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January 16, 2025
Tree of heaven photos (left to right): bark of a mature tree, leaf scar and bud, leaf arrangement, and young tree.
Tree of heaven (Ailanthus altissima), an aggressive invasive tree that loses its leaves each fall and can damage roads and structures, was confirmed for the first time in Dakota County in September 2025. Tree of heaven is listed as a Prohibited Eradicate noxious weed, which means regulations require all above and belowground parts of the plant to be destroyed. It is also a host for spotted lanternfly (Lycorma delicatula), an invasive insect pest that causes damage to a wide range of plants, including fruit and vegetable crops.
Tree of heaven presents unique management challenges. Practices such as mowing or cutting without applying herbicide will stimulate aggressive lateral root and shoot growth. Hand pulling requires diligence, as even small root fragments can generate new shoots. A combination of basal bark and foliar herbicide treatments has been shown to be the most effective management strategy, and continued monitoring is necessary to treat regrowth.
Because of these management challenges and potential threat of harboring spotted lantern fly, this new infestation brought together a team from several organizations to assess the area and develop a comprehensive management plan. Staff from the Minnesota Department of Agriculture (MDA), Minnesota Department of Transportation (DOT), Dakota County Soil and Water Conservation District (SWCD), and the United States Forest Service (USFS) met with impacted landowners, mapped the infestation, collected core samples to determine the age of the trees, and developed a survey plan for the surrounding area to inspect for additional plants and signs of spotted lanternfly.
The infestation site is approximately one acre and includes a DOT right-of-way and two private land parcels. There are approximately 10-15 large trees, 15 feet or taller, on the private land parcels. The DOT right-of-way contains a mass of shorter trees that were likely mowed in the past.
The DOT began planning a foliar treatment for their right-of-way and the MDA awarded the SWCD a small grant to cover the initial treatments on the private parcels. Core samples collected by USFS revealed that the larger trees are at least seven years old. The source of the original plants is unknown.
While cold temperatures and snow halted further management work in 2025, these organizations are prepared to resume treatment in spring of 2026. Coordinating treatment timing between the DOT and the SWCD will be crucial to prevent aggressive regrowth. Education and outreach will focus on plant identification, and additional mapping and surveying will help define the extent of the infestation.
For more information on tree of heaven, please visit the species webpage.
Smarty Plants Episode Spotlight: Making Plans for a Healthy Garden
Smarty Plants is a podcast exploring invasive insects and noxious weeds that threaten Minnesota’s natural and agricultural resources.
An essential part of garden planning is ensuring that the seeds or plants you choose are free from disease and noxious weeds. In this episode of Smarty Plants, learn how a little proactive planning can help you start the spring season with healthy plants and seeds.
Subscribe to Smarty Plants today so you don’t miss an episode!
In the Field: Seed Potato Certification
Potato fields in O'ahu, Hawai'i
Every winter seed potatoes make a long journey from East Grand Forks, Minnesota all the way to O’ahu, Hawai’i. It is there that Minnesota Department of Agriculture (MDA) seed potato inspectors evaluate the potatoes for the presence of diseases or pathogens. This is a critical step in the certification process and allows the MDA to preview what may be planted across the state in the coming months.
While Minnesota is blanketed in snow and ice, Hawai’i offers a warm climate where the potatoes can grow quickly and without exposure to pests or pathogens that could cause false positives. For many years, the MDA and other state certification groups have partnered with a farm in Hawai’i to cultivate these potatoes. This unified approach to certification provides a common inspection process and creates an excellent venue for collaboration.
Through seed potato certification, the MDA ensures that the seed tubers used to produce the potatoes consumed across the country are free from disease and other pathogens. These diseases and pathogens can significantly impact crops including effects on yield and quality. While seed potatoes are inspected and certified each summer, they must first be deemed eligible to enter the certification process, which takes place in Hawai’i.
This year the MDA will evaluate nearly 100,000 potato plants for 16 growers. Any plants inspected in Hawai’i that are suspected of being infected will be confirmed through laboratory testing. Results are typically shared with growers the first week of February, allowing those producers to market their seed across North America.
Learn more about seed potato certification.
Help Protect Minnesota Forests from Invasive Pests
Look for the MDA certified logo.
Moving untreated firewood can spread harmful pests like emerald ash borer, spongy moth, and Asian longhorned beetle; species that have destroyed millions of trees across the United States. Even native pests like carpenter ants and bark beetles can hitch a ride on firewood and cause problems for homeowners.
Help stop the spread:
- Buy firewood where you burn it! Locally sourced wood is less likely to carry invasive pests.
- Use MDA certified firewood with the official seal. View the list of Certified Firewood Producers in Minnesota.
- Avoid transporting hardwood firewood across county or state lines. It is illegal to move hardwood firewood out of Minnesota quarantined counties unless it is MDA certified. Violations can result in fines of up to $7,500 per day.
Visit the MDA's Buying Firewood webpage for more information.
January Weed of the Month: Rowan Mountain Ash
Planted and pruned trees can have a rounded canopy.
A 3-year phase out of rowan mountain ash started Jan. 1
By Monika Chandler, Minnesota Department of Agriculture - Rowan mountain ash, Sorbus aucuparia, is an attractive tree with a rounded canopy, white flowers, and bright orange to red fruit. This species is specially regulated on the Minnesota Noxious Weed List. On January 1, 2026, a 3-year phaseout of the tree began giving nurseries across the state time to adjust their stock. This tree will not be allowed for sale in Minnesota starting January 1, 2029, to prevent the planting of more rowan mountain ash trees. There is no requirement to control existing rowan mountain ash trees now or past the 2029 phaseout.
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