NURSERY AND GREENHOUSE STOCK FROM OUTSIDE ALASKA: SOURCES OF INVASIVE PLANTS?

Authors: CONN, JEFFERY; STOCKDALE, CASIE

Submitted to: Committee For Noxious Invasive Plant Management Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2005
Publication Date: 10/25/2005
Citation: Conn, J.S., Stockdale, C.A. 2005. Nursery and greenhouse stock from outside Alaska: sources of invasive plants?. Committee For Noxious Invasive Plant Management Annual Meeting.

Interpretive Summary:

Technical Abstract: Prevention of new invasive plant species is a cost-effective and practical approach for Alaska. A relative lack of invasive species combined with few roads and ports make prevention feasible. It is important to know the relative size of the various pathways used by plant species to gain entry into the state. This knowledge helps to more efficiently target early detection efforts and aids agencies and legislators in prioritizing which pathways to target first as part of a prevention effort. Several invasive plant infestations in the Anchorage area have been blamed on seed hitch- hiking into Alaska in contaminated soil from ornamental plant containers. Because ornamentals are watered and fertilized, exotic plant species growing in this soil are likely to become established. We began a study in 2005 to determine the species and number of seeds of exotic plant species being brought into Alaska each year in soil from ornamental plant containers. A second objective was to determine if soil type, supplier or pot size is an important predictor of the exotic seed density in the containers. A survey was made of most major nurseries and box stores in Anchorage, Fairbanks and Juneau to determine who the suppliers of ornamentals were and what sizes of pots were being sold. We also surveyed pots to determine if weeds were growing from them. Fourteen species of exotic plants were found in this survey. Plants were bought from each supplier in the following categories: 10 vegetable starts, 5 herbaceous perennials, 5 small woody (pots 1-3 gal), 3 large woody (>5gal), and 3 balled and burlapped. Soil was removed from the pots and 2000 ml of soil was incubated in a 2cm – thick layer in flats in a heated greenhouse. Seedlings were counted and identified. A total of 57 broadleaf and 7 grass species were found. More seedlings were found in mineral soil and the fewest in potting soil. Balled and burlapped plants had the greatest number of seedlings and vegetable starts the fewest seeds per liter of soil. There were large differences between suppliers in the number of seedlings/L soil, suggesting that some suppliers are supplying a cleaner product than are others.