Backyard Invasions: Noxious Weeds in Seattle's Greenspaces

1. Backyard Invasions: Noxious Weeds in Seattle's Greenspaces Sasha Shaw King County Noxious Weed Program 206-296-0290 sasha.shaw@metrokc.gov

2. Agenda • Definitions • Impacts of Invasives in Urban Areas • Invasive Vines, Trees, Shrubs and Other Plants • What Can We Do? • Resources

3. What is a Weed? • a plant out of place • takes water, nutrients or habitat from desired plants (subjective) • threatens an area’s values or benefits

4. Are All Weeds Bad All the Time? • Lots of weedy plants are used by birds, insects and people • One person’s weed can be another person’s pride and joy • Native plants used to be called weeds • and still are for some! American goldfinch lunches on bull thistle seeds

5. What are Native Plants? • Adapted to local climate and soils; foundation for local ecosystem • Co-evolved with native animals • Provide food, shelter, nesting materials for wildlife Gumweed (Grindelia integrifolia) on Puget Sound beach, native to Pacific coast from BC to California

6. What is an Invasive Weed? • Non-native, aggressively spreading • Destructive • Competitive • Difficult to control Invasive knotweed spreading into an open forest

7. Good Plant Bad Weed • Some invasive weeds resemble native plants • Invasive weeds exploit conditions similar to their home range and don’t have natural enemies keeping them in check Bleeding Heart (Dicentra formosa) Herb Robert (Geranium robertianum)

8. What is a Noxious Weed? • Non-native plant that impacts agriculture, wildlife, human health, land values or natural resources • Defined and regulated by state law (RCW 17.10) • control required only where weed is not widespread • goal of law is to prevent spread of new invaders to un-infested areas

9. What are the Weed Classes? • Class A Weeds – new invaders, control required statewide, still a chance to eradicate • Class B and C Designates – control required in King County, still have a chance to stop them from getting established • Non-Designates and Weeds of Concern – widespread invasive weeds in King County, control not required but definitely a good idea whenever possible!

10. How do weeds get here?

11. Noxious Weeds Run Amok: Orange Hawkweed: from garden store to mountain meadow

12. Impacts of Invasive Weeds

13. Environmental Impacts Invasives like English Ivy transform forests and natural areas, hurting trees, native plants and native wildlife species

14. Diverse wetland habitat in the Nisqually delta provides food and shelter for many different kinds of birds and animals. Purple and garden loosestrife in Portage Bay choke out native plants and destroy wildlife habitat.

15. Impacts to Waterways Restoration crew removes reed canary grass that had filled in a stream channel, increasing flooding and reducing fish habitat

16. Impacts to Recreation Fragrant water lily and Eurasian watermilfoil in Lake Sammamish

17. Impacts to Public Health Giant Hogweed - Sap sensitizes skin to UV radiation, resulting in severe burns, blisters, painful dermatitis and scarring.

18. Dan DeLong/Seattle Post-Intelligencer Impacts of Invasives in Seattle

19. Seattle Urban Nature Project • City-wide Surveys 1999-2000 and 2005 • 8,000 acres of public lands in Seattle • Classified habitat types throughout the city • Recorded species names and percent cover • Study of all forest types in Seattle • Mapped density of invasives Ella Elman & Nelson Salisbury, Ecologists (206) 522-0334 www.seattleurbannature.org

22. 11% 20% 9% 25% 18% 17% In 47% of Seattle’s forests, the majority of the plant cover consists of invasive species Invasive Plant Species Citywide

23. Most Prevalent Invasive Species

24. Invasive Trees:An Overlooked Threat • Seattle has 2500 acres of forested parkland • 60-70% of tree regeneration in Seattle’s forests is non-native • Shade tolerant species are the biggest threat: English holly and cherry laurel are the worst • European species of mountain-ash, hawthorne, and cherry are found throughout Seattle’s forests • If nothing is done, 30 to 40 years from now our forests will look dramatically different than they do today

25. Tree Regeneration Conifer/madrone Forests Conifer/deciduous Forests

26. Distribution of English holly and cherry laurel Red and orange high density Yellow moderate Green low Case Study: Deadhorse Canyon Inventory

27. Invasive Trees: Evergreen English holly Portugal laurel Cherry laurel

28. English Holly(Ilex aquifolium) • Tree 15 to 50 feet tall and 15 feet wide • Bark smooth and gray • Leaves glossy, persistent, dark green, wavy and spiny • Flowers are small and white • Berries are bright red or orange and found in small bundles like the flowers

29. English Holly(Ilex aquifolium) • can form thickets of large, densely packed trees in shady forests or open areas • spreads by seeds eaten by birds; can establish in remote areas • re-sprouts indefinitely from cut stumps so digging is best non-chemical method

30. www.PlantSystematics.org http://bellquel.bo.cnr.it/scuole/serpieri/erbario Holly Look Alike:Tall Oregon Grape

31. English Laurel or Cherry Laurel (Prunus laurocerasus) • Evergreen tree or shrub to 20 feet high • Leaves leathery, glossy, 3 to 7 inches, slightly toothed • Flowers white, fragrant, in elongated clusters • Native to Eastern Europe, Asia Minor • Common landscaping hedge

32. English Laurel (Prunus laurocerasus) • Fast-growing • 25 inches or more per year • Fruit fleshy, black with a large pit (stone) • Widely escaped in local natural areas and woodlands • Highly toxic if ingested • poisonous parts: wilted leaves, twigs (stems), seeds

33. Invasive Trees: Deciduous European Mountain-ash English Hawthorne Sweet Cherry Norway Maple

34. English Hawthorne (Crataegus monogyna)

35. European Mountain-ash (Sorbus aucuparia)

36. A small to medium sized tree, generally to 50 feet, with a broadly rounded crown Leaf 2 to 5 inches long with serrated margin Flowers showy, white, one inch across Cherries sweet, dark red to nearly black, 1/2 to 1 inch across European Sweet Cherry (Prunusavium)

37. www.hort.cornell.edu Norway Maple (Acer platanoides) • Common shade tree • Escaping into Seattle forests • Similar to native bigleaf maple, but the leaf is not as large or deeply cut • Seeds spread their wings wider and have no bristly hairs

38. Invasive vines • Form dense groundcovers excluding all native plants • Climb up and smother trees • Add weight to tree canopies English ivy Old man’s beard

39. Class C Noxious Weed – Control Not Required English or Atlantic Ivy(Hedera hibernica, H. helix) Ivy leaves are evergreen, lobed, dull green, with light veins

40. Class C Noxious Weed – Control Not Required English or Atlantic Ivy(Hedera hibernica, H. helix) • mature ivy leaves are shiny green and not lobed • umbrella-like clusters of greenish-white flowers in the fall • black, berry-like fruit in winter, seeds mature in spring

41. Class C Noxious Weed – Control Not Required English Ivy Ivy mats smother understory plants and tree seedlings - changing the natural succession patterns of forests. Ivy climbs trees, weighs down branches, shades leaves, damages bark

42. Class C Noxious Weed – Control Not Required Old Man’s Beard(Clematis vitalba)

43. Class C Noxious Weed – Control Not Required Old Man’s Beard or Wild Clematis Old Man’s Beard on trees in Ravenna Park Old Man’s Beard covering trees at Magnuson Park

44. Invasive Shrubs Scotch broom Himalayan blackberry • Form dense thickets excluding all native plants • Establish in disturbed sites • Spread by birds, wind and people

45. Himalayan Blackberry(Rubus armeniacus or Rubus discolor)

46. http://www.nic.funet.fi Evergreen Blackberry(Rubus laciniatus) http://www.biopix.dk

47. Himalayan Blackberry(Rubus discolor)

48. Good Guy Look Alike:Native Trailing Blackberry(Rubus ursinus)

49. Class C Noxious Weed – Control Not Required Scotch Broom (Cytisus scoparius)

50. Scotch broom removal with weed wrenches Class C Noxious Weed – Control Not Required Controlling Scotch broom with weed wrenches at Marymoor Park