PGRs on Perennials: Controlling Lavender ‘Phenomenal’ Flower Stalk Growth

By Joyce Latimer, Virginia Tech

If you are still shipping spring lavender, you might be interested in ideas on keeping those flower stalks somewhere close to the shipping cart. A few years ago, Peace Tree Farm released the new, vigorous lavender ‘Phenomenol’ and at their request, we evaluated the growth retardants, Dazide, Dazide/Citadel tank mix, Piccolo 10 XC and Concise, for regulation of flower stalk growth.

Liners were donated by Peace Tree Farm and planted in trade gallon plastic pots in August, bulked in the greenhouse until October and overwintered in a cold frame in Blacksburg VA. The PGR treatments were applied when flower stalks emerged in early May, as foliar spray applications at the label recommended volume. The Dazide treatment was re-applied at two weeks after the initial PGR applications.
We measured flower stalk height at 2, 4 and 6 weeks after treatment and noted the number of days to first open flower.

Lavender ‘Phenomenal’ was responsive to all the PGR treatments but the appearance and delay in flowering varied with the treatments. Check out the details in the photos below.


In summary, Dazide applications resulted in moderate control of flower stalk growth but delayed flowering about 6 days. The tank mix of Dazide and Citadel gave less control with the same delay in flowering. Piccolo 10 XC resulted in light to moderate control with no delay in flowering. Concise gave excellent height control but delayed flowering up to 7 days.

Which PGR should you test? For pictures of the finished plants, check out the video blog at:

Watch the video and make your own decision!