Not much time goes by in our week before we are asked if we carry the holy grail of plants. You probably know these ‘dream’ plants. These are plants that will take nearly any growing condition and thrive with colorful flowers to boot.
Mostly folks are looking for plants that can survive being inundated with water and then survive being dry as a bone for a couple of summer months. Sounds impossible, and these plants may seem few and far between but we have quite a few plants that fit the bill.
As you will recall in our earlier post about slowing storm water with the right plants we mentioned the various zones found in retention basins and bioswales. The plants people are looking for are those that do well in the third and fourth hydrologic zones, Zone 3 and 4. These are plants characterized by their ability to be regularly (Zone 3) or periodically (Zone 4) inundated with water at some points and to withstand droughts at other times. Sounds like an impossible task, but as usual, there are plants for that!
Once again we recommend looking to nature for inspiration. Where in nature are you most likely to find plants experiencing this type of hydrologic cycle? Near waterways. Look to riparian zone plants. These plants are often flooded as creeks and rivers swell with spring and summer rains and then dry out during the summer months as the water level drops. These plants are often part of a system that includes a diversity of soil types, frequent disturbances and variable topography in addition to the changing hydrology. We encourage you to get up close and personal with these plants – go take a hike or a paddle and see what is growing where and with whom. This is the best inspiration for landscape planning.
There are a variety of trees, shrubs and herbaceous plants that will fit this bill. For a list of trees and shrubs that will work in these extreme garden areas try this manual or this one or this one. We mentioned a few plants for each zone in our previous post, but it seems people are looking for more variety and ideas when it comes to the inundated-then-droughty areas of projects. Below you will find plants that will do well in either of these zones. There are many more that will do well in one or the other zone but these below you can expect to do well in either frequently inundated or infrequently inundated areas that dry out in the summer.
Sedges and Rushes (Need we remind you that no matter the conditions…there’s a sedge for that?)
Other Herbaceous Perennials
Some projects where you may include some of these plants are rain gardens, pond edges and in some cases even greenroofs – remember these roofs are not dry all the time, they are inundated with rainwater and then dry out.
Speaking of plants drying out, anecdotally, one we have noticed on our paddling adventures along rivers is closed bottle gentian (Gentiana andrewsii). These do not make any of the lists we have found for stormwater plantings but there it was thriving along side a river, up to its ankles in high water and high and dry in the summer months when the river is low. That is to say these lists are not all inclusive and perhaps something works for you in these conditions that is not recommended on the lists and BMPs and specifications. We encourage experimentation. If you have a hunch the plant will do well in this type of situation, try it and let us know how it goes!