I am already getting questions on when to plant in the St.Louis area, so I thought I’d do a little research on the weather averages.
May 1st is my standard answer for best planting date and it seems to stand the test of time. While you can certainly put in tougher plants like pansies, most annuals and more tender plants need the warmer temperatures.
If you look at the graph below, you can see that while the Normal Lows for April are in the 50’s by the end of the month, the Record Lows can be in the 20’s and 30’s. The Climate Graphs for May also show that there are no instances of freezing weather in the last fifty years.
May 1st seems to be a good planting date in this area. If you want to live dangerously you can plant earlier, but I would look at the 10 day forecast to be safe.
“Unseasonably warm weather in March over the eastern half of the United States prompted early growth of many agricultural and horticultural crops, ranging from wheat in the Central Plains to fruit trees and pastures across the Southeast and parts of the Midwest. March monthly temperatures averaged between 2 and 6°F above normal in these areas, and this was the second warmest March on record for the entire U.S.”
Sounds like today doesn’t it. Actually, it was 2007. Read on to see what happened.
“Arctic cold followed in early April with over 1500 weather stations breaking or matching record low temperatures. The magnitude and duration of the cold temperatures was particularly noteworthy in a climatological sense. Low temperatures in the teens occurred throughout the eastern half of the country, and freezing temperatures lasted almost a week in some areas. ”
One would think that with all the information you see on global warming that it would impact everyone’s local growing situation. In some cases it does and some it doesn’t. It depends on where you live and even in which county you live.
If you look at the data from the University of Missouri annual average temperature, (charts) it looks like we naturally have a wide change in average temperatures.
On the other hand if you look at the data from the Arbor Day Foundation, it shows that while many of the counties show increases in temperature, some do not. It almost looks like there are waves of heat across our country with cooler bands in-between.
What this means for you depends on where you live. Likely you may be able to grow some plants that never would have made it in the past.
New 2012 USDA Hardiness map
The USDA just came out with a new 2012 map which is somewhere in between the Arbor Day Map and the 1990 map.
The USDA says, “The new map is generally one 5-degree Fahrenheit half-zone warmer than the previous map throughout much of the United States. ”