Spring has sprung … and so has the Garlic Mustard

Spring has sprung … and so has the Garlic Mustard

Springtime is a time of hope and optimism. As the weather breaks and temperatures rise, people like to spend time outside. And all of that “indoor time” from the previous months contribute to a little “springtime optimism” that creates lists full of gardening and yard projects for the ambitious homeowner.

But you’ll rarely find “fighting with Garlic Mustard” on anyone’s list.

That’s because Garlic Mustard, a fast-spreading and highly invasive weed, can overwhelm you with its ability to grow just about anywhere, the path of destruction it leaves in its wake and its tenacity (some call it down-right stubbornness) when it comes to removal.

What You Should Know About Garlic Mustard

Garlic Mustard can grow in most soil types and can grow in full sun or full shade. It’s an equal-opportunity invader and its roots produce a chemical that is toxic to other plants.

Mowing Garlic Mustard doesn’t control it. The plants will bolt and seed. Many homeowners resort to hand-pulling the plants when they are in bloom and easy to identify (during April), but must revisit pulled sites frequently to make sure more Garlic Mustard hasn’t popped up to replace their lost comrades.

Left unattended, Garlic Mustard can spread quickly. Each plant can produce up to 5,000 seeds which can remain viable in the soil for up to 5 years.

How to Identify Garlic Mustard

(From the East Multnomah Soil & Water Conservation District Website

Garlic mustard (Alliaria petiolata) is a biennial, meaning each plant lives its life over two growing seasons. Seedlings emerge in early March, forming a rosette of leaves the first year. The leaves are alternate, triangular to heart shaped, have scalloped edges and give off an odor of garlic when crushed. The odor can be used to distinguish garlic mustard from native plants like evergreen violet (Viola sempervirens), piggy-back plant (Tolmiea menziesii), fringecup (Tellima grandiflora) and non-native plants such as silver dollar plant (Lunaria annua).

Garlic mustard also has a distinct “s” shaped curve at the base of the stem. Garlic mustard flowers during the second year of growth. In March and April of the second year, plants send up a flower stalk from 12 to 48 inches tall, topped with a cluster of white four-petaled flowers. The seeds form in narrow, green seed pods that originate from the center of the flowers and turn brown as the seed matures. The plant dies after producing seed and the brown, dried out stem with the brown seed pods remain through winter.

How to Control Garlic Mustard

Hand pulling and herbicides are the two most effective methods of controlling Garlic Mustard. While hand removal may work for small patches that can be re-visited frequently, herbicides are often used for large infestations. Over-use of herbicides that manage to kill off other native vegetation that may compete with Garlic Mustard only results in less competition for the Garlic Mustard seeds that germinate the following year.

Herbicides don’t kill Garlic Mustard seeds.

The video below provides more instructions on how to deal with Garlic Mustard:

What is Riverdale Doing About Garlic Mustard?

Riverdale is currently conducting an audit of the invasive species in the City-owned woods, trails and other greenspaces. We have also been asked by Arconic to audit their property as well since so much of it lies next to Riverdale’s. Scott Community College is conducting a similar audit.

We all know the audits will report a significant population of Garlic Mustard within the City’s geography – but the audits will help us identify the areas where widespread treatment is called for. In subsequent years, the City expects to spend a significant amount of money to gain control and then manage the Garlic Mustard spread in the City. 

Residents are encouraged to inspect their own yards and the wooded areas around their homes to identify patches of Garlic Mustard. If possible, we ask residents to pull and manage what patches they can and to let City Hall know if there are patches that are just too big for them to handle on their own.

By working together, the City, its residents and local business and education concerns can stem the tide of Garlic Mustard, saving all parties hundreds of thousands of dollars in habitat replacement, unnecessary erosion damage and worse. 

Thanks for your help.

City landscaping projects begin

City landscaping projects begin

Earlier this year, the City of Riverdale selected Quercus Land Stewardship Services, from Black Earth, WI, to plan, install and maintain the landscapes of the City’s parks and public places as part of a three-year program. Alex Wenthe, the owner of Quercus, is a Quad City native and familiar with the area. The company also has other clients in the community.

Quercus Land Stewardship Services (QLSS) is a small business located in Southwest Wisconsin
that specializes in ecological restoration and vegetation management. Their services include urban
and suburban restorations like retention basins, rain gardens, native landscaping and more.

Alex and his team were in Riverdale this week, starting the project (worth between $20 – $25,000 per year). In addition to the landscaping work they will be performing, Quercus has also been engaged to conduct the year-long, invasive species audit of City property as well as assisting the City in the preparation and implementation of a tree management plan which is intended to address the large number of damaged and standing-dead trees on City property.

We thought it might be helpful to provide some idea of how they view Riverdale’s current landscaping and how Quercus will be helping the city create attractive, sustainable landscapes in the community that all residents can enjoy.

Assessment and Recommendation

As cited in their proposal, Quercus gave the following review of Riverdale’s current situation and vision of the future:

Preliminary site assessments show that current landscaping on City property is in need of repair and maintenance. The existing pants are overgrown and the mulch groundcover has deteriorated significantly. Ornamental plants were mainly used in the initial installation, which often need continued care and maintenance to survive. Some of the current plants are also considered invasive and should be removed.

Quercus only uses plants that are native to the area. Native plants increase habitat/food sources for declining species like bees and butterflies. They also increase water infiltration, decrease erosion, require less maintenance, and survive at a higher rate. Native landscaping doesn’t mean “messy” either. Our native plantings are still formal and aesthetically pleasing.

We recommend using only plants native to Eastern Iowa going forward. There is no need to remove most of the existing plants, however when they die naturally we will replace them with natives. Also when beds need supplemental plants, only natives will be used. This will help keep costs down while transitioning to native plants over the three year contract period. Costs for this recommendation are included in the estimate.

Another recommendation is to make your own mulch. New mulch provides a “fresh” look that is hard to replicate, however mulching every year can get expensive. Rather than spending money to remove invasive and undesirable trees, then more money bring in new mulch. We will do both in one step. We will cut down the trees, chip them into mulch, and use them in the landscaping beds. We use only inert woody material and make sure no invasive seeds are included in the mulch. This technique is both budget friendly and environmentally conscious. Costs for this recommendation are included in the estimate.

The third recommendation is to improve the natural areas around the parks, especially highly visible or high use areas. A specific are to improve is the Northeast corner of Bi-centennial park. There are many old (100 yrs+) oak trees in this area that would benefit from understory clearing and possible replanting. This would improve the park’s usability, aesthetics, and ecological health. We could even add trails as desired by the city. Costs for this recommendation are not included in the estimate.

There are many other intricacies of this project that are difficult to discuss in a written proposal. All of our decisions will be based on our company philosophy to improve the places we work for all creatures, humans and otherwise. Many of our landscaping recommendations will be similar to recommendations made through the vegetation survey. By using Quercus for both the vegetation survey and landscaping contract, we believe you will save time and money and have a better  overall product. We are a professional, flexible, and responsive company that aims to increase the long-term heath and viability of your park system.

Where Will the Work Be Done?

According to the RFP issued by the City of Riverdale in December, the contractor selected to install and maintain the City’s landscaping is expected to handle weed, leaf and other debris removal, trim and maintain all bushes and ground cover, sweep and blow off walkways in City spaces and remove all debris and landscape materials. The contractor is also expected to provide playground-approved mulch for the City’s two playgrounds.

Specifically, work will be performed in the following areas:

  • City Hall
  • Parks:
    • Volunteer Square Park
    • Bicentennial Park
  • Playgrounds:
    • Bicentennial Park Playground
    • Peggy’s Park Playground
  • Trails:
    • Mississippi River Trail (Arconic Rest Stop)
    • Mississippi River Trail (Arconic Parking Lot/Bellingham Bike Station)
    • Duck Creek Bike Path Trailhead/VanGundy Park
Riverdale seeks qualified consultants to conduct a vegetation study in 2020

Riverdale seeks qualified consultants to conduct a vegetation study in 2020

(Update 09/24/19) – The City of Riverdale has issued an RFP (Request for Proposal) from a qualified arborist or vegetation consultant to conduct a study of invasive species in the City’s parks and wild spaces during calendar year 2020.

The City Council approved RESOLUTION 2019-37, which authorized the publication and distribution of the RFP to qualified vendors/consultants. The budget for the project was set at $10,000. Earlier this year, the City set aside up to $20,000 to study the invasive species problem in Riverdale and deal with it accordingly.

A copy of the RFP can be found here. The study is expected to be conducted in the areas indicated as “Active Parks” and “Vacant” areas on the map.

(NOTE: This map of the City of Riverdale with areas of particular interest can be downloaded here.)

Project Details:

Scope of Work:

The City of Riverdale seeks the services of an arborist or certified professional to identify which plants exist in which public (or City-owned) areas of the City. A comprehensive herbaceous and woody plant survey is expected. Sampling conducted for the survey should occur in all four seasons throughout the calendar year 2020. A complete copy of this RFP can be viewed by clicking here.


$ 10,000 (estimated)

Project Bid Date:

Proposals due: November 30, 2019 (see RFP for a more detailed schedule)
Selection made: December 10, 2019

Project Start Date:

Work begins: January 1, 2020
Study completed: December 31, 2020

Project Completion Date:

Report to City Council due: January 31, 2021



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