Make the Most of Self-Seeding Plants
Expand your garden without expanding your planting budget. Allow self-seeding annuals and perennials to fill the voids in existing or new planting beds.
The seedheads of both coneflowers (Echinacea) and Rudbeckia provide food for the birds and add winter interest to the landscape. Equally assertive plants require the same growing conditions and can be left to duke it out on their own. Just keep the more timid plants away.
The bright white flowers of feverfew (Tenacetum parthenium) scattered throughout the garden can provide unity as they quickly multiply.
Plant seeds of hollyhocks (Alcea) and other biennials two years in a row to insure yearly bloom. And if you prefer a more neat-and-tidy garden, deadhead or better yet, call in your friends looking for a few free plants.
A bit more information: Tired of weeding out unwanted seedlings? Mulching with organic matter such as shredded leaves, evergreen needles and other organic matter will help suppress sprouting of offspring and weeds. Or use sterile varieties that don't produce viable seeds.