The Gardens at Wave Hill

Five Principles of Landscape Design That You Can See at Wave Hill and Use in Your Own Garden

 Sometimes the process of fine-tuning your garden or landscape can seem a daunting task.  One way to make it easier is to use public garden spaces as a resource for seeing landscape design principles put into practice.  Wave Hill in Riverdale is a public garden and cultural center which is nearby, fun, beautiful, and a source of inspiration in every season.  Originally an estate, the property was donated to the City of New York in 1960, and over several decades the gardens were restored and reinvented by the internationally acclaimed horticulturalist Marco Polo Stufano.  Wave Hill “is renowned for its intimacy of scale and its carefully cultivated serendipity: at Wave Hill, even the most seasoned gardeners can take joy in the unexpected.”  Wave Hill is one of my favorite gardens, and I’d like to share with you some of the lessons it has taught me.

Design Principle 1:  A garden should have “good bones”.  The “bones” of a garden include pathways, structures (arbors, trellises, pergolas, gazebos), statues, containers, walls, fences, ponds, fountains and all the different materials they are made from, as well as the trees and shrubs.  “Bones” also include the geometry of the space; how the elements relate to each other.  Get a map of Wave Hill from the Visitors Center.  It’s a simple, almost stylized map.  To evaluate the “bones” of your own garden, start by making a similar map of your landscape.  Look at how the walkways are situated.  Are they curved?  Do they lead to any surprises?  Where are the planting beds relative to the walkways?  Are you invited in?  At Wave Hill, you enter from the far end of the parking lot on a narrow path.  Directly in front of you in the far distance are the Palisades.  In the middle distance is a pergola.  Notice that the path does not lead directly to the pergola.  Instead, it curves to allow you to slow down and begin to meander through the garden.  

The pergola at Wave Hill in winter, with the silhouette of a hornbeam beyond and the Palisades in the far distance.

 As you walk through the garden looking at bones, notice how the perennial garden is situated to the side, surrounded by a rustic fence that sets the tone for what’s inside.  You need to walk through it to see what’s in it.  Each bed is a mini-garden in itself, and a lesson in how you can set up your own small perennial garden without being intimidated.  Each bed has its own “bones” – notice how large shrubs, small trees and even garden ornaments provide structure to each bed.  This can be best appreciated in winter – find a day to visit when the paths aren’t covered with snow, and notice the strong axial structure of the perennial garden.  

Continue through the perennial garden and emerge on a small side path that leads you toward the herb garden.  The designer has made use of the old stonewalls and the foundations of the old greenhouses, to plant in and among them.  This is much more interesting than if those elements had been removed.  The walls provide a backdrop for the plants; a contained and defined area that is clearly designated.  Also notice how the planting beds for the herbs have been defined – each bed is essentially the size of one of the bluestones used for the path, creating a strong symmetry, and beds are divided from one another using bluestone set on edge.  The herb garden is constructed on the footprints of old greenhouses, with the old walls as a backdrop and bluestone paths giving access to all the planting beds.

Design Principle 2:  Strive for four-season interest.  Yes, you can have flowers in winter!  At Wave Hill if you visit in February and March, you'll see winter jasmine (Jasminum nudiflorum), witch hazel (Hamamelis X intermedia), and cornelian cherry dogwood (Cornus mas) in bloom in late winter.  Additional elements with winter interest include red and yellow twig dogwood, pussy willows, black pussy willows, architectural trees (like magnolias, beech, hornbeam), seed heads, exfoliating bark, and berries.

Lagerstromia (Crapemyrtle) bark is fabulous anytime, but especially glowing in the winter sun.

Design Principle 3:  Plant a tree!  At Wave Hill you will find lots of “specimen” trees, both large and small.  A “specimen” tree means that the tree has been planted by itself or in a small grouping so that its attributes can be appreciated.  You'll see Lagerstromia (Crape myrtle), Parrotia, Magnolias, Paperbark Maple, English Oak, Dawn Redwood, Elm, Copper Beech, Weeping Beech and Hornbeam.  You can have any of these trees in your landscape as well, provided you have the appropriate conditions of wet-dry-sun-shade for the tree you’ve fallen in love with.  Notice how the trees at Wave Hill are placed relative to the paths and the beds in places that “make sense” visually – they are connected to their surroundings.  Notice that many of them are simply planted with a mulch circle around the base.  This is an excellent way to include a specimen tree in your own landscape, without feeling that the tree needs to be under-planted or included with other shrubs in an elaborate island.

Design Principle 4:  Add annuals effortlessly to your landscape by using containers.  The strategy used by the designers at Wave Hill to add annuals to the garden is to plant a single type of annual in a container and then group containers together.  Containers with different shapes and sizes are selected, then arranged to form a tapestry of color, height and texture.  When one type of annual gets past its prime, the container is simply removed from the design and a new one is introduced.  Using this trick, you can keep your annual displays looking fresh all through the season.

Design Principle 5:  Take time for tea.  At Wave Hill, outdoor chairs are moveable, plentiful and weatherproof.  You can bring a chair under a tree, out into the sun or under the pergola.  You can sit by yourself or in a group.  Talking, reading, or just sitting is the order of the day.  You can sit on the terrace by the Café and be amazed by the majestic view of the Palisades.  Sip tea.  Munch on a cookie.  Have lunch.  Invite a friend.  Recharge your batteries.  Revel in the changes of the seasons.  Take this principle to heart for your own garden.  Sit in it.  Enjoy it.  Take a break.  Feel the quiet even as you hear all the noises of birds and kids and distant (or maybe not so distant) leaf blowers.  

Wave Hill is located 675 West 252nd St., Bronx NY.  Call 718-549-3200 or visit www.wavehill.org for more information.

Colored Stems and Leaves

Have you ever wondered why some trees and shrubs have colored stems and leaves?  

Colored leaves are important for landscape design, since the interplay of colors and textures adds beauty and interest.  

Forest Pansy Redbud leaves

Ninebark 'Diabolo'

Colored stems, like those of red twig or yellow twig dogwood, are an excellent way to add winter interest to a landscape.

So here's what I've found out Leaves and stems contain pigments – molecules that absorb specific wavelengths of light.  Chlorophyll gives leaves their green color because it absorbs all wavelengths except green.  Carotenoids produce yellow and orange colors – plants that are orange or yellow (corn, carrots, daffodils, bananas) are rich in these pigments.  Anthocyanins absorb blue, blue-green, and green light, so that reflected light appears red.  Anthocyanins give color to cranberries, red apples, concord grapes, blueberries and tree and shrub varieties with purple leaves.  Unlike chlorophyll and carotene, anthocyanins are not attached to cell membranes, but are dissolved in the cell sap. Because anthocyanins are in sap, stems and twigs can be red as well.

During summer, high levels of chlorophyll production cause leaves to appear green, largely by masking other pigments.  Water and nutrients flow from the roots, through the branches, and into the leaves.  The sugars produced by photosynthesis flow from the leaves to other parts of the tree, where some of the chemical energy is used for growth and some is stored.  The shortening days and cool nights of fall triggers a cascade of changes in trees, including decreased chlorophyll production (so that other pigments are unmasked and the leaves turn from green to yellow, orange or red) and increased amount of sugar in the sap (because the tree is not growing anymore).  In some trees, as the concentration of sugar in the sap increases, the sugar reacts to form anthocyanins. These pigments cause leaves, twigs and stems to turn red.  (Also an indicator of when anthocyanin-containing fruit is ripe – high sugar content in the cells). 

The range and intensity of fall color is greatly influenced by the weather.  Low temperatures destroy chlorophyll, and, if they stay above freezing, promote the formation of anthocyanins.  Bright sunshine also destroys chlorophyll and enhances anthocyanin production.  Dry weather, by increasing sugar concentration in sap, also increases the amount of anthocyanin.  So the brightest fall colors are produced when dry, sunny days are followed by cool, dry nights.

Some botanists also think that anthocyanin production is protective – by producing this pigment the plant is protecting itself from potential damage from UV rays that can be very intense in the winter.

As the tree starts to grow again in spring, the stored nutrients start to be used up, the sap starts to flow and the tree starts to produce leaves.  The anthocyanins break down so that the bright color of the stems fades. 

Because the genetic make-up of the individual tree or shrub determines the balance of pigments and the factors that influence their production, different cultivars can be selected based on the intensity of the red/purple color of their leaves and stems and its sensitivity to length of days and weather conditions.  That’s undoubtedly why some purple-leaved cultivars look mainly green at the height of summer and others look purple all the time, as well as why the purple color is less intense in some cultivars if they’re not getting enough sun – not enough sugar in the sap to support anthocyanin production in that particular cultivar.  Also why new cultivars of red twig dogwood can be selected for brighter red stems.

Deer resistant evergreens

I've designed and installed plantings all over Westchester County: the shores of the Long Island Sound, the hillsides along the Hudson, homes next to golf courses, lakes and wooded areas, and rural areas in the northern part of the county.  Many of these plantings were done without benefit of deer fencing in deer-infested areas.  There are a handful of trees and shrubs that are my go-to  plants in these situations. These are the ones you should try if you have deer wandering through your property unchecked and have had problems with deer browse damage on your existing plants.  The caveat is, of course, that if the deer get hungry enough they may eat plants that they've never eaten before.  So no guarantees!  But try them anyway!

Evergreens that are deer-resistant are the most important category, since they  are integral to the "bone structure" of your garden, and are important for privacy screening as well.  The most reliably deer-resistant evergreen is boxwood.  Deer really leave it alone!

Other broadleaf evergreens that I often use are skimmia (Skimmia japonica), andromeda (Pieris japonica) and sweetbox (Sarcococca hookeriana).  If I want to add some flower power and have the right conditions, I plant hybrid mountain laurel (Kalmia hybrids).  New Kalmia cultivars are entering the Nursery trade every year, with more spectacular bloom colors and compact, neater silhouettes.

Another excellent choice is American holly (Ilex opaca).  It takes shade, and is actually found in the forest, but it doesn't mind some sun either.  It is a tree, though, so give it enough space.

The needle evergreens (conifers) that I turn to are Norway spruce (Picea abies), Oriental spruce cultivars (Picea orientalis), Colorado Blue spruce and its cultivars (Picea pungens),  limber pine (Pinus flexilis) and concolor fir (Abies concolor 'Candicans'). 

A few favorite deer resistant ornamental trees and shrubs

Ornamental small deciduous trees and shrubs lose their leaves in winter, so they're only at risk of being devoured during the growing season. There are quite a few choices in this category, but I have a few favorites that are reliably left alone, and that have other qualities that make them interesting and valuable additions to the landscape.

Flowering quince (Chaenomeles speciosa) is a thorny shrub which flowers in very early spring and you can cut branches in late winter to force indoors.  Amelanchier or Shad (Amelanchier hybrids) is a multi-stemmed small tree with delicate white flowers in early spring, juicy berries beloved by birds in summer, beautiful fall color and showy bark in winter.

Of course, nothing can beat American dogwood (Cornus florida) for beauty in the spring, and new cultivars are becoming available that are much more disease resistant than the species.

I also love I also love the less commonly planted enkianthus (Enkianthus campanulatus), fothergilla (Fothergilla gardenii) and Virginia sweetspire (Itea virginica) - all have spring flowers and spectacular fall color.  And viburnums are versatile yet beautiful, so I use them often.  Both doublefile viburnum (Viburnum plicatum v. tomentosum) and fragrant viburnum (e.g. Viburnum carlessii and other cultivars) have beautiful flowers, a dense habit, berries and good fall color.  ■

Enkianthus blossoms

Enkianthus Fall color

Deer browsing and biodiversity: upsetting the balance

"A growing number of Westchester and New York State biologists believe that heavy deer browsing exacerbates the effects of other human-created impacts on the environment such as habitat loss, invasive species proliferation, soil degradation and erosion, acid rain, and pesticides – which together jeopardize the survival of many wildflowers, hinder regeneration of trees and other plants, and potentially threaten important ecological services (e.g. quality of drinking water supplies) provided by healthy forests." 

William S. Greenawalt, Esq., Chairman Citizens’ Task Force on White-tailed Deer and Forest Regeneration

The picture on the top shows a healthy forest floor, with a diversity of plants on the ground, seedlings and small trees.  The second picture shows an over-browsed forest floor, carpeted with the invasive weed garlic mustard and no seedlings or small trees visible.  You can see this for yourself if you go for a walk in the "woods" - check how far you can see(because there are no small trees or shrubs blocking your view!), how much barberry you encounter, and look for small trees - you won't find many!  At the Lasdon Arboretum they've set up an area with a fence where you can look on one side and see what the deer have done, while directly on the other side you see the expected biodiversity.

The deer are nibbling away at the natural diversity of the eastern forest.  Studies show an alarming lack of tree seedlings per acre, and once-dense thickets of rhododendron and mountain laurel are sparse and open.  In some areas of Pennsylvania, where scientists have carefully documented the forest undergrowth, there is simply no viable regeneration of trees and shrubs going on at all.  The white-tailed deer population devours shrubs, saplings, wildflowers and other underbrush - each deer chewing up thousands of pounds of plants and acorns a year.

This phenomenon is referred to as "deer over-browsing".  For many young plants, deer bite off the whole stem of the plant, including its flower, so no seed is formed, thereby preventing reproduction.  Slow-growing trees spend many years in the forest shrub layer before they can grow beyond the reach of deer.  But the biggest threat is not the loss of individual species, but a gradual overall reduction in plant diversity resulting in a “simplified” forest that is less able to bounce back from disturbance, whether natural or manmade.

“In a diverse system, there is always another species that can take up the slack,” said Larry Rhoads, Supervisor of the Forest Pest Suppression Section, PA Dept. of Conservation and Natural Resources.  “If one species is affected by an insect or a disease, there’s another that can move in, shifting the balance. When the forest consists of little more than red maple and hay-scented fern, there’s no backup, no ability to shift and take up the slack when one species is affected, and thus no resilience.” 

Nor are impacts limited to plants.  Some understory birds, most of which are neotropical migrants that journey between Eastern forests and the tropics each year, have been declining 3-5 percent a year. Studies suggest that is largely because of increased nest predation on those species. Deer may be making those species more vulnerable to predation.

 “If you’re trying to nest in the lower six feet of the forest and there is no lower six feet, you’re sticking your nest out in a very obvious place and it’s being hammered relatively soon in your nesting phase,” said William McShea, a research scientist with the Smithsonian Institution’s Conservation and Research Center.

Also, when some species are over-browsed, other plants less desirable to deer take their place. Those new species may be able to outcompete native species that were decimated by the deer population.  So even if the deer population is reduced, and maintained at lower densities over time, diversity may still not be reestablished. 

Too many deer!

One of the most frustrating things that can happen when you install a new mixed shrub border, garden, front foundation planting or annual display is waking up  to find that  some of your new plants have been eaten! Very often, the culprits are whitetail deer.   We've developed so much of the open land and woodlands that their habitat inevitably overlaps with ours.  Yet there's still enough open space for them to find shelter, allowing them to reproduce freely.

What do deer eat in their "natural" habitat?  In most areas, deer eat just about any type of vegetation or mast they can find. They can be picky eaters; if it doesn't taste quite right, a doe will spit it out. Fawns learn which plants, nuts and fruits to eat from their mothers.  A deer's sense of smell tells it whether a plant is good to eat. That's why many strongly scented plants, such as most herbs, are not favored by deer.  That's also why strong scents are used as deer repellants.

Deer forage consists of forbs and mast.  Forbs are herbaceous flowering plants that are not graminoids (grasses, sedges and rushes).  Examples of forbs include clover (which is growing in your lawn), sunflowers (which you're trying to grow for fun) and azaleas (which you were hoping would add curb appeal this spring).

The term "mast" was probably first used to describe a food source for domestic livestock.  Its definition is: "the fruit of oak or beech or other forest trees used as food for hogs and other animals.”  In wildlife biology, mast refers to the fruits of woody plants.  All trees and shrubs produce some type of fruit.  Mast is often characterized as either "hard" or "soft".  Hard mast consists of hard shelled seeds that have a relatively long shelf life and are high in fat, carbohydrate and protein - it's high in energy content, and is a key food source for survival during the winter.  Examples of hard mast include acorns, hazelnuts, hickory nuts, beechnuts and walnuts.

Soft mast is fleshy perishable fruit that is high in sugar, vitamins and carbohydrates.  Soft mast can be an important source of moisture for wildlife in times of drought, as well as a crucial energy source for some species during migration.  Examples of soft mast include cherries, crabapples, apples, persimmons, pawpaws and blackberries.

"The most serious impacts of deer on Westchester County’s flora, fauna, and ecosystems result from browsing of plants for food. Deer consume an average of 4 to 8 pounds of forage per day; one deer can eat one ton of vegetation annually."

William S. Greenawalt, Esq., Chairman Citizens’ Task Force on White-tailed Deer and Forest Regeneration

In winter, deer are often forced to feed on twigs and other woody browse, which are low in nutrients. So if they come upon some really tasty evergreen leaves or buds, they chomp away.  In early spring, when buds start to swell and leaves start to sprout, plants are particularly vulnerable because the deer may be pretty hungry by then.  

The Final Report of the Citizen's Task Force on White-Tailed Deer and Forest Regeneration was issued October 28, 2008, and is available online.  The report explains the history of the problem, cites statistics about deer density in the county and reviews the various methods that could potentially be used to address the deer overpopulation.  There's also analysis of the pros and cons of each idea.  

Soil is Not Dirt!

I'm taking Soil Science at NYBG this semester - its a fascinating combination of chemistry, biology and physics - and I just want to let you know that soil is not dirt.  It's a complex mixture of minerals, organic matter, air and water with well-defined structure that varies with the exact components.  

Our instructor defined soil as: "the natural loose covering over most of the earth's land surface that serves as the medium for plant growth".  

To support plant growth, soil needs to provide

• both root penetration and anchorage - it's physical consistency needs to be loose enough for root penetration but solid enough to anchor the plant
• water
• air
• needed and essential nutrients