13 Best Perennials You Should Be Planting In September

Just because the leaves may start changing colors soon in some regions does not mean that September has to be the end of your planting season. In fact, there are plenty of fall and spring plants that do especially well when planted in September. Fall-blooming perennials, like Asters and snapdragons, are great for adding color and life to your garden in colder months when the leaves begin to change. While most fall perennials won't bloom immediately, they should have enough time to establish their root system before the first frost if you plant them in September. Plus, they won't face the threat of heat or drought from the hot summer months. This helps to prepare them for strong, beautiful blooms the following season. 

The goal of planting in September is similar to that of spring-blooming perennials (like grape hyacinth, hellebore, and sea holly), in the sense that they have time to establish a strong root system before the frost comes. Fall-planted perennials, however, should be ready to bloom at the beginning of the next season in most cases. This also means less work in the spring when annuals demand most gardeners' attention. Start prepping that fall to-do list for the garden of your dreams with these 13 perennials you should be planting in September.

Asters are a genus of summer and fall-blooming perennials with bright purple, blue, gold, pink, red, or white flowers that grows best in USDA hardiness zones 4 to 8. Asters can be planted in the ground either spring or in early fall when there is no threat of frost. Growing from seeds can be unreliable, however, if you do choose to plant from seeds, September is the best time to allow the root system to spread. Most commonly, Asters are planted from transplants. You will want to acquire a mature plant for transplant, which may even bloom before winter. 

Beardtongue (Penstemon digitalis) has a long bloom season in the spring and summer, sporting purple and white tubular flowers that are great for luring hummingbirds to your yard. You can plant seedlings of this perennial anytime in the spring, summer, or fall in USDA hardiness zones 3 to 8. September is an ideal time to plant, depending on your climate, because the plant needs at least 4 weeks to become established before the first frost. This will also ready the plant to bloom the following season. 

Bee Balm (Monarda didyma) grows in USDA hardiness zones 4 to 9 and blooms in summer. However, this is a perennial that you should deadhead for blooms that keep coming well into the fall. Bee balm can be planted in the ground in the spring or the fall, but placement is more important than timing. These stunning pink flowers are great for attracting pollinators to your garden, but they are susceptible to problems caused by shade and too much moisture, particularly mildew and fungus. They prefer full sun, well-drained soil, and plenty of space.

Blazing star (Liatris spicata) has 50 different varieties that can grow in USDA hardiness zones 3 to 8 and produces blooms in the summer. However, it takes a few seasons for this plant to start flowering. Transplants should only be planted in the spring, but seeds can be sown in September because they need cold to properly germinate. You could wait until later in the fall to sow the seeds when the ground has frozen, or you could put the seeds in your fridge for 4 to 6 weeks before planting in September.

Crown imperial (Fritillaria imperialis) is a perennial grown from bulbs in USDA hardiness zones 5 to 8. The flower blooms in spring with orange, red, or yellow blooms. Crown imperial bulbs are fragile, so you should take extra care when planting. These unique blooms will do best when planted in the fall, so September is the perfect time to start preparing. Crown imperial likes moisture-rich soil and full sun and needs at least 12 inches of space between each bulb. Be sure to plant bulbs sideways to prevent bulb rot.

Grape hyacinth (Muscari) is another perennial that grows from bulbs and blooms in the spring. Fall is the ideal time to plant the bulbs in USDA hardiness zones 4 to 8. They are commonly planted in large quantities for ground cover or as border plants, but they can also be grown in containers. Many gardeners also use them to attract pollinators and as companion plants. Grape hyacinths can grow in full or partial sun and moist, well-draining soil with a tolerance for clay, loam, or sandy soil.

Heather (Calluna vulgaris) is a perennial that is usually grown as a ground cover in USDA hardiness zones 4 to 6. Although they are often planted in the spring, they can do just as well when planted in the fall. September is a good time to plant to avoid issues from frost, especially if transplanting from container plants, because the roots are delicate and they need time to establish before the frost. Once they are transplanted, heathers will need plenty of water. It is also a good idea to choose a good mulch to help the plant retain moisture.

Hellebore (Helleborus) is a spring-blooming perennial with beautiful cream, green, pink, purple, red, or white flowers that should be planted in fall in USDA hardiness zones 5 to 8. Hellebore can also bloom in winter once it's fully established. September is the perfect time to plant the seeds because they need to chill in moisture for 60 days to germinate. Hellebore can take up to four years to fully bloom, though some blooms may appear in year three. These flowers make great ornamental additions to shade gardens, but note that they are toxic to humans if eaten.

Japanese anemone (Anemone x hybrida) grows beautifully in full sun and partial shade in USDA hardiness zones 4 to 8. It produces pink, purple, or white blooms in both fall and summer. While they can be planted at any time, September is particularly favorable due to the warmer soil leading into the cold season. Japanese anemone are most frequently sold as seedlings in the early fall. Japanese Anemone is picky, so you should take care to plant it somewhere that stays moist but not too wet. In drier conditions or locations, you may need to mulch over winter.

Monkshood (Aconitum), also known as wolfsbane, has over 250 species that grow in USDA hardiness zones 3 to 7. This stunning blue, purple, or white flower is used in gardens with good moisture or for mass planting. You can expect to see blooms throughout the summer. September is the perfect time to plant the seeds so they will be ready in the spring. If not planted in the fall or winter, seeds need to be started indoors. It's crucial to note that all parts of this plant are poisonous for both humans and animals, so grow it with caution.

Sea Holly (Eryngium planum) is a perennial that blooms in summer and continues blooming into the fall in USDA hardiness zones 5 to 9. They grow best when the seeds are sown directly in the ground in colder seasons. September in many areas also offers ideal growing conditions for transplants; however, they can be more difficult to establish than seeds. Sea Holly prefers full sun and occasionally dry soil with good drainage. The plant is also resistant to several common garden challenges, including deer, rabbits, and drought.

Snapdragons (Antirrhinum majus) bloom in the summer and fall in USDA hardiness zones 8 to 9. They can be planted from seed or transplanted when temperatures become very cold at night. September provides the perfect conditions because snapdragons can not withstand a hard frost while they are being established. For placement, choose a spot that has full or partial sun and rich, well-draining soil. If you don't plant snapdragons in the fall, you will need to prepare them early in the spring before the last frost of the season.

Stonecrop (Sedum spp.), also called live-forever, grows in shallow soil in USDA hardiness zones 3 to 10, making it a fantastic ground cover for rock gardens. You can expect to see blooms in the summer and fall. It does best in full sun, especially in regions with cold winters. You can plant stonecrop anytime in spring or late summer. However, in northern climates, September is the latest you will want to plant transplants to give them time to establish a root system. For southern climates, you may be able to plant later in September or even into October.