Rain gardens are a wonderful natural way to help clean the runoff from roadways. Simple indentations with water loving plants that catch and filter the water.
Location: Lemon Grove, CA
posted 6 years ago
Thank you, Diane. I have been considering this. My concern is that I am in Southern California where it doesn't rain for many month at a time and don't want to spend water on water hungry plants.... So far, I did a silt trap and am mulcting my catchment ditch, but think I will try to plant some cleaning plants and see if they'll survive the summer. do you have some specific recommendations? I am catching water from a whole street block from a culvert I cut into and damed up.
Here's a list of some drought tolerant plants for Southern Claifornia
http://www.lvmwd.com/home/showdocument?id=711 They include yarrow, showy penstemon, desert mallow, wax myrtle, and bay laurel.
But with the extreme droughts in California right now, getting any plants started may be really difficult. I really hope you get more rain in California soon!
Location: Lemon Grove, CA
posted 6 years ago
Are the pants on this list considered water cleaning plants? I know them as drought tolerant, but didn't think I could employ them to clean the runoff. The pictures you see are rain from streets in a one block radius caught from an 1/2 inch rain event. The ditch has pretty much percolated the water into the soil within 3 days. So, when it rains, I have a lot of flow and anything might be under water for several days - then come summer, nothing for month at a time..... Currently, I have a chain link type fence where the water enters covered with some large leaves. That works pretty well to catch solids, like cigarette butts, candy wrappers, cups and so forth. I also have a bunch of Geraniums growing along the ditch and the leaves catch a bunch of gunk. That only helps for so long since I have to trim them to clean the trash out - they do grow fast. Then, at the dam site, I have a silt trap - a basin with some rocks behind to allow solids to settle. Then, the ditch is mulched and whatever manages to grow, I allow and encourage it. I am basically asking if, instead of the silt trap or in addition to, some cleaning plants would be advisable, or if it wouldn't make a difference since the water moves through pretty quickly if it rains more then 1/8 of an inch.
Since this area is functioning as a catch basin from the road, screening out the debris like cigarette butts is important, and I would help protect my garden from that, sand and gravel that washes in from the road by removing it. It sounds like you have set up a filter to deal with that, which I think is really good.
I can help with some basic principles. If you are having heavy flows of water followed by drought, mulching plants and building up the organic matter in your soil in that area will help. A rich, healthy layer of soil helps hold rainwater and prevent flooding and also helps plants survive drought. Now for the more difficult part-California plants that are drought tolerant but will be happy with an occasional onslaught of water, retain and filter it. These plants will also have to hold your soil to prevent erosion and help the soil thrive.
Wax Myrtle is a shrub that is pretty tolerant of varying soil types and works well in a rain garden, Pacific Ninebark is also pretty tolerant of different types of soil so it might be a good bet. It filters well, too. Birds love red currant (it prefers the shade) and it filters well. California Fan Palm likes desert oasis and works well in rain gardens to filter. It also produces an edible nut. Common Yarrow and Columbine might be good to mix in. Santa Barbara Sedge doesn’t need water, but will grow thick with water and it will filter well. California fuchsia likes water but also handles drought. California buckwheat is a drought tolerant plant that will filter water well in a rain garden, too. Butterflies love this plant. Deer Grass might work, too.
I would speak to someone with on the ground localexperience, and it might still take some experimenting. Tell them whether the area is sun or shade, and what type of soil you have. I would try the California Native Plant Society or a local nursery like Las Pillitas Nursery in the San Diego area. The San Diego Botanical Garden would also be a great source of information http://www.sdbgarden.org/
GREAT ideas so far, really build up that organic matter for water holding in the soil and protecting the surface from evaporation. If you access to some flat stones they may also shield the surface from the sun, and give you a dry path to work from when it is wet (someday).
One other thing I could suggest, although it looks as though you have some shade already from the pictures is to plant some drought hardy shrubs or small trees close to your rain garden to shade the area cooling it and reducing evaporation. Good luck!
Jeff, thanks for the link to the plastic eating fungi! I did put some mushroomcompost with the wood chips - forgot to mention it. At this point, the water is supposed to be gone within 3 days, hydrating the soil and hopefully, with time, eliminate the need to water much.