Take cuttings and gather seeds from the plants that are already in your yard. Friends, family and neighbors might contribute as well. Perennials, like daylilies, digitalis and irises, benefit from being dug up, divided with a spade or knife and then replanted in a new location.
Buy seeds instead of six packs of plants or 4 inch pots. For the price of one 4 inch plant you can get enough seeds to grow an entire border. Both annuals and perennials are available as seeds. Start the seeds indoors six to eight weeks before the last frost in spring and you'll have a head start on your flower borders. Hollyhocks make a tall border. Cosmos at 4 feet high are a few feet shorter.
Buy smaller containers of plants rather than the larger containers. Annuals, like lobelia, moss roses and sweet alyssum, are readily available as six packs. They make low tidy borders. Space the plants a little closer together than recommended to get the border to fill in quickly. Compensate the closer spacing with additional fertilizing. Four inch pots of plants have a broader offering than six packs. Many perennials like chrysanthemums are available in pots. One gallon size pots offer a good sized plant for a modest amount of money. Five gallon sizes are about three times the cost as the 1-gallon size. After a year both the 5-gallon plant and the 1-gallon will be roughly the same size.
Roses make a splendid border when they're in full bloom; while you can grow new roses from cuttings they will take a few years to get to bloom. Additionally patented roses shouldn't be replicated at home since that violates the patent. Roses are available in the spring in bare root form and in the summer as container plantings. Other plants that make colorful borders are gardenias, camellias and azaleas.