Plant for color. A cottage garden is, above all, vibrant. You can use an exuberant mix of colors, go for something bold or stick to softer shades. A color wheel can be a great guide for choosing colors, whether you want them to contrast or complement each other.
Design tip: If you're new to designing with color, choose a theme color or colors, such as pinks, blues or purples, much like you would for colors inside a house. The different shapes of the individual plants you choose will give you variety; the repetition of color will have a calming and harmonious effect. As you get bolder, add a pop of contrasting color — yellow nasturtiums mixed in with blue pansies and delphiniums, bright red lupine nestled among white Shasta daisies and pink echinacea or a bright orange black-eyed Susan scattered about in a sea of lavender.