The giant coneflower or great coneflower is a favorite amongst novice and seasoned gardeners. It’s easy to care for and its flowers attract gorgeous butterflies!
Scientifically known as Rudbeckia maxima, these plants have striking waxy green-blue leaves that appear in rosettes. The foliage has cabbage-like blades which is why this plant is also known as cabbage leaf coneflower.
Whether you’re growing these for their color, size, drought resistant characteristics, or simply as a cut flower for your gardens…let’s learn how to properly grow and care for it.
|Common Name(s):||Great coneflower, giant coneflower, large coneflower, cabbage leaf coneflower|
|Scientific Name||Rudbeckia maxima|
|Height & Spread:||5-7′ tall and 3-4′ wide|
|Soil||Tolerant of a wide range from sandy to clay|
|Water:||Dry to medium|
|Pests & Diseases:||Susceptible to powdery mildew, slugs, and snails on young plants.|
A wonderful wildflower, Rudbeckia maxima belongs to the plant family of Asteraceae. These plants are native to the southern United States and are found growing in moist and sunny locations such as pastures, meadows, and fields.
The plant has about 5′ stems that sprout attractive blooms with bright yellow daisy-like petals that surround a big elongated bright brown cone made of seed heads. 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, as the tall flower stalks and gorgeous yellow flowers combine well with other tall Rudbeckia varieties like Rudbeckia Irish Eyes and Rudbeckia laciniata.
Rudbeckia Maxima Care
You can grow these plants in mass plantings on the edges of your water garden or in your wildlife garden. You can also grow them around your house as protectors for other plants. The long stems provide excellent deer resistance.
Light & Temperature
Giant coneflower plant needs lots of sunlight to thrive. It can also grow in mostly sunny locations such as lightly shaded 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.
Your plant will thrive if you happen to live in USDA Plant Hardiness Zones ranging from 5 to 9.
Water & 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 still cause rot and decay, so be sure not to drown the soil – an average or medium amount of water is fine.
This perennial plant 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.
You can fertilize your plant by using a water soluble feed. Feed your great coneflower once every two weeks in the summer blooming season (June).
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 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.
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 can prune or deadhead your cabbage leaf coneflower so that new blooms appear during bloom time.
If you cultivate your Rudbeckia maxima plant outdoors in your garden, then make sure to keep it in direct sunlight. It should get at least 6 hours of full sun exposure every day to thrive and grow to its tallest height.
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.
Powdery mildew is a fungal disease that your great coneflower plant can contract. It will harm the 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. You can also apply a good quality fungicide if the problem is too severe. Be sure to prune off all affected areas.
Q. How do I encourage more flowers to bloom on my great coneflower plant?
A. If you want more blooms, cut the spent flowers as that will encourage new growth. Also, make sure to plant it under full sun and keep it in moist soil.
Q. Can I divide my large coneflower?
A. Yes, the best time to divide it is in spring. Simply dig up the entire plant, split it, pick out any weeds or grass, and then re-plant it where you want.
Q. Why are my maxima rudbeckia not growing tall?
A. It is probably due to a lack of sunlight and moisture. Try to add increase watering and place them in a sunny location.
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