Rhododendron 'Robleza'

Summary

South Coast Research & Extension Center (South Coast REC/SCREC) is located in Irvine California, this site has a sandy loam soil and plants are irrigated with reclaimed water. UC Davis is located in Davis, California, this site has a silty clay loam soil and plants are irrigated with potable water. More information about the field sites is located in the Nuts & Bolts section.

Autumn Bonfire™ is a dwarf azalea with vivid red flowers, whose buds  garnet buds stand out against the green foliage. 

UC Davis Trial Results - Davis, CA

In the early spring before data collection began, there was a short period where the plants were covered in bloom and more red than green. This cultivar was very slow growing in Davis, attaining only a fraction of its listed height (3.5’ x 3’) in two years. Azaleas are known for preferring slightly acidic conditions and good water quality, as well as rich, well-drained soil. None of these conditions are found in our UC Davis site where the soil is heavy and neutral, and the water contains boron. This may account for the decline in foliage ratings in October (Table 24a). Significant differences in quality ratings between the treatments began in June and continued through October in at least one, if not all, of the following parameters: foliage quality, vigor, and overall appearance. The high treatment was significantly better in overall appearance than the moderate or the low treatment. However, by October, even the moderate treatment had better overall appearance than the low, though the difference was not statistically significant over the whole treatment period. It should also be noted that the low treatment failed to re-bloom in Autumn. At UC Davis no differences in growth were observed. As with other plants trialed in the shade, it is possible that Autumn Bonfire™ would prefer a location with morning sun and afternoon shade, rather than continuous semi-shade. Based on the combination of data collected, we recommend irrigating Autumn Bonfire™ on high water in WUCOLS zone 2 to obtain the best quality plants.

South Coast REC Trial Results - Irvine, CA

At South Coast REC, use of reclaimed water proved to be detrimental to plant health. At no time did plants achieve acceptable appearance, even at their first rating in May. By September, all but one plant on the low irrigation treatment had died, and plants on the other treatments had been showing poor foliage quality since May. For these reasons, we do not recommend using Autumn Bonfire with reclaimed water and cannot at this time make a recommendation for irrigation level in WUCOLS Region 3.

Growth and Quality Data

Click Here for Complete Data Set - UC Davis

Click Here for Complete Data Set - SCREC