Case Studies, March 2018

Natives and Invasives at the Water’s Edge: A Case Study

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This is considerably longer than my other posts, but it’s full of topics for discussion, if you have the time. Fear not, it’s the exception, not the rule!

As a landscape designer, I get to wear many hats – including, but not limited to, those of horticulturalist, artist, interpreter, arbitrator and organizer- sometimes several at once. One of my favorite hats is that of problem solver. While wearing that hat I get to stretch myself to come up with a landscape for someone that will not only make them feel better about something that has been a negative in their lives but will turn that negative into a positive rather than simply neutralizing it. I enjoy the challenge, taking the parameters that are in place and figuring out what will satisfy all “needs”, while also giving the voice to the “wants”.

Such a puzzle is always a thought provoking experience, and none more so than one I encountered in a job I was involved with a couple years ago. The job involved wetland restrictions, shoreland buffer zones, invasive plants, trespassing, angry neighbors, and frustrated homeowners. I was called in with the landscape company that I design for, to solve the problem; and the deeper we dug into the various facets of that problem the more complicated it became. When investigating the issues in depth, parts of them that had seemed to be in accordance with each other at first proved to be quite disperate in actuality, and had to be reconciled before any progress could be made. What follows is my attempt to describe all these differences, and how they deserve to be pondered. There are many soap-boxes to be climbed on along the way, but I’m going to try to stay away from them as much as possible, for whatever you believe, there’s always another way of looking at things. We will see how well I do! I will also explain how, in the end, we resolved the issue, for better or worse. I like to think it was for the better.


It all began on a beautiful, newly purchased property in Maine, with a house on a hill overlooking rolling lawns down to the water. The view was spectacular. We had previously walked around with the owners to discuss doing some landscaping at some point the following spring. A week or two after our visit, we got a call from the owner, who lived out of state at the time, asking for our help. He had contacted a local tree company to do some clearing on the property and somehow, through a series of miscommunications and lack of awareness, a large portion of the clearing had been done within the 100 and 250 foot buffer zones from the high tide mark, which is essentially illegal. And to add insult to injury, some of it was on their neighbors land. Both the town Conservation Commission and the Maine State Department of Environmental Protection have been called in and were asking for reparations to be made, the neighbors were furious, and the homeowners were understandably upset and confused about what needed to be done.

The Letter of Violation sent to the homeowners stated that a total of approximately 5550 square feet of understory growth had been cut, and in order to fix the transgression, a design or plan of action for the two areas in question needed to be submitted. The plan was required to be comprised of native plants, enough to satisfy the “point system” (more about that in a minute), and had to be installed prior to a certain date. The sizes of these plants and planting distance was dictated in detail, (in some cases to my horticulture horror, but that’s another story), as were the strict guidelines for any further cutting and for regular inspections. No permits of any kind would be issued for the property until the situation has been resolved, and the homeowners were very lucky that there was not a steep fine involved as well. To complicate matters, both areas involved were choked with invasive species.

After this very long introduction which, believe it or not, is actually a highly abbreviated version, we were faced with two areas of concern that needed to be sorted out, described briefly as follows:

  1. Replace the cleared area on the neighbor’s property with a  native planting that would satisfy the point requirements and both appease the neighbors and create a garden that the homeowners would enjoy.
  2. Create a plan for the area adjacent to the water that had been cleared, the goal being to populate it with native species, and as best possible, deal with the invasives.

Although at first glance, this might seem like a fairly simple thing to do, it was easier said than done because of a number of factors. No one was questioning the need for, or the value of using native plants. In these days of extreme weather conditions they do well with the least amount of intervention – after all, they are meant to be here. And encouraging and enabling native  plants to grow and thrive is the right thing to do for a number of reasons, not the least of which include the habitats and protection they afford wildlife. The complication came from the opposing side, the invasive species that were vying for the same patch of soil. And each of the areas where he wanted to plant natives had to be treated differently.


The area which had been cleared along the property boundary area straddled the property line and was approximately 86ft x 15ft,  incorporating a steep, stony banking. From what we were able to see, much of what had been cut to the ground (no roots of been disturbed) was Multiflora Rose (Rosa multiflora), Staghorn Sumac (Rhus typhina) and Oriental Bittersweet (Celastrus  orbiculatus). The neighbors had no intention of doing anything to reduce the further exuberance of the invasive species in this mix, preferring to allow the unruly tangle to grow back, and stated that they would request that any new planting be done on the homeowner’s side of the property line. The homeowners were happy to comply with this request because it meant that they would have control over the new plants. (This was also good because the DES required that the new plantings be replaced should they not survive a minimum of 5 years. Had the homeowners planted the new plants on the neighbors property, they were not have been allowed to cut the remaining  Bittersweet back and thus the plants would not have survived… you see the problem.)

As nothing could be done about the invasive species in the area besides cut them back from the property line, the next issue was to make sure that the proposed trees and shrubs satisfied the point system established by the State. In case the  reader hasn’t come across such regulations before, I will attempt to sum them up in a nutshell:

Basically, for every 625 square feet (25 x 25’) there has  to be eight or more points, as represented by the size of the trees and shrubs in that area. The points awarded to each tree or shrub are as follows:

Diameter of tree at 4.5 feet above the ground Points

2 to <4 inches 1

4 to <8 inches 2

8 to <12 inches 4

12 inches or greater 8

Multi-stemmed shrubs are assessed based on the number and thickness of the stems and the ultimate height of the plant.

One problem that we ran into in this area was that using the diameter of a tree at 4.5 feet above the ground is what is commonly done in forestry. In the nursery trade, however, the diameter of a tree is measured 8 inches above the ground. As a normal tree will typically flair at the base, a tree that is 4 inches in diameter at 4.5 feet above the ground is likely to be more like 6.75 inches in diameter at the base, thus having a much larger root ball than a tree whose diameter measures 4 inches at the base and requiring more disturbance in order to plant it. It was important, therefore, that we all be on the same page when talking about what sized trees and shrubs were required to replace trees whose stumps were all that remained.


As the area in question covered roughly the equivalent of two 25 x 25 square-foot areas, a total of 16 points was needed. In the end, the following native plants were chosen to satisfy the requirements, each chosen because of its suitability to the bright, sunny location and its contribution to the landscape. As natives, these plants are well adapted to the area, therefore needing less water and fertilizer, which was another important consideration so close to the water.

(1) Quercus palustris, an oak whose branches typically bend downward and so is a great choice to create a privacy screen, with brilliant scarlet fall foliage. 2 points.

(5) Amelanchier canadensis ‘Glenform’, an upright Serviceberry which would fit the narrow space better than some of its wider cousins. It flowers in the mid spring, producing edible berries and attracting pollinators and wildlife. Bright fall foliage is an added benefit. The multi trunked, large shrub/small trees counted as 2 points each, for a total of 10 points.

(8) Prunus maritima, Beach Plum. Much loved for its edible fruit (great jam) and spring flowers. This native is also salt tolerant, making it a great choice for a seaside hedge located not far from the road. One point each, 8 points.

As the area could support additional plants, we decided to err on the side of a thicker screen and a better neighborly relations and used 20 points worth of plants instead of the required 16.

Having been given the blessing of the homeowners, the neighbors, the Conservation Commission and the DES, these plants were installed along the edge of the property line. They will grow into an attractive privacy screen which will attract wildlife, require less maintenance, and demonstrate that a native garden can be just as good, if not better than a non-native one. It will require vigilance, however, as the last time I was over checking on the plants, I had to unwrap a 6 foot strand of Bittersweet that had already crept over from the neighbors’ property and  wrapped itself around one of the Amelanchiers!

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The scene when we first came on site.
The following spring, the invasives on the neighbor’s side were making a comeback as we prepared to plant.
27 May 2015
The finished planting.


Although this area it was completely on the homeowner’s land and there were no neighbors to add to the mix, it seemed to me to be more complicated. To begin with, although there had been a couple larger trees taken down, the majority of the clearing seemed to be of Sumac and invasives and the trimming of old stumps to ground level.  This was difficult to be sure of in the beginning as it was late fall and the plants had gone dormant, but when spring arrived it became clear that other than one or two small trees that had been cut down, what had been  done was basically a basal pruning, (cutting the plants to ground level,) and the Sumac and the invasive species were making an enthusiastic bid to take over the area once again.

Early October, 2014 after clearing.

So now the question was, “What to do?”. The invasives should be dealt with so that whichever native species were to grow there would survive. But being only yards from the water brought up its own issues concerning how to deal with them. We were under a time deadline from the DES to complete the reparations and so we didn’t have a luxury of smothering the area with black plastic, plus we didn’t want to kill the Sumac, which is considered native in the State of Maine and was already well-established. We didn’t want to dig, thus compromising the integrity of the banking, yet for the long-term survival and success of any planting, the invasives had to go. At war was the reluctance to use herbicides (we didn’t have a pesticide license anyway, so that would have to be contracted out),  the desire to dig as little as possible, and the need to end up with a native buffer as soon as possible. Add to that the fact that a plan had to be agreed upon concerning the number of trees to be planted and how much of the past decade’s worth of clearing the homeowner was responsible for. (Despite the fact that they had owned the property for less than a year, they were responsible for replacing the whole decade’s worth, apparently.) We have a lot to decide in a short period of time.

The answer seem to be found in the saying, “We have very little time, and therefore we must proceed very slowly.” Thanks to a couple of very positive, cooperative meetings with town and state DES officials in which they allowed us to have extensions to the deadline, we ended up implementing a watch-and-wait strategy whereby we would give the plants a month or two to make a comeback and then see where we stood. When recheck time came, things were much clearer. The banking was bursting with healthy Sumac, some of it already over a foot tall. The oak tree which had been cut down was already producing suckers. Likewise, unfortunately, the Bittersweet and the Multiflora Rose were also doing well, but at least at this point we could tell our friends from our enemies. At the next meeting it was decided that a licensed pesticide applicator would be hired who knew the safest way to tackle invasives at the water’s edge, and they would carefully spray them but leave the Sumac alone. A period of time would be allowed for possible regrowth, at which time the second spraying would be done if necessary and then the situation would be assessed again. Now, I know there will be those who shudder at the thought of spraying, but the consensus was that spraying was the lesser of all evils. It resulted in the root zone of the banking being left intact, and the native plants being given room to grow and multiply, and as it was done carefully during a dry spell, there should have been no danger to the water’s ecosystem.

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We flagged the good guys vs bad guys for spraying.
June 16 2015
A month later, the Sumac was definitely winning.

Ultimately, the invasives were beaten back, and by late summer, nine months after the original clearing, the Sumac was over 6 feet tall. At our last meeting with the DES officials, it was decided that the Sumac should be allowed to grow unencumbered until the next season, at which time it could be thinned to approximately 40 plants. The sprouts of the Oak which had been cut down were also to be allowed to grow for a season, after which time one shoot would be chosen as the new leader and the rest removed. Points-wise, this was more than enough to satisfy the requirement, and so we did not need to disturb it any further with new plants, which would have had consequences to the ecology of the area not just from the digging, but also with the watering etc. that is necessary to help a new plant establish. Although the designer in me would have  loved to have created a waterside native garden, this was definitely the right thing to do.

By late summer the Sumac was going strong.

All this is just the tip of the iceberg, but I think that even the tip hold interesting points for discussion. Using native plants is easy to be on board with, as is getting rid of the invasive species that are threatening their existence. But the wetland/shoreline buffer zones are important too, so should we be getting rid of invasives at any cost in order to plant natives, at the possible expense of the fragile area that borders our waters? Here, the Venn diagrams don’t overlap as much as you might think. I think the answer is that yes, invasives must be discouraged and natives encouraged, but while being very mindful that the common area is small and that solutions must be found within that area. The price is not doing so is too great.

We were very grateful for the open-mindedness of the people that we worked with to come to the solution to this problem (two problems, really,  as there were two areas of concern.) We sorted through issues pertaining to need of plants versus laws, definitions of cutting versus clearing, and reparation versus restoration, to name a few, and in the end, kept the portion of the Maine seacoast which the laws were written to protect, protected. This is the whole point, after all. And I like to hope that in the end, the landscape ended up better than it had been when the whole story started.

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