I overwinter tulips in containers over the winter(I have 3 six foot long planters on my porch with plastic liners that lift out), then after they bloom in the spring, lift out the bulbs and plant annuals. Last year I had all sorts of problems with spider mites. This year, something weird is going on again with the plants, and after googling 'reusing soil' found that this might be the problem. Does anyone else do this (maybe for window boxes?) Getting new soil would really be expensive just to have tulips for a week....I'm thinking about ditching the tulips next year, although they are so darn pretty :(