ISSN 1188-603X

No. 504 May 5, 2016 Victoria, B.C.
Dr. A. Ceska, 1809 Penshurst, Victoria, BC, Canada V8N 2N6


The 7th Wilf Schofield Bryophyte and Lichen Foray will be exploring Northern Vancouver Island near Port Hardy and Port McNeill area, British Columbia. For further information contact Olivia Lee at or 604 822-3344.


From: G. Mitrow & P.M. Catling

With many invasive alien plants spreading in Canada there is often a lot of interest in management programs that exist in adjacent regions of the United States. While gathering information for an article on Garlic Mustard as part of a regular series on Canadian invasive plants (Catling & Mitrow 2015), we gathered information on the nearby states, but not all of that could be included in our article. However, it may increase dialogue and be helpful to management on both sides of the border, to know what is being done and recommended nearby.

Garlic Mustard, Alliaria petiolata (Bieb.) Cavara & Grande (Brassicaceae), is one of the most important invasive in North America. Among the valuable documents reviewing its history, ecology and management are those by Cavers et al. (1979), Nuzzo (2000), and Rodgers & Stinson (2008). Some of the important websites covering adjacent regions are also listed at the end of these notes.

Prevention and Control recommended in adjacent states

In ALASKA, Garlic Mustard was found in Juneau and in Auke Bay where it is considered a growing problem. The invasiveness rank is 70 on a scale from 0 to 100 (0 being not problem and 100 representing a major threat to native ecosystems). A network of Juneau-area collaborators has been battling Alaska's Garlic Mustard infestations for several years, but the Invasive Species Advisory Council recommendation has spurred a new, intensified effort. The Forest Service is a member of the newly-created Juneau Cooperative Weed Management Area, a group that includes the City and Borough of Juneau, Alaska Cooperative Extension Service, the Juneau Watershed Partnership, the Natural Resource Conservation Service, and the Central Council of the Tlingit and Haida Indian Tribes of Alaska. The intensified campaign against Garlic Mustard will be overseen by the Cooperative Weed Management Area at the downtown site, and the Regional Office and Juneau Ranger District at the Auke Bay site. The campaign will include public education, scouting for additional infested sites, and managed and monitored control efforts.

In WASHINGTON, eradication is required state-wide and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species. It was first identified in Seattle in 1999 and listed as a "Class A Noxious Weed" in 2000. The King County Noxious Weed Program is working closely with landowners to prevent new infestations and eradicate existing populations. Cooperation and vigilance will help keep Garlic Mustard out of woodland areas throughout western Washington. The majority of the known infestations in King County in Seattle parks and nearby private properties, but Garlic Mustard has also moved into Bellevue, areas along the Cedar River, North Bend, Tukwila, Shoreline and other parts of the county. Early detection is critical, containment and eradication of new sites is of the highest priority. Regional collaboration to share information and build partnerships to combat Garlic Mustard will be the key to stopping this plant in the Pacific Northwest. People are asked if they see Garlic Mustard in regions outside of King County, to notify the local or State Weed Board or Conservation District Office.

In MONTANA Garlic Mustard is not considered as a noxious weed. It was reported for the first time in Daniels County in 2013. In May 2015 it was also found in Lewis and Clark County. Because it is not well-established in Montana (Daniels County infestation was eradicated; Lewis and Clark County infestation is being eradicated), prevention and early detection and rapid response are the management priorities for the state. It is recommended to hand-pull small infestations. Mowing second-year plants before seed development is also effective. Spring prescribed fires can be used and are most effective on first-year plants. There are several chemical control options, and the best one depends on the situation. In most cases, applications should be applied at the rosette to bolting stage.

In NORTH DAKOTA, Garlic Mustard has been recorded but not listed as a noxious weed, but is part of an integrated weed management program.

In MINNESOTA Garlic Mustard is a "Prohibited Noxious Weed". The biological controls are under investigation, but none are approved for release at this time. One insect being studied is Ceutorhynchus scrobicollis, a crown and stem-mining weevil. It is suggested to manually pull plants in early spring prior to flowering (seed set is almost coincidental with flowering) and cutting plants back to the ground as they bolt for flowering. Sites are monitored as cutting may need to be repeated. If mature flowers (or seed pods) are present, plants should be disposed of onsite or contained (e.g., bagged) and removed to an approved facility. Prescribed fire in spring to top-kill basal rosettes and seedlings is recommended. Follow-up treatment with herbicide is considered imperative after seedling germination to further slow growth of infestations. An herbicide application to foliage with formulations of triclopyr, metsulfuron-methyl, or imazapic is used. Glyphosate or 2,4-D can be applied after native plants have entered dormancy and Garlic Mustard is still active.

In WISCONSIN, Garlic Mustard it is "Restricted". Control of either small or large infestations requires a long term commitment, since the seeds of Garlic Mustard can remain viable in the soil for five years. Studies indicate that even when cut, flowering Garlic Mustard may form viable seed. In the case of small infestations plants can be hand removed but care must be taken to see that the entire root system is removed. Best results are achieved when the soil is soft. For larger infestations of Garlic Mustard, or when hand-pulling is not practical, flowering stems can be cut at ground level or within several inches of the ground, to prevent seed production. If stems are cut too high, the plant may produce additional flowers at leaf axils. Once seedpods are present before the seeds have matured the stalks can be clipped, bagged and removed from the site to help prevent spreading of seeds. This can be done through much of the summer. Repeated annual prescribed burns in fall or early spring will control this plant, while "flaming" individual plants with propane torches has also shown preliminary success. As for chemical control, herbicide containing Glyphosate should be applied during the dormant season to avoid damaging native species. If applied after germination, glyphosate will significantly reduce seedling populations. Bentazon appears suitable for use in many forest communities but should be tested further before widespread use. Suggestions on handling the seed bank problem with Garlic Mustard include immediately catching new populations which may not have a seed bank as well as removal of the green reproductive stage in autumn and winter.

In MICHIGAN this plant is considered "Invasive". "The Garlic Mustard Challenge" is an annual event run by "The Stewardship Network". People from across the Great Lakes region and beyond are encouraged to protect their local native ecosystems by pulling this invasive plant. In 2015, the goal was to collectively pull 200,000 pounds of Garlic Mustard and to have 50 Garlic Mustard free sites reported! It's a competition. Anyone can have a positive impact on their environment. Where Garlic Mustard is not well established, efforts are focused on detecting and eradicating new satellite infestations before a seed bank develops (i.e. dormant seeds in the soil). Monitoring should focus on areas where Garlic Mustard seeds are likely to be dispersed and find disturbed areas suitable for germination. Trails, parking areas, transportation corridors and recreation sites in suitable habitats are known sites of early infestation. Once Garlic Mustard has established an invasion front (several years of flowering plants), the goal is to prevent further seed set until the seed bank is exhausted; a period of up to 10 years. Depending on the site characteristics and infestation level, pulling, cutting, applying herbicide or repeated fire will be required. Biological control is being studied.

In NEW YORK, Garlic Mustard is "Prohibited and Regulated". It was first planted in Long Island, New York in 1868 as an edible garden plant. It was commonly kept as a potted herb whose prolific seeds were dispersed by wind to nearby fields and forests. Effective management requires a long-term effort. Hand removal of plants along with the roots, is effective for light, scattered infestations. Flowering plants can be cut low to the ground in spring to prevent seed production but cut plants can re-sprout. Careful hand removal and bagging of plants with mature fruits can be done as soon as fruits are present. Systemic herbicides containing glyphosate are effective but repeated treatments are usually needed because of the large seed stores in the soil. Researchers are investigating potential biological control agents but none are available at this time.

In VERMONT Garlic Mustard is a "Class B Noxious Weed". For small infestations it is suggested to hand pull plants in the spring before they flower. Pull slowly, grasping plants at the stem base and make sure to remove the "S" shaped tap root. Put all plant parts into a bag to decompose. For large infestations it is recommended to use a glyphosate herbicide, such as Round-Up® or Rodeo®. It can be sprayed on remaining green leaves in the late fall when all other plants are dormant.

In NEW HAMPSHIRE Garlic Mustard is a "Prohibited Invasive Species". It is recommended to pull it before it flowers in spring, removing crown and roots, tamp down soil afterwards. If in flower it is to be cut, when producing seeds, cut by being careful not to scatter the seeds, then bag and burn or send to the landfill. In Maine Garlic Mustard is considered "Invasive". It is controlled by hand in early season when plants are young and soil is moist. If you do not get them early you will have to burn them each year for 3 to 5 years in order to get rid of it. Remove root mass as completely as possible, as root fragments remaining in the soil may eventually re-sprout. Tamp the soil after pulling plants to limit further growth. Complete plant removal before flowering starts, or at least before plants produce seed. If some seeds develop and stay on site, they can remain viable for at least five years, so control methods should continue at least five years for the desired results. When hand-pulling is not possible, cut flower stems close to the ground, before seed formation. This method is less effective than hand-pulling, because of re-sprouting. Chemical control is used for severe infestations of Garlic Mustard; an application of one percent solution of a glyphosate-based herbicide is effective, although repeat applications will probably be necessary to deal with dormant seeds. The herbicide may be applied at any time of the year, including to rosettes in winter, as long as the temperature is above 50 degrees F and there is no rain for eight hours after application. In winter most native species are dormant and less likely to be damaged from an herbicide application. Use herbicides responsibly and follow manufacturer's directions. Contact the Maine Department of Agriculture for information on restrictions that apply to the use of herbicides. Consult a licensed herbicide applicator before applying herbicides over large areas.

States adjacent have similar concerns and recommendations which need not be repeated. The "Garlic Mustard Challenge" in Michigan is noteworthy because here an organized approach may lead to focused control were it is most required to reduce impact. The need for early detection and prevention of establishment is emphasized.

Literature Sources

Catling, P.M., G. Mitrow and A. Ward. 2015.
Major Invasive Alien Plants of Natural Habitats in Canada: Alliaria petiolata (M. Bieberstein) Cavara & Grande. Canadian Botanical Association Bulletin 48(2):51-60.
Cavers, P.B., M.I. Heagy, and R. F. Kokron. 1979.
The biology of Canadian weeds. 35. Alliaria petiolata (M. Bieb.) Cavara and Grande. Canad.J.Pl.Sci. 59: 217-229.
Department of Agriculture, Conservation and Forestry. 2013.
Maine Invasive Plant Fact Sheets.
King County Washington. 2015.
Noxious Weeds.
Kurtz, C.M.; Hansen M.H. 2014.
An assessment of Garlic Mustard in northern U.S. forests. Res. Note NRS-199. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 5 p.
Minnesota Department of Transportation and Office of Environmental Stewardship, Roadside Vegetation Management Unit. 2015.
Minnesota Noxious Weeds.
Montana State University and Montana Noxious Weed Education Campaign. 2015.
New Hampshire Department of Agriculture, Markets & Food. Cygan D. [2015]
North Dakota Department of Agriculture. 2015.
Noxious Weeds.
Nuzzo, V. 2000.
Element stewardship abstract for Alliaria petiolata (Alliaria officinalis) Garlic Mustard. The Nature Conservancy, Arlington, Virginia, USA. (
NYS Department of Environmental Conservation, NYS Department of Agriculture and Cornell University. 2014.
New York State Prohibited and Regulated Invasive Plants.
Rodgers, V.L., and K.A. Stinson. 2008.
Ready or not, Garlic Mustard is moving in: Alliaria petiolata as a member of eastern North American forests. Bioscience 58: 426-436.
United States Department of Agriculture, National Agricultural Library. 2015.
Garlic Mustard.
Wurtz, T. 2011.
Mustard, knapweed and hogweed, oh my! The current status of selected invasive plants in Alaska. US Forest Service, Forest health Protection Fairbanks, Alaska.
King County Washington. Noxious Weed King, County, Washington. 2015.


From: G. Mitrow & P.M. Catling From: G. Mitrow & P.M. Catling

Following presentations and posters explaining value of collections, and indicating the strategic actions that can increase efficiency and support, we have been asked to make some notes available. These presentations have been aimed at collection managers, clients, researchers and students. A presentation base on this kind of information can increase profile end support. The text providing a basis for our presentations follows. We begin by introducing our own collection as an example. Of course all collections have an interesting history, special values and provide services.


1. History
The Agriculture and Agri-Food Canada National Collection of Vascular Plants (DAO) was started by James Fletcher in 1886 when he donated his personal collection of 3000 dried plants to the department. This collection has grown to be the largest vascular plant herbarium in Canada with over 1,500,000 specimens. It has been maintained and funded for over a century which suggests a long period of value. One of the oldest specimens is a Gentiana collected by Mrs. Percival in 1820. It is still useful and in excellent condition today.

2. Location
It is housed in the William Saunders Building which is named after the first director of the Central Experimental Farm. It is a spectacular heritage collegiate gothic structure built in 1935 on Agriculture and Agri-Food Canada's Central Experimental Farm in the heart of Canada's capital.

3. What It Is
This herbarium is strictly a collection of vascular plants and each specimen is pressed, dried and then glued on light white cardboard sheets along with a collecting label indicating place and date of origin and other related information. Each sheet is stamped with its unique collection number and the acronym DAO = Department of Agriculture Ottawa. It is estimated that the collection includes 20% of the plant species found on earth. The origin of the specimens is 65% Canadian, 20% USA, 10% Europe, Africa, Australia, Russia and Asia, 5 % Central and South America, Mexico, West Indies, Bermuda and Bahamas. It is well represented in crops, crop relatives and pests of temperate regions reflecting the mandate of Agriculture and Agri-Food Canada (AAFC).

4. How it is organized
Our specimens are filed in the collection largely according to evolutionary sequence with the most primitive vascular plants such as (ferns & fern allies) which existed in the dinosaur age, then we proceed with grasses, sedges, orchids, willows, buttercups, so on and so forth, ending with sunflower family. For easy filing and retrieval of material, we use a color code system separating the material geographically. The specimens are filed by family, genus and species, then varieties, cultivars, etc.

5. Its Major Values
The specimens identified are essential in providing authoritative identifications and accurate information. The improvements in classification system are ongoing. New plant species are discovered every year, families and genera are sometimes split and renamed. There are 2300 species of new plants described by scientists each year worldwide and some of these originate from North America. The DAO herbarium holds over 5,500 type specimens which are extremely valuable taxonomically since these represent the specimen originally used to describe a species and they define the use of the name. Other areas in which the collection is extremely important is in the development of new crops, improvement of crops and control of pests. It is also used to house voucher specimens, as for example species of "Marquis Wheat", a cultivar produced in 1892. This plant is still available in the collection for researchers studying crop evolution, to help maintain a superior crop. We can obtain genes of old crops from voucher herbarium specimens and it is often the only source left available. Accurate naming of plants is crucial for the protection of Canadian borders and can save billions by preventing entry and establishment of foreign pests. These collections document the world's flora and provide a constant and permanent record of botanical diversity. This role is increasingly important as the rate of habitat destruction increases. Now with the improvements in technology, we are able to use the material in ways that we never dreamed possible only a decade ago, such as discovering and predicting changes in the earth's atmosphere. With respect to the future, who knows what the possibilities will be.

6. Services Provided
By consulting the plant collection and botanical library, curatorial staff and in-house botanists provide an ongoing service. Each year the collection enables between 2000-3000 identifications and responds to information requests from 600 clients. The clients are within AAFC, Canadian Food Inspection Agency, other federal departments, herbaria in Canada and worldwide, provincial ministries, universities, museums, and private and public sectors. We receive 200 herbarium research visitors and provide 40 tours, receive 50 loans and send out 30 loans, there are about 2000 specimens incoming and outgoing as exchange of research material.


1. Old Cooperation
We have been interacting with other collections for many years with regard to incoming and outgoing loans, exchange and collaborative research projects. Recently a need for increased efficiency and reliable funding has led to co-operation in new areas.

2. New Cooperation
We now extensively share information on "Strategic Actions" to address challenges that we have in common in areas of: a) Communications; b) Informatics; c) Pest Control; d) Humidity control; e) Human Resources Planning and f) Other strategies.

a) Communication
Many collections throughout the world have experienced reduced financial support due to economy and trend. Curatorial staff now needs to spend substantial time to explain value of collections. They play a vital role in society by supporting one or more and of many functions such as: Plant systematic research; other research, identification of pests and pathogens; teaching; management of environmental problems; public health and safety; support for rules and legislation; monitoring environmental changes, and national security.

The ways of communicating about these values in order to obtain support include: Regular meetings with management; websites; publications (newsletters); presentations/posters; by telephone, emails and tours; open houses; and by providing courses or workshops.

One of the most important examples of communication occurs when we attempt to influence upper management decisions with regard to collection support. We have found that an annual report has proven to be very useful and is an important tool to obtain confidence of upper management. It is a way of making information readily available whenever needed to promote the collection. Benefits, uses and achievements are highlighted.

b) Informatics
Digitization of collections is expanding rapidly and there are many advantages in doing this such as: (1) Data is backed up and archived; (2) loans, exchange of research material may be more easily tracked; (3) maps can easily be produced and analysed (biogeography); (4) label production is simplified; (5) time is saved in data entries since there is less repetition and fewer errors (with pop-up menus); (6) sometimes data and image are sufficient instead of sending out the physical specimen resulting in less risk of damage to specimens in shipment; (7) accelerates client service responses (self-serve web-portal) and (8) on-line information reaches a larger audience. Increased efficiency may lead to more success in obtaining support. There are opportunities in bioinformatics to explore. Digitization can be accomplished with a diverse combination of human support; within house, other herbarium, research staff, post-docs, students, volunteers, and through collaboration projects. We have also been able to connect to special national and international projects using digitization such as the Global Plant Initiative, Natureserve and Canadensys.

c) Pest Management
Another important area of strategic actions is in the protection of the collection. Entomologists were studying a major pest insect of dried plant collections because of damaged to stored food and tobacco. They discovered how to control it. It could be done by lowering the temperature, and from their discovery we implemented the climate control system in our collection storage areas in 1992. Since that time, by keeping the rooms at 17-18 degree Celsius, the infestation problem of the Tobacco Beetle (Lasioderma serricorne) was eliminated. This technology has been passed on to herbaria worldwide with great success. We also freeze all incoming material to eliminate pests and regularly spot check in various areas of the collection for pest occurrences using traps.

d) Humidity & Water Protection
More recently we have acted strategically in regard to water and humidity control by having a new High Voltage Air Conditioner (HVAC) climate control system installed. This new one eliminated the overhead water pipes used with the older cooling system. Breakage or leakage of these water pipes can do irreparable damage to specimens. As for the humidity, below 30% relative humidity (RH) is too dry and leads to brittleness of specimens making them more vulnerable to breakage. Over 70% RH encourages mold growth, damaging specimens, compromising chemical and DNA analysis, and also develops a health issue for staff due to mould. The fluctuation of RH causes mechanical stress. It occurs when water absorption causes expansion and contraction, changing size and shape, this leads to cracking, splitting and warping. The recommended RH for plant collections is 40% ± 5. A Friedrich Model D70BP dehumidifier was installed in collection rooms. It can effectively control humidity in an 800 square foot room, having the capacity to remove 70 pints/day. We regularly check the humidity and temperature variation using automatic monitors. To develop these solutions, we had extensive discussions with other curatorial staff and passed on the results.

e) Human Resources
There are a number of strategic actions surrounding human resources and one that is very important for us is the volunteer program. From 1940 to 1970, the collection grew rapidly and this resulted in a significant backlog which included 40,000 specimens. We benefited greatly from volunteer help in reduction of this backlog. The work was started in 2013 and is almost completed. The first step was to do an inventory of work needed to be done including an evaluation of the condition and value of the material. We then prepared a brief report estimating number of hours to clear the backlog and value of specimens to be processed. All staff members participated in this project, ranging from (hand written) label interpretation, plant identification, label preparation, mounting and databasing. The collection books of previous staff were extremely useful during processing this material. Backlog specimens should be properly stored and protected since we never know what we can find until it is processed. Older specimens in backlog cannot be obtained elsewhere and are essential for certain kind of scientific research. Among material revealed in our backlog were: (1) Historical specimens collected in 1886 by Agnes Saunders, wife of first director of Agriculture and Agri-Food Canada; (2) collections of James Fletcher who started the DAO herbarium in 1886; and specimens collected by early botanist Catherine Parr Trail in 1894 and (3) Unpublished type specimens. The advantages were that specimen became accessible for study and provided space by reducing storage. The way we approached the DAO backlog clearing project, was with the help of volunteers and afterwards we were able to get financial support to hire help and continue working on this project. There is much more to say about volunteer programs, but two most important things are to ensure it is for these workers, a rewarding experience with recognition of their contribution. This can lead to decades of support by the same volunteers.

f) Other strategic actions
The day to day operation of a plant collection requires a large amount of supplies and equipment. We regularly purchase glue, mounting paper, herbarium packets, shipping packaging material, etc. The basic equipment required are microscopes, cabinets for storage, freezers, plant presses and dryers. Cooperative sharing of information on the best suppliers or purchase of larger quantities of material with other collections has often resulted in better quality supplies at reduced cost.

Strategic actions are also necessary in the area of storage space and best practices. The automatic compactor system has rubber gasket seals but these no longer fit tightly and this presents a risk of water with the fire repression sprinklers, light exposure, dust and pests infestations. The available space to insert new material in the collection is limited and considering anticipated rate of growth, we are facing a serious problem to store the irreplaceable heritage material. Some specimens are filed in cabinets outside of the main collection and not subject to protective climate control. Since other collections have faced this same problem, we consulted the herbarium management staff to receive their suggestions. We then requested support from management for a feasibility study that considered solutions. It was approved and the study was completed in 2012, we are now working on one of the options.

Another problem was with our electric compactor system in the most used section of the collection (wheat, barley, etc. families). We are gradually converting it to a mechanical system following consultation with other herbaria. All of these upgrades can be transferred to a new facility. This work was initiated in 2015, funding was requested along with justification, presented to management highlighting the saving in repairs and to have access of material for research. Then new cabinets were purchased and old cabinets onsite were used as swing space. This involved team effort between curatorial staff, term employees, students and volunteers. The transition ran smoothly and all material was kept in order and remained accessible to research scientists during the renovation.


Collections play an increasingly important role in society. In order to ensure that they can evolve to meet current and future needs, curatorial staff actions must be co-operative and strategic. Their success is dependent upon their role as part of a national and international network. It is a mistake to view a collection in isolation.


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Catling, P.M., Mitrow, G., and Cayouette, J. 2009.
"The Agriculture and Agri-Food Canada National Collection of Vascular Plants.
Mitrow G. & P. Catling. 2014.
Valuing and processing herbarium Backlog. (June)
Mitrow, G. and Catling, P.M. 2012.
Value of herbarium to farmers featured in "The Ontario Farmer Magazine" - January 2012 Issue.
Mitrow, G. and Catling, P.M. 2011.
"Evaluation of a collections network as a source of information on economically important plants." Collection Forum, 26(1-2), pp. 70-87.
Mitrow G., P. M. Catling, B. Kostiuk and B. Brooke. 2014.
Kamloops Herbarium (ACK0 Transferred to AAFC National Collection of Vascular Plants (DAO).
Mitrow G., P. M. Catling and A. Ward. 2014.
Preventing Humidity and direct Water Damage in a Dried Plant Collection (DAO) (June)
Thiers, B. [continuously updated].
Index Herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden's Virtual Herbarium.

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