Tuesday, May 18, 2010

Rain garden, one year on

A year ago today I finished my rain garden, and what a wonderful first year it's had! Let's have some classic before-and-after shots! Here is what it looked like when I started:

Here is is completed last spring:

And here it is today!

What is in this rain garden? A mix of water-loving Midwestern natives: cardinal flower (Lobelia cardinalis), obedient plant (Physostegia virginiana), swamp milkweed (Asclepias incarnata), golden alexander (Zizia aurea), Pennsylvania sedge (Carex pensylvanica, which is NOT a good choice I found), porcupine sedge (C. hystericina) and owl-fruit sedge (C. stipata).

Many of the plants are still in the "creep" stage of the classic "sleep, creep, leap" development cycle of perennials. But some are already exploding from the combination of lots of water and sun.

The zizias have reached about 2' tall if not more, which is pretty much as tall as these plants usually get. Clearly they love being in the rain garden.

But you'll notice one half of the garden is very robust while in the other half the plants are still rather small. Why? The difference in sun exposure in just this small 6-foot stretch of garden is significant. The plants near the southern edge get a couple more hours of light per day than those at the northern end. It surprises me that such variation takes place in only 6' of space!

A number of sedges (genus Carex) are perfect for rain gardens because they love moisture but will tolerate dry spells once established. Carex is an enormous genus, so you can find sedges that like sun and moisture or sun and dryness, shade and moisture or even dry shade. In this regard they're more versatile than grasses and can handle the variable conditions in a rain garden that is periodically flooded.

This garden is my first experience growing various sedges, and I really encourage you to add some if you are growing a rain garden or need a grassy plant in a challenging site (see above paragraph about their diversity). While I was researching an article on sedges a while back, Dr. Andrew Hipp, plant systematist at the Morton Arboretum and author of Field Guide to Wisconsin Sedges told me that sedges reward close examination, and he was absolutely right!

Look at the inflorescence of this porcupine sedge (C. hystericina) and click to enlarge:

It looks a little prickly but also kind of dainty...a little like a bottle brush, which is its other common name.

Compare that to the owl-fruit sedge (C. stipata):

Its inflorescences look like spiky burs that would be painful to touch (they're not). Close inspection reveals remarkable variations between these cousins in the genus Carex.

I mentioned earlier that Pennsylvania sedges were not a good choice for the rain garden. I think it's too moist for them. Of the four I planted, three survived and the two doing the best are on the berm and hence stay drier than those in the trough. Bless these plants for liking dry shade! If you grow them, site them somewhere other than the rain garden.

My other piece of advice would be to keep the berm of your rain garden at a very gentle slope. Mine is too steep and I have mulch erode off the sides and pile up on the plants below during rainstorms. I just clean them off once the water has been absorbed, but it's a nuisance that could have been avoided. (See the right side of the photo below for the erosion issue.)

Overall, growing a rain garden has been a rewarding experience, both from an environmental standpoint and an aesthetic one. Every time I see the garden brimming with water I'm pleased because that's water that is not ending up in a storm sewer or joining an erosive flood in a nearby river, and it's on its way to recharging our underground aquifers (which I then use too extensively for all the laundry and dishes around this place, so it's the least I could do!). On top of that, I've watched the zizias and sedges burst into vigorous growth, and the later bloomers (obedient plant, lobelias, etc.) are all growing and thriving.

It took some hard labor and careful plant choices, but this rain garden was well worth the effort, and I must add it's required barely any work since its early days. Happy birthday, rain garden!


Rose said...

Thanks for the tips on the sedges. There's nothing like experienced advice from other gardeners to help in plant selection. Rain gardens are something I'd really like to learn more about, but the topic seems to get pushed down to the bottom of my priority list these days. I'm wondering, do you have a basement? I can't plant anything right next to the house because we have some drainage issues, and with a finished basement, I don't want any problems there. I was thinking about putting in a rain garden further away from the house, though.

Mr. McGregor's Daughter said...

Congratulations on the raingarden's birthday. It's coming along nicely. I'm still toying with the idea of a raingarden for the area where the rainbarrel overflow gets dumped. It's not surprising the Pennsylvania sedge doesn't like being in a raingarden - it's thriving in my extremely well-drained soil.

rambleonrose said...

Rose--The typical wisdom is that rain gardens should be 10 feet from your house. My house is on a slab, and I tested this location to make sure the drainage was adequate before digging the whole thing. If I had a finished basement like you, I would not have it so close to the house. But if you've got a little swale or low spot farther out in the yard, you're good to go!

MMD--Yeah, the Penn sedge was a misstep, but I figure one plant mistake is a pretty good percentage so far!

Commonweeder said...

I'm glad you explained why your rain garden is so close to the house. I attended a workshop on rain gardens and was fascinated to find out how much run off they can handle, and how important that is to municipal rain management. Some towns in Massachusetts have programs to set up rain gardens for this purpose. Great post about an important topic.

garden girl said...

It's looking great Rose. Well done!

I'm gradually planting the swale in our wayback yard. It's large, and there's plenty of room for some shrubs - so far, winterberry hollies, pussywillows, and redtwig dogwood. Planting a rain garden or bioswale is such a rewarding learning experience, and another good way we can do our part protecting the environment. Kudos!

Gail said...

Your rain garden is looking fantastic~I love sedges~C&S is blessed with native ones popping up here and there~I like even the weedier looking ones. gail

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