Harvesting Rain: Rain Gardens and Vegetated Swales

Rain garden in Mother Nature's Backyard

Your home roof is likely the largest impervious surface in your garden.   Last month (February 2013) we talked about gutters, downspouts and rain chains which can be used to collect and direct roof water.  This month and next we consider methods for infiltrating the water from impervious surfaces into the ground.

 

Why infiltrate rainwater?    Rainwater is clean, free water. As our planet heats up, methods to capture and use rainwater become increasingly important.  Some of the benefits of keeping rainwater in your own garden include:

1. Saving money – rain water is free water
2. Conserving a valuable and increasingly scarce resource – water
3. Helping replenish the ground water
4. Providing habitat for insects and birds
5. Providing a place to plant interesting stream and pond-side plants
6. Teaching children the values of conservation and water-wise gardening
7. Deep watering your garden’s trees and shrubs (in winter/spring in our area)

 

One simple but effective infiltration tool is the rain garden or vegetated swale.  Rain gardens/swales capture water that would otherwise run into the storm drains - and allow it to percolate into the ground.   They make sense for many home gardens and are becoming increasingly popular throughout the world.

What is a rain garden?  A rain garden is a small garden where runoff from impervious surfaces (roof, driveway, patio, walkway) is directed. Rain gardens are like leaky ponds – they hold rainwater just long enough for it to soak into the soil.     Because they only have standing water right after a rainstorm, you don’t have to worry about mosquitoes and other problems associated with standing water.  Rain gardens are often planted with wetland plants that help hold the soil and make the garden beautiful and life-friendly.

 

What do rain gardens look like?  

 

 

Almost all rain gardens have these common features:

 

• An intake area (often a downspout, pipe, channel, etc.)
• A shallow depression (like a shallow pond) to hold water briefly
• A layer of gravel or rocks to help the water to soak in
• Wetland plants that take occasional flooding & hold the soil
• May have: an infiltrator device - to help water soak in faster

 

Rain gardens can be any shape – from round like a pond to linear like a dry stream bed (these are called vegetated swales).   The size of the rain garden is based on the amount of water that needs to soak in.  The shape depends on your needs and tastes – and the available area.

Rain garden designs often have a regional ‘look’.  For example, rain gardens in places with summer rain (for example, Pennsylvania) are often kidney-shaped flower gardens located in low areas of the lawn.  But there’s no reason that all rain gardens need follow this design.  In summer-dry regions like Southern California, rain gardens can be completely dry from late April through October.  In these regions, a rain garden can serve a dual-purpose - functioning as a water infiltrator in winter and something else during the dry season. 

A little creativity can suggest ways to make your home rain garden meet your needs and tastes.  Here are just a few ideas of what a Southern California rain garden might look like:

• An unmowed ‘lawn’ in a slight depression
• A concrete planter featuring plants that can survive winter flooding
• A summer pathway with gravel and pavers
• A summer seating area, often featuring pavers or stone slabs set in gravel
• A ‘dry creek bed’ planted local native streamside plants
• A Japanese (Zen Garden) or Mediterranean style gravel garden (maintained as a formal gravel garden during the dry season)

 

As rain gardens become more common, landscape architects and homeowners alike are developing more creative and functional designs.   We suggest you search the internet for designs that inspire and work well with your lifestyle, climate and garden.

Does my rain garden need to be planted?  No, in fact some very successful rain gardens contain no plants at all.  However, there are several good reasons to select a planted rain garden.  First, the plants serve as habitat for birds, butterflies and other insects.  They may even provide food for your family.  So, a planted rain garden is usually more life-friendly than one with no plants.

A second reason to plant your rain garden is that it will be cooler.  In our climate, planted areas play an important role in keeping gardens cooler during the hot, dry summer.  If you live in a mediterranean climate, this can be an important advantage.

 

Another reason to include plants in a rain garden is that their roots help rainwater infiltrate more quickly.  Roots help keep the soil texture open, allowing water to infiltrate better.  This is obviously an advantage in a rain garden.

 

Finally, a rain garden provides the ideal place to grow plants that like a little extra  water.  These include some wonderful native pond-side and stream bank plants.  Planting a rain garden with these plants – and using rainwater to water them during the rainy season – allows you to enjoy these beautiful plants.

 

Building a Rain Garden

 

Check your soil drainage to determine if your soil is suitable.   Dig a 1x1 foot hole and fill it with water.  Let the water drain out completely.  Fill the hole again and check after 1 hour.  If the water drains at least 1-2 inches per hour your soil is suitable for a rain garden.

Choosing a location is key to designing a successful rain garden.  The location should either be near the impervious surface(s) it drains or in a place where water can be easily diverted to it.   Ideally, a rain garden that infiltrates water from a large surface (such as a roof) should be at least 8-10 ft. rom any structures or utility lines and 3 ft. rom sidewalks and walkways.  Rain gardens that drain patios or walkways are usually located fairly close to the surface they drain – usually 1-2 feet away.   In Mother Nature’s Backyard, the water from half of our small roof runs down our rain chain, into an infiltration pot and then directly into our rain garden. Ideally, the rain garden would be located a bit further from the structure.  However, the small amount of drainage area, coupled with the depth of our rain garden, made our location feasible.

 

Rainwater from the north half of the roof flows down the
 rain chain into a  large pot and then into the rain garden

 

 

Determining the size and depth of the rain garden is fairly easy. First you need to determine how much rain falls per hour during a good rainstorm.  Then you convert this amount to cubic feet.  In our area of Southern California, we rarely get sustained rainfall that exceeds ¾ inch per hour.  Therefore a rain garden in our area should be able to contain at least 3/4 inch (.0625 cubic ft.) of rain that falls on the impervious drainage surface. This is probably the least amount of rain fall you should plan for – even in the desert, a rainstorm can drop an inch or more of rain in an hour.   

If you live in an area with heavier rainfall, you’ll need to increase your estimate accordingly: 1 inch per hour = 0.083 cubic feet; 1.25 inches = 0.104 cubic feet; 1.5 inches = 0.125 cubic feet; 1.75 inches = 0.146 cubic feet.    To convert any rainfall per hour to cubic feet simply multiply the rainfall amount by 144 and divide this number by 1728. 

 

Next determine the area of the impervious drainage surface by multiplying the length of the surface times its width.  For example, a 20 by 30 ft. roof has an area of 600 square feet.  Multiply this by the cubic feet of rainfall (0.0625 in our area) to get the total cubic feet of water from the drainage area (600 x 0.0625=37.5 cubic feet).    This is the amount of water your rain garden will need to contain before it infiltrates into the ground.

Most home rain gardens are 1-3 feet deep (with most of the depth filled with gravel or dirt – see below).  Decide on a depth and divide the cubic feet of water (37.5 cubic feet) by the depth (2 feet) to get the surface area of your rain garden (37.5 / 2 ft. = 18.75 square feet).   In this example, an oblong rain garden that is 3 ft. wide by 6 ½ feet long and 2 feet deep will do the trick.   It’s prudent to make your rain garden a little larger than the calculated size and to also plan an overflow area in case of heavy rainfall.  Mother Nature is full of surprises these days!

 

 

 

The shape of the rain garden may be dictated by the site or designed by you.  Gardeners often find that rounded shapes are most pleasing; but the design depends on your needs and the design of your home and garden.  You can easily lay out the basic shape for your rain garden using a garden hose.  As long as the size is adequate, the shape of the rain garden is up to you.   Our rain garden is oblong with rounded edges and a dry-stone wall on the walkway side to provide stability and a decorative appearance.

  

 

Digging the rain garden can usually be done with a shovel and a little effort.  We had a little mechanical help, but did much of the digging with picks and shovels – even in our heavy, debris-filled soil. The excavated area should have gently sloping edges.   Pile the excavated soil around the edges to create a small berm around the rain garden.    You can see our fully excavated rain garden above.  Because our area in Mother Nature’s Backyard is limited, our rain garden is fairly deep - about 3 ½ feet at its deepest point.  Because the rain garden is filled with gravel and a layer soil, only the only the top part is visible (see photo below).

 

Rain garden is filled with gravel and smooth.  Next a 6 inch layer
of soil was placed over the gravel layer.

 

 

Fill the bottom of the rain garden with at least 6-12 inches of gravel. This will help the water to infiltrate better.   If your rain garden is deeper than 2 feet you can use more gravel.   The surface of the gravel layer should be at least 8-10 inches below the level of the surrounding soil.  Rake the gravel to make it level.

Cover the gravel with 4-6 inches of garden soil (use the excavated soil).  This will be sufficient for the bottom plants, many of which will grow through the gravel layer and into the soil beneath the rain garden.

Smooth/compact the berm to create gently sloping edges.

Plant the rain garden with appropriate plants (see below).

Mulch around the plants with an appropriate mulch.  Depending on the plants, this may be an organic or inorganic mulch (see our July 2012 posting on ‘Garden Mulches’).   In Mother Nature’s Backyard we used chunks of sandstone left over from the stone pathways to create a color-coordinated inorganic mulch at the bottom of the rain garden.  The plants on the berm are lightly mulched with wood chips until they grow to cover the area.

 

Choosing Plants for Rain Gardens

 If you live in Southern California,  we suggest choosing California native plants for their beauty, life-friendliness and suitability. Otherwise, consider using plants native to your own local area.   You will need to choose two types of plants:

Plants for the bottom of the rain garden.  These plants will be briefly flooded after a rainstorm and the ground will be seasonally moist.   You need to choose plants that normally grow along streams or around ponds and lakes (riparian plants).  These plants are often short (1-3 feet) and grass-like.  Some typical examples are rushes, spike rushes, and some annuals and perennials like annual Monkeyflowers (Mimulus) and even Miner’s Lettuce (see February 2013 Plant  of the Month).

Plants for the upper sides and berm.  These are plants that like damp soil in winter and spring. This area will likely be too damp for the most water-wise local plants (like local native Salvias), particularly if your soil drains slowly.  However, there are many lovely plants to choose from.  These range in size from grasses and sedges to large shrubs and even trees. 

A list of California native plants appropriate for the bottom and sides of rain gardens is available at: http://www.slideshare.net/cvadheim/south-bay-native-plants-rain-gardens-swales-213

A talk on rain gardens & vegetated swales (complete with discussion of some appropriate plants: http://www.slideshare.net/cvadheim/infiltration-gardens-2015

  

Additional Resources on Rain Gardens

http://raingardens.spawnusa.org/rainwater-harvesting-principles.html

Brad Lancaster's Rainwater Harvesting for Drylands and Beyond, Volumes 1 & 2

http://www-csgc.ucsd.edu/BOOKSTORE/Resources/GS3%20Rain%20Gardens_8-10-09.pdf

LA Rain Gardens - http://www.laraingardens.org/  

http://www.landscapedesignerlosangeles.com/Rain_Gardens_and_Bio-Retention.html

 

You can also e-mail your Water Zone questions to: mothernaturesbackyard10@gmail.com 

 

 

 

 

California Gourmet: Recipes for Native Greens

Last month (February 2013) we talked about California native plants that can be eaten as raw or cooked greens.  We covered some general topics like growing and harvesting native greens; and we also provided a list of California native greens plants.  If you haven’t read that post yet, you might want to start there.

Each type of wild greens has a unique flavor that’s difficult to describe. You’ll probably love some and not care for others.  So assess the flavor each time you use a new species.  If the greens can be eaten raw, taste a little sample (see the Native Greens List referenced in February 2013). If you like the taste, then include them in salads, tacos, sandwiches or any other situation where you regularly use lettuce or raw spinach.  Miner’s Lettuce is a mild greens plant that most people like uncooked (see Plant of the Month, February 2013).

We also suggest that you taste test new cooked greens before you include them in a recipe.  Steam a few leaves in the microwave or on the stove and try them.  The taste for greens is truly individual; some of us like/use greens that are stronger flavored while others prefer the mild types. 

If the flavor is too strong or bitter, you might want to try boiling a few leaves, changing the water and then boiling again.  This usually makes the greens milder tasting; some of the flavor chemicals leach out and others are changed with boiling.

Cooking with wild greens is fairly straightforward.  On the other hand, the unique flavors of California native greens inspire the creative cook in all of us.  We’ve provided some favorite recipes below to get you started.  But you can substitute wild greens in most recipes calling for spinach, kale, chard or wild greens.  Many traditional regional recipes include native greens.   So try our native varieties in any favorite greens dish.

We suggest you used the milder tasting greens (like Miner’s Lettuce, Island Mallow (Lavatera) and young Atriplex (Quailbush and other) in recipes calling for spinach.  Other mild greens include Mimulus species, Sidalcea, Camissonia species and Oenothera elata.  Note that young greens are almost always milder than older greens.  Substitute more piquant greens in recipes calling for kale, chard or wild greens. 

 

Basic Recipes

These are basic recipes for preparing any type of greens.  The cooking times will vary depending on the type of greens; you’ll have to keep testing for tenderness until you become experienced with an individual type of greens.  

Many cooks like to add ingredients to flavor or season the greens.  Some typical additions include sautéed garlic or onions, mushrooms or peppers; lemon juice, vinegar or a favorite bottled sauce; salt, pepper and other spices; toppers like nuts, sesame seeds, shredded cheese, etc. 

 

Sautéed Native Greens
1 ½ lbs (4-5 C.) native greens 3 Tbsp olive oil (or other oil if preferred) ½ cup water Vinegar, lemon juice, hot pepper sauce, salt & pepper to taste (optional)
Wash greens, remove tough stems and cut into 1-2 inch pieces.  Heat oil in large, heavy saucepan.  Add greens and cook for 1 minute.  Add water and increase heat to medium high.  Cover and cook for 5 minutes.   Decrease heat to medium, remove cover, stir and cook until liquid has evaporated.  Season to taste and eat as a side dish or vegetable.                                                                         Serves 4   Note: if desired, you can sauté 2 cloves of garlic or ½ cup chopped green onions in the oil before adding the greens.

 

Steamed Native Greens – Stovetop or Steamer
1 ½ lbs native greens Water to fill steamer/pot to just below the steaming basket (or according           to steamer instructions) Seasonings (optional): salt, pepper, lemon juice, vinegar, etc.
Wash greens, remove tough stems and cut into 1-2 inch pieces.   Cover bottom of steamer pot with enough water to nearly touch the steamer basket.  Use a large lidded pot fitted with a metal colander or folding steamer basket if you don’t have a steamer pot.  Some cooks put the steamer basket into the pot before heating the water.   Cover pot and heat water to boiling.  Turn down heat.   Place greens in steamer basket/colander, then place steamer basket into the pot (or place greens into steamer if it’s already in the pot).  Cover pot.   The lid should fit loosely or be positioned to allow steam to escape.  Steam the greens until they are tender – usually 2-6 minutes.  Remove from heat, season to taste and serve.                       Serves 4

 

Steamed Native Greens - Microwave
1 ½ lbs native greens 1-2 Tbsp water (or according to microwave cookbook instructions) Seasonings (optional): salt, pepper, lemon juice, vinegar, etc.
Wash greens, remove tough stems and cut into 1-2 inch pieces.    Place greens and water (if needed) in a large, microwave-safe dish or bowl.  Cover.  Microwave on high until greens are tender (to taste) – usually 2-6 minutes.   Season to taste and serve.                                                                                                 Serves 4

 

Boiled Native Greens
1 ½ lb native greens Water to cover Seasonings (optional): salt, pepper, lemon juice, vinegar, etc.
Wash greens, remove tough stems (if any) and cut into 1-2 inch pieces.  Bring water to boil in a large pot.  Add greens and cook until tender – 5-20 minutes depending on the greens and how tender you like them.  If the greens are too tangy for your taste, boil for 5 minutes, drain off the water and replace with fresh water.  Then continue boiling until tender.   Drain, pressing out any excess water.  Toss with favorite seasonings.  Eat warm.                                             Serves 4

 

Frozen Native Greens (for use later)
Fresh native greens, any amount Water for steaming
Wash greens, remove thick/coarse stems and cut into 1-2 inch pieces.   Steam over boil water or in the microwave for 2-3 minutes.   Greens should be wilted but not yet soft.  Remove from heat.  Plunge greens immediately into very cold (ice) water.   Remove from water when cooled, blot dry and freeze as you would any vegetable.  To use, thaw then sauté, steam or boil until fully cooked.  The cooking time will be shorter than for fresh greens.

 

Other Recipes Using Native Greens

Native cooked greens can be used in so many ways.  Here are a few recipes to get you started. 

 

Frittata with Wild Greens
1 ½ lbs wild greens, prepared by steaming, sautéing or boiling 4 eggs 2-3 Tbsp olive oil (or other oil) Salt, pepper, other seasonings to taste
Wash greens, remove tough stems (if any) and cut into 1-2 inch pieces.   Prepare green using method of choice.  Cool the greens and slice them again to make small pieces.  In a bowl whisk the eggs and seasonings.  Stir in the prepared greens.  Heat oil in frying pan.   Pour in the egg/greens mixture and cook over low heat (pan may be covered to help eggs to cook).      When first side is golden brown, loosen the frittata, then invert frying pan over a plate.  Slide the frittata back into frying pan to cook the second side.  Carefully slide the finished frittata onto a plate and serve – hot or warm.

 

Sautéed Greens with Nuts and Raisins
¼ cup pine nuts (or slivered almonds) 2 Tbsp olive oil 2-4 cloves garlic (to taste) ¼ cups raisins or dried currants 1 lb native greens ½ to 1 tsp red pepper flakes (optional) ½ cup dry white wine or water Salt & pepper to taste
Wash greens.  Remove any tough stems and chop.  Heat a large, heavy pot or sauté pan on medium heat.  Add nuts and brown them for several minutes, stirring often.   Remove nuts from pan and set aside.  Add oil and garlic – sauté for 30 seconds.  Add prepared nuts, raisins and greens and mix well.  Sauté, stirring often until greens begin to wilt – several minutes.  Add wine/water and red pepper (if desired).  Stir well, then continue cooking until liquid boils away.  Remove from heat, season and eat.                                                                          Serves 2-3

 

Sweet and Sour Wilted Greens
½ sweet onion, sliced (or ½ cup green onions, sliced) 1 Tbsp oil (olive or other) 1 ½ lb native greens (tangy greens work well) 1/2 cup water 3 Tbsp balsamic vinegar 2 Tbsp honey 1 tsp fresh ground ginger 4 Tbsp melted butter or margarine Salt, pepper to taste
Wash greens.  Remove tough stems (if any) and chop.  Heat oil in large, heavy pot.  Add onions and cook until softened – 4-5 minutes.  Add greens, and cook until slightly wilted.  Stir often so it doesn’t burn.  Add water and cook until greens are tender – about 5-7 minutes.  Drain.    Prepare dressing by whisking together vinegar, honey, ginger and butter/ margarine.    Add dressing to greens and toss well.  Season to taste.  Serve warm as a side dish or vegetable.                                                                 Serves 4-6   Note: tangy/piquant greens work well in this recipe

 

Wild Greens Corn Fritters
1 2/3 cups flour 1/3 cup polenta meal (or corn meal/masa) 1/4 cup milk 1 egg, beaten 8 ounces mixed leaf greens 2 cloves garlic, minced 3 tbsp fresh herbs such as parsley, mint, and chives Salt & freshly ground pepper 3-6 tbsp olive oil
Wash greens.  Remove large, tough stems and chop into small/medium pieces.  Mix the flour, polenta, milk and egg together in large bowl. Cover it and let it rest for 30 minutes.  Cook greens and garlic in boiling water for about 10 minutes until tender.  Remove from heat and plunge greens into cold water to blanch.   Pat greens dry and add to flour mixture.   Add salt and pepper to taste.    Form mixture into rounded fritters about ¾ inch thick.  Heat olive oil in frying pan over medium heat.  Cook the fritters until golden brown – about 5 minutes per side.  You may want to cover the frying pan to insure that fritter cook through.   Serve warm as a snack, appetizer or side dish.  Nice dipped in plain yoghurt.

 

Wild Greens Fritters
1 pound fresh wild greens 1 tablespoon butter 1 tablespoon olive oil (not extra-virgin) plus more for frying the fritters 1 medium shallot, chopped 1/4–1/2 cup of fresh mixed herbs, (parsley, thyme,  sage, chives, etc) 2 large eggs 1/4 cup all-purpose flour 1/2 teaspoon freshly grated or ground nutmeg 3 heaping tablespoons grated parmesan cheese Salt and freshly ground pepper to taste
Wash greens.  Remove large, tough stems and chop into small/medium pieces.  Let drain in a colander.  Heat the butter and 1 tablespoon of olive oil in a large heavy skillet over medium heat; add the chopped shallot. Sauté the shallot gently, stirring until it starts to turn translucent. Shake most of the water off the greens and add to the pan, using tongs to turn it as it wilts and cooks (about 2-4 minutes). Season the spinach with a pinch of salt.  Transfer to bowl to cool. Chop fresh herbs and set aside.  Whisk the eggs lightly in a medium  to break them up, then whisk in the flour, nutmeg, cheese and salt and pepper to taste. Mix in the herbs.   Chop the cooked greens into small pieces.  Add to batter mixture and mix well. Pour olive oil into frying pan to just cover bottom.  Heat until hot.  Carefully drop Tablespoonfuls of batter into hot oil.  You can fry 4-5 at a time.   Flatten each fritter slightly with back of spoon.  Fry fritters, turning with a spatula, until golden brown on both sides.  Drain on paper towels.  Serve hot or at room temperature.  May be reheated in oven.                                                                   Makes 8-10 fritters

 

Easy Torta Rustica with Wild Greens Filling
12 oz mild or tangy young wild greens (Atriplex – Saltbush – works nicely) Several sprigs of fresh herbs (if using native Salvia or Sagebrush (Artemisia)                                           remove the sprigs after you sauté the greens) 2 Tbsp olive oil ½ cup water Salt, pepper to taste (no salt needed with Atriplex) Biscuit mix – enough to make 10-12 biscuits
Wash greens.  Remove any tough stems and chop.  Heat olive oil in a large, heavy pot or sauté pan on medium heat.   Add greens and sauté for 2-3 minutes until greens are wilted.  Add water and fresh herbs.  Cover and simmer on medium heat for 5 minutes.  Remove cover, remove Salvia and Artemisia sprigs (if used) and continue to stir until water has steamed off.  Remove from heat.    Prepare your favorite biscuit mix (or use refrigerated biscuits).  Grease a 10-12 inch pie pan.  Line the bottom with 1/3 inch layer of biscuit mix – press with fingers to form an even layer.   Pat greens dry and spread evenly over the biscuit mix.   Roll out the top layer of biscuit mix to fit the top of the pie pan.  Gentle place over the greens.    Bake at 350° F for about 12-15 minutes – until top is golden.   Let cool 5-10 minutes, slice into wedges.   Eat warm or cold – tasty either way.

 

Cheese and Greens Bake
12 oz fresh or frozen wild greens, prepared ½ cup shredded cheese 4 beaten eggs 1/3 cup milk ½ cup all-purpose flour ½ tsp. baking powder Salt (if desired)
Wash greens.  Remove tough stems and chop into 1 inch pieces.   Prepare greens by sautéing, steaming or boiling.  If greens are very tangy we suggest you boil them in several changes of water until they suit your taste.   Cool the greens and blot dry.   Grease a 10 x 6 x 2 inch baking dish (or larger for thinner slices – up to 9 x 13 x 2 inch).  Combine eggs and milk.  Beat in flour, baking powder and salt.  Whisk until smooth.  Stir in greens and shredded cheese.  Pour into greased pan, spread evenly.  Bake at 350° F until golden brown – 25-30 minutes.   Slice and serve.     Makes a nice side dish or appetizer.

 

Wild Greens Pesto
3 cups (packed) fresh wild greens leaves 3-4 cloves garlic 1/3 cup olive oil 1/3 cup grated parmesan cheese 1/3 cup pinenuts (optional) ¾ tsp salt
Wash greens and remove tough stems.  Place all ingredients in a blender or food processor.  Process on high until it resembles a smooth paste.   Taste and add more salt to taste (if needed).  Place in a covered container and let sit for 2-3 hours to let the flavors age.  Use within a week in any dish calling for pesto.  Can be frozen for later use (freeze in an ice-cube tray to get serving-sized portions).

 

Wild Greens Party Dip
12 oz wild greens, prepared 1 cup mayonnaise 1 cup sour cream (light/low fat is fine) 1 package dried vegetable/onion soup mix
Wash greens.  Remove tough stems and chop into 1 inch pieces.   Prepare greens by sautéing, steaming or boiling.  If greens are very tangy we suggest you boil them in several changes of water until they suit your taste.   Cool the greens and blot dry.   Whisk together mayonnaise, sour cream and soup mix.  Add cooled greens and mix well.  Chill overnight in the refrigerator.   Serve as a dip with raw vegetables, bread chunks, chips etc.