Sustainable Landscaping

Update: 2018-05-26

It’s not about plants, not entirely. But it seems that, in one agricultural area, pollinators (bees) under stress have ceded their pollinating responsibility to a couple of species of exotic (read invasive) flies. See: J. R. Stavert, D. E. Pattemore, I. Bartomeus, A. C. Gaskett, J. R. Beggs, “Exotic flies maintain pollination services as native pollinators decline with agricultural expansion, Journal of Applied Ecology (British Ecological Society), 22 January 2018. The only thing surprising about that is that people consider it surprising.

Added references

Updated again below, `Plants of the future’, 2018-05-03

Update, 2018-04-29:

While my first thoughts and reasons for this post were simply to collect together a number of links pertaining to an interesting subject, regarding which there appeared to be some controversy, I have received several reactions to the material, many supportive and positive, others strongly adverse. This indicated to me that this is an area worth knowing more about, and, so, I have pulled quote a number of technical articles from the fields of Ecology, Forest Management, and Invasive Species Studies which I am currently reading. I intend to at least supplement the links below with additional ones explaining states of knowledge at present. I may include some comments summarizing what I have read. In other posts, in the future, I may do some modeling along these lines, since diffusion processes modeled by differential equations are of significant interest to me, whether for biological and physical systems, or diffusion of product innovations, via, for instance, the Bass diffusion model. Those results won’t be posted here, though.

Sustainable landscaping as described by Wikipedia, and by Harvard University. See also the Sustainable Sites Initiative. It’s a lot more than eradicating invasive species. In fact, that might be harmful. There’s a lot of questionable information out there, even by otherwise reputable sources like The Trustees of Reservations. See also their brochure on the subject where they recommend various control measures, including chemical, even if it is not their preferred option. There is evidence Roundup (glyphosate) is indeed effective against at least Alliaria petiolata, with little harm for common, commingled biocenostics.


(Above from M. Rejmánek, “What makes a species invasive?”, Ecology, September 1996, 3-13.)

Four inspirational books:

I dove into reading Professor del Tredici’s book as soon as I got my copy. Here is part of what he has to say from pages 1-3:

Perhaps the most well-known example of a “spontaneous” plant is Ailanthus altissima or tree-of-heaven, introduced from China. Widely planted in the Northeast in the first half of the nineteenth century, Ailanthus was later rejected by urban tree planters as uncouth and weedy. Despite concerted efforts at eradication, the tree managed to persist by sprouting from its roots and spread by scattering its wind-dispersed seeds …

Although it is ubiquitous in the urban landscape, Ailanthus is never counted in street tree inventories because no one planted it — and consequently its contribution to making the city a more livable place goes completely unrecognized. When the major of New York City promised in 2007 to plant a million trees to fight global warming, he failed to realize … that if the Ailanthus trees already growing throughout the city were counted he would be halfway toward his goal without doing anything. And that, of course, is the larger purpose of this book: to open people’s eyes to the ecological reality of our cities and appreciate it for what it is without passing judgment on it. Ailanthus is just as good at sequestering carbon and creating shade as our beloved native species or showy horticultural selections. Indeed, if one were to ask whether our cities would be better or worse without Ailanthus, the answer would clearly be the latter, given that the tree typically grows where few other plants can survive.

There is no denying the fact that many — if not most — of the plants covered in this book suffer from image problems associated with the label “weeds” — or, to use a more recent term, “invasive species.” From the plant’s perspective, invasiveness is just another word for successful reproduction — the ultimate goal of all organisms, including humans. From a utilitarian perspective, a weed is any plant that grows by itself in a place where people do not want it to grow. The term is a value judgment that humans apply to plants we do not like, not a biological characteristic. Calling a plant a weed gives us license to eradicate it. In a similar vein, calling a plant invasive allows us to blame it for ruining the environment when really it is humans who are actually to blame. From the biological perspective, weeds are plants that are adapted to disturbance in all its myriad forms, from bulldozers to acid rain. Their pervasiveness in the urban environment is simply a reflection of the continual disruption that characterizes this habitat. Weeds are the symptoms of environmental degradation, not its cause, and as such they are poised to become increasingly abundant within our lifetimes.

(Slight emphasis added by blog post author in a couple of places.)

The fact that ‘r-strategists’ are the best invaders is not surprising because the overwhelming majority of biological invasions take place in human- and/or naturally-disturbed habitats. Our modern landscape is mainly disturbed landscape.

(Above from M. Rejmánek, “What makes a species invasive?”, Ecology, September 1996, 3-13.)


Links with some quotes and discussion:

S. L. Flory, K. Clay, “Invasive shrub distribution varies with distance to roads and stand age in eastern deciduous forests in Indiana, USA”, Plant Ecology, 2006, 184:131-141.

Some quotes:

If roads are important corridors for exotic plants or if roadside edges provide good habitat for exotic plant growth, then one would predict decreased exotic plant density with increased distance to roads. In support, the prevalence and cover of exotic plants has been shown to decline with increasing distance to road in a number of ecosystems.

Independent of distance to road, successional age might determine susceptibility of a community to exotic plant invasions. Young forests typically have higher light levels (Levine and Feller 2004), fewer competitors, and less litter than older forests (Leuschner 2002) while mature forest interiors are known to have lower light availability, cooler temperatures, and higher humidity than forest edges (Brothers and Spingarn 1992). We would therefore expect, based on levels of light penetration and microclimatic conditions, that older forests would have higher densities of invasive shrubs near the forest edge than in forest interiors and fewer invasive shrubs overall due to less recent disturbance events and less favourable environmental conditions. We would also expect that younger forests would show weaker correlations of densities of invasive shrubs with increasing distance to road since light levels are higher throughout young forests. This would result in an interaction between distance to road and forest age.

The goal of this study was to quantify the density of invasive exotic shrubs along roads in eastern deciduous forests of varying successional ages in Indiana. Eastern deciduous forests cover much of the landscape east of the Mississippi River. Most of this region has been fragmented by urban and suburban development and roads such that ninety percent of all ecosystem areas in the eastern US are within 1061 m of a road (Riitters and Wickham 2003). We specifically addressed the following questions (1) Does the density of invasive exotic shrubs decline as the distance to a road increases? (2) Does the relationship between density and distance to road differ among exotic shrub species? and (3) Are invasive exotic shrubs less common in mature forests than in young successional forests? Answers to these questions will help develop a predictive framework for plant invasions and better inform management strategies.

This study suggests that roads may contribute to the spread of invasive plants in eastern deciduous forests. We found a highly significant effect of distance to road over all species and for four of seven individual species … One possible mechanism for high densities of invasive shrubs along roads is that exotic shrub propagules are distributed evenly by birds with respect to distance to road and simply survived at a greater rate near the road due to better growth conditions. These conditions might include higher light conditions or increased nutrient or water availability … Better survival and growth of exotic shrubs might also be due to decreased competition with native understory species. Native species may not survive as well along roadsides where runoff from pollutants and exposure to herbivores is greater … A second possible mechanism is that exotic shrub seeds are distributed by birds and other animals in a pattern that parallels the distribution of shrubs that we found. This would mean that the density of dispersed seeds declines with increasing distance to the nearest road but that survival is unaffected by distance to road. A third possible mechanism is that exotic shrub propagules were initially distributed along roads by animals and vehicles and are invading the forest from the roadside edge.

Successional age has been shown to affect exotic plant establishment in old fields in Minnesota with younger successional aged communities more susceptible to invasions and older communities more resistant (Inouye et al. 1987). Our results show that forest successional age plays a similar role in the distribution of invasive shrubs in eastern deciduous forests with invasive shrubs found in greater densities in young and mid-successional forests than mature forests. This is likely due to a combination of factors including differences in light regimes … Exotic shrubs would have survived and grown much more successfully where they did not have to compete with existing trees or intact forests. This hypothesis could help to explain why we found fewer shrubs near the road in mature forests than young and mid-successional forests.

S. L. Flory, K. Clay, “Effects of roads and forest successional age on experimental plant invasions”, Biological Conservation, 2009, 142, 2531-2537.

A. M. Carlson, D. L. Gorchov, “Effects of herbicide on the invasive biennial Alliaria petiolata (Garlic Mustard) and initial responses of native plants in a southwestern Ohio forest”, Restoration Ecology, 2004, 12(4), 559-567.


Although Alliaria has been labeled a severe threat to deciduous forests (Nuzzo 1994), there has been little study of the effects of Alliaria on native plants. A removal study showed that Alliaria had negative impacts on forest floor vegetation of a somewhat disturbed lowland forest (McCarthy 1997). Alliaria petiolata has been shown to be equal to or more competitive than two of three native understory species from this forest (Meekins & McCarthy 1999). However, Alliaria did not significantly affect the growth of any of four herbaceous species via allelopathy (McCarthy & Hanson 1998).

Our objectives were to determine the extent to which Alliaria changes the community on a small scale over several years and whether herbicide application is an effective control mechanism for Alliaria in upland mesic deciduous forest — a necessary step before widespread removal attempts are made (Hager & McCoy 1998). In addition, trial removal should reveal other responses to Alliaria elimination, such as erosion and invasions of other exotics (Westman 1990; D’Antonio & Meyerson 2002), and thus inform management and restoration decisions. This study addressed the following questions: (1) What is the effect of fall Round-up application on the density of Alliaria; (2) What is the effect of fall Round-up application on other wintergreen herbs; and (3) What is the effect of the first year of reduced Alliaria density on forest floor vegetation and the demography of native herbs and tree seedlings?

Their conclusions are that glyphosphate is effective against at least Alliaria petiolata, with little harm for common, comingled biocenostics, although they could not rule out variability in Alliaria numbers being due to natural variation, since the study before report lasted but two years.

P. H. Gobster, “Invasive species as ecological threat: Is restoration an alternative to fear-based resource management?”, Ecological Restoration, 2005, 23(4), 261-270.


By extending a culture of fear into the realm of the natural environment, it is questionable whether scientists and managers will gain resources or public support to more effectively manage invasive species. It is quite possible, however, that it could change the way we as a society perceive and experience natural environments, and do so in a way that erodes the restorative benefits that such environments can uniquely provide.

Because the management of invasive species is often central to restoration projects, the preceding discussion has as much relevance for the field of ecological restoration as it does for invasion biology. Are restorationists also prone to using fear about invasives to generate public support for their work? In a similar analysis of media stories, popular books, and academic journal articles focusing on ecological restoration I found some evidence of this happening, though not to the extent that I did with work focusing solely on invasives. Some restorationists see invasives as severe threats that can destroy entire ecosystems if vigilant fights against them are not kept up. Others view particular species, such as buckthorn, as the bane of restoration projects, describe them with terms like “rapacious” and “choking,” and charge them with “bringing a cancer on the land.” One reason why restorationists may not seem as fearful about invasives is because they have other things to express their fears about. Land fragmentation, development, fire suppression, and illegal plant collection are
additional problems that restorationists see threatening natural areas today. What separates communications about restoration from those focusing on the science and management of invasive species, however, is not just the degree of fearful and negative language. In the restoration writings I also found a wealth
of counterbalancing language that I felt much more positively and effectively communicates the importance of restoration endeavors.

Note the term invasive with respect to organisms and plants has definitions which do vary, and have even been the subject of a U.S. Presidential Executive Order (No. 13112).

M. Rejmánek, D. M. Richardson, P. Pyšek, “Plant invasions and invasibility of plant communities”, in Vegetation Ecology, 2nd edition, 2013.


Some 2500 yr ago, Heraclitus of Ephesus said that ‘All things change … and you cannot step twice into the same stream’. Today, ecologists would not only say the same about streams but also about vegetation. Plant communities change with time due to changes in the environment (Chapter 7), biotic interactions (Chapter 9) and invasions of alien species and genotypes, introduced intentionally or accidentally by humans. Invasions have received detailed attention only recently. There have always been migrating taxa, but now the rate of human-assisted introductions of new taxa is several orders of magnitude higher. In California, for example, more than 1000 alien plant species were intentionally or non-intentionally introduced and established viable populations over the last 250 yr. In the Galápagos Islands, over 3 million years of their history, only one new plant species arrived with birds or sea currents every 10,000 years. However, over the last 20 years the introduction rate has been c. 10 species per year, or some 100,000 times the natural arrival rate (Tye 2001).

At the regional scale enormous differences in presence and abundance of invaders among different communities (ecosystems) within one area seem to be the rule. An overview is now available for Central Europe (Table 13.1). Alien species are concentrated mostly in vegetation of deforested mesic habitats with frequent disturbance (Pyšek et al. 2002a,b). In general, native forests harbour a low number and proportion of both archaeophytes (introduced before 1500) and neophytes (introduced later); alien species are completely missing from many types of natural vegetation, e.g. bogs, natural Picea abies forest, and rare in many natural herbaceous communities. Herbaceous communities of extreme habitats and/or with strong native clonal dominants (Nanocyperion flavescentis, Phragmition, Nardion) seem to be most resistant to invasions of both archaeophytes and neophytes. In general, Californian lowland communities (Fig. 13.2) are more invaded than corresponding communities in Europe. However, there are some important similarities. Open and disturbed communities are more invaded, while undisturbed forests are less invaded.

Can we say anything conclusive about differences in invasibility (vulnerability to invasions) of particular ecosystems? Analyses of ecosystem invasibility based just on one-point-in-time observations (a posteriori) are usually unsatisfactory (Rejmánek 1989). In most of the cases we do not know anything about the quality, quantity and regime of introduction of alien propagules. Nevertheless, available evidence indicates that only very few non-native species invade successionally advanced plant communities (Rejmánek 1989; Meiners et al. 2002). Here, however, the quality of common species pools of introduced alien species — mostly rapidly growing and reproducing r-strategists — is probably an important part of the story. These species are mostly not shade-tolerant and many of them are excluded during the first 10 or 20 years of uninterrupted secondary succession (Fig. 13.3), or over longer periods of primary successions. However, some r-strategists are shade-tolerant. e.g. Alliaria petiolata, Microstegium vimineum and Sapium sebiferum. Such species can invade successionally advanced plant communities and, therefore, represent a special challenge to managers of protected areas.

This is all related to the Verhulst model of (biological) population growth which, incidentally, bears a close formal relationship to the Bass diffusion equation, mentioned elsewhere here. The difference is that Bass is additive and Verhulst is multiplicative.


J. A. Catford, P. A. Vesk, D. M. Richardson, P. Pyšek, “Quantifying levels of biological invasion: towards the objective classification of invaded and invasible ecosystems”, Global Change Biology, 2012, 18, 44-62.


(Low intensity development practices above. Click on image to see a larger figure, and use your browser Back Button to return to blog.)

(Disconnect roof runoff and manage the flow on the spot!)

(Professor del Tredici): Absolutely, in the city of Berlin, it is illegal to use herbicides. Somehow a decision was made that this is how it’s going to be, and people seem willing to accept the weeds and not use Round-Up. And that is what it takes to change the system: if you want to ban herbicides, you have to learn to live with weeds.

Update: Plants of the Future

This Web site shows and argues how the ruderals, the marginals, the unsightly, and the invasives will come to dominate a climate-disturbed landscape.

About hypergeometric

See and
This entry was posted in adaptation, American Association for the Advancement of Science, argoecology, biology, Botany, Carl Safina, complex systems, conservation, ecological services, Ecological Society of America, ecology, Ecology Action, environment, fragmentation of ecosystems, invasive species, land use to fight, living shorelines, New England, population biology, population dynamics, quantitative biology, quantitative ecology, sustainability, sustainable landscaping, water as a resource. Bookmark the permalink.

One Response to Sustainable Landscaping

  1. Weinberg, Ellen says:

    Hi Jan,

    Thank you for this information on sustainable landscaping/“invasive” species, plant toolkit, and all.


    Ellen Weinberg

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