Verbena are good annuals for sunny dry sites. They are available as upright compact plants and as low growing groundcovers. Continuous bloom with clusters of star-shaped flowers at the ends of branches.
Can be cut back to shape or to keep in bounds if necessary.Cold tolerant annual. Attracts butterflies. Also consider Verbena bonariensis (Brazilian Verbena) as an excellent tall (3') annual for interesting blooms and ability to attract butterflies. Easy from seed and will self sow readily.