Six on Saturday: Rain Gardens

Both Caladiums and most ferns appreciate moist soil and can survive for quite a while in saturated soil. Ferns planted in wide strips as ground cover can slow down and absorb run-off from summer storms.

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It’s still raining here.  It has been raining off and on for days, but mostly on.  We’re under a multi-day flood watch and a flash flood advisory.   A tropical storm inundated us not long ago and another formed off of our coast yesterday, and even heading out to sea it pulls historic rains behind as it moves away.

The ground is already saturated and every little plastic saucer under a ceramic container overflows.  I smile at the thought of how long it will be before I’ll need to water the garden again.  August usually is a wet month, and welcome after hot, dry stretches in July.  But the tropical storm season forecast for 2020 is unlike anything we’ve ever known before.  (That is our new catch phrase for 2020, isn’t it?  Unlike anything we’ve ever known before?)

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Scarlet cardinal flower, Lobelia cardinalis, is a classic rain garden plant. It thrives in moist soil but will survive short droughts, too.  This clump grows in the wetlands area of the Williamsburg Botanical Garden.

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We have a program in our county that helps homeowners install rain gardens.  A friend is known for her beautiful rain garden designs. When working with local government and the Master Gardeners, county residents can have significant portions of their costs reimbursed.

The idea is very simple and elegant:  Rain gardens are dug a few inches below grade to catch and hold run-off from heavy rains.  Water loving plants growing in the rain garden help soak up the run-off, even as it settles into the ground to replenish the water table, instead of running off into local waterways, and eventually the Chesapeake Bay.  Unlike ponds, they don’t hold standing water indefinitely.  Most absorb and process the run-off soon after a rain.

Rain gardens help catch pollutants that wash off of lawns and streets so those nutrients and chemicals can be recycled and trapped by vegetation.  This helps reduce the amount of pollution flowing into creeks, the rivers, and eventually the Chesapeake Bay.  They also provide habitat for small animals like turtles, toads, frogs, dragonflies and many types of birds.

Even when we don’t excavate and engineer a formal rain garden, there are things we can do to help slow the flow of water across our yards and capture a portion of that rain water before it flows into the local waterways.  We’ve built a number of terraces in the steepest part of our yard and planted them with plants to help slow the flow of rain water.  We also have several ‘borders’ of shrubs and other vegetation to break the flow of run-off and absorb it.

In fact, the slogan of our county Stormwater and Resource Protection Division is, “Plant More Plants.”   Plants buffer the falling rain, help protect the soil from erosion, slow run-off and absorb large quantities of water, returning it to the atmosphere.  Just planting trees, shrubs, ground covers and perennial borders helps to manage the abundant rain we are getting in recent years.

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Zantedeschia, or calla lily, thrives in moist soil.  Some species will grow in the edge of a pond, and these work very well in rain gardens or wet spots where run-off collects.

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But when the ground is as saturated as it is today, we worry that even some of our plants might drown!  You see, most plants’ roots want air pockets in the soil.  Saturated soil is a quick way to kill a houseplant, and it can cause damage to the roots of some trees, shrubs and perennials, too.

As our climate shifts and these rain soaked days grow more common, it helps to know which plants can take a few days of saturated soil, and maybe even benefit from the extra water in the soil.  Many of these plants process a great deal of water up through their roots and vascular systems to release it back into the air.

You have heard of the Blue Ridge Mountains in western Virginia?  Well, that blue haze comes from moisture released by the many trees and shrubs growing on the sides of the mountains.  Some trees thrive in constantly moist soil.  Try birches, willows, swamp dogwoods, white ash trees, and beautyberry bushes.

Plants release both water vapor and oxygen back into the air as a by-product of their life processes.  Some plants, like succulents, release very little water, and that mostly at night.  They will quickly die in saturated soil.  In our region they need to be planted higher than grade on ridges and mounds, or be grow in freely draining containers.

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Colocasia and some types of  Iris grow well in saturated soil or even standing water.   Abundant water allows for lush growth.

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Plants with very large leaves, like our Caladiums, Colocasias, Hibiscus, Alocasias, Calla lilies, Canna lilies, ginger lilies, and banana trees use large amounts of water and release water vapor from their leaves throughout the day.  Some types of Iris also perform very well in saturated soil.  They can live in drier soil, but do just fine planted in the edge of a pond or in a rain garden.  Ferns are always a classic choice for moist and shady areas of the garden.  Their fibrous roots help to hold the soil against erosion and perform well as ground cover on slopes.

Those of us living in coastal areas where flooding has become more frequent can use plants to help deal with the inches and inches of extra rain.  We can build ponds and rain gardens, or even French drains and rock lined dry gullies to channel the run-off away from our homes.

We are called on in these times to wake up, pay attention, and find creative and beautiful solutions to the challenges we face.  We are a resilient people, by taking every advantage, even in the choices of plants we make, we can adapt to our changing world.

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Iris ensata, Japanese Iris,  grow with Zantedeschia in the ‘wet’ end of the Iris border at the Williamsburg Botanical Garden. Clumps keep their foliage most of the year, blooming over a long season in late spring and early summer.  These are excellent rain garden and pond plants.

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Woodland Gnome 2020

 

Visit Illuminations, for a daily quotation and a photo of something beautiful.

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Soil Security

Saxifraga stolonifera, Strawberry Begonia

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Gardens offer endless surprises and seemingly endless challenges.  One hopes to discover most of the challenges in the first year or two.  Better to address them right off and be done with it, right?  But that’s not how this business works…. things change….

Ours is a very steep property.  Our bit of James City County spreads across ridges and ravines.  We happen to live and garden on the slope of a ravine.  Water drains down across the yard to a creek running through the ravine, which flows to a pond and then out to College Creek.   Managing all of that water during a heavy rain remains a challenge for us.

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This area suffers serious erosion in heavy rain, and is frequented by voles.  It is hard to get anything much to grow here.  We have just added the stones to offer some protection and planted a dozen seedling Hellebores to help hold the bank.

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Our county’s division of  storm water management staff advise:  “Plant more plants!”  I take that advice to heart, regularly, and have struck up a working relationship with one of the staffers.  They work with the local Master Gardeners to help homeowners design rain gardens to catch some of the run-off after a heavy rain, and offer grants for those who install them.

I like that proactive, cooperative approach.  This spring, I’ve done a bit of reading about how to construct a rain garden.  And one of the first things I realized is that steeply sloping land isn’t a very good place to site one, unless you are prepared for a major project of earth moving and engineering to construct a berm on the down slope side.

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This was our steep, eroding slope before our work began this spring.

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As I thought about rain gardens, and walked our property looking for a place to catch run off and use it in a new planting bed, my partner pointed out a new erosion problem on the very shaded and inaccessible slope beside and below our driveway.

This is an area we’ve largely neglected over the years.  Towering, mature Ligustrum shrubs cast deep shade across this slope.  Their leaves drop here year round, and the ground has been covered in a tangle of Vinca vines and wild growth.  Where there is bare earth, it has been covered with fallen leaves. I planted  some Mahonia and Hydrangea in this area when we first took over the garden, and they have expanded, but never bloomed.

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Daffodils have replaced Caladiums here at the base of our driveway, where a great deal of water runs off when it rains.  An Autumn fern has thrived here for five years or more, and I decided to expand the planting last summer.

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But last summer, I began clearing some of this strip, nearer to the drive, and planted it in Caladiums, Zantedeschia, Ajuga, Oxalis, some transplanted Liriope and a few ferns.  We enjoyed it enough that when we dug the Caladiums in October I planted Daffodils and Arum in their place.

Below this planted area, we noticed a new area of erosion a few weeks ago.  Storm water had found its way into a vole tunnel, and a whole piece of the bank had collapsed.  There was a gorge, partially filled with leaves and other debris.  Finding that bit of erosion sealed the deal that we would invest our time, energy, and gardening dollars in fixing this neglected, and now crumbling, bit of the garden.

Too steep for a single ‘rain garden,’ we decided to create several terraces to catch and slow the flow of water down the slope, directing the run-off from one planted area to another.  We found several Rhododendron shrubs to anchor each terrace, and planted the first right into that nasty gorge to stabilize it.  We found some sturdy trapezoidal concrete blocks for building the terraces.  They fit together snugly to make a secure wall.  We installed the first ones below that Rhododendron to hold it in place.

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The first Rhododendron we planted to stabilize a gorge caused by erosion over a vole tunnel. We planted in the hole and stabilized the area with two concrete blocks.

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We trimmed up the lowest Ligustrum branches to let in light and make the area more accessible and raked back the leaves and debris.  Then, we studied the area for several days to decide where to place our blocks to form natural terraces.

After building the terraces, and planting three more of the shrubs, I began filling each terrace with plants.   I selected a variety of perennials which will thrive in shade, tolerate a lot of moisture, hold and cover the soil by spreading, put down extensive root systems, and stop voles with their poisonous roots. Oh, and did I mention they also must repel deer?

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The terraces before today’s torrential rain.

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Remember our mantra:  “Plant more plants!”  It was going to take a lot of plants to fill these spaces.  Luckily, we have a pretty steady supply now of a few perennials which fill these criteria.  They are ours to dig, divide, and transplant as needed.

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Divisions of Strawberry Begonia transplanted from another part of our garden. Each division will send out numerous stems, with a tiny plant growing at the tip of each.  They will form a thick mat over time. 

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I was able to transplant Hellebore seedlings, Ajuga and Saxifraga stolonifera in nearly unlimited quantities from other parts of the garden.  The Hellebores have  poisonous roots, and so I planted them around each of the Rhododendrons to protect their roots from curious voles.  I also planted them below the lowest row of blocks to form an additional vegetative barrier for any run-off.

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This Rhododendron is ringed with seedling Hellebores.

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I purchased holly ferns, Japanese painted ferns and Autumn Brilliance fern.  Although the Japanese painted ferns aren’t evergreen, they spread wonderfully and give about 7 months of presence here.  I also purchased some little 2″ Columbine and Heuchera and a couple of quart sized Tiarella .

I prefer to buy the smallest pots of perennials I can find to  minimize the size of the holes we must dig.  Living on a slope, we dig as little as possible.

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Tiarella is a shade loving native perennial which runs and spreads over time. It blooms each spring, feeding hungry pollinators early in the season. It resembles Heuchera, but proves more deer resistant.

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Heuchera is the only perennial in our palette for this new bed which may be grazed from time to time.  I am willing to take the chance for its beautiful foliage.  The rest of these plants have already proven themselves in our garden and I have confidence in using them here.  They are tough and thrive in our climate and soil.

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Heuchera ‘Melting Fire’ and Athyrium niponicum ‘Pictum’ anchor the end of this terrace. I will add Caladiums next month when the weather is settled.

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And this was surprisingly good soil!  While we have clay in other parts of the garden, this was good, rich dirt.  Although I had stocked up on compost, I was able to build these beds without adding a great deal.

The key to planting on sloping ground is a good gravel mulch.  We’ve learned over the years to minimize digging, top dress and even out the ground with compost, and then mulch heavily with gravel. Finally, we pack this all down firmly with hands and feet.

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Columbine and Tiarella anchor this terrace. Two tiny lady ferns, grown from bare root starts, will one day flourish in this moist bed.

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We discovered that the first gardener on this property often used a large stone or hunk of concrete or brick to anchor shrubs he planted on slopes.  I’ve followed his lead and often anchor a newly planted shrub or perennial with something heavy to hold it in place until it establishes.

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Dryopteris erythrosora ‘Brilliance’ will eventually grow to three feet. This evergreen fern has interesting spring color on new growth. We have anchored it with stones as it sits at the top of the slope.

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We’ve been working on this new area over the past week or so.  We have been trying to fix the erosion ahead of the heavy weather forecast for this week.  The rains have shown us the weak spots, and where more work was required.  We had to go back and re-pack the area around the first Rhodie’s roots, for example.  And we also placed some stones above it to divert the flow of water around it from the slope above.

A front came through mid-day today, with torrential rain, about an hour after I finished the last of the planting and gravel mulch.  We were pleased that the terraces held.

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Additional erosion after today’s rain left roots exposed. It showed us additional engineering was needed where water pours off of the driveway.  The terra cotta pots helped anchor plastic bags to protect the Hydrangea on the right during freezing weather in March.  It is slowly recovering and finally pushing out new leaves.

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There were only a few spots of erosion, and only one Hellebore partially washed out on a terrace this time.  But the path along this slope was badly eroded.  Ligustrum roots were exposed where the path was washing away.

We studied the path the water took from driveway to ravine, noted where the gravel had washed out, and re-engineered parts of the project.  Translation: Back to Lowes for more concrete blocks, a few more bags of gravel and a bag of topsoil.

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Additional engineering should slow the run-off flowing into the path from heavy rain.  My partner placed the blocks to divert the water’s flow.  We’ve added topsoil and gravel over the Ligustrum’s exposed roots in the path.  Sadly, some daffies may be sacrificed in the process….

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We aren’t quite sure why the erosion on this bank suddenly got worse in the last year.  We must have made some small change in how the water flows, without even realizing it, when I planted the Caladiums last summer.  But whatever the cause, the problem was getting worse with each heavy rain.

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“Soil security”

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When you live on a slope, stable soil is a measure of security as heavy weather blows through.

We’ve created terraced beds throughout the garden, planted lots of shrubs and perennials, and dumped hundreds of bags of pea gravel on this property over the years.   We rarely visit our favorite garden center without adding a bag or two of gravel or compost to our order. It is an investment in holding the soil in place and keeping our home’s foundation stable.

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We trust that these new terraced beds, and the reinforced path we’ve created for water to flow down our sloping garden, will meet the challenge of heavy rain and the run-off it generates.  But more than that, we trust they will grow into beautiful additions which bring us many years of enjoyment.

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Woodland Gnome 2017

 

Note: I don’t often like to show parts of our garden that aren’t ‘beautiful.’   We have a lot of rough edges here in our Forest Garden.  It is a work in progress. I hope the techniques we use to hold the slope and garden on uneven land will help others trying to garden in similar circumstances.

I’ll show you this bed again as the plants grow in.  We trust that it will soon be one of our most beautiful areas, filled with photo-worthy foliage and flowers.  We expect it will attract the attention of our turtles, lizards and toads as the season progresses, too.  

For the Daily Post’s

Weekly Photo Challenge:  Security

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Columbine