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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Friday - August 09, 2013

From: San Antonio, TX
Region: Southwest
Topic: Container Gardens, Planting, Herbs/Forbs
Title: Growing conditions for Giant Coneflower from San Antonio
Answered by: Barbara Medford

QUESTION:

Rudbeckia maxima is considered to be a perennial plant for the sun but I have had a difficult time maintaining it in a pot in full sun before attempting to plant. Do you feel that it will survive and thrive in the sun in the San Antonio area with temperatures reaching 105? Will it need deep soil and lots of water?

ANSWER:

Here are the growing conditions for Rudbeckia maxima (Giant coneflower) from our webpage on that plant:

"Growing Conditions

Water Use: High
Light Requirement: Sun , Part Shade
Soil Moisture: Moist
CaCO3 Tolerance: Low
Drought Tolerance: Low"

And

"Native Habitat: Found in moist open places. Forming beds in low ground, sandy or silty soils; east Texas west to East Cross Timbers. Seems pretty drought resistance despite its swampy origins."

From this, we are inferring a need for part shade (2 to 6 hours of sun a day) in such a hot summer, as well as lots of water. The problem for plants in pots in either extreme heat or cold is that a few inches of potting soil and the sides of a pot are not much insulation for the roots. Its native habitat appears to be low places and swampy soil, indicating some shade during the day. Also, the insulation of the earth around any roots is more valuable than any kind of pot material for the preservation of the roots. We would suggest you either move the pots to a shadier spot, or transplant the coneflowers into soil earlier in the season, before the heat becomes so intense.

 

From the Image Gallery


Giant coneflower
Rudbeckia maxima

Giant coneflower
Rudbeckia maxima

Giant coneflower
Rudbeckia maxima

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