Rain Gardens II: Back to the Future

When designing a forest garden, you have to think big.

I'm not just talking big in terms of big space: small spaces can have big yields, big beauty, and big health benefits for all creatures involved just as easily as sprawling acreages can.

I'm talking big trees. That cute little sapling you want to plant could grow into a 30 foot wide behemoth that takes over your entire yard.

When you design a permaculture garden with trees in it (ie, a forest garden), you have to plan the future before you plan the plants that you want to plant now. If you see what I mean.

In my observations of the natural forests near my house, I've come to notice a few useful things to consider while planning a future forest, and trying to understand what actions need to be taken now in order for that forest to become a reality in a few years. There are lots of pieces to this puzzle, but for now, I want to talk about water.

Trees need water! Usually, they need a fair amount of it!

In my last post, I talked about possible designs for maximizing natural irrigation in your garden by including a rain garden in your design. A rain garden won't just help things grow this year, though. It can be a vital part of your forest as it matures THROUGH TIME.

(cue sci-fi music)

Seriously though. If you start with a rain garden with the initial plantings of a forest around it, then everybody gets water and all is well. As the shrubs and trees of your garden grow and develop the architecture of a forest, they will overtake the rain garden from above in the form of shade, and from beneath with roots. Those roots will increase the soil's capacity for storing water, taking over the heft of the responsibility from the rain garden.

But the rain garden does not disappear!

Instead, it continues to maximize irrigation, and fosters little tiny microclimates within your growing forest garden for all sorts of other plants to grow.

Rain Gardens - The Way of the Future

I live in the Ghost watershed. Here on the Eastern slopes of the Rocky Mountains, spring melt and rain runoff trickle through the cracked stone, around giant mountains, and eventually meet with other springs and tributaries to form rivers. Those rivers provide the water for much of the rest of North America.

Sort of a big deal.

Oops.

Living in a watershed comes with responsibilities. This picture shows what can happen when those responsibilities are cast aside like so much used kleenex.

This road sits about 2 meters above the ranch pastures on either side of it. Those pastures were likely seasonal wetlands before. But now, they are tilled yearly to encourage the growth of hays and grasses for the cattle to eat. This prevents the growth of solid soil ecosystems, and also prevents the anti-erosion action of water loving bushes that would have flourished here otherwise. The cattle compact the soil, further reducing its water holding capacity. You can see the result.

Let's filter some water, baby!

To provide some contrast, here is a picture taken only a few days later in a natural, seasonal wetland, which is being enjoyed by one of my devastatingly beautiful dogs. During the summer, fall, and winter, this plateau on the slopes of the foothills does not have standing water.

But when the spring melts and rains come, this area is ready to deal with it. Notice the thriving water loving plants, the criss-cross of twigs and leaves under the waters' surface, and the standing, living trees in the photo's background.
Not only does this area support a thriving community of living things (you should hear the frogs and birds), it is able to hold and filter massive amounts of water, before releasing them into the river below.

You can bet your bippy that the moist forest below this wetland, between it and the river, relies for moisture in the dry summer months on the soils and plants that are storing it in this picture. Unlike the cow-poop rich runoff in the first picture, the water that filters through the wetland in the second picture will be clear and clean.

How can we imitate this wonderful, water-conscious strategy in our own gardens?

Easy!

It's called a rain garden. The idea is to create a low-lying patch of well-draining soil with many water-loving, probably native, and hopefully otherwise useful (ie medicinal, food for us, food for local insects, etc.) plants. Mulch around these plants with stones or pebbles for beauty, remembering that during heavy rains, the pebbles will be submersed. You could even get wild and install a rain-powered fountain or something crazy, or get creative with the kinds of things that you plant around your rain garden, inside your rain garden, down hill or up hill from your rain garden.

It's fun!

For example: Let's say you want to grow some dry-soil loving sea buckthorn, which has the added benefits of producing a highly nutritious fruit, being beautiful, attracting beneficial insects, naturally fertilizing your soil, and forming an impenetrable hedge to keep the dogs out of wherever you don't need any bones buried, thank you very much. Let's say you also want to grow some water lovers, and some plants that need frequent watering, but don't need to be up to their eyeballs in water.

Plan a curving line of sea buckthorns along the north side of your planting. Depending on the amount of sunlight and wind you get, you can plant those sea buckthorns with a deep curve, coming down the east and west sides of your planting, or a shallow curve. There are benefits to both: a deep curve keeps wind (and dogs) out, but can shade the plantings within the curve, while a shallow curve invites much more sunlight during morning and evening, and during marginal seasons. Allowing more sun into your planting has obvious benefits, but shade isn't a bad thing. There are lots of beautiful plants that would thrive in a partly shady environment, like ferns, bleeding hearts, and currants, just to name a few. See my posts on shade plants and shade polycultures for more ideas.

Next, plan your water garden to fit inside the sea buckthorn's curve, just south of it. It's probably smart to plan for a path between the north side of the water garden and the south side of the sea buckthorn hedge. Make sure that the water garden is lower than the sea buckthorns, in its own little depression. This works best if there is already a natural, south facing slope. If there isn't, don't worry: just dig for the water garden and use the excess soil to make a little hill for your sea buckthorns to stand on.

The final piece of the puzzle are the 'needs reliable water' plants. For me, that would be my "high production bed" of vegetables. It could also be shorter berry bushes that get thirsty easily but won't block the sun, or a flower garden that does best with good irrigation. Plan for these plants to sit down-hill of your water garden, which is itself downhill from your sea buckthorns, in its little depression. This bed should not be in a depression.

Here's how it works:

When it rains, water will run off of the sea buckthorns and into the rain garden, preventing the buckthorns from getting too much moisture. The flat depression of the rain garden will fill with water, making the pretty water plants happy. Your steady-irrigation garden of vegetables or flowers below it will get a good watering from the rain. Once the rain stops, the water caught in the rain garden will seep into the soil and downhill: watering your steady-irrigation vegetable/flower garden for days to come!

The exact shape(s) of your water-conscious planting can be limited only by your imagination. You could put a little island in the middle, or include a bridge that crosses it, or train your sea buckthorns to grow over it on trellises or arbors or even pergolas (such fancy words, those). You could surround it with an actual pond, making the rain garden a natural filtration system for your water feature. You could make IT into an actual pond, albeit quite a shallow one, though that would limit its use for irrigating things downhill from it. You could put lights underneath plants so that when it rains it looks real spooky. As for what to plant in the water garden, you now have the perfect excuse to go and find a wetland, and take note of the kinds of plants growing in it.

The options are literally endless!

I hope that this simple planting arrangement idea, hereafter referred to as "Kathryn's Brilliant Sea Buckthorn Water Garden Irrigation Extravaganza," has gotten your creative juices stirring.

Can't wait to install my own!