Lecture: Steep Slope Gardening—A Case Study, October 20

Steep Slope Gardening: Diverse planting of conifers and perennials make inviting entryway.Gardening in the Mountains presents:
Steep Slope Gardening—A Case Study

Thursday, October 20, 2016
11:30 a.m. – 1 p.m.

NC Cooperative Extension
Buncombe County Center
49 Mount Carmel Road
Asheville, NC

Presenter: Beth Leonard, Extension Master Gardener Volunteer

A 50% slope is not for garden sissies, but with planning, perseverance, and technique, you can turn your steep hillside into a garden paradise. This case study follows a homeowner’s five-year transition from bare clay and weedy growth to green and luscious. See how she used both hardscape and plantings to create a welcoming entry along a conifer hillside, transform a meadow, and embrace the woodland. Follow her steps—define goals, analyze the site, choose the right plants, and manage maintenance.  Recognize how different areas of your property may require different approaches and learn handy techniques for working on steep slopes.

The talk is free but registration is requested by calling 828-255-5522.
You are invited to bring a brown bag lunch.

You’re Invited! Fall Open House, October 27.

Visit the new location for Buncombe County’s Soil & Water and Cooperative Extension. Enjoy chili and cornbread, activities, and meet the staff.

When:  Thursday, October 27, 2016
Time:  4 to 7 p.m.
Where:  49 Mount Carmel Road, Asheville, NC

Please RSVP before October 20 by calling 828-255-5522.

Open House, October 27, 2016

Fall Arrived on September 21. Get Ready to Plant!

Regardless of the thermometer reading, fall is in our future! With fall comes the best time for planting many woody—as well as herbaceous—perennial plants. Plus, nurseries often have fall sales to move their existing stock.

Keys to successful fall planting
If you find plants you like, you might think: “Where can I put this particular plant?” A better question is: “What plant best fits my landscape scheme for this spot?”

  • Before you buy have a site in mind.
  • Be sure that spot meets the desired plant’s requirements for sun, moisture, and nutrients.
  • Know how much space the plant needs and how quickly that plant will spread. Don’t bring home an invasive “Backyard Bully”!
  • How about the soil pH? A soil test will tell you if you need to lime or add any nutrients.

The results of a soil test may change your mind. Consider choosing plants that will match the site characteristics. 

Woody plants have additional needs
Trees—and even large shrubs—need special attention to their future size. Pruning may not be a viable answer to a tree that is shading too much of your homestead or threatening a power line, or a shrub that’s blocking a view. Consider how the planting will work in all four seasons. And think about how your placement will affect your neighbors, too. You can’t call in a moving company to cure a poor decision if your planting outgrows its space.

Are you prepared to do your own planting?
When looking at a woody plant you intend to plant yourself, consider the size, shape, and weight of the root ball. How is the root ball contained or restrained? You’ll need to remove that container or restrainer during the planting process, so be sure you have the appropriate tools. It is best to discard burlap or wire that may restrict future growth. 

Before you plant, examine the root ball. Are there broken or circling roots? Many horticulturalists recommend carefully washing off the planting medium to correct any root problems before planting. At a minimum, remove circling or broken roots and then score or cut through the root ball to encourage root growth. For more information about root systems of woody plants see: http://gardenprofessors.com/little-ball-of-horrors/  

Planting and irrigating
Backfill with the soil you removed when you dug the planting hole, and water as you fill. Tamp the soil gently; you don’t want to compact the soil, just put it in contact with the roots. Roots will continue to grow all fall and winter as long as the soil is not frozen at their level, so keep the root ball moist.

Finish by spreading mulch over the root ball. Not only will mulch retain moisture, but the mulch “blanket” helps maintain a stable temperature, so that a surge during a warm spell won’t cause the plant to prematurely break dormancy. But don’t mound mulch around tree trunks or shrub stems.

Pick a cool day and enjoy the exercise.

Article written Glenn Palmer, Extension Master Gardener Volunteer.

Gardening on Slopes: A Recap of Tips and Techniques

For the past few weeks, we’ve shared a series of blogs about gardening on slopes. Here’s a recap of the tips and techniques covered.

Before you plant

  • Spend a year looking out your windows before you ever put the first plant in the ground. What do you see—or would like to see? What problem areas need fixing?
  • Analyze your site, define your goals, and develop a plan.
  • Resolve stormwater runoff problems.
  • Tackle weeds now—and forever.
  • Install steps, paths, and hardscapes.
  • Do research to find the right plant for the right place. Be aware of the growth habits of different varieties within a plant species.

When you plant

  • Camouflage the slope so it’s not so overwhelming to look at. Do this by varying your plant heights, shapes, colors, and textures.
  • Create backdrops and focal points. These are places the eye stops and rests as you survey the garden. Use plants that act as visual markers of slope edges or entranceways to different parts of the garden.
  • Buy plants in small containers—one, two, and three-gallon sizes. They’re much easier to plant than large root balls, they establish themselves quicker, and they will soon catch up in size—and save you money in the process!
  • Slopes can be dry. A drip irrigation system is very effective and eliminates the need to drag heavy hoses up and down the hillside.
  • Reduce maintenance on slopes wherever you can. Fill in with ground covers and evergreen shrubs. Use reseeding flowers. Let your plants grow together and happily cohabitate.
Steep slope garden uses diverse plantings for visual interest, privacy, and erosion control.

Steep slope garden uses diverse plantings for visual interest, privacy, and erosion control.

While gardening on slopes can be challenging, those slopes need not intimidate you. With good gardening practices, you can create a beautiful and enjoyable steep slope garden paradise to enjoy for years to come.

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: It’s Never—Ever—Maintenance Free

Regular maintenance keeps slope gardens tidy and healthy.Minimal maintenance is an oft-stated and laudable goal when it comes to slopes. But know that there’s never a maintenance-free garden—except maybe Mother Nature’s forests! We maintain to help our plants grow and establish, and to keep our gardens tidy and healthy.

Initially, you’ll find yourself crawling around on your slopes to pull weeds and fertilize new plantings. But if you’re persistent, if you install a good base of mulch or groundcover, and once your plants become established, maintenance gets easier and easier each year. If you’ve selected the right trees and shrubs for the space, you should have to do very little pruning beyond developmental pruning the first couple of years. If you’ve planted or seeded annuals and perennials, you may need to clean up spent flower heads and stems at the end of the season. Ornamental grasses need to be cut back in late winter. If you have grassy paths, you’ll need to string-trim or mow. If your paths are mulch, gravel, or wood chips, you will need to periodically refresh them.

I grab a bucket and walk through my garden once a week, hand-pulling weeds when I see them. This way, they never get out of control. At the same time, I look over my shrubs for signs of disease or insects that need attention. My grassy paths get a string trimming once every three weeks during the growing season. I allow perennials and annuals—echinachea, poppy, heliopsis, coreopsis, and cosmos—to reseed themselves freely on my steep slopes. Then I spend one nice day in December or January removing the spent flower stems and cleaning up the bank. I estimate about four to eight hours a week of maintenance in my half-acre steep slope garden.

My biggest maintenance challenge is replenishing mulch every other year as it decays and enriches the soil. I use double-ground hardwood mulch that knits together and sticks nicely to the slope. Climbing the hills and spreading the mulch one bucketful at a time is not an easy task. But as my groundcovers and shrubs fill in, I need less mulch each year and even this task is becoming easier.

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: What about Irrigation?

Because steep slopes tend to be dry, plants may need irrigation, at least until they are well established. The most effective way to provide moisture on slopes is by drip irrigation, either with soaker hoses or perforated pipe. It’s easy for a gardener to install soaker hose, but you’ll probably want to hire a professional for an elaborate irrigation system with timed zones and buried pipe.

Soaker hoses
If you choose to use soaker hoses, run regular garden hoses from your house hose bib to the top of your hill. Then connect your soaker hose to the garden hose at the high point. Snake the soaker hose back and forth across the slope, but keep it continuously moving downhill. Circle the soaker hose a couple of times around trees and large shrubs. For large areas, you may need several downhill soaker hose runs. Toggle switches can be used to switch the water flow from one hose to another. Use metal pins to secure the hose to the slope and then bury it under mulch. A good covering of mulch—such as ground hardwood or pine fines—will reduce your irrigation requirements by helping to retain soil moisture and keep plant roots cool. 

How much to water?
The general rule for watering gardens is to apply one inch of water per week. It may take up to 1½ hours of continuous irrigation to distribute an inch of water through a soaker hose system. On slopes, it’s best to cycle the water flow on and off every 20 to 30 minutes. Water for 20 minutes, then let the water soak into the slope for 20 minutes, then water again for 20 minutes until you’ve applied the needed amount of water. On and off cycling reduces runoff down the slope and encourages more water to soak deeply into the soil.

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: Solve Problems with Plants

Sun. Shade. Wet. Dry. Tall. Short. Spreading. Contained. Don’t be intimidated by your steep slope. Start with your objective, identify any gardening problems you need to solve, and then select your plants. With thousands of plants to choose from, you’re bound to find the right ones for your space.

Diverse planting of conifers on slope

Diverse planting of conifers on slope.

Low maintenance, erosion control, and all-season interest—especially during winter months—are typical gardening goals on slopes. Our acidic soils and a sunny hillside make an ideal environment for conifers. Nurseries will present you with an almost unlimited variety of conifer shapes, sizes, and colors from which to choose—spruce, cypress (Chamaecyparis spp.), pine, hemlock, arborvitae, and juniper. Conifers require little—if any—pruning, and typically are disease and insect free, making them well-suited for low-maintenance hillsides. Just know the natural growth habit of the variety you select. Is the conifer you choose a tree, shrub, or groundcover? A Norway spruce (Picea abies) can grow into a 90-foot tall tree, while a dwarf globosa blue spruce (Picea pungens ‘Globosa’) will remain a compact shrub, only three to four feet tall. While the variety of junipers can be mind-boggling, there’s nothing better to cover and hold a dry, hot slope than a spreading juniper (Juniperus horizontalis). Just be sure you have enough space because some junipers like ‘Shore’ and ‘Blue rug’ will spread ten feet or more.

Nellie R. Stevens hollies

Nellie R. Stevens hollies hide retaining wall. Daylilies outline path and camouflage lower holly branches.

Hollies (Ilex spp.), like conifers, suit our WNC environment. They come in a vast variety of shapes, sizes, and colors. Some are evergreen; other are deciduous. ‘Nellie R. Stevens’ hollies are workhorses and provide outstanding privacy screens. There’s nothing prettier in the winter than the native winterberry holly (I. verticillata) covered with red berries—‘Red Sprite’ is a great cultivar. If you’re looking for an evergreen holly that thrives in moist soils and sends up shoots from root runners to hold soil on steep slopes, try the native inkberry holly (I. glabra). Japanese hollies (I. crenata) are often the perfect size for foundation plantings, but are highly susceptible to diseases, including root rot in poorly drained soil.

Moisture lovers
Shrubs that like wet soil and work especially well near the bottom of a steep slope or in an area that takes lots of stormwater runoff include sweetspire (Itea virginica), summersweet (Clethra alnifolia), and red twig dogwood (Cornus sericea). Plant these, give them lots of room to grow, and ignore.

Ornamental grasses
Ornamental grasses are excellent choices for dry, sunny slopes and they mix well with other shrubs and perennials either in masses or as individual specimens. Your ornamental grasses will need maintenance in the late winter—namely climbing your slope to cut them back to near-ground level just before new growth emerges. For shady spots, think ferns and hostas.

Shrubs for flowers and fall color
Shrubs such as hydrangeas, viburnums, and fothergilla add colorful interest to your slopes. Again, know the growth habit of shrubs you choose. Some viburnums can reach 12-feet tall, hydrangeas may need staking on a steep slope when their spreading branches are heavy with blossoms, and Fothergilla major tops out at 10 feet, but dwarf Fothergilla gardenii is a modest 3-feet tall at maturity.

Perennials and annuals
Speaking of staking—do you want to grow perennials or annuals on your slope? If so, be sure they have sturdy stems or plan on staking them. Tall flowers flop, especially after a heavy rain.

Ground cover: Green-and-Gold (Chrysogonum virginianum)

Green-and-Gold (Chrysogonum virginianum)

We often want low-growing groundcovers to hold the soil on our slopes and carpet the ground beneath shrubs and trees. I’ve already mentioned creeping juniper for sunny, dry slopes. If your hillside is part sun to shade, try pachysandra—either the native Allegany spurge (P. procumbens) or the Japanese variety (P. terminalis). At less than six-inches tall, spreading, and evergreen, pachysandra makes a pretty groundcover summer and winter. Or you might cover your slope with low-maintenance creeping red fescue—a fine-bladed grass that stays green in winter. Other low-growing choices are green-and-gold (Chrysogonum virginianum) and creeping St. John’s wort (Hypericum calycinum), although both brown out during the winter. Perennials such as dwarf crested iris, catmint, stachys, and ajuga all make good groundcovers on slopes.

Avoid bullies
Warning! Never plant invasive species such as English ivy or periwinkles (Vinca major and V. minor) as a groundcover. And beware other aggressive groundcovers such creeping raspberry (Rubus pentalobus). While only English ivy climbs and helps kill trees, you’ll need to dedicate many gardening hours to pulling trailing vines to keep any of these plants in bounds.

Analyze your site, have a plan, install your hardscape and access paths, and spend time thoroughly researching your plant options. You will then be ready to select the right plant for the right space on your garden slope.

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: Access Required to Traverse the Hillside

If you can’t get to the garden, you can’t garden! Creating access on a steep slope is challenging and can be expensive. Access means steps and paths. Steps help get you up and down the slope. Paths get you across the slope. Both are essential for maintaining and enjoying your garden.

Pressure-treated lumber steps

Steps of pressure-treated lumber on steep slope.

Steep slopes need steps—unless you like climbing up the slope on all fours, or sitting while sliding down. Options for step materials include flat rock boulders, stepping-stones, pressure-treated timbers, or rot-resistant logs. Flat rock boulder steps will last more than a lifetime but will be the most costly choice. You’ll probably want to hire a professional to bring in equipment and set the boulders. An alternative to large flat boulders is to dig stepping-stones into the slope. Stack the stepping-stones and mortar them together to create risers. You can also build a nice-looking, easy-to-traverse staircase out of pressure-treated timbers. Eventually though, the wood will start to rot and have to be replaced. A very simple, easy-to-install, and relatively inexpensive step system uses rot-resistant logs—such as locust—cut into the slope and backfilled with dirt or gravel. Adding a stepping-stone to the tread behind each locust log riser will provide solid footing as you climb up and down.

Access to steep slope garden with paths, steps, and terraces.

Paths, steps, terraces, and low boulder retaining walls provide access to steep slope garden.

With steps in place, turn your attention to creating paths across your steep slopes. The best paths to amble through the garden with visitors will be at least three to five feet wide. Terraces will give you maximum walking and gardening space. A professional landscaper can build terraces into the hillside and use retaining walls to hold back the slope. But “goat paths” just wide enough to allow you comfortable access—a foot or two—will also provide safe access into the garden. Cut into the hillside a bit and level out your path with the excess dirt. Use small boulders or vertical timbers to shore up the lower edge of the path and to retain the hillside along the upper edge of the path. Complete your paths with stepping-stones, gravel, wood chips, mulch, or grass.

Planting pockets
While you’re building steps and paths, consider using boulders or timbers to create a few planting pockets on the slope. They don’t have to be large—no more than a foot high and four or five feet long. Backfilled with soil, these mini-terraces make just enough level planting area for a nice, accessible flowerbed or small vegetable garden. 

Think about footholds
Leave large rocks, tree stumps, and tufts of grass in place across the slope. They will provide much-needed footholds and landing spots when you traverse the hillside to maintain your garden. My favorite steep slope gardening tool is a pair of sturdy hiking boots. The treads and strong ankle support have saved me many a slip down the hill!

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: Start with a Plan

My last blog stressed the importance of analyzing your site. But before you ever put the first plant in the ground, define your goals and have a plan. Know where you’re headed and what you want to accomplish. What’s your garden style? Are you formal or informal? Do you want a well-defined, nicely manicured garden? Or are you okay with a more random, natural look? Do you want lots of flowers? A place for vegetables? Do you like showcasing specimen plants? Do you want your garden to provide privacy, places to entertain, four-season interest, or minimize maintenance?

Diverse planting of conifers, perennials, and ground covers on entryway slope.Starting from scratch
When I moved into my house, the bulldozed, empty, front slope of red clay was my number one priority. It wasn’t very pretty or inviting to visitors walking up my sidewalk. I wanted to block my views to the street above me. I was most concerned with how the bank would look in winter. I didn’t want deciduous shrubs that offered no winter color or foliage. And given the steepness of this bank, I knew that I couldn’t always be climbing up and down it to prune shrubs or deadhead flowers. The area received full sun, so a conifer garden was a natural fit for the site and my goals. I chose conifers sporting a variety of shapes, heights, colors, and textures. I used different creeping junipers as ground covers to reduce mulch requirements and control weeds. None of these conifers require regular pruning, which minimizes maintenance. At street level, right at the top of the bank, I planted three hardwood trees. They offer privacy and block my view of the house above me. At the bottom of the slope and along the front sidewalk, I installed perennials to provide a colorful and cheerful contrast to the conifer hillside and a welcome greeting to my visitors. 

Don’t rush!
I often suggest spending an entire year looking out the windows of your home before starting a landscaping project. Become acutely aware of what you see at every season of the year—both near and distant views. Envision how you’d like those views to look five or more years down the road. Then set priorities. Most of us cannot afford to create an instant landscape and it may take several years to achieve your vision. Incremental gardening lets us incorporate change and learning as we go. Spend time visiting the NC Arboretum, The Botanical Garden at Asheville, and the Biltmore Estate to see how different plants behave—their mature size, seasonal characteristics, and how they look in the landscape. And don’t forget to research the plants that interest you, but be sure the information you gather is appropriate for plants conducive to our mountain environment. The North Carolina Extension Service website at https://www.ces.ncsu.edu/ is an excellent source of research-based gardening information.

Article written by Beth Leonard, Extension Master Gardener Volunteer.

Gardening on Slopes: Analyze Your Site

Before you develop a landscape plan or buy the first plant, analyze your site so that you can match your garden goals and plant characteristics to your specific environment. Important site characteristics include sun, shade, moisture, and wind patterns. Identify problem areas such as erosion, standing water, invasive plants, and weedy or overgrown areas. Locate focal points to highlight or preserve. These could be a wildflower meadow, rhododendron thicket, specimen tree, nice rock formation, or even a dry streambed.

How steep is it?
Site analysis takes on special importance when your property is on a slope. Take time to calculate the steepness of your slope: Rise ÷ Run = Slope %. You cannot push a garden cart or ride a lawnmower on any slope over 40% steep. If your slope is over 55% steep, you cannot walk up it without foot- and handholds. The steepness of your slope becomes a critical factor for what you choose to plant and how you maintain it. Note if your property has deep ravines. Because cold air settles in low-lying areas, the bottom of your slope may not be the best place for marginally hardy plants or early-blooming azaleas. 

What should you look for? Is an area full sun or deep shade? How many hours of direct sun does it get in a day? Is the sunlight gentle, morning sun, or hot, baking, afternoon sun? How do the light patterns change with the seasons? At what time of day is your garden shadowed by a permanent structure like your house?

When monitoring sun and shade patterns, note how the mountain slopes themselves may cast deep and long shadows. Vegetable gardens, roses, and sun-loving perennials need about six hours of direct sunlight a day to thrive. 

Water Management in Rain Garden

Rain gardens, dry retention ponds, and swales help manage stomwater runoff.

Look at soil moisture levels and stormwater drainage. Steep slopes can be very dry because rainwater runs off quickly, rather than being absorbed into the soil. You may need to consider drip irrigation for plants on steep slopes. You may have areas of your property that stay very moist or have standing water. These may be candidates for rain gardens. And if you have erosion problems, decide how you’ll resolve those before you plant. While serious erosion problems may require stormwater management solutions, choosing the right plants to anchor the soil might fix minor erosion. 

Soil characteristics
Our acid mountain soils usually best suit acid-loving plants—azaleas, rhododendron, and conifers. And mountain soils are often notoriously low in phosphorus. Do soil tests around different areas of your property to determine pH and mineral content. You’ll find soil test kits with “how to” directions at the Buncombe County Extension Office. The results will help you decide what fertilizers and other amendments to use.

The lay of the land
Analyze your visual perspective. If you’re looking up the slope, what will you see? Is it a view of plain tree trunks or leggy flower stems? If so, think about hiding unsightly views by layering your plants. Place the tallest plants toward the top of the slope, then step down to mid-sized, bushier plants, and finally put the shortest plants at the bottom of the slope closest to you. The same concept works in reverse, if you’re looking down the slope. Put the short plants at your feet and the tallest plants farthest away. The low-growing plants help extend your field of vision and won’t make you feel closed in when you walk near the sloping hillside. The tall plants create a backdrop to anchor the garden, much like the walls of a room. An integrated mix of plants by size, color, and shape also helps camouflage and add to the interest of a steep slope.

Article written by Beth Leonard, Extension Master Gardener Volunteer.