One of the things that struck me about Seattle on my very first visit were the amazing flower displays at Pikes Place Market.
There were outside vendors with huge bunches of flowers, not only locally grown roses, cut flowers and orchids, but more exotic imports as well. The second thing that struck me is that, outside of the Netherlands, I've never seen anything like the incredible variety of cut tulips (especially from Jonkheer Greenhouses, located in Mt. Vernon). Huge mounds of cut tulips were standing on tables in March, and not just gorgeous solid color red and yellow and orange tulips, but scarlet, and black and purple, and brilliant multi-color frilled Parrot tulips. I discovered, from the vendor, that Washington is known for its acres of tulip fields, especially up around La Conner, and that the vendors contract with specific growers as much as two years in advance. And if that's not enough blooms for you, you should check out the Lake Union Wholesale Florist.
You'll notice that there are flower boxes along the roofs at Pikes, and at other buildings all over Seattle; those are filled with seasonal flowers.
It might be pansies in January or February, and along about March you'll some tulips and a lot of daffodils, and then in fall, if you're lucky, you'll see vibrant richly colored Dahlias, the official flower of Seattle since 1913, and planted widely in Seattle's parks and gardens, and in many home owners' yards. The Puget Sound Dahlia Association maintains a Dahlia Garden in Seattle's Volunteer Park in the Capitol Hill district. There's also a Conservatory, with five separate greenhouses, with Bromeliad House, Palm House, Fern House, a Seasonal Display House, and a Cactus House. You can read about hours, and tours here. I note that's not far from Seattle's Asian Museum.
You do not want to miss the Washington Park Arboretum, on Washington Lake Boulevard East, just east of downtown Seattle, and south of the University of Washington's main campus.
The Arboretum is on the shores of Lake Washington; for much of the Arboretum, you would never know you're in the middle of an urban center. Washington Park is a City of Seattle park; the Washington Park Arboretum is a joint project of the University of Washington, the Seattle Department of Parks and Recreation, and the nonprofit Arboretum Foundation. The Washington Park Arboretum is the official arboretum for the state of Washington; it has notable collections of Maples, and other large trees (particularly conifers and oaks), large collections of various Holly species, and a well-respected collection of Camellias. There are self-guided tours, and a collection of .pdf guidess regarding seasonal plant and bird highlights.
The Arboretum also contains Seattle's Japanese Garden;
3.5 acres of artistic garden and landscaping in the southwest corner of the Washington Park Arboretum. There are paths, benches, and an an authentic Japanest Tea House. The garden closes for several months in winter, but it is usually open from 10 a.m. to dusk. There are free tours, covered in the price of admission. Admission is free for children under five, $3.00 for students and senior citizens, and $5.00 for adults. You can find the hours and other information here.
Seattle's Kubota Garden is Japanese-inspired naturally landscaped gardens designed by a master gardener. They are in south Seattle, on 9817 55th Avenue S. and are owned by the City of Seattle and maintained by the Department of Parks & Recreation. They are open, free of charge to the public, during daylight hours. The official Web site is here. The Kubota Garden is particularly worth visiting because it's 20 acres of carefully landscaped streams, ponds, waterfalls, bridges, rocks and plants use Japanese traditions and native Washington plants.

