Walks:
http://www.gardenguides.com/resources/walks/
In "find a garden"; Search on "Oregon" for list of garden walks in the Oregon area for 30+ walks.

Rhidodendron Gardens:
http://www.gardenguides.com/resources/walks/garden.asp?i=15234

Iris gardens:
http://www.schreinersgarden.com/

Japanese Garden:
http://www.japanesegarden.com

Portland rose gardens:
http://www.rosegardenstore.org

Peony garden:
http://www.peonyparadise.com

Oregon gardens in Silverton:
http://www.oregongarden.org

Tulip garden:
http://www.woodenshoe.com

Lilac gardens:
http://www.lilacgardens.com

Tom Mcall preserve:
http://www.oregonhiking.com/photos/200.html

Hiking in Oregon:
http://www.orgonhiking.com
http://www.trails.com/stateactivity.asp?area=10005