To find discount landscaping plants, watch for nursery sales, ask for discounts on plants with broken branches, and wait until the end of the season. Some plants, such as lilies, ferns, hostas and columbines, are available in bareroot form in bulk packages at much cheaper rates than potted plants.
Waiting until the end of the season is a simple way to buy landscape plants at a discount. As summer winds down, nurseries and home improvement stores want to clear out their stocks of plants. They often discount the plants significantly over the regular prices. The plants are older since they've been sitting around all summer, but if they still look healthy, they are a cheap way to fill out your landscaping.
A similar discount usually applies to plants with broken branches even during the season. If the plant looks sickly overall, pass on it. If it otherwise looks healthy, a broken branch shouldn't affect the plant.
If you don't want to wait until the end of the season, scour the ads of local nurseries and home improvement stores to find plant sales. Many offer sales on some or all of their plants, even early in the season, to boost sales. Make a list of the plants you want, and wait patiently until they go on sale.