Rely on hardscaping. Boulders, laid out in natural-looking formations and dug one-third of the way into the soil, are good year-round anchors that complement their flower companions. In addition, a picket or rustic fence makes a fitting backdrop to a cottage garden, adding order to the visual chaos of mixed plantings.
Add a fun accessory. It provides a convenient focal point, and, if you use it as a planter, a stage for plants so they're not lost among their peers. Old wagons, fertilizer spreaders, bins, and baskets make good additions. Use them in moderation to avoid a junkyard effect.
Use long-lasting annuals. Melampodium blooms all summer without any coddling. Love-in-a-mist (Nigella) can't match melampodium's length of bloom, but it offers ornamental seedpods that last into winter. Love-in-a-mist also reseeds itself without becoming a pest, making your job easier.
Make a path through the garden. Paths offer visual relief from crowded plantings. More important, they make the garden more welcoming and easier to maintain. Consider who will be walking through the garden and in what kind of shoes. This will help you decide whether to go with a soft surface such as gravel or wood chips, or a firm surface such as concrete. A grass path is an easy alternative where foot traffic is low, but it will require regular mowing.