Garden Design

Seven steps to a weather-resilient garden

by cathym on July 3, 2020

by Judy Bigelow

Weather-resilient plants are those that can withstand extremes in weather and thrive long-term under these conditions. Whether you are planning a new garden or want to fortify an existing garden that is suffering from drought, flooding, unpredictable frosts, heat waves, or storm damage, the following guidelines should help improve the survival rate of your plants.

STEP ONE
Identify microclimates in your garden. Microclimates are localized areas that have their own temperature range, moisture level, and air circulation. They are created by southern (warmer) versus northern (colder) exposure, location in full sun or shade, water drainage and soil type, terrain and slopes, and proximity to water bodies, trees, and man-made structures such as buildings. There can be a wide range of different microclimates within your backyard. For example, you may notice that certain plants growing next to a fence or at the bottom of a slope often get damaged by late spring frosts or an early fall frost. This is called a frost pocket and is caused by cold air sinking downward and being trapped by the fence, creating a natural bowl effect. You might also notice that next to your house, which absorbs heat during the day and radiates heat at night, you can grow more tender plants. Urban areas with clustered buildings and dark pavement can act as heat islands. 

Take advantage of microclimates. This rosemary isn’t hardy in our area, but it survived last winter tucked into a protective nook.

STEP TWO
Keep a garden journal. Record your observations about the microclimates in your backyard and which areas seem most vulnerable to extreme weather conditions. At the same time, do a site assessment in which you determine how much sun the garden beds receive, what type of soil you have (sandy, loam, or clay) and its drainage, and the physical terrain. A sunny site will be warmer and dry out more quickly than a shaded one. Clay soil holds more moisture than sandy but has poorer drainage. Low-lying areas are usually wetter and have less air circulation than the top of a hill. Look for other factors, such as runoff of storm water from gutters and paved or hardscaped surfaces than can cause periodic flooding. Coastal areas may be more prone to damage caused by salt water and high winds. 

For an existing garden, be sure to also record which plants have performed the best over several years and which ones have not done well or have died. What are potential threats and current problems? Are the right plants in the right sites? Is a soil test needed?

STEP THREE
Make a plan. For a new garden, it’s a good idea to draw a sketch of the overall design with approximate dimensions and notations of any issues you’ve discovered during your site assessment. Do contact utility companies before you dig to avoid hitting underground lines. Plant selections should be appropriate not only for your USDA climate zone, but also for the microclimate and conditions of the site. To further ensure durability, plants should be low maintenance, reliable, and disease resistant. Many native plants possess these qualities and attract native species of pollinators and other beneficials. Biodiversity of plants, which means a wide variety of plant species, will increase the chance of success of the garden because of reduced risk of disease and pests and less competition for the same nutrients. Locally grown plants are generally best suited to your USDA climate zone and their transportation uses less fossil fuel. Before you buy a plant, find out if it’s aggressive and might take over the garden and examine it to make sure it’s healthy. 

To make improvements in an existing garden, decide what issues need to be addressed. If intermittent flooding is a problem, a simple fix might be to redirect downspouts. On steep slopes, a swale or ditch could be dug to channel water away. Chronically wet sites might benefit from the installation of French drains or conversion into rain gardens. Dry sites, whether sunny or heavily canopied by trees, require drought-tolerant plant selection and good mulching. Windy sites may need a windbreak and plants that are flexible and resist storm damage. Frost pockets often have temperatures lower than the regional USDA climate zone and should have cold-hardy plantings. Beds suffering from excessive summer heat can be partially shaded by plantings of trees and shrubs nearby. 

STEP FOUR
Prepare the site. For a new garden, the least labor-intensive method of dealing with turf is not to remove it, but to incorporate it into a soil building process. In the no-till or “lasagna” method, sheets of newspaper or cardboard are laid down over the lawn with successive layers of compost and biodegradable, undyed mulch. This method is most economical in not requiring the purchase of soil amendments because the topsoil is preserved and the grass gets converted into nutrients. Although sustainable, this method will take several months to fully break down the turf. Meanwhile, holes can be punched through the sheet layer and plants dug into place. For details, see the Oregon State University Extension Service website on sheet mulching.

In amending the conditions of an existing garden, regardless of the problems or soil type, compost is always a good solution. It improves soil structure and aeration, drainage of wet, clay soils, retention of moisture in dry, sandy soil, and moderation of soil temperature. In addition, compost enriches the soil with nutrients and microbes that produce a healthy growing medium for plants. When turning compost into the soil, minimize disturbance of soil layers and take care not to injure roots of established plants. 

STEP FIVE
Planting and mulching. Do your homework on the plants you have selected as to their mature size and tendency to spread. Allow sufficient space between them for growth and proper air circulation. Be aware of the path of the sun and how taller plants might shade shorter plants and the soil throughout the day. Once plants are arranged and in the ground, water well and then spread mulch over the entire bed, keeping it a few inches from the stems and trunks. Mulching not only inhibits weeds, but also reduces moisture loss from the soil. Dry sites are best covered with undyed wood mulch (black mulch absorbs heat and can increase local temperature), chopped leaf mulch, or other natural, sustainable mulches. Extra mulch, such as seedless straw, applied before winter can insulate the ground and help prevent freeze-thaw cycles in the soil that cause upheaval of shallow-rooted plants. In spring, remember to thin out the mulch so emerging plants aren’t smothered, and the soil can warm up.

All of the above applies to an existing garden bed that is undergoing renovation or reorganization. When moving plants to a more suitable location, try to time this when they are near dormancy, in early spring or fall. This will lessen the stress, especially if they are already struggling.

Proper mulching helps to suppress weeds.

STEP SIX
Maintenance and protection. Water management is essential, especially for new plants. To help them establish a robust root system, provide a minimum of one inch of water per week. Use a rain gauge, moisture sensor, or the “finger test” to determine when watering needs to be done. To decrease evaporation losses, water early in the morning and at ground level to thoroughly soak the soil surrounding the roots. This efficacious practice, as opposed to overhead sprinkling, conserves water and lowers your water bill. Rain barrels can collect excess rainwater runoff from gutters helping to prevent erosion and flooding in borders next to the house. On a dry day, this stored rain barrel water can be distributed via perforated soaker hoses laid around the garden. 

To enhance the resilience of the garden to extreme weather, additional measures may be taken. Row cover, made of a lightweight white material, can protect plants from either frost or excessive heat. It also has the feature of shielding vegetables from pests, such as flea beetles. Other strategies to prevent frost damage include cold frames, newspaper cones (around roses), and overturned pots to cover individual plants that are removed the next morning once the air has warmed. Shrubs that are susceptible to cold winter wind damage can be protected with burlap wraps, piles of conifer boughs (recycle your Christmas tree), or temporary windbreak barriers. Trees that are at risk of storm damage and breakage, particularly if they are close to a residence, should be correctly pruned.

Soaker hoses help with water management.

STEP SEVEN
Monitoring and evaluation. Throughout all four seasons of the year, continue to monitor the garden beds and make notes in your journal. Keep track of the conditions of the microclimates, as well as precipitation and extreme weather events, to see how the garden is holding up. Then make an evaluation. Are the plants vigorous and attractive in appearance? Is the garden flourishing and do some plants need to be divided? Were there any unexpected weather events and how did the plants fare? What other issues, such as weeds, pests, diseases, or poor soil, need to be attended in an ongoing manner? Have new problems arisen or does an old problem require a more proactive approach? 

Native plants, like this mildweed, are often sturdy and resiliant.

Gardening is always a work in progress and is further challenged by a changing climate. Keen observations of variable weather patterns and how they affect your garden microclimates will help you to modify your landscape or to adapt as necessary. Choosing sturdy, resilient plants over the finicky, short-lived exotics will save you money and frustration and is a key to success. By following these seven steps, you will be on your way to becoming a resilient gardener.

Judy Bigelow is a Master Gardener, CCE Monroe County.

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Native plants and pollinators

by cathym on May 11, 2020

by Lisa Ballantyne

Native plants are indigenous to a region. They have existed there for a very long time—have adapted perfectly to its conditions and support the local ecosystem, including important pollinators. 

Since the plants, animals and insects have co-existed for many, many years there is often a symbiotic nature. Certain plants attract certain insects. For instance, swamp milkweed, Asclepias incarnata, is a primary host plant for Monarch butterflies. Highbush blueberry is an excellent food source for mining bees, mason bees, and long-tongued bumble bees. 

Monarch caterpillar on swamp milkweed. Photo courtesy Liz Ballantyne

Interest in returning to having native plants in our yards and gardens has certainly been surging. Gardeners are looking for native trees, shrubs and perennials. Fortunately, the availability of these plants is beginning to grow with more and more choices available every year. 

As is well known, many of our native pollinators have been struggling to survive. Some believe that a lack of native plants plays a role. Much land has been cleared for housing, farming and other development. To counter this habitat loss, we are beginning to see farmers leaving wider hedgerows as an increase in pollinators means higher yields. We as homeowners and consumers can do our part by planting more native plants to support pollinators. Reducing or even eliminating lawn areas and replacing with natives can go a long way in providing food and habitat that has long been lacking. 

It is important for our native pollinators to have a food source from early spring to late fall. When adding new plants to your garden or yard try to be conscious of the need for early-, mid- and late-season flowering plants. 

EARLY BLOOMING Pussy willow. Photo courtesy Flickr: Bambe1964
MID-SEASON BLOOMING Spicebush swallowtail on wild bergamot. Photo courtesy Flickr: Candy & Kasey

Early blooming native plants include wild geranium (Geranium maculatum), pussy willow (Salix discolor), and raspberry (Rubus spp.). Mid-season natives would be plants such as wild bergamot (Monarda fistulosa), swamp milkweed (Asclepias incarnata) and American basswood (Tilia americana). Late season flowering native plants might be cardinal flower (Lobelia cardinalis), buttonbush (Cephalanthus occidentalis) and New England aster (Symphyotrichum novae-angliae). 

LATE BLOOMING New England aster. Photo by Jane Milliman

There is no question that the natural world is a complicated balance of plants, animals, insects and environmental factors such as weather. When one goes out of balance, so go the others. Often, we humans can unwittingly have a hand in throwing off that balance. Planting more native plants, can be our way of starting to put things right. 

Lisa Ballantyne is co-owner of Ballantyne Gardens in Liverpool, NY. She and husband Tim have a nursery and landscaping business that promotes organic gardening, gardening for wildlife, and native plantings. 

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by Michelle Sutton

Two good plants for the “high and dry” part of the rain garden or bioswale: goldenrod (Solidago ‘Fireworks’) and narrowleaf ironweed (Vernonia lettermannii ‘Iron Butterfly’). Photo by Michelle Sutton

MINI-GLOSSARY OF ESSENTIAL TERMS

Stormwater is the excess water from rain events and melting snow that doesn’t immediately infiltrate soil, but rather flows across the soil surface. Stormwater infrastructure is costly to municipalities, and haphazard stormwater runoff is harmful to ecosystems because of streambank erosion, excessive sedimentation, bacterial and fertilizer contamination of waterways, and more.   

Bioswales are strategically located trenches in the earth that are lined with porous materials and plants in order to slow stormwater runoff so that it can infiltrate and be cleaned by the soil. Bioswales and rain gardens are both constructed to slow water movement, but bioswales are designed to handle a specific amount of runoff from a large impervious surface, such as a roadway or parking lot. Plants in bioswales assist with stormwater infiltration and provide ecosystem services like wildlife habitat creation and urban heat island cooling. 

Rain gardens tend to be smaller than bioswales and are more commonly used for residential stormwater management. As defined by the Cornell Urban Horticulture Institute, rain gardens are “constructed vegetated depressions used to temporarily retain stormwater runoff from impervious surfaces during storm events typically of one inch or less. Using plants and distinct engineered substrates, pollutants are filtered and water infiltrates into the soil over a period of one to 2 days.” 

SMALL-SCALE STORMWATER MANAGEMENT
Jeanine “J” Fyfe is an education and design specialist at Rochester-based Broccolo Tree and Lawn Care. “Rain gardens are like all stormwater management systems,” she says. “Because they help keep our watersheds healthy, rain gardens benefit everyone.”

“Patience is needed for rain gardens, because the plants take time to establish,” Fyfe says. “While conventional drainage systems are about diverting water—and can sometimes divert water right over to the neighbor’s, creating more problems—rain gardens are about keeping water in place and allowing it to recharge the groundwater.” 

Fyfe explains how the rain garden system has to be set up properly and given time to flourish. For instance, natural fiber logs, like those filled with coir (coconut fiber) can be used to hold earth in place until plant roots are established. Shoreline and slope erosion can be controlled with natural fiber logs along with appropriate plants that hold the soil and help filter rainwater runoff.

As she does with all types of gardens, Fyfe looks at the rain garden through an ecosystem lens. Rain gardens are an opportunity to create habitat, attracting insects whose presence attracts frogs and birds. “A barren, wet area is just an invitation for mosquitos to breed, so plants are a must to house the creatures that will keep the ‘bad bugs’ in check,” Fyfe says. She prefers the use of native plants wherever possible, primarily because she regards them as the best food sources for local pollinators. She also steers clients clear of unwanted aggressive or potentially invasive plants.   

The first question Fyfe asks clients is, “In addition to stormwater management and beauty, what purpose(s) do you want your rain garden to fulfill?” This could include erosion control, privacy screening, and/or maximum wildlife appeal. Then she delves into site assessment: Is the site wet all the time, or just in spring? How dry does it get in summer? How much light does it get and during which parts of the day? What is the existing soil like, and how fast does infiltration currently occur? What other specific challenges exist? 

This assessment guides the selection of the appropriate soil amendments and plants to match the site. Starting with trees like maples (Acer spp.), willows (Salix spp.), and some oaks (Quercus spp.) that prefer moist areas, Fyfe’s selection trickles down to shrubs such as chokeberry (Aronia spp.), dogwoods (Cornus spp.), sumac (Rhus spp.) and summersweet (Clethra spp.), followed by perennials and ground covers like ferns, spiderwort (Tradescantia spp.), and lobelia (Lobelia spp.). “Grasses like tussock sedge (Carex stricta) look great massed together and can cover lots of territory, linking areas together to provide a natural, meadow-like appearance,” she says.

Plants on the upper slope or edge of rain gardens and bioswales must be drought tolerant. Photo by Michelle Sutton

• • •

One major plant selection consideration for rain gardens and bioswales is the differing microclimate in the bottom vs. the top of the system. Designers usually think in terms of the “low and moist” vs. the “high and dry” parts of the rain garden or bioswale. However, depending on the site, the whole rain garden might become quite dry in summer, which means that the plants chosen would have to tolerate both wet and dry conditions.   

If your rain garden will cover a larger area, consider incorporating woody plants. The Cornell Woody Shrubs for Stormwater Retention publication is a superb resource. As explained within: “While a wide variety of herbaceous plants such as soft rush (Juncus effusus), swamp milkweed (Asclepias incarnata), and Joe-pye weed (Eutrochium spp., formerly Eupatorium spp.) are often successfully used in these spaces, they can present maintenance issues because of the need to annually cut back dead foliage and stems. Utilizing woody plants decreases the need for additional seasonal maintenance while successfully adding aesthetic and functional vegetation to stormwater retention practices.” The publication includes dozens of research-tested suggestions for woody shrubs that can tolerate both wet and dry conditions.   

TIPS FOR A SUCCESSFUL RAIN GARDEN

• The slope of the land will determine the needed depth of the garden (see savetherain.us for the calculation).

• A two- to three-inch covering of well-aged shredded hardwood mulch helps with weed control and drainage and can give a more attractive look to the garden. Pine bark nuggets and other wood chips are not recommended because they will wash out more readily. 

• For the first few years of the rain garden, weed management is crucial until the desired plants are established and can shade out competitors.  

• At maturity, properly selected plants in the rain garden shouldn’t require supplemental water. However, mature plants may look better if watered during a drought.

• Snow can be “stored” in the rain garden so long as any woody vegetation isn’t overloaded to the point of breaking branches.  

• If the rain garden is near paved surfaces that get treated with deicing salt in winter, select salt-tolerant plants. 

KEY UPSTATE RESOURCES

Save the Rain
savetherain.us

H2O Hero Water Education Collaborative
H2Ohero.org

Rochester Museum and Science Center-Green Infrastructure
rmsc.org

The Cornell Botanic Gardens Bioswale in fall, 2012. Photo by Chris Kitchen Photography and Design (ckpad.co)
Interpretative signage for the bioswale. Photo by Michelle Sutton
Designer rendering of the bioswale.
A glimpse into the luxuriant center of the Cornell Botanic Gardens Bioswale in fall, 2018. Photo by Michelle Sutton
The Cornell Botanic Gardens Bioswale in late summer, 2012. Photo by Chris Kitchen Photography and Design (ckpad.co)

THE ULTIMATE BIOSWALE
Completed in 2010, the bioswale at Cornell Botanic Gardens is, like all things at this central New York public garden, horticulture at its highest level. The stunning bioswale was designed and engineered to slow and filter runoff from the adjacent Nevin Welcome Center parking lot. The plants in the bioswale are bound to be of interest to homeowners as they design their rain gardens.

  • Plants in the Cornell Botanic Gardens bioswale were chosen for strong root systems and the ability to withstand both wet and dry conditions. 
  • Most of the plants in the bioswale are native to the central New York region. Seven cultivars of native switchgrass (Panicum virgatum) are used, and about 68 different flowering perennials add color, pollinator value, and wildlife habitat. These perennials include showy goldenrods like Solidago ‘Fireworks’, narrowleaf ironweed (Vernonia lettermannii ‘Iron Butterfly’), and various cultivars of sneezeweed (Helenium spp.), coneflowers (Echinacea spp.), and false indigo (Baptisia spp.). 
  • The bioswale mitigates stormwater runoff to nearby Beebe Lake, protecting the lake from storm surges and erosion. 
  • To increase the rate of infiltration, the bioswale soil is a one-to-one-to-one ratio mix of coarse sand, screened loam, and Cornell compost. 
  • In a 2015 study, Cornell researchers Palmer and Powell found that the bioswale was reducing peak stormwater flow rates by 81% and reducing runoff by 31% (78,000 gallons annually). 
  • As water infiltrates through the bioswale, sediment and pollutants are filtered out. Soil and root microorganisms help break down harmful bacteria and trap heavy metals along with excessive nitrogen and phosphorus. The bioswale has been shown to remove 80% of the average annual total suspended solids (dry weight of suspended particles).

Michelle Sutton (michellejudysutton.com) is a horticulturist, writer, and editor living in New Paltz.

Special thank you to Ithaca-based Chris Kitchen for use of his Cornell Botanic Gardens Bioswale photos. Contact info: 

Chris Kitchen Photography and Design
facebook.com/ckpad
ckpad.co
(607) 280-9573 

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