Walt's is absolutely amazing. When Seattle Organic Garden wanted to go "organic" I started to hang out here and get good seed and advice and now we are 100%. well...95% organic.
Great place, great team that will tell you what to plant and when to plant them. I am growing lettuce right now in March!
Walt's is the absolute best place to buy soil for your garden. There is no comparison between the high level of quality of the products they carry and the normal stuff you find at nurseries. Everything I planted in the soil from Walt's has done spectacularly, and they will formulate custom blends based on your planting and nutrient needs.
They also always have a smaller, but well-picked selection of plants that work well in Seattle. You can also find seeds, supplies, tools, and nutrients here.
The people who work here are incredibly nice and there's always great conversation whenever we stop by.
Also, bring your dog! They love seeing dogs there and all the organic smells will keep your pupper super interested/happy.