Removing Invasive Plants from Stanley Park

English Ivy, Blackberry, Lamium, Periwinkle : Volunteers Needed

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Blackberries

Blackberries have made large inroads into the wild west of the park since the 2006 windstorm, in the blowdown areas especially. Clearing them is just as 'possible' as clearing the English Ivy proved 'possible'. Most everyone knows and can recognize a blackberry plant by its thick vertical canes that dry up after a few years. You know the thorns and pick the berries for jam. Once the cane has reached the limit of its support it arches over. At this point secondary stems sprout. It is these that flower in June and set fruit on top of competing plants. Blackberries never branch in the form of normal bushes. In early spring you can spot blackberry plants far back from the trail by their distinctive form.

When trying to positively identify the invasive Himalayan Blackberry, look for any lobes on the side leaflets. If they exist it is highly probable the plant is NOT a Himalayan. It will either be a Salmon Berry or one of the other blackberry species shown below. The only time Himalayan leaflets have side lobes is when the plant is young and the leaves are a compound of three, not five leaflets.

More and more frequently I am hearing the argument that blackberry plants should be left - because their thorny thickets provide birds with shelter and escape from predators. I find this argument questionable and self-serving.
I have seen no evidence of this in wild areas, except for the odd raccoon hiding from (ignoring) heckling crows.
Maybe the outfits organizing volunteer 'stewardship' work recognized that nobody will volunteer for this prickly work, or decided that clearing the plants is a lost cause , so they turned a negative into a positive?
Any acreage cleared in the wilds will not make no impact on the huge acreage of existing plants that will never, ever be cleared. Cannot those birds supposedly using a particular shelter not relocate?
Since the blackberries being cleared are foreign, the birds managed just fine before the invasion.

           Invasive Himalayan Blackberry (Rubus armeniacus)                                 Vertical canes eventually arch.

Stanley Park Invasive Plants - invasive Himalayan Blackberry..Stanley Park invasive plants - arching canes of Himalyan blackberry

In addition to the well-known Himalayan Blackberry there are two other non-native invasive blackberry plants in the west. The Cut-Leaf Blackberry grows like the Himalayan but its leaves are very frilly. These are not common in Stanley Park but do crop up. Normal people will not be able to distinguish the second, Alleghany Blackberry (Rubus allegheniensis not shown), from the Himalyan. It is native to the North American east but not to the west.

           Invasive Cut-Leaf Blackberry (Rubus laciniatus)                           Native Trailing Blackberry (Rubus ursinus)

Stanley Park Invasive Plants - invasive Cut-Leaf Blackberry..Stanley Park Invasive Plants - native trailing blackberry

In Stanley Park there are two native species. The Trailing Blackberry is a small trailing plant without an upright cane. You can wrap its stem around your fist. Sometimes it grows vertically but only by using the support of other plants. Its leaves are more pointy than the Himalayan and are always compounds of 3 (never 5). The image above from UBC shows the lobes on the outside edge of the side leaflets, that I have found common in Stanley Park. Sometimes the center leaflet has lobes also. The leaves vary between plants and on the same plant. You won't think of it as a 'blackberry' so there will be no confusion of identification.

          Native Blackcap (Rubus leucodermis)         with distinctive blue stem

Stanley Park invasive plants - native blackcap..Stanley Park invasive plants - native blackcap

The second native, the Blackcap or Black Raspberry, has the same growth pattern as the invasive Himalayan, except you will immediately notice the stems are "blue and smooth". The leaflet's lobe showing in the image above is not always present. The underside of the leaves is clearly paler. Technically you should leave these "blue and smooth" plants in place. But they cross-pollinate with the invasive species. The fact that I have found so very few individual plants of this specie indicates to me that their gene pool is probably far from pure. If they are growing at the side of trails, where yearly weed-whacking will never allow them to mature, it seems reasonable to protect the downside risk by pulling them up along with the foreign species.

Clearing I Have Done

The map below identifies the trails I have cleared and the areas I have worked. Many of these are not finished. The areas refer to spots with many plants, from 20 to 100. The multitude of single plants are not worth mapping.

Stanley Park Invasive Plants - Blackberry patches cleared

When to Work

  1. It is much easier to pull up the blackberry's trailing root when the soil is wet and soft. In Vancouver this means before late spring. But, any plants found in swampy areas (many) are more easily pulled later in the summer after the soil has firmed up enough to walk on.
  2. It is more easy to spot the arching canes of plants far back through a sea of Salmon Berry in the early spring before any leaves come out, or the Salmon Berry bloom in April.
  3. It is easier to drag the pulled up plants out to the trail in early spring before the leaves come out, because the thorns will catch on the leaves.
  4. Blackberries flower in June, after, but slightly overlapping the Thimble Berry's similar white flower (in May). The showy white flowers (white/pinkish to a greater or lesser degree) can be eaily seen through the woods, and over the top of a sea of Salmon Berries. This allows you to spot plants you could not see in spring. The problem with waiting for flowers is that your physical access may now be near impossible.
  5. Plants may be growing at the edges of grass lawns. It is much easier to pull the Blackberry's roots through sod in early spring while the grass is dormant.
  6. After Parks staff use a weed-whacker along the sides of trails, spotting plants is difficult and not worth the time/effort. Best to wait until plants have been allowed to grow back.

Go Prepared

  • Dress appropriately. Don't go out without safety glasses. Good ankle boots are necessary for rough terrain. Cardboard stuck into the top of your socks will protect your shins from scratches. A hat will prevent the thorns catching your hair. Wear two layers on top. An outer layer, tightly woven, will still allow the thorns to penetrate, but the second layer will protect your skin. The top layer will get torn and shredded.
  • Gardening gloves are necessary. Leather is great. Cheap rubber palms are not sufficient. Look for heavy-duty models. Or spread a thin layer of "Freesole" urethane glue over the rubber. It will not impair the flexibility of your fingers, and thorns will not penetrate it. It is a wonderful product for all kinds of other uses as well.
  • Take along a hand cultivator and keyhole saw. These are your 'two hands' so you don't have to grasp the thorny stems.

How to Work

Volunteers working in Stanley Park's wild woods will not be grazing sheep, or applying chemical herbicides, or using roto-tillers. These methods may (or may not) work in other areas, but not in the Stanley Park wild areas where individual Blackberry plants are dispersed among native plants in inaccessible areas. Volunteers must use hand tools and muscle power. The method that is guaranteed to NOT work is to tug the cane tops off the root-node. This ensures the plant grows back and causes the root-node to send out additional roots, making the job of pulling up the root (if ever done) harder and harder.

  • Blackberries will often grow toward the sun, so approach the stand from its backside.
  • There are always many old, dry canes restricting your access and causing problems for other plants. Before starting to dig the roots knock down these old canes and break them up with your feet on the ground. It would be better if they could be removed completely, but you will find that is next to impossible.
  • Some videos show using a spade to cut around the Blackberry and lift the root node. This method will not work in the wilds. Most often the Blackberry's root is inter-twined with other plants' tough roots. Your spade would need to be very sharp indeed to cut through that mass. You also need to be standing up to use a spade. In the wild you don't have that room.
  • I recommend using two tools - a hand cultivator (two or three pronged) and a keyhole saw. Be careful walking through the woods while carrying these. Keep them pointed away from your body so if (when) you stumble they don't stab you. Better to attach them somehow to your belt. Use one tool in each hand to manipulate the canes.
  • Some people say to cut off the vertical cane before trying to dig up the roots. I disagree. (a) Plants with their roots attached wilt within a week and are more easy to dispose of. In contrast cut canes dry out stiff and don't decompose - a much harder disposal problem. (b) Leaving the canes attached allows yout to drag the pulled plant out of your way by the root ball. (c) If you cut the cane and pull it out to the trail before digging the root -- will you be able to find that root when you return?
  • Use the cultivator to scratch the soil away from the root node. This exposes one thick trailing root and other smaller roots. Hook a finger under each individual small root and pry it out. When all that remains is the trailing root, use both hands to pull from underneath the node. Pull out as much as you can.
  • Sometimes you can only pull up a foot or two of the trailing root. Other times you cannot budge the node. Then use the keyhole saw to cut through the thick roots. This leaves cut roots in place. A small proportion of these will start new plants in a year or two. But the proportion is small and not a reason to conclude the work is pointless.
  • Before removing the plant, check that none of its canes has curved down the the ground and re-rooted. Just pulling from the parent's base will cause the cane to break, leaving the rooted tip in place.
  • Grasp the plant by its root end to pull it out of the woods to a collection site. Try to minimize snagging other plants too badly.
  • It is important to remove the pulled plants. (i) Any canes left behind will confuse volunteers doing upkeep work in later years. (ii)The canes need to be removed to allow you access deeper into the stand. Room it tight enough even when the pulled plans are cleared. Sometimes you have no choice but to leave them in place. Try to fold the canes like an accordian down onto the ground under your feet. You will see that this only works for one or two plants at most.

Re-Growth

Digging up the roots is hard work but a permanent fix. Sure, upkeep will be necessary but they don't 'just grow back'. The critical factor for re-growth is sunlight. Clearings in most of the wild west of the park are in heavy shade. Re-growth is minimal.

Here, sunny sites tend to be directly adjacent to paths and lawns. Growth from dormant seeds is rare. The re-growth comes from the cut roots left behind. You have to dig deeper to catch that old root, but now you will find it less strongly anchored and easier to pull out. It is necessary to re-visit twice a year for a few years - in late June and October. Because access is so easy, this upkeep takes only minutes.

Where To Work

The same logic for prioritizing English Ivy work applies to Blackberries as well. Target the few plants what will clear large areas. Completely clear areas with a defensible border. Work to expand cleared areas instead of starting new isolated patches. Prioritize wild areas with an 'ecology' to save.

But there are complications. The decision 'where to work' involves a trade-off between factors.

  • Very often it is not possible to see how much work will be required when you first start work on a site. The full extent of the problem only appears as your work goes on ... and on.
  • While most areas of the west park will continue little changed over the next decade, the blow-down areas from the 2006 wind storm are rapidly changing - both from nature's attempt to regenerate, and from Parks staff weed-whacking large swaths . Maybe an ounce of prevention now will prevent a much larger problem later.
  • Access into windstorm blown-down areas was often only possible in the short periods after weed-whacking. As at 2016 many of the blow-down areas have new growth that makes access to clear (or even see) blackberries impossible. These areas must be left on the back-burner until the new growth has matured and the understory clears.






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