Bartlett on Gardening: Q: How the @#%* do I make my Ruellia bloom?

Do you have gardening questions for Dear Ann [Bartlett] (the MASTER! GARDENER!)? Email them to with GARDENING QUESTIONS in the subject line!

Dear Ann [Barlett] (the MASTER! GARDENER!),

I"m sending a pic of my Mexican petunias. (The official name is something that begins with an R; you'll know what it is I expect, you being a MASTER! GARDENER! and all.) These are in my front yard and they get full sun. I bought them at Lowe’s, full price, because there's a stand of them in the traffic circle in front of the Dade County courthouse, and there used to be an even prettier one at the Trenton McDonald's (imagine that! A nicely-landscaped McDonald’s!) and they were so tall and lush and beautiful.

That was three years ago. My Mexican petunias grow like weeds, multiply like rabbits and are no trouble to grow but---they...don't...bloom! They stand there all summer doing nothing. Then in September they have two or three little blooms at the periphery here and there but nothing to write home about. Whereas at the courthouse, they've been blooming more or less all summer.

I checked back at the McDonald’s, too (and whether or not I got one of those chocolate-

dipped ice cream cones while there is not germane to this inquiry and I cannot imagine why anybody would bring it up). There they had probably stopped paying the landscaper because big trees and bushes had subsumed their Mexican petunia patch--but where you could still see them the flowers were still blooming their neglected little hearts out! (right)

A plant person who was at my house in June said the reason the courthouse flowers did so well was the heat from all that pavement. I nodded and believed. But later I realized this has been the hottest summer in history this side of hell, with temps in the 90s practically every day since the beginning of June, so I ain't buying it.

Ann, my question is, succinctly:


--Hot Under the Collar

Dear HUC,

Ruellia is a perennial native to Mexico. It is cold hardy to zone 8, and it loves heat, sun, humidity and moist soil. In frost-free areas along our Gulf Coast, it never goes dormant, flowering from May until November.

Here in zone 7, it appears to have good winter survival, but must grow back from its rhizomes once soils warm in the spring. No doubt this is one factor in the delayed flowering.

I did some observations of my neighbor's many clumps of purple ruellia. The one flowering best is on the west side of her masonry mailbox located on the hell strip between the street and sidewalk. This would seem to confirm the opinion of your plant person. The heat from the pavement warms the soil earlier in spring and intensifies that heat all season.

Though this summer has been hotter than Satan's furnace, we must accept the reality of micro-climates in our gardens.

--Ann [Bartlett] (the MASTER! GARDENER!)

Miss Ann

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