In Part I of this series we took a look at the rainfall data from the Big Bend in West Texas. In Part II we will look at the data from South Texas. For the purposes of this article, South Texas is defined as Atascosa County, DeWitt County, Gonzales County, Guadalupe County, Karnes County, and Wilson County. Although there are certainly plenty of other areas of South Texas where bluebonnets bloom, these are the areas with which I am most familiar.
Though there are many contributing factors for a bluebonnet bloom, the most important by far is rainfall. Below, rainfall maps showing the departure from normal rainfall are presented for each month from September 2021 to January 2022.
Because the purpose of this series of articles is only to attempt to identify the locations that are most likely to have bluebonnets, rainfall is the only bloom factor that is examined. I have chosen to omit the data from February because it is not available at the time of this writing, and also because I believe it is the least important month in terms of affecting a bluebonnet bloom, even though in all likelihood it does have some bearing on the bluebonnets' development.
Seed germination period
Rainfall during what I term the seed germination period is more crucial for bluebonnet development than rainfall during any other period. The germination period runs from sometime in September to sometime in November. This doesn't mean that bluebonnet seeds can't germinate during other months of the year, just that this is when the large majority of them will germinate, if they are going to do so.
Rainfall in September 2021 was average or better in much of the area in question, with parts of Atascosa, Bexar, Gonzales, Guadalupe, and Wilson Counties seeing anywhere from a half an inch to four inches above average. The whole of Karnes County was one to three inches below average, and DeWitt County was mostly below average as well. The most noteworthy areas were the southern half of Guadalupe County and the northwestern portion of Wilson County.
October 2021 rainfall was well above average across the area. The majority of Gonzales County saw as much as five to eight inches above normal. The entirety of Guadalupe County received above average rainfall, as much as eight inches above normal in places, and the northeastern two thirds of Wilson County received anywhere from a half and inch to eight inches above normal. Atascosa County was less fortunate, with the majority of the county seeing up to two inches below the average. Overall, this is great news for the wildflowers.
November 2021 rainfall was below average in parts of Atascosa, Gonzales, and Guadalupe Counties, but average or above average in Karnes and Wilson Counties, with parts of each receiving up to two inches more rainfall than normal.
Rosette development period
The rosette development period runs from sometime in November to sometime in February. This is the period when bluebonnet rosettes are going through a process known as vernalization and developing their root structure. While rainfall is still important during this time, it is not nearly as important as it is during the seed germination period.
December 2021 rainfall finally began to show the effects of La Niña, with the entire region receiving between a half an inch and two inches below average rainfall.
January 2022 rainfall was just as disappointing as the rainfall in December 2021. The entire area, except for the eastern third of DeWitt County, received between a half an inch and two inches below normal.
Rosette development period - observed rainfall
The above maps have shown monthly departure from normal rainfall, however, I think in the scenario presented by the amount of rain that fell during the seed germination period in Gonzales, Guadalupe, and Wilson Counties, it is important to illustrate that although rainfall was below average across the region in question during the first half of the rosette development period, the area did not go completely without rain. As shown on the observed rainfall maps below, the three aforementioned counties all received some rain in December 2021 and January 2022.
The majority of Gonzales, Guadalupe, and Wilson Counties all received from a half an inch to an inch and a half of rain in December 2021.
Most of Gonzales and Guadalupe Counties, and the northeastern portion of Wilson County received between a half an inch and an inch and a half of rainfall in January 2022.
2022 South Texas bluebonnet forecast
Predicting a bluebonnet season is difficult to do with accuracy due to the fact that there are so many different factors are involved in a bloom that are impossible to evaluate. Each wildflower season is unique and presents different opportunities.
Based on the data shown above, I believe South Texas is going to be the star of the show in 2022. Southern Guadalupe County, western Gonzales County, and northeastern Wilson County are all primed to have a good spring for wildflowers. I do not expect to see many bluebonnets in Atascosa County or Karnes County this year, and most likely will spend very little, if any, time there.
Rainfall in Gonzales, Guadalupe, and Wilson Counties during the seed germination period looks somewhat similar to how it did in 2018 leading up to the 2019 wildflower season, which was a very good year in South Texas. The difference is that the 2019 season rainfall was more widespread during the seed germination period in the fall, and saw a little more rain during the rosette development period than did this year. That fact notwithstanding, I am very much looking forward to exploring Gonzales, Guadalupe, and Wilson Counties in March and April. Hopefully, rain will continue to fall in February so that the bluebonnets can continue to develop. South Texas has already received another inch to two inches of precipitation in areas of the noted three counties in the past five days (the first five days of February).
In Part III of this series we will take a look at the data and forecast the 2022 bluebonnet season in the Texas Hill Country.
Merlo, J. (2020, January 11). Contributing factors for a bluebonnet bloom (Part I). Retrieved from https://www.jasonmerlo.com/gallery/contributing-factors-bluebonnet-bloom-texas/
Merlo, J. (2020, January 16). Contributing factors for a bluebonnet bloom (Part III): South Texas. Retrieved from https://www.jasonmerlo.com/gal...
NOAA. (n.d.). Advanced Hydrologic Prediction Service. Retrieved from https://water.weather.gov/precip/#
Vernalization. (2019, December 17). Retrieved from https://en.wikipedia.org/wiki/Vernalization