Great Coneflower is a highly drought-tolerant accent flower. It is very attractive to butterflies. Goldfinches enjoy their seeds. This perennial can be grown in full sun to part shade and grows up to 1.8 m tall.
Whether you’re growing these for their color, size, drought-resistant characteristics as xeriscape plants, or simply as a cut flower for your gardens…let’s learn how to properly grow and care for them.
I. Appearance and Characteristics
A wonderful wildflower, Rudbeckia maxima belongs to the plant family of Asteraceae. These plants are native to the southern United States (in Texas, Louisiana, Oklahoma, Arkansas, and South Carolina) and are found growing in moist and sunny locations such as pastures, prairies, meadows, and fields. Today people incorporate them in cottage gardens and pollinator gardens.
The plant has about 5′ sparsely leaved flower stalks that sprout attractive blooms with bright yellow rays of daisy-like petals that surround a big elongated bright brown cone made of seed heads. The bluish-green leaves of the plant relate to its common name, cabbage leaf coneflower.
The seed cones often persist through winters and attract goldfinches to your garden! The leaves at the base are also attractive, as they are bluish and form a basal clump right at the bottom of the plant.
These are fantastic companion plants, especially in a cottage garden or pocket prairie, as the tall flower stalks and gorgeous yellow flowers combine well with other tall Rudbeckia varieties like Rudbeckia Irish Eyes and Rudbeckia laciniata. These plants are native to a large portion of the southern US and don’t require a ton of care once they’re established.
II. How to Grow and Care
Light and Temperature
A giant coneflower plant needs lots of sunlight to thrive. It can also grow in mostly sunny locations, but also tolerates light shade areas of your garden. However, too much shade will thwart the growth of your Rudbeckia and prevent it from flowering. So, make sure to plant it under full sun to see the beautiful yellow blooms of the plant.
Morning sun is preferable to afternoon sun. In areas that are hot year-round, provide some light shade to limit the amount of watering you need to do. Your plant will thrive if you happen to live in USDA Plant Hardiness Zones ranging from 5 to 9. When temperatures dip below 40°F, your coneflower may brown and enter winter dormancy.
This is no issue as the seed heads are forage for small birds, the stalks harbor overwintering insects, and the plants readily self-seed to re-emerge in the upcoming spring.
Water and Humidity
Great coneflower plants can be fairly drought tolerant, but they grow taller and bloom much quicker in moist conditions. So, keep soil moisture relatively high during the growing season. Overwatering will cause rot and decay, so be sure not to drown the soil – an average or medium amount of water is fine.
In the heat of summer, water your plants at least a couple of times a week to keep them happy. As fall and winter arrive, you won’t have to water as much. Use morning irrigation routines that employ soaker hoses or drip irrigation to slowly and deeply water the plants, avoiding direct contact with basal foliage.
Soil
The perennial giant brown-eyed Susan can actually tolerate a fairly wide range of soils – even flooded or drought-inflicted soils for short periods of time. However, your great coneflower plant will truly thrive and reach its tallest height in moist, organically-rich sandy or clay soils. Sandy soils aren’t as suitable, and poor soils should be avoided if possible.
You can amend a sandy soil with well-rotted compost. Overall, well-drained soils are the key to success with these plants.
Fertilizing
You can fertilize your plant by using organic fertilizers. However, this might be too much nutrition for a plant that tends to draw in essential nutrients from the soil. An annual dressing of rich soil or compost in spring or fall is enough to keep your giant coneflower happy. Too much fertilizer could make it so your flowers don’t perform as well.
Repotting and Transplanting
Relocate your plant before new stem growth in spring. That will give the roots several weeks to fully form and adjust in their new soil. Make a hole at least 8-10″ deep in the soil under full sun. Uproot your plant from its original pot or space in the garden without damaging the roots and place it in the center of the hole. Fill the hole with more soil and pat it to even out the surface. Water the plant till the soil is moist.
Pruning
You can prune or deadhead your cabbage leaf coneflower so that new blooms appear during bloom time. However, leaving them provides winter food for song birds, and the stalks house overwintering insects. Whichever you choose, when you cut your stalks, leave the basal foliage on the plant.
Propagation
These plants multiply from rhizomes via self-seeding and form vast colonies that cover a large surface area. You can also divide them every 4 years in spring. You may want to divide the rhizomes in fall if Rudbeckia maxima is taking over an area of your garden.
To divide the plant in fall or spring, use the same process mentioned in the last section, but instead of moving the entire plant, locate growth points on the plant’s rhizomes, and carefully separate them into the size you desire. Then plant them in the same way you would during a transplant or repot.
If you’d like to start the seeds yourself, broadcast them in trays. Before you sow them, place them in a bag of sand, and put it in the freezer for a couple of weeks. Then remove them and place them in the soil of your tray under a thin layer of soil or vermiculite. Keep the soil moist, and in about 2 to 3 weeks, they’ll sprout. Thin young plants to 12 to 24 inches as they mature.
Pests and Diseases
- Common Pests
You need to protect your Rudbeckia maxima plant from snails and slugs. They can attack your plants and leave huge holes in the foliage and even eat the seedlings of your plant. To prevent such pests from attacking your plant, keep your garden tidy. Eliminate all hiding spots such as fallen foliage. Make sure your soil is not too wet and shaded since that type of soil is an ideal hiding spot for such pests.
- Common Diseases
Powdery mildew is a fungal disease that your great coneflower plant can contract. It will harm the bluish-green leaves of your plant and turn them yellow. So, make sure to place your plant in direct sunlight and ensure proper spacing to increase airflow. Water properly, and don’t feed your plant fertilizer in winter. Remove damaged foliage. Usually, when the weather gets hot and dry you won’t have as many issues with powdery mildew.
- Growing Problems
These issues arise when you grow giant coneflowers in improper conditions. Too little sun will slow growth and prevent blooms, and so will too much sunlight. Fertilizer and water applied in amounts that are too high or applied at the wrong time will decrease blooms overall.
Finally, if you don’t control some of the spread of the plant, it can self-seed and take over the garden. If you’re having issues with this, deadhead spent blooms, and spread the seeds elsewhere, or divide the plant.