which regenerates plants from cut segments. Digging up those roots may be impossible because they grow under rock and concrete. The plant looks like a bamboo, with jointed hollow stalks, growing from a crown, that dry out in fall. The roots can be identified by their red colour. The floppy heart-shaped leaves are also easy to spot. Those in Stanley Park have a concave base with red veins in early spring. Their exact species is debatable.

Stanley Park invasive plants - Japanese Knotweed Stanley Park invasive plants - Japanese Knotweed

Never mentioned on the web, are the low tussocks of tightly packed leaves,that grow without any upright cane. At most they have foot-long trailing stems. These leaves are much more narrow and pointed but the concave base is the same give-away. Many times there is no single tap root, but a mass of tiny roots. Other times, along with the mass of tiny roots, there is a single thread leading down to a deep larger rhizome. At #2 (below) there was an established crown. These are not a result of root pieces left behind after digging, because they have sprouted in the areas where no work has been done other than chemical spaying. I don't know if these become bamboo stalks in a second year.

The 2011 Ecological Action Plan (page 10) funded $12,000 for a three year course of chemical herbicide. In spring 2017 (six years later) all sites still had healthy growth, except for #8 and #10 (where I could find no current or dead plants). Evidently either chemicals don't always work or their application by Parks was too inefficient. Digging with a hand cultivator I found only a small root at one site, so in mid-June I tried to dig up most of the outstanding plants numbered on the map below. I believe I cleared about half.

The inter-intra-city organization created to deal with the really bad invasives (ISCMV) produced a Knot On My Property brochure for the public. I believe its advice is very false. They tell you to attempt nothing yourself. Their only solution is to hire professionals with access to chemicals. Why? (1) Because supposedly you are incapable of collecting and disposing of plant material, and (2) because they imply that all root systems are too large to dig out.

Their one visit in 2017 shows that they have no game plan for the individual sites. They won't dig up plants. They won't inject chemicals into either the stems or roots. They won't revisit sites they know are only half sprayed. They won't use landscape fabric. They tell volunteers to not clear. They are being paid to simply show up and spray without thinking, caring or taking responsibility ..... a waste of taxpayers' money, with the huge downside cost of allowing others to wrongly believe the problem is being taken care of.

............. How to Clear ..................

With most invasive plants, information on the web is full of doom and gloom, predictions of failure, and excuses for inaction. Example for Knotweed ..."Reproduction can occur from as little as 0.7 grams of stem or root tissue. Buried rhizomes can regenerate from depths up to 1 m, and are able to remain dormant for many years." For other species I have found a big difference between claims that something 'can occur' and what actual does occur. But I am finding that the dire warnings are indeed correct for Knotweed. I found a one inch piece of thoroughly rotted root sending out a healthy shoot after lying exposed on a rock, in heavy shade for a year. I am finding new shoots in the second year from plants that lay dormant all the prior year.

Your first step should be to use a hand cultivator to see just how large the root is, and dig it up if possible. A few minutes and the job is done ... while ISCMV is still repeatedly spraying the same plants 6 years later. I have dug up more than 15 root systems, so far without any evidence of regrowth from pieces left behind. I would not suggest using a spade because the roots are pulpy and easily broken. Even the force from tilting a hand trowel is sufficient to break the root - leaving you to fish around for what was left. Young plants have a straight, tapering, tap root. Simply pulling it up will cause the tip to break off. Better to grasp the crown and twist in a circle to loosen the soil first. Yes there is the possibility that you leave a bit of root behind, but so what? Dig up the much smaller resulting plant when it appears.

When the root you see is white and straight but not tapering, and a bit smaller than a pencil, it is a shoot from a larger root traveling below. Simply pulling this up will not accomplish anything by itself - but you might as well. I have been leaving rock salt used for winter de-icing in the hole, thinking it may help stress the larger root. Documentation has shown some success from flooding plants with sea water.

For those plants with roots too large to dig up, the second choice is to inject chemicals either directly into the root, or into the hollow base of the bamboo-like shoot. Spraying chemicals is obviously far less effective and more dangerous. In Canada, access to and permission to use these chemicals is restricted to those who complete an extensive training in the use of all chemicals. So this method cannot be used by the pubic.

There is plenty of web advice saying that weekly knocking back of new growth will eventually exhaust the plant. I found at sites #4 and #9 below that new shoots were originally fast growing and re-sprouting. But a month later only tiny red buds showed after a week. The following spring the roots at #4 restarted their efforts. At #9 those roots I exposed the year before have not sent up new shoots. I am still hopeful this strategy will work. I leave any root partially dug up exposed to the sun in order to create stress and dry it. This allows me to spot new buds of growth immediately. I am guessing that the only thing accomplished by breaking off the root would be to trigger the remaining plant to expand in another direction.

Covering large areas with a plastic tarp accomplishes the same thing - to limit the plants ability to photosynthesize with leaves. Parks has refused my request for landscape fabric (forget tarps which are unsightly), and the spot they previously used fabric (#11) was never maintained, so I cannot say whether it works better than knocking back. Obviously it has to be maintained by pulling back periodically to clear soil and plants from growing through and on top, and to knock back growth occurring below.

Stanley Park invasive plants - Japanese Knotweed

............. Work at Specific Sites ..................

  1. This area is the circle created by the equestrian bridge ramp. It was a huge infestation at the start. By spring 2017 there were only 8 individual shoots. One was outside the circle. Two were sprouts from roots too deep for me to clear. Six had root systems I believe I cleared

    The next spring 2018, there were four sprouts from spots different from the 2017 (I am pretty sure). One had its own root that I removed, and three were from traveling deeper roots. This seems to validate the knowledge that root systems can go dormant for years. Again there was one shoot outside the circle (a different place) but this time I gave up digging before I found any root. I leave the resulting holes dug.

    The major problem now is that the plot has been colonized by Bindweed, which is just as much a problem. The spot is right in the middle of a huge wild area (both east and west of the causeway) that is otherwise clear of Bindweed. So this point source of further contamination is a major problem. If ISCMV did indeed spray chemicals in July '17 they did nothing to kill the bindweed.

  2. This is a marshy area with only speckled sun just beyond the trail paving. There were 4 plants with barely any roots at all and one large root system that the chemical treatments had killed. In later summer a few more new plants without roots sprouted. I dug up all the growing plants.

    In 2018 I found a tussock with an established crown at the front-East. I believe I have cleared all its roots. Two sprouts in the center came from one small root I cleared.

  3. Behind the left bench, against a tree, one plant is growing from a root that I believe travels under the tree to a second plant on the right. If there is re-growth I will make the effort to dig up the complete root, as it would only be about 3 feet long.

  4. This area has huge, extensive roots growing into the bank. I cleared two plants from up the gully and another two from the bottom. But there are two other roots still sending up sprouts, that are too big to dig up. My July '17 request that ISCMV drill holes in the roots and inject chemicals was ignored.

    I am hoping that by exposing as much of the roots as possible, and weekly knocking back new growth, the root will be exhausted. I found that slicing off the top of the crown delayed re-growth, but I worry that by doing so the root is more likely to sprout elsewhere. So I just knock back the sprouts and hope the plants keeps trying at same spot.

    In spring '18 the exposed root sent up new shoots again. Two new sites sent up shoots from cut roots that I had not cut the year before, so they must have stayed dormant from before I started. I continue knocking back weekly.

  5. This area is between the first 1bench - 2bench combo. The chemicals have worked on the main clump at the north end, and another crown half way between. But in 2017 a young plant was growing close to the middle dead crown. I believe I got all the root. In early spring 2018 there was a weak sprout from the deeper root at the north end.

  6. This is the wet grotto. In spring 2017 I dug up some plants growing in dry soil at the entrance, and also a half dozen higher on the open ledge, but there are dozens in the dripping wet grotto. I left a plant at the entrance for ISCMV to kill with chemicals. Its roots are hidden inside a steep bank protected by a log. Cutting away the log would destabilize the bank. ISCMV sprayed in July when the plants were wet (off label) and the spray washes off. In spring 2018 that plant in the bank re-grew along with a second and third that is obviously from the same deeper root. I will leave them for ISCMV spraying again this year.

    In late fall '17, after three months without rain, most of the dripping had stopped, so I did a comprensive dig to remove all possible roots. The 'soil' remained sodden. This makes it impossible to see or feel the roots. In some places the roots have traveled through cracks in the sandstone rock. Pulling away the rock could compromise the cliff, so I don't feel free to do so without permission (which I know would be refused). I knowingly left behind lots and lots of roots. I figured any re-growth won't be a bad as what I started with.

    Landscape fabric should be used - all other methods have been tried - but that method seems to be on ISCMV's 'we don't do' list. In the fall of '17 I requested that Parks drop off a bolt of fabric for me to install. They refused. In the spring of '18 the roots I had dug the prior fall and left to dry in a pile, were clearly still viable and sprouting, so I bagged them, leaving the bags for Parks to pick up for disposal. Parks dumped out the contents of the second bag, forcing me to repeat my work and lug it to the nearest bin.

    The only remaining option now is for me to dig up new sprouts weekly, leaving the root behind. I doubt this will be as effective as knocking back the new sprouts from exposed root at #4.

  7. This spot is just south of the steps. The chemicals have killed two plants in front. I dug up a third in between the two. In July ISCMV sprayed a fourth plant growing from a crack in the rock wall. In spring 2018 there was healthy new growth. I knocked out a lot, but not all of that root. What is need is a long-shank chisel. I used a sharp wood 1X4 but its point broke off. I stuffed a black-out bag into the crack to block the sun.

  8. I could find no remaining evidence of this spot beside 3rd Beach. The chemicals must have worked. My request to Parks for confirmation the site had been cleared was ignored.

  9. Just around the corner from the top of 3rd beach is an area with 9 plants growing in early summer and 3 more showing in late summer. There is evidence of about 4 crowns successfully killed by chemicals. It is possible that 2 late sprouting plants came from the roots of a plant that appears dead. I dug up the rest, leaving behind root in only two places. I left 6 holes not filled in so that digging farther will be easy. My July '17 request that ISCMV drill holes in the roots and inject chemicals was ignored.

    In spring 2018, another of the 'dead' crowns started sprouting again after lying dormant for at least a year. There was also a new sprout from a deep root. The two roots exposed in 2017 have not re-sprouted. I will monitor and knock back new growth.

  10. I could find no remaining evidence of this spot near the lookout above the gun tower. The chemicals must have worked. My request to Parks for confirmation the site had been cleared was ignored.

  11. There are three sites here. I am leaving these for ISCMV because there is little more that I can do. Site A is a large grove of about a dozen mature plants at least 10 feet tall, a bit back from the path up the hill. ISCMV spraying in 2017 brought down the front rank of plants but did not touch the deeper plants. Regardless, even by July 2018 none of the patch was regrowing.

    Stanley Park invasive plants - Japanese Knotweed

    Spot B, back from the trail, is now grown up with Blackberries. I have not investigated because access is difficult. The Blackberry root systems will make clearing the Knotweed roots much more difficult, if not impossible.

    At spot C past SPES efforts have created a criminal mess. It seems that long ago landscape fabric were laid over a very large area ..... and then nothing was done to maintain it. The Knotweed grew through the fabric, leaves fell and created new top soil, grasses and blackberries colonized the new soil. So now we have fabric I cannot pull up. Under the one edge I found there are healthy Knotweed still growing .... but I cannot get access to dig out.

    There are also Knotweed growing from crowns in the new soil, sending out roots sideways because they cannot go down. And also Knotweed growing through the fabric. I believe I have cleared all the plants living in the new soil and the accessible plants under one edge. Unlike any other spots, the plants growing above the fabric are connected, not by rhizomes, but by old hollow stems. This might be because the area was used to pile salvageable logs during the windstorm clean up. Those logs may have pushed stems down into the ground, prompting them to root themselves. That would mean the fabric was laid before the 2006 storm.

    Further back behind spot C, under a large fallen tree, one plant is still sending up healthy shoots (only a few weeks after ISCMV sprayed so they must have forgotten this plant). I dug down about a foot without finding the bottom. This plant must be attacked with chemicals, or a shovel is necessary for deeper digging. I covered it with a dark-out bag for the winter, but removed it in spring so that there will be shoots for spraying.


Hedge Bindweed (Morning Glory) - all cleared within my territory

There are two types of Bindweed - both in the Morning Glory family. I believe it is Hedge Bindweed, Calystegia sepium, that is in Stanley Park. The arrowhead leaves look similar to the Field Bindweed, except not so pointy at the trailing edge. Like all Morning Glory this plant twines around anything vertical. It prefers sun so I am hoping it will not thrive in the shade of my territory. The extensive root system makes clearing difficult. Any pieces left behind can and will start new plants. You can scratch backwards along the root when it is growing in loose soil. But when growing among other plants, their roots prevent access to the bindweed's roots.

Stanley Park invasive plants - Bindweed Stanley Park invasive plants - Bindweed

Bindweed is spreading mainly from the cultivated gardens on the West side of the park, along the Seawall clockwise. I have found only two small spots within my territory - on the north edge of Hollow Tree park and north of the hydrant on Bridle Path. I have cleared both but return regularly to find one or two new shoots.

Stanley Park invasive plants - sites cleared of Bindweed

In May of 2017 I decided to try to protect what I thought at that time, was perfectly clear seawall going clockwise from Siwash Rock. To make Siwash Rock a 'hard stop' I decided to clear south to the 3rd Beach exit road. This would be the 'no-fly zone'. It would provide a cleared boundary to the huge wild west half of the park. In June, after the higher sun reached the shady north slopes, I found two spots of bindweed already beyond the Rock. I felt there was no choice but to give up the no fly zone idea. IMO the idea of protecting such a huge area of wild, with so little work would be worth the effort, IF those two spots could be cleared. But one would require cutting down and digging up the roots of about 15 - 20 feet of bushes. It would not be difficult for Parks. The real politic is that they will never do it.