There is also an annual version of baby's breath - not quite as ethereal as the perennial type, but it flowers quickly from the initial sowing, which makes it extremely handy. Most of us think of Queen Anne's Lace as a weed, but it, too, functions beautifully as filler, from its fern-like foliage to its lacy flowers. So if it insists on growing in your gardens, maybe you should let it. Within reason, of course. Nigella grows quickly from seed and can be kept going throughout most of the growing season, so it is a great way to fill unwanted gaps while you wait for slower perennials to catch up.
Most annuals make great fillers, since they grow so quickly and have such long flowering periods.
The All-Important Foliage Fillers Foliage filler is more functional than flower filler. It not only adds texture to the garden, but also helps to determine its shape. It works in the garden exactly the way it works in a flower arrangement. Flowers don't last the way leaves do. So the foliage will be in the garden all season long.