Speaking Your Mind
Seeding Design Shortcomings:
Growing Carrots in the Desert

“Drastically disturbed soil” at FHWA’s Flowery Trail Scenic By-way, WA.

Re-capping the Challenge

Re-establishing sustainable native plant growth on drastically disturbed soils in harsh environments is a tall order by anyone’s standards. We are talking here about restoring disturbed land to its former natural vegetative state that existed prior to its being disturbed. Not surprisingly, there are few in the moisture-parched Western U.S. having much success at meeting this challenge, despite the vast amount of knowledge that has been accumulated from years of research on the ecology and developmental morphology of native plant species by intelligent and dedicated individuals.

The good news is that sustainable establishment and growth of native plants is being successfully accomplished, and on a consistent basis in select venues following a carefully orchestrated program. However, much still needs to be done before this success permeates throughout the seeding industry, sufficient to chip away at that “85% disappointing performance” estimate and the consequent casual observer’s conclusion that the reclamation seeding industry is “fundamentally flawed” (see Fundamentally Flawed, Western Chapter News Winter 2003).

So why are so many seeding projects turning out “disappointing”? Let’s first look at some shortcomings of CONVENTIONAL DESIGN.

No Need to See the Patient

First and foremost, conventional seeding design pays scant, if any, attention to soil composition and conditions apart from perhaps broad characterization into unspecific categories such as sandy/loam/clay, prompted by concerns over immediate soil stabilization. But soil mineral balance and the health of soil microorganisms within the soil biota, the crucial building blocks of vibrant soil and plant life, escapes the notice of most reclamation practitioners. “Soil is soil. Some-thing to seed into, or build a road with”. Unbelievably, some designers never even visit their seeding sites, let alone seek an analysis of soil samples taken from their seeding sites.

While there is a growing realization that topsoil is critical to re-establishing sustainable plant growth, apathy towards preserving topsoil belies any suggestion that many in the industry understand to what extent “living” topsoil is crucial to seeding success. “Topsoil” is often viewed as whatever soil happens to be placed “on top”, and even stockpiled topsoil is often allowed to become sterile due to ineffective stockpiling techniques.

Feed ‘Em Cake

Second, conventional seeding techniques invariably take a purely agronomic approach to re-establishing native plants on a disturbed site. This fundamental error, repeated so often, ignores the essential facts that native species obtain nutrient and moisture differently than agronomic and ornamental species. In addition, native species have different requirements for germination and establishment. Drill seeding into living native soils may work fine, if it is appropriate to cover subject species, and if Nature cooperates with sufficient moisture to both germinate and nurture young seedlings to the point their roots and mycorrhizal associations are established. In addition, the major outstanding question in this equation is the ability of the soil to adequately provide sufficient soil microorganisms to support establishment. It’s when we attempt to grow native plants on drastically disturbed soils (read “sterile”) that we run into difficulties. Steep slopes only compound the problems faced in revegetating disturbed soils.

Feeding Sugar To Kids

Steep slopes only compound the challenges faced in revegetating drastically disturbed soils (Victor, CO).

Admittedly, many have progressed beyond the “wood fiber mulch + 16-20-0 + tackifier + seed” recipe (and its beefed up and impendent successor, the bonded fiber matrix) so ably marketed by Weyerhaeuser during the ’80s and early ’90s. Unless one is operating in the rain shadow perpetual dampness west of the Cascade Mountains, even Weyerhaeuser’s mantra of “seed it each year for five years” is not going to cut it in the harsh environment of low rainfall, low nutrient levels, high soil temperatures, heavy metals, soil salinity, low organic matter, mineral imbalances so prevalent in the semiarid West. The “sugar-shot” approach to replenishing what soil physicists like to term depleted “nitrogen pools” works fine for irrigated ornamental plant species, but this ill founded approach ignores the fundamental requirement of native species, which have relatively low nutrient requirements. This single dimensional analysis of native plant ecology is without empirical foundation, and unsupported by credible research literature concerning native revegetation, not to mention unsupported by evidence of success in the field.

Garbage In, Garbage Out

Removing “cellulose mulch” from failed conventional seeding site (Truckee, CA).

Analogous to the ’70s fascination with anything spit out by (and thereby authenticated by) a computer, some well meaning practitioners in search of organic alternatives have embraced composting of whatever is close at hand, or what might be politically correct to save from the landfill. Composting was the “pixie dust” of any and all waste products, theoretically converting organic materials of questionable mineral and suspect nutrient value into soil amendments for the garden. All too often, however, we have forgotten the “garbage in, garbage out” lesson we learned in the early days of computers. Cost benefit analysis of various compost materials is required to ascertain what, if any, value a subject compost material may have, and the benefits to the target plant species, relative to the cost for moving and applying this bulky material at the revegetation site. The question must be asked: What appropriate nutrient and what quality of organic matter is contained in the subject volume of compost?

Consequently, human waste by-product (and heavy-metal) sludges and decomposed garbage have been fired out onto soil surfaces in an effort to boost organic material on drastically disturbed soils. And much like the largely unsuccessful organic-enhancing efforts of the ’60s where farm paddocks were treated with truckloads of cellulose-laden sawdust, elevated levels of carbon immediately locked up whatever minimal nutrient existed in the soil. Likewise, composted yard waste is high in cellulose and little more, and thus of little benefit to the revegetation effort, however politically correct it may be.

Growing Weeds and Poisoning Your Soil

Countering this cellulose induced nitrogen lock-up with timely treatments of nitrogen fertilizer wins you points for effort, but only grows weeds as a consequence. There are few better ways to trigger the invasion of cheat grass and other invasive weeds into your reclamation plot (which may win you short-term satisfaction points from your clients if they only understand “any form of green is good”). Unfortunately, one is also unknowingly poisoning (like chlorine in a swimming pool) the very ecology one is hoping to nurture for long-term native plant establishment. Our pre-occupation with what we can see and control on the soil surface has blinded us to the devastating side effects of chemical fertilizers upon soil microorganisms and their ecosystem, upon which most native species are dependent for sustained growth.

Designs That Are Working

“Good designs are ones that perform across time.” Not surprisingly, there is no magic recipe of products for successful native plant reclamation projects, because each site is unique in soil, aspect, altitude, slope, microbial composition, plant species, precipitation, seasonal temperature fluctuations, etc. But there are a limited number of recipes of approach, either one of which will dramatically increase your chances of a successful seeding effort, that concentrate first and foremost on rejuvenating the soil ecology that must ultimately sustain the shrubs, forbs and grasses that are native to your site.

An example of one such “recipe of approach” is the Growing Soil Technologies™ developed by the Native Plants Alliance team of designers, academics, researchers and seed specialists drawn from throughout the Western U.S., individuals who are informally linked by a mutual passion for successfully growing native plants in harsh environments. To obtain some insight into their methodology of approach, go to NativePlantsAlliance.net and make your way to the “Growing Soil™” technical paper.

What is stimulating about the Growing Soil Technologies is that the merger of soil science, botany, plant morphology, knowledge of native seed and structural engineering has not only been working on a consistent basis for some 8 years now, but that it is also working successfully on sites that have responded unacceptably to conventional seeding design approaches. What began in the semi-arid deserts of Idaho with Summit Associates (Boise, ID) has been equally successfully implemented by

Most native plants require the symbiotic relationship with site-specific mycorrhizal fungi to survive in harsh environments. Their tiny filaments encase and extend from the roots, dramatically increasing the plant’s ability to collect moisture and nutrients.

the likes of Jones & Jones (Seattle, WA) and the FHWA (Vancouver, WA) in Montana, Washington, and Oregon; by leading native seeding specialist Western Botanical Services (Reno, NV) in the Tahoe Basin of California and Nevada; mine sites in Wyoming, Idaho, Utah and the Rocky Mountains of Colorado, as well as by seeding contractor SunWest Golf & Reclamation growing native plants in the desert environment of Cabo San Lucas, Baja California.

As the Growing Soil title suggests, all efforts to re-establish sustainable native plants growth revolves around re-establishing a healthy soil food web in the sterile soil, in setting the stage for the natural re-establishment of site-specific mycorrhizae and related soil microorganisms to nurture and co-exist in symbiotic relationships with the successional native species from early seral stage through to climax species. It all begins with the site analysis, and the examination and interpretation of soil analysis from the sample taken at the site. The soil dictates what is required to be done to establish desired growing conditions for the selected species, transcending manufacturer’s specifications. This is in addition to selecting site appropriate early seral stage species for the revegetation effort, and knowing how to put out the seed effectively.

The irony of the situation is that many of the similarly successful associated “recipes of approach” are also heavily grounded in working closely with Nature. For example, where minimal financial resources have limited access to modern machinery and/or manufactured products, practitioners unwittingly avoided many of the counterproductive side effects of wood fiber mulch and/or chemical fertilizers. Similarly, the avoidance of heavy machinery minimized the destruction of soil structure and any active soil food web, and thereby increased a seeding project’s chance of success. Finally, the absence of “modern improvements” has at times mandated the stringent salvaging of topsoil which has been shown to be far more valuable than it was ever given credit for.

Plant Species Selection

Once one has restored the mineral balance of one’s soil and taken steps to re-establish a healthy soil food web, the issue of plant species selection must be addressed. It was not so very long ago that we realized how ill advised our efforts were in attempting to grow ornamental and agronomic species at revegetation sites, and in specifying introduced forage and turf species into our reclamation projects. In an effort to improve sustainability of plant growth, we began to take note of what plant species were growing immediately outside our disturbed areas and to plant what we saw.

Checking out the patient: collecting soil for analysis to determine the true extent of the seeding challenge (Truckee, CA).

Notwithstanding the logic of this strategy, we again fell short of Nature’s threshold conditions for success. It was not until we more closely mimicked the natural successional process, by seeding with early seral stage (pioneer) species, that we set the stage for climax species to ultimately re-establish themselves on disturbed sites.

Innovative Blind Alleys

Over the past 8 years, much has been made of inserting mycorrhizal fungi into the revegetation equation. After all, mycorrhizal associations (fungal colonies) are found in a broad range of habitats, being present in the root systems of the majority of indigenous plant species on arid and semiarid lands of the American West.

In regions with low rainfall, where soils tend to be low in organic matter and low in available P and N, mycorrhizal fungi plays a vital role in assisting the root systems of dominant species of indigenous vegetation to access moisture and nutrients from the soil. By way of example, 96% of the native species in the Great Basin have mycorrhizae associations. More than 30 years of research worldwide has proven the roles of mycorrhizal fungi, in association with other soil microbes, are necessary for plant survival in these ecosystems.

Yet successfully revegetating drastically disturbed soils with mycorrhizae-inoculated native plant seedlings has proven an elusive objective, as reasonable as it may have seemed at the outset. Notwithstanding the logic of this practice, field experience over the past 6 - 8 years would clearly indicate that we are again falling short of Nature’s threshold conditions for success. In all likelihood, looking only at mycorrhizae fungi in isolation will one day be shown to be myopic; we should be looking at the entire fauna and flora of a disturbed site, in much the same way as the Growing Soil Technologies sets out to do. It’s a subtle, but critically important concept to grasp: one is not so much growing native plants per se, as one is nurturing early seral stage plant species in tandem with mineral balancing + biological amendments in an effort to “set the stage for the natural re-establishment of site-specific mycorrhizae fungi and the other functioning components of the soil food web.” Absent the revival of a functioning soil food web, the much-heralded hardy native plant species have little chance of survival.

Raising Your Chances of Seeding Success

1. Retain a successful designer, by which I mean a designer who can take you and a native plant botanist to at least 5 performing sites that span “2 years of established native vegetation through more than 4 years since seeding took place” time frame. Wherever possible, talk at length with the client’s representative who was on site at the time of the seeding to (a) confirm your candidate designer truly was the designer; (b) what difficulties (if any) occurred during the implementation of the design; (c) what was done to resolve such difficulties (if any); (d) what was the design’s specific objectives; and (e) how did the end product match up to the design’s objectives.

   Far too many clients are hiring designers who have no track record of success, notwithstanding their professional qualifications. Be wary of engineers who believe seeding is simple. Remember: Nature is utterly intolerant of any weak link that slips into your seeding project.

2. Analyze your soil properly and have the analysis interpreted by an individual knowledgeable about soil balance and nutrient levels required for native species. Otherwise, you’re shooting in the dark and wasting both money and time.
3. Make the effort to re-balance your soil.
4. Retain your designer to be on-site at the time the seeding project is implemented.
5. Be wary of project engineers who: (a) have yet to acknowledge that native revegetation reduces major maintenance expenditures; (b) feel conventional seeding techniques “have been around a long time, and therefore good enough for them;” (c) believe that because seeding is the last phase of a project, it is the least important. With all due respect to engineers, it is often the most visible (as seen by surrounding communities) and therefore the most critical part of a construction project.

This article was first printed in the Western Chapter of IECA Newsletter, Spring 2003. Written by Peter McRae, President Quattro Environmental, Inc.

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For other articles in this series, check our Articles page.

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