September 29, 2014
I have several 3 year old Baptisia australis plants in the same area. All are doing great, but one. I have no clue as to why one of my plants leaves turned yellow (lighter green), compared to the others. I noticed the stalks are brown, compared to the fresh light green of the 7 other plants. The plant flowered this year and it is about 3 feet/3 feet. There seems to be a film on the stalks. Thanks for your advice.
September 30, 2014
Your plants sound like they are doing well. There are a few possibilities for why one plant looks different. One is that it may not have matured fully; another is that it may be a slightly different cultivar; another is that there may be some insects or disease - check for aphids or scale insects:
Another possibility is that this one plant is just not as strong as the others. This happens sometimes, there's no real reason, but anyone who's gardened for very long has seen it. At any rate, here's an article that might give you some more information: https://www.gardeningknowhow.com/ornamental/flowers/baptisia/growing-baptisia-plants.htm