Tag: polyculture

From Beloved to Invasive: How does it happen?

On By durhammastergardenersIn benign non-native plant, bird friendly habitat, bugleweed, conservation, crape myrtle, Durham NC, ecological sustanability, ecology, gardening, Gardening information, gardening NC, heavenly bamboo, hellebore, how plants become invasive, Invasive Atlas of the United States, invasive plants, Japanese stiltgrass, lenten rose, lesser threat invasive plant list, liriope, monkey grass, nandina, native ecology, native ecologynative plant ecology, native plants, Natives, NC biodiversity, NC conservation, NC Native Plants, New Hope Bird Alliance, non-native plants, ox-eye daisy, perennials, polyculture, privet, protecting native plants, Rose of Sharon, Russian olive shrub, sustainable garden design, sustainable gardening, sustanability, Uncategorized, urban garden, urban gardening, watch list for invasive plants

By Jeannie Arnts , North Carolina Extension Master GardenerSM volunteer of Durham County

I have volunteered as a recorder for the New Hope Bird Alliance (formerly Audubon) Bird Friendly Habitat (BFH) team since 2018. The BFH team, consisting of a plant expert and a recorder, visits homeowners’ yards to identify native and invasive plants and make recommendations for improvements to achieve an ecologically beneficial habitat for birds, insects, and other wildlife. Since I have joined the group, plants previously recognized as non-native, non-invasive plants have been moved onto the “Watch List” or “Lesser Threat Invasive” list. Other plants previously considered lower threat have been moved to a higher threat category. The question arises, “What is it that changes a benign non-native into an invasive?

When is a Plant Determined to be Invasive?

Plants are categorized as invasive once they disrupt the ecology of intact, functioning eco-systems, leading to loss of biodiversity and habitat degradation. This results in huge economic damage valued in the billions of dollars to agriculture, forestry, and personal property. Invasive plants compete with our natives for critical and often limited resources like sunlight, water, nutrients, soil, and space. Anyone who has ridden the train at the Museum of Life and Science in Durham and seen the Russian olive shrubs (Elaeagnus sp) overtaking the landscape along the tracks or been on a hiking trail in many Triangle forests and seen the stiltgrass (Microstegium vimineum) engulfing the entire ground cover of the forest floor can easily see the impact of invasive species.

Russian olive shrubs (left) out-compete native plants and dominate riparian areas primarily in central and western USA. Japanese stiltgrass (right) was accidentally introduced into Tennessee around 1919 as a result of being used as packing material for porcelain from China.  it has invaded many woodlands in North Carolina. (Image credit: NC State Cooperative Extension)

What Factors Influence a Plant to Become Invasive?

Biologists have been “vexed for decades” by the question of what causes some plants, once thought to be benign, non-invasive exotics, to become a risk to our eco-systems due to their invasive characteristics. The ecologist, Charles Elton, wrote the book, The Ecology of Invasions by Plants and Animals, in 1958 and, more than 100 years earlier, Charles Darwin pondered this question during his voyage on the Beagle (1831-1836). Johnny Randall, former Director of Conservation Programs at the NC Botanical Garden, noted that one reason plants become invasive is that in their new environment, they no longer have natural controls, such as pests, pathogens, and herbivores. This gives them an advantage over native plants that have been part of a region’s ecology for millennia; consequently, the invasives often out compete the natives.1

In addition, a plant’s propensity to become invasive is a function of the plant’s own biology, including a relatively short generational period, large seed production, its ability to reproduce asexually (without the need for fertilization), and having large fleshy fruits, such as those produced by Autumn or Russian olive trees (Elaeagnus sp), privet (Ligustrum sp.) and heavenly bamboo (Nandina sp.) With this latter trait, birds will eat the berries and deposit the seeds far from the original location of the plant.

A non-native, is especially prone to invasion when it sets its roots in a “matched habitat” similar from which it came, i.e., their native ranges tend to have similar temperature extremes, precipitation levels, and seasonal cycles. Stiltgrass (Microstegium vimineum) is an example of a plant that meets most of the criteria for becoming invasive. It is an annual that produces up to 1000 seeds per year, has no natural controls, reproduces asexually, and its seeds are distributed by the wind. In addition, the seed bank may take up to five years to germinate. Many gardeners who think they have eliminated stiltgrass on their property one year are befuddled to find a number of plants from the seed bank sprouting the next summer. The good news is that if you continue to manage the stiltgrass, you will have fewer plants each year.

Beloved Plants that Become Invasive

I think we can all agree that we want stiltgrass eliminated from our property, but there are non-native plants that have been beloved by gardeners for generations that are being added to the invasive lists, much to the consternation of gardeners. One example is the lenten rose (Helleborus orientalis).

Some hellebores  have started to escape into woodland areas and are able to stifle our favorite native understory flowers. They prevent seedlings of other plants from getting established as dense mats of their offspring grow. (Image credit: NC Extension Toolbox, Bob Gutowski CC-BY-NC-SA-2.0; Jim Robbins CC-BY-NC-4.0).

There are many good reasons that hellebores are such a beloved plant: they bloom over the winter months when very few other plants are blooming; they require little care; they are deer and rabbit resistant; they tolerate a wide range of light conditions; including light shade; and they survive even deep frosts. Unfortunately, they meet many of the conditions that place them at risk to become invasive in our region: they have no natural pests or pathogens; they can successfully fertilize themselves (although bees will seek nectar and pollen from the plants); and they produce a multitude of fertile seeds. While there is not a perfect native substitute for hellebores, the gardener may consider planting a matrix of sedges (Carex species), coral bells (Heuchera americana), and ferns, many of which are host plants, to provide winter interest .

While not yet on the invasive lists in N.C, another beloved plant that is of concern is the crape myrtle (Lagerstroemai indica). Its spread is being tracked in Southern states by the Invasive Atlas of the United States and the plant’s spread is being watched with caution by conservationists in N.C. Each flower of the crape myrtle produces a prodigious number of seeds that are carried or blown far from the mother plant. I have had a crape myrtle in my yard for probably the past 40 years and it has only been recently that I have seen it sprouting up elsewhere in my yard and ¼ acre woods.


Crape myrtles are seen along roadways and in gardens in North Carolina but conservationists have raised concerns because it outcompetes many native plants (Image credit: NC Plant Toolbox, skdavidson)

Liriope (Liriope muscari and L. spicata), bugleweed (Ajuga reptens), Rose of Sharon (Hibiscus syriacus), and ox-eye daisy (Leucanthemum vulgare) are all common ornamental plants that have been added to the NC Invasive Plant list as “Low Threat” species. While they have the potential to harm our local ecology, they are not yet doing so.

Liriope (Liriope muscari), bugleweed (Ajuga reptens), Rose of Sharon (Hibiscus syriacus), and ox-eye daisy (Leucanthemum vulgare) are plants that many of us have in our garden. They are considered to be “Low Threat” to native plants of North Carolina. (Image credit: North Carolina Toobox, Manuel-CC-BY-2.0; Jim Robbins-CC-BY-NC-ND; Frank Mayfield, CC-BY-SA-2.0)

As gardeners, we can control the spread of potentially invasive plants in our own yards or we can choose to remove them and plant a native that supports our native ecology. A follow-up blog will suggest options to consider for replacing invasive plants with natives that power our ecosystems.

Notes

  1. Personal communications Peter Schubert, NC Invasive Plant Council, October, 2024 and Johnny Randall, former Director of Conservation Programs, NC Botanical Garden, October 2024.

Resources and Additional Information

NC Invasive Plants List adopted by NC-IPC, November 16, 2023NC Invasive Plant Council
https://nc-ipc.weebly.com/uploads/6/8/4/6/6846349/invasive_plant_list_-_ranked_-_2023-11-16.pdf

Grzędzicka, E., Assessment of Habitat Selection by Invasive Plants and Conditions with the Best Performance of Invasiveness Traits, February, 2023. https://www.mdpi.com/1424-2818/15/3/333

Invasive plant Atlas of the United States University of Georgia-Center for Invasive Species and Ecological Health, October 2018 https://www.invasiveplantatlas.org/index.cfm

Jones, M., Gaster, R. Invasive Species, NC Cooperative Extension, Lee County, July 30, 2019 https://lee.ces.ncsu.edu/2019/07/invasive-species/

Moony, H.A., Cleland, E.E., The Evolutionary Impact of Invasive Species, Proceedings of the National Academy of Sciences. May 2001, 98(10) 5446-5451 https://www.pnas.org/doi/full/10.1073/pnas.091093398

Moorman, C, Megalos, M, Douglas, K. Invasive Plants and Your Forests, NCSU Extension Publication. Revised September 11, 2024. https://content.ces.ncsu.edu/invasive-plants-and-your-forests

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A Better Way to Think About Soil

On By durhammastergardenersIn cover crops, Durham, how to improve soil, no-till gardening, plant fungi, plant-microbial relationship, polyculture, regenerative agriculture, rhizosphere, soil, soil health, soil microbes, soil test, Uncategorized

By Peter Gilmer, NC State Extension Master GardenerSM volunteer of Durham County

(Image credit: Pixabay)

Spring is coming, and the soil temperature is rising. Soon enough, it will be time to direct seed and to transplant the garden. Is my soil ready? What should I do to get it ready? Do I need a new soil test?

Many of us know that a soil test can be helpful, particularly when it comes to pH and lawn care. The usual soil test results recommend adding nitrogen, plus or minus phosphorus (P) and potassium (K). My results have always shown a reasonable pH, P and K values in the normal range, and the default recommendation to add nitrogen (N). As you may know, nitrogen is not actually measured. Is this enough to care for my soil?

Microbial Role in Soil Health

There is a way to build better soil, and it requires thinking about how soil works. These ideas come from the growing movement sometimes called regenerative agriculture. The basic ideas are simple, ideas that many of us sort of know. Soil function depends on microbial life, and the key to strong soil performance lays in promoting a healthy biome. Although there are other important players, we will focus on bacteria and fungi.

It turns out that these tiny organisms feed the plants by providing what the plant needs in the form that the plant requires for uptake. The essential nutrients, including nitrogen, phosphorus, and potassium (along with others) are already in the soil in nearly inexhaustible amounts, but are either remote from the plant’s reach or not in a plant-available form. The microbes are able to reach far beyond the root tips and can process the nutrients into plant-available form for uptake by the roots. There is no need for us to put the nutrients there when the microbiome is healthy. There are exceptions to this rule to be mentioned later. There is need to promote the microbial life central to soil health.

The Plant-Microbial Relationship

Before we get to the “how to” regarding microbial health, let’s review the role the plant is playing in getting its nutrient needs met. The plant is the energy source (food) for the bacteria and fungi in the soil. In other words, it is the plant that feeds the microbiome. This food is in the form of carbohydrates (sugars) produced by the plant via photosynthesis. It is estimated that 30% of the carbohydrates produced in the plant leaf are given to the microbiome. This ancient, essential relationship between soil, microbes, and plant has evolved over millions of years. Our job is to promote this functionality. It is not our job to provide nutrients directly. They are already there, in abundance.

How To Support Soil Microbes

Minimize Soil Disturbance

How do we support the microbes? The ideas are simple and basic for most gardeners. First, we need to minimize disturbance. This means less tilling. Why? Because tillage disrupts the microbial-plant dance that makes it all work. Soil aggregates, those tiny bundles of soil packaged with the help of microbes, are destroyed, and the ability of soil to hold onto water reduced drastically. The rhizosphere, the micro environment where fungi, bacteria, and root cellular membranes make critical exchanges, is disrupted physically in the process of tillage. So, step one, reduce disturbance.

The area of soil surrounding the plant root, the rhizosphere, is teeming with microbial activity. (Image credit: NC State Extension)

Of course, when planting anything, there will be disturbance. When I put a transplant into the ground, I dig (disturb) an appropriate-sized hole. What I do not do is turn over (till) the entire bed. Initially, tillage is useful in establishing a bed in an area that historically was lawn but is not used annually to clear the bed of weeds. Tillage disrupts the microbiome and doesn’t control the weed either.

Cover the Soil

Second, we should always cover the soil, either with living plants or with materials derived from dead plants (mulch). Exposed soil does not do well with direct sunlight, falling rain, and wind. In the garden, coverage is best done with cover crops in between planting seasons and wood chips or mulch where the paths are located. In a planting bed, coverage might consist of a perennial ground cover that not only covers the soil between plantings, but also puts another living root into the soil. Large areas of mulch in a planting bed might initially look good, but over time will get weedy, and the mulch cover does not provide a living root to feed the microbes.

Planting beds flush with cover crops consisting of radish, crimson clover, and rye, with wood chips covering the walking paths. (Image credit: Peter Gilmer)

In terms of cover crops, there is much that goes into the decision as to what cover crops to use. There are warm season covers (like buckseed) and cool season options (like crimson clover). There is the need to terminate the cover crop when the time is right to plant the main crop. This might involve mowing followed by a silage tarp. There are cover crops that winter kills. Terminating the crop before it goes to seed is critical. Polyculture, meaning multiple types sown at the same time, is better than a mass planting of a single crop. A full discussion of cover cropping goes beyond the scope of this article.

Acting as a living mulch, crimson clover is interplanted with cool weather vegetables. This cover crop provides weed suppression, erosion control, and maximizes the number of living roots in the soil–all while adding to the nitrogen pool through nitrogen fixation. (Image credit: NC State Extension)

Maintain Living Roots

Third, we should keep a living root in the soil as much of the time as possible. Remember, it is the plant through its roots that is feeding the microbiome and getting essential nutrients in exchange. The plant heals the soil. Remember when a field in fallow was considered good, a way to let the soil rest? All along the soil really needed living roots pumping fuel (carbon) to the microbiome. Planting something in between the main crop is an effective way of getting more roots in the soil. For example, you may have heard of marigolds being planted in between tomato plants.

Choose Diversity in Planting

Fourth, we should diversify whenever possible. Plants are not all the same, and they have unique relationships with their microbial partners. Monocultures are not nearly as healthy and resilient as polycultures.

Encourage Regenerative Animal Grazing

Finally, specifically in the world of farming, grazing animals can play a major role in restoring soil health. We cannot delve into this fascinating relationship in this article, but grazing animals (think bison) have played a major role for millions of years in keeping soil healthy. While this might not be applicable to the home gardener and not something I do myself, grazing is a powerful tool in managing and improving soil health.

To summarize, what should I, the home gardener, do to ensure healthy soil in my garden?

  • Minimize tillage
  • Keep soil covered
  • Keep living roots in the soil
  • Diversify plant life

I did mention that there are exceptions to these rules, and one that I should highlight is lawn maintenance. We have learned that lawns are poor supporters of the greater ecosystem. They are generally monocultures with superficial root systems, and do not develop healthy microbial life. Lawns are therefore more dependent on fertilizers and irrigation systems, all the more reason to reduce their size whenever possible.

Below you’ll find some of the best resources that I have encountered on the topic of soil health. I encourage you to dive deeper into this fascinating world.

  • Brown, Gabe.  “Dirt to Soil.  One Family’s Journey into Regenerative Agriculture. “ Chelsea Greensboro Publishing.  2018.  This is a fascinating story, well told, of going from frequent tillage and fertilizer to cover crops and soil carbon capture.
  • Frost, Jesse. “The Living Soil Handbook.” Chelsea Green Publishing. 2021. This is a great how to reference book for vegetable farming.
  • Lowenfels, Jeff and Lewis, Wayne. “Teaming with Microbes.”  Timber Press.  2010.  This is where my journey of discovery began.  It was given to me by a fellow Master GardenerSM volunteer.
  • Lowenfels, Jeff. “Teaming with Fungi.” Timber Press. 2017. I knew next to nothing about fungi, and this book introduced me to these critical microbes who are critical to many basic life functions on this planet.
  • Lowenfels, Jeff. “Teaming with Bacteria.” Timber Press. 2022. If you want to know more about the rhizosphere, this is the book for you. What an incredible relationship between microbe and plant root.
  • O’Hara, Bryan. “No-Till Intensive Vegetable Culture: Pesticide- free methods for restoring soil and growing nutrient-rich, high-yielding crops.” Chelsea Green Publishing. 2020. This guy is the master at growing vegetables and knowing what inputs (homemade compost teas) are needed and when.
  • Still, Jon. “A Soil Owner’s Manual.” 2016. A 75-page, concise overview of soil management that you will likely read more than once.

Happy gardening this spring. Go microbes!

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Resources and Additional Online Information

Learn more about soil testing with NC Cooperative Extension’s handy online guide chock-full of resources.

https://durham.ces.ncsu.edu/2020/05/nows-the-perfect-time-to-test-your-soil

For a detailed look online about the benefits of no-fill farming, check out resources by Penn State University, North Carolina State University, and Cornell University.

https://extension.psu.edu/no-till-farming-and-healthy-soils-work-hand-in-hand

https://plants.ces.ncsu.edu/garden_detail/vegetable-no-till-garden

Take Me Out to a Tarped Field

Planting cover crops is an excellent way to maintain soil health, suppress competition from unwanted plants like weeds, and stem erosion. See NC State Extension and Clemson Cooperative Extension’s online sites about how to use these plants in traditional agriculture and in raised beds.

https://growingsmallfarms.ces.ncsu.edu/growingsmallfarms-covcroplinks

https://caldwell.ces.ncsu.edu/2022/07/try-cover-cropping-a-guide-for-home-gardeners

Cover Crops in Raised Beds

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