We are coming into the most wonderful time of year to be a Texan when the bluebonnets finally begin to emerge once again as winter turns to spring. After a disappointing bluebonnet bloom across most of Texas in 2020 and an almost year-long pandemic that won't go away, hopes are higher than ever that this year will hold something spectacular in store.
Last year, we looked at the contributing factors for a bluebonnet bloom in an attempt to identify not only how much rainfall is necessary, but when that rainfall is most needed and what temperatures best promote a successful bloom. In the first of this four-part series, we will take a look at the rainfall and temperature data from the Big Bend in West Texas. Rainfall maps showing the departure from normal are presented for each month from September 2020 to January 2021. For the sake of this article, we will assume that average rainfall will yield an average bluebonnet season. Due to a lack of available data for the region during some of the pertinent months, rainfall totals have been omitted.
Seed germination period
Rainfall during what I term the seed germination period is the most crucial time for rainfall during bluebonnet development. The germination period runs from sometime in September to sometime in November.
September in the Big Bend is the end of the monsoon season, and in September 2020 the region was in a drought. It is a not a good omen when what is supposed to be the wettest time of the year is below average in rainfall. Only the northern parts of the Chisos Mountains and the area downriver from Mariscal Canyon received above average rainfall. Strike one.
October is generally considered by those who study such things to be the most important month for rainfall in order for bluebonnet seeds to germinate. As we can see on the map, the entire Big Bend received well below average rainfall. The real story, however, can be found here, here, here, and here. Of the four locations where the NOAA records rainfall within Big Bend National Park, the only site that recorded any rain was Panther Junction with a total of .07 for the month. Strikes two and three. We could just stop here since nothing else will really matter in terms of getting bluebonnets to bloom, but for the sake of continuity we will proceed on to November.
November 2020 was the last chance for the Big Bend region to get bluebonnet seeds germinating. The average rainfall on the western side of Big Bend National Park, however, was way too little, too late. And to add insult to injury, the dearth of rain only increased on the eastern side of the park.
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.
The Big Bend benefitted from several inches of snow near at the end of 2020, which pushed rainfall totals up.
January 2021 rainfall was about average across the Big Bend except for the area in and around the Chisos Mountains where it was below average yet again.
It's not even worth discussing temperatures after such a poor amount of rainfall from September to January.
2021 Big Bend 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. With that said, I feel very confident in saying that there will not be very many bluebonnets blooming in the Big Bend this year. Those few that are blooming will be along roadsides which gather more rainfall due to runoff from the adjacent paved roads. It's so disappointing to see after waiting an entire year in hope of a good bloom, and even more so after seeing what was possible during 2019's bluebonnet superbloom.
In Part II of this series we will take a look at the data and forecast the 2021 bluebonnet season in South Texas. Stay tuned...
Castolon Cooperative Precipitation Data. (n.d.). Retrieved February 05, 2021, from https://www.weather.gov/maf/cl...
Lajitas Cooperative Precipitation. (n.d.). Retrieved February 05, 2021, from https://www.weather.gov/maf/cl...
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 12). Contributing factors for a bluebonnet bloom (Part II): The Big Bend of Texas. Retrieved from https://www.jasonmerlo.com/gallery/contributing-factors-bluebonnet-bloom-big-bend-texas/
NOAA. (n.d.). Advanced Hydrologic Prediction Service. Retrieved from https://water.weather.gov/precip/#
Panther Junction Cooperative Precipitation Data. (n.d.). Retrieved February 05, 2021, from https://www.weather.gov/maf/cl...
Rio Grande Village Cooperative Precipitation Data. (n.d.). Retrieved February 05, 2021, from https://www.weather.gov/maf/cl...
Vernalization. (2019, December 17). Retrieved from https://en.wikipedia.org/wiki/Vernalization