Know your invasive species so you don’t plant a problem

By Gooseberry Peter

Spring is upon us, and people are looking forward with eager anticipation to summer gardening and landscaping projects.

When planning your summer plantings there are many factors to take into consideration like color, vigor and resistance to pests. Not the least among these considerations is whether the plants themselves may be pests. Gardening and landscaping can sometimes accidentally spread weedy and invasive plants, but there are steps you can take to ensure that you don’t plant a problem.

Avoid known “problem plants” when purchasing seed or nursery stock. European bird cherry and chokecherry trees (Prunus padus and P. virginiana) are great examples. Both are popular ornamental trees in Alaska, are known to be extremely invasive, and yet are still available to purchase and plant. While local retailers are becoming increasingly savvy about not selling known invasive plant species, you can still buy just about anything online. Use native plant species if possible.

Read species composition lists on flower seed mix packages to see if they include any weedy or invasive ingredients. The degree to which a plant may be weedy or invasive may vary depending on location. Foxglove (Digitalis purpurea), for example, is highly invasive in Southeast Alaska but isn’t in colder parts of the state. Does the package have all the species listed? Online product descriptions often don’t list all the species used in a seed mix.

Buy locally produced seed whenever it is available to help prevent introducing new weedy or invasive species to Alaska. All seed sold is inspected for the presence of weedy contaminants that are legally prohibited. However, laws can lag behind our knowledge of what we should not plant and even inspected products can sometimes contain plant problems. Using locally sourced seed increases the likelihood that any contaminants are at least local weed species and not new weeds imported from Outside.

Look out for hitchhikers in nursery stock. Undesirable plants may be growing in the pots and root wads. Nothing kills the enjoyment of a newly planted fruit tree more than seeing the newly sprouted thistles that came with it in the potting soil. Long-lived perennials are most likely to have these hitchhikers, but pay attention to any potted plants you might buy.

Avoid using uncomposted manures as these may carry viable weed seeds. If available, use local, certified weed-free straw and gravel for mulch, erosion control and landscaping. Clean all gardening and landscaping equipment (especially if you are renting or borrowing) prior to use so you don’t move unwanted seeds or other material from infested areas to clean areas. Monitor all plantings closely to identify and control any undesirable species that may emerge.

Want to learn more? Cooperative Extension Service offers a great publication called “Don’t Plant A Problem” that is available online or at your local Extension office. Contact your local Extension agent with any questions regarding plant identification, managing weeds, gardening or landscaping or call 877-520-5211 (toll free in Alaska). You may also visit us at www.uaf.edu/ces, where you can search through our publications library and submit questions through the Ask an Expert portal.

To conclude my first column, I’d also like to share a little about me and what I do. My name is Gooseberry Peter and I work for the University of Alaska Fairbanks Cooperative Extension agriculture and integrated pest management team. My professional background is mainly in field biology and natural resources management. I have an undergraduate degree in conservation sciences, certificates in ecological restoration, ethnobotany and permaculture, and minors in agriculture and horticulture. On a given workday I may find myself delivering produce safety training to growers, placing monitoring traps for insect forest pests, surveying for invasive plants, or consulting with community members and partner agencies. I love researching and sharing information about a wide variety of topics from identifying plants to harvesting wild edibles, managing pests, certifying weed-free products and more.

Gooseberry Peter is the agriculture/integrated pest management program assistant for Cooperative Extension Service, a part of the University of Alaska Fairbanks, working in cooperation with the U.S. Department of Agriculture. For questions, he can be reached at gpeter3@alaska.edu or 907-474-6829.