PPDL Picture of the Week for
July 25, 2011

Heat Tolerance of Lobeila (Lobelia erinus)

Roberto G. Lopez, Ph.D., Assistant Professor and Floriculture Extension Specialist, Purdue University

In recent years, several new lobelia (Lobelia erinus) cultivars with improved heat tolerance have been introduced into the market. These new cultivars will continue flowering during the heat of the summer unless night temperatures remain in the 70’s or above. During the past week, much of the upper Midwest and Eastern U.S. have experienced record high temperatures that have exposed the limits of these new lobelia cultivars. Now is a great time to see which lobelia cultivars can hold up to the summer heat.

In Figure 1, we can see a side-by-side lobelia container trial in Chicago, IL where flowering of most cultivars has declined due to extreme temperatures of 90 and 70 °F during the day and night, respectively, for more than 10 days. Once the stressful conditions have diminished, plants should be sheared to encourage branching.


Click image to enlarge

Lobelia heat stress trial

Fig. 1. Extreme nightly temperatures of 70 °F have impacted the visual quality and flowering of most lobelia cultivars in a shaded side by side container trial in Chicago, IL. 

Fig. 2. This lobelia cultivar under full sunlight was not influenced by extreme nightly temperatures of 70 °F in a side-by-side container trial in Chicago, IL. 

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service