Native Plants, and the Drought of 2012

The Drought of 2012

As I write this post, there are cloudy skies above and we're getting teased by a smattering of showers heading in our direction. I'm not getting my hopes up, we've seen this sort of weak storm pattern already a couple times this summer without much to show for it. Its Friday July 13th, and Madison WI has officially received less than 1/2" of rain since June 1st (and I'm pretty sure it didn't rain the last week of May either). On an average year, we would see 6.75" of rain during that period. As you can see below, we're now in a "Severe Drought":

Still, I don't think that image shows the local severity quite as clearly as it could. Check out this map of precipitation totals for the past 30 days, showing a big red bullseye of 'nada' in south central Wisconsin. UPDATE: they updated the map shortly after I wrote this blog post, there was originally a bull eye of red immediately southwest of Madison. I captured this image on July 16th, click here for the current condition.

Here's another "fun" map, showing that moisture in the top 4" inches of soil is as low as it can go in our area. Bear in mind that the counties in central WI and western MI typically have very sandy soil, making it even more remarkable that we can match their low soil moisture in the loamy soils here in southern WI.

Corn is now wilting and dying in the fields. The non-native cool-season grasses that dominate our lawns and roadsides are brown, and almost completely desiccated. We're now seeing several accidental grass fires daily in Madison, which is completely unheard of for this part of the world. Earlier this week I saw two burned out areas in just a 1 mile stretch of I-90.

So What Does This Mean for Native Plants?

We always promote the hardy, drought tolerant nature of native plants. But conditions like these will impact any plant. Expect to see native plants responding to the drought by wilting back, flowering for shorter-than-normal periods of time (or not at all), and/or partially (or completely) dying back above ground. These are all signs of stress, but they are also adaptive responses. The plants are making a measured response to the lack of soil moisture, much like you might cut your spending if you found yourself temporarily out of work. For the most part, though some native plants may look like they are suffering this summer, almost all will survive this drought just fine and be vibrant and healthy again next year.

Native planet out "in the wild" are similarly effected, which can be easily seen in any walk in the woods or in the prairie. The effects seem worse in prairies and savannas because of the drying effects of direct sunlight and hot/dry winds. Some species do better than others under these conditions. Severe droughts like this can have an impact on the species assembly in natural areas, meaning that populations of drought tolerant plants may increase as a result of the drought, while the populations of other species may decrease. Here's hoping that many of those shallow-rooted garlic mustards just won't be able to hack it!

Hairy wild petunia that I photographed earlier this week is showing no signs of stress due to the drought.
 I notice a new flower budding this afternoon.

Black-eyed susan is also thriving despite the drought. They, and the above petunias have extremely hairy leaves and stems which slows airflow around these surfaces, reducing the amount of water which is lost due to evaporation.

Pagoda dogwood is a woodland species, its growing here in nearly full sun. The leaves are 'flagging' a bit, but you can see this hardy shrub is still finding enough water to develop fruit which the birds are quickly devouring.

Wild bergamont, rattlesnake master and false sunflower are all a little wilty due to the drought, but they are flowering non-the-less. At the lower left you can see some obedient plant which is dying back due to drought stress. No doubt it will be back and bullying other plants around next year.

Situations where you SHOULD water

Overall, native plants should survive, even thrive during this drought. However, there are a few exceptions. Here is when you should be watering:

Flowering perennials and grasses that were planted this year:

These baby plants haven't gotten a substantial enough root system yet to tolerate completely dried out surface soil. Water to soil saturation 1-2 times a week.

Trees planted in the last 4-5 years:

Because we need plants that are a small enough to move around and plant, the root system of container grown and especially balled-and-burlaped trees are much smaller than their wild counterparts of similar size. It takes several years for trees to grow out their root systems after they are planted. So these need to be watered thoroughly for them to survive. They should be watered very heavily 2-3 times a week. Shrubs will need some attention too, but will generally survive better than trees.

Right plant, Wrong Place:

We always talk about planting the right plant in the right place for best success. Sometimes we push the limits a bit because we something we really like should work pretty well in a spot under normal conditions. A good example is rain gardens, my rain garden has a number of wet prairie and wetland edge plants that need more moisture than their more mesic counterparts. Really, for a rain garden, you want plants that can withstand flooding, but are otherwise well suited for the 'normal' condition of your garden. In my case, I have marsh milkweed, cardinal flower, marsh blazing star and culver's root that are all flowering, but they are shorter than normal and less vigorous. I'm starting to wonder if the blue lobelia will bloom, and I have had at least one wetland sedge bite the bucket. The panicled asters on the other hand are doing a little too well... may have to thin those out this fall.