Revision 4 April 29, 2003 - revision history is at the bottom of document

Invasives Action Plan
for a Norway Maple Invasion
in the Acton (MA) Arboretum

Prepared by:
Jim Snyder-Grant
Acton Land Stewardship Committee, and
Acton Conservation Trust

Location

The Acton Arboretum is a busy, year-round site near the center of Acton Massachusetts, with a wide variety of native species and forest types, and an extensive trail system.

The invaded area covered by this plan is a west-facing slope in the Arboretum. It is bordered on the north and west by a private/public land boundary and a privately-owned pond, and  bordered on the south and east by trails. It is marked as 'Plan Area' in this map of the arboretum.  The area is approximately 1 acre.

Current Conditions

The plan area is an upland  forest, with extensive Norway Maple (Acer Platanides) invasion, and some native maples remaining.  The largest native trees are a variety of pine trees. Other invasives include Burning Bush (Euonymus alatus), Showy Bush Honeysuckle (Lonicera bella) and Multiflora Rose (Rosa multiflora). These additional invasions are much smaller in count and extent than the Norway Maple. The slope averages 15 degrees. The plan area has an informal trail at the bottom of the slope, and is bounded by well-used trails around most of the rest of the area. 

This area was informally surveyed by Tom Tidman (Acton Director of Natural Resources), Dean Charter (Acton Director of Municipal Properties, and Acton Tree Warden), and the author on March 18, 2003. A more complete inventory is an early part of the plan, and the results will be appended to this document.

Desired Conditions

Any work in the Arboretum must be consistent with the Arboretum master plan. One of the major themes of the master plan is to "encourage forest succession by controlling non-native invasive species".

In particular, the section of the master plan on the upland forest includes this message on shorter and longer term goals:

"In terms of our five year management criteria our initial focus will be the removal of both European buckthorn and Norway maple." [Editors note: There were very few glossy buckthorn identified in the plan area.]
 
"With respect to long term management both on a ten and fifteen year time frame, we will consult with both the town tree warden and members of the Friend’s Arboretum staff to begin to establish a healthy understory in this area. It is likely that we will introduce native species such as striped maple, sugar maple and American beech to the forest." [Editors note: it might also be good to introduce more native bushes back to this area as well]

So, this plan to remove Norway Maple is consistent with the larger plan, but it is only an early step in fulfilling the larger vision of this part of the Arboretum.  Removing the Norway Maple will help allow more room for  the native trees to grow, and will allow a more mixed understory to develop.

Background Information

Good information about the risks of Norway Maple can be found on the University Of Connecticut's invasive plants web site.  (The Acrobat reader is needed to read the PDF file there)

A photo of Norway Maple (not from the Arboretum - from the fine folks at the New England Wildflower Society) is here.

I consulted two professionals with experience in treating Norway Maple. Their advice is consistent enough that I have used it as the basis for the plan.

From Chris Mattrick, Senior Conservation Programs Manager, New England Wild Flower Society, Framingham, MA:

"I am assuming that these individuals have never been cut before. I would guess that you could hand pull out anything 3/4" or smaller. With a weed wrench you can pull anything that is up to 2"" in diameter. From 2" up to 4 inches I would recommend cut and paint treatment. If you get beyond that I would not recommend girdling but a basal bark treatment. Girdling will cause a massive amount of sprouting. With basal bark treatment you are putting alternating slashes in the trunk of the tree with a hatchet and then spraying a 30% herbicide solution into those cuts. It may take up to three years and three treatments to effectively kill large individuals."

From Margot R. Bram, Ph.D., Patrick Center for Environmental Research, Academy of Natural Sciences in Philadelphia:

"We did a two-year study of removal techniques for small Norway maple trees only.   Our 3 treatments were: cut only, cut plus immediate application of Garlon to the cut stump, and removal by weed wrench.  We had 60 trees in each treatment.  To keep things consistent, all trees were less than 2.5 inches at the base, which is the largest tree a large Weed Wrench can pull.  After one year, we had total mortality for the weed wrench, and nearly total mortality for the cut + Garlon (only 2 out of 60 survived).  Eighty percent of the cut only trees resprouted. However, after two years, many of the cut only trees were dead, with only 13.3% resprouting.  So, it appears that even cutting alone, after two years, is somewhat effective.

Risks of Taking No Action

Without management, it is anticipated that this area would become increasingly dominated by the invasive Norway Maple, crowding out the Sugar Maple and other native trees. This would be in violation of the master plan for the arboretum, and the invasion would continue to spread beyond the plan area.

Plan

This plan is in seven stages: educational material, site prep, initial inventory, cut and pull, herbicide treatment, clean-up, and follow-up

Educational Material

Because this section of the Arboretum is well-traveled, and because one of the three over-all  goals of the Arboretum is to "provide an educational experience for the community on environmentally sensitive land management", some material will be prepared to explain what is going on for visitors. This will consist of a short introduction to the issues of invasive plants, some information about Norway Maples, and a condensed version of this plan. A draft of this material has been reviewed by the Friends of the Acton Arboretum. The final version needs to be approved by the Director of Natural Resources before being posted at the Arboretum entrance and near the work site. This material may also form the basis of an article in the local paper, the Acton Beacon.

The current draft of this material is here.

Site Prep

The site will be marked off with stakes into squares, each approximately 20 yards on a side. That will make approximately 18 squares (6 x 3), using 28 stakes. The squares will be numbered on a master plan, and the numbers will be used to track the work being done, and to track tree inventory. At the corner of the site nearest to the Arboretum entrance, a laminated copy of the educational material will be posted.

As a guide for the volunteers who will be pulling, and as a start on the inventory task, small maples that are not Norway maples will be flagged. This approach will allow for the least amount of tagging: Most of the small maples are Norway maples

Initial Inventory

An inventory will be taken in two phases: Norway Maples will be counted as they are removed or treated. There will be separate counts for each size of maple (less than 1 inch, 1 inch to less than 2 inches, etc.) in each of the marked squares.  Non-Norway maple trees, of larger than one inch, will be inventoried separately, by volunteers who have basic tree identification skills. As the inventory information is developed, it will be appended to this plan.

Cut and Pull

Removal will proceed as follows:

These first two pulling tasks can be done at any time by volunteers who can at least identify maples vs. non-maples (the non-Norway maples will already be flagged):

All cut and pulled  material will be stacked in piles for later chipping or other safe disposal by town crews.

  The day-to-day implementation of this plan is being tracked in a separate document.

Herbicide Treatment

The plan  calls for cut-and paint treatment with roundup for medium sized trees (2 1/2 inches to 4 inches), and a basal bark treatment for larger trees. In both cases, Glyphosate (Roundup) will be used. Application must be done by certified town staff in accordance with manufacturer's recommendations and approved practices for state-licensed applicators.

Round-up is one of the low-toxicity biodegradable herbicides that does not require an advanced license to apply. Herbicides should always be used as a last resort. Experts have assured me that a no-herbicide treatment for the larger trees is very unlikely to work. In the plan area, most of the Norway maples are still small enough to be pulled by hand, and no herbicide will be required for them. I think it is important that we understand what is the minimal use of herbicides that will be needed. One of the Arboretum goals is an "educational experience for the community on environmentally sensitive land management".

I confirmed with Chris Mattrick that Glyphosate (Roundup) is the right treatment for Norway Maple. Dr. Bram mentions Garlon in her report. (generic name: triclopyr). Chris' experience is that Garlon is best for bittersweet and swallowwort, but doesn't work so well on trees.

Clean-up

The pulled and cut material will be stacked in piles near the upper trail. The piles will be oriented perpindicularly to the trail, to facilitate the use of a chipper by town staff later. The chips will be used on Arboretum trails. After all the work is done for the season, the stakes, tags, and educational material will be taken down.

Follow-up

Each spring for 5 years, after leaf-out of Norway maples, the trees should be re-inventoried. Any Norway maple seedlings should be pulled and disposed of. Progress notes should be written each year, appended to this document, and sent to all interested parties (Natural Resources, Municipal Properties, Conservation Trust, Friends of the Arboretum, etc.). Success will be measured by a radical decrease in Norway Maple, and a gradual increase in other trees, especially the native maples. A full 5 years is anticipated for monitoring, re-measuring, and pulling sprouts that grow from the seedbank or from resprouted trees. The only herbicide treatment that is anticipated in subsequent years is additional basal bark treatments for any larger trees that need it.

Open Issues and Next Steps

Budget and Materials
Need to work with the town and with the Friends of the Acton Arboretum to obtain supplies and equipment.  It looks as if most or all of what is needed can be borrowed or donated.
Volunteer coordination & scheduling
As the work gets started, it will become more clear how much time and effort is needed, and thus how wide a net we need to cast for volunteers. It appears that two of us will be the spending the most time in the Arboretum, but  other volunteers will be needed.
 

Summary

This plan is intended as a first step in dealing with many high-priority invasive plant sites in Acton. I look forward to working with town staff and volunteers to make this plan happen. Your feedback on this plan is greatly appreciated.

Jim Snyder-Grant
jimsg 'at' newview 'dot' org
978 266-9409

Revision History

Rev. 0 March 26, 2003
Rev. 1 April 11, 2003 - Arboretum plan quotes, and revised recommendations plus sources
Rev. 2 April 22, 2003 - Added link to draft educational material, changed timing of inventory, added link to Adobe reader.
Rev. 3 April 27, 2003 - Friends of Acton Arboretum feedback - many improvements. Biggest change is cut & paint added as option in year 1. Plus: disposal recommendation, added open issues section, fixed typos, better phasing plan, removed irrelevant Siberian elm info
Rev. 4 April 29, 2003 - integrate Director of Natural Resources review comments - mostly just closing open issues.