Selecting Trees for Rooftop and Terrace Gardens

City gardeners and landscape designers know that choosing the right tree for a rooftop or terrace garden can be quite the challenge! Environmental factors range from the amount of sunlight and wind exposure to the amount of space available and the rooftop's weight limitations. There's a lot to consider, and frankly, a lot that won't work.

Look at it this way: Got a rooftop garden on the 12th floor with no other tall buildings around? That's sort of like a mountain top – full sun and high winds – think pine trees or birches. What about a smaller, shadier space with a taller building or two around? This is more like the edge of a forest – partial sun, can't get too big, very cold – think dogwoods. Imagining what naturally occurring environment most closely resembles your outdoor space can be a big help in selecting plants, and hopefully save you a lot of headaches and $$ spent on replacing dead stuff. 

Here's a list of trees that grow well on rooftops:

- Eastern White Pine (Pinus strobus), Limber Pine (Pinus flexilis "Vanderwolf's Pyramid")

Loves full sun, and can handle high winds and harsh winters. Bonus, they're evergreen!

- River Birch (Betula nigra)

Full sun is best, and being multi-branched helps it handle wind well. Small leaves offer dappled shade and turn golden yellow in autumn. *Might experience some leaf-drop in summer, but that's normal.

by rkla studio

- Eastern Red Cedar (Juniperis virginiana)
Another great evergreen with pretty berries to boot. They tend to stay narrow and upright, so good for small spaces. It prefers full sun, and can handle a lot of wind. Do not plant it near your apple trees.

- Crape Myrtle (Lagerstroemia sp.)
Due to a mix of climate change and the propagation of some hardier cultivars this pretty flowering large shrub/small tree is now usually able to handle NYC's challenging climate. They love full sun, grow pretty quickly, and have a long blooming period later in the summer (flowers come in a multitude of colors and have a lovely fragrance). Their fall color is also awesome.

- Flowering Dogwood Tree (Cornus florida), Kousa Dogwood Tree (Cornus kousa)
These gorgeous spring-flowering (white or pink) trees can do full sun or part shade. They have a wider spread, so give them space. Awesome red fall color, and pretty berries keep them showy throughout the seasons. Birds love them too.

Staghorn NYC also designs rooftop gardens – check out some of ours on our website or email us for a no-fee initial consultation.

Garden Design Challenge: Bee Allergies

Recently, I encountered a project challenge that was entirely new to me – How do I design a garden for a client with a severe allergy to bee stings? First of all, the client understands that a 100% bee-free garden isn't possible unless we're talking about constructing some sort of bio-dome, and we're not. After doing some research I found that what we can do is design a garden space that is, shall we say, less alluring to bees. Normally, I design gardens that do quite the opposite by re-establishing and/or supporting native habitats – and pollinators (like bees) are a crucial part of that. But with some careful finagling I think it'll be possible to design a healthy, sustainable garden without attracting too many stingers.

How do we begin? We think like a bee.

So what makes a flower attractive to a bee? A few key characteristics:

• structure–easy access to nectar/pollen. Can the bee's body/proboscis reach the nectar? If the blossom is too long and narrow, no.

• scent–pretty straight forward. Most highly fragrant flowers have a lot of nectar - a big draw for bees - so it's something to consider when selecting plants for bee avoidance.

• color–blues and purples are easiest for bees to see, and therefore, especially attractive. Reds, on the other hand, looks black to a bee, so they generally ignore them. 

Now that we've got this information, some strategic choices can be made in selecting plants for the garden that won't attract bees, but will attract other important wildlife like hummingbirds and butterflies. 

Here's a list to get you started:

Cardinal flower – A great native flower that the butterflies and hummingbirds adore.

Red Coneflower – Double petal or classic, it's a gorgeous pop of color. 

Crocosmia –Not a native, but the hummingbirds still love it. 

Double-petal or "ball" Dahlias – The petals are too compact for most bees to get to their nectar, or they're sterilized. They come in a delightful array of colors. 

Penstemon– Another native, some bees won't be able to reach the nectar because of the shape of the flower.

Coreopsis "Mahogany Midget" – More reds, prolific bloomers. 

Gaillardia "Sundance Red" or "Arizona Red"– Native and also red, the butterflies are big fans. 

Feverfew– A nice non-red option, and bees are generally turned off by it's fragrance.

Columbine– Native or not, some bees struggle to reach the nectar because the flowers are facing downwards.

Ornamental grasses– Go to town with these guys. They're an important part of a healthy ecosystem, but the bees aren't interested

Ferns– Lush and lovely, they're great for you and of little interest to the bees. 

Want more info on all things bees? Check out the American Beekeeping Federation's website 

Before & After: Park Slope Backyard

In the spirit of today's snow, I've opted to do a "Before & After" post on a backyard we designed last winter and installed in spring. The first time we laid eyes on this Park Slope backyard it had at least a foot of snow covering it (and not much else), but take a look at that "After" shot – lush, fragrant plants to the max! Check out more photos of this project and some of our other gardens here.