Buddleias prefer to be planted in a full sun with fertile, moist, well-drained soil. Try adding lime to the soil for increased growth and better floral quality. They are also moderately drought tolerant once established. Since they frequently die all the way back to the ground in northern winters, it is best to cut back all of the old wood to about 12" in the spring. Doing so will result in more compact plants. They will quickly grow back to their normal height by fall and will flower just as prolifically in late summer since they bloom on new wood. You may notice that the flowers tend to be longer and deeper colored in cooler weather. Buddleias tend to break dormancy late in the spring, so don't worry if you don't see anything happening with them when your other shrubs start to leaf-out. These are very durable and reliable plants.