How to design a small urban garden in six steps

Marie Viljoen knows a thing or two about gardening in tight spaces. After all, her first terrace in Brooklyn measured just 66 square feet, yet she managed to turn the sliver of a room into an outdoor oasis with a small grill, a table and chairs, and dozens of plants: roses, herbs, figs, lilies, strawberries, vines, and more. Her micro garden grew into a blog and a book, both named after the tiny terrace’s size. Here, Viljoen shares her time-tested strategies for small urban gardens.

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There is very little as luxurious in a city as coming home to your own green retreat where you can smell the roses. Or pick the blueberries. Or dine beneath the light-polluted stars while watching a migrating hummingbird feeding on scarlet runner bean flowers.

Each outdoor space is unique, with attendant challenges and possibilities, but this six-step guide will give you a sound strategy for tackling the creation of your leafy refuge.

1. Create a blueprint for your garden

Measure your space. Then draw it on graph paper or touchscreen. It does not have to be pretty, but the scale must be accurate. For printed portability it is best if the sketch fits onto a standard sheet of paper (8.5" x 11"). Convert each linear foot to a scale that will fit on the paper. A half or quarter inch per foot is easy.

Now that you are looking at it objectively, you can see how and where things will fit.

2. Allocate space

How will you use this garden? Are you going to eat meals there? Barbecue? Grow fruit and flowers? What about storage?

Once you know what you want, add your stuff to the sketch: a table, seating, a barbecue. Planters. A shed. How big is the table, and how wide those chairs? Draw them to scale. Consider furniture that does double duty—a table that doubles as a stool or plant stand—and pieces that can be folded up and moved out of the way.

3. Incorporate hardscaping

What does your space need, in terms of construction? Be realistic about what is essential for safety, or for building codes.

Aesthetic elements such as fences, decks, and stonework will depend on your budget. Professional hardscaping is expensive, but the chances are good that it will be done well and will last many years.

Two caveats: Place nothing on an unprotected roof membrane and never block the drain.

For simpler fixes, like hiding ugly chain-link, go it alone. Birch or bamboo poles make an effective screen doubling as a trellis for climbers. You hate the floor tiles? Cover them with landscape fabric and an inch of pea gravel or crushed stone. The walls are a blah beige? Paint them turquoise or cerise; in a small space color is very big.

Is there a water source? You will need one. Hauling a watering can from the kitchen is not all it’s cracked to be.

4. Know your climate and sun exposure

Choosing appropriate plants for your garden, no matter what size, is all about location.

The U.S. is divided into USDA Plant Hardiness Zones. Plants are hardy to a zone that defines how much cold they can withstand. Knowing your zone allows you to choose the right plants for your region and ensure they thrive in your available space.

In cities, even southern exposures might mean full shade, cast by the building across the street. Establish how much direct sun your garden receives; different plants require different light. Don’t guess: observe and record. Even in a small space, one side of your garden might be different from another. Also pay attention to the wind; rooftops and balconies often endure heavy wind gusts that can wreak havoc on many plants.

5. Choose plants that work together and fit your climate

Add plants to your sketch using color markers.

In horticultural literature and on plant labels, plants are described as suitable for full sun (six-plus hours of direct sun); semi-shade (three to six hours of direct or intermittent sun); or full shade (no direct sun). Based on your note-keeping choose plants best suited to your exposure and micro-climate.

A collection of plants that blooms or produces throughout the growing year is more compelling than one where it all fizzles out after spring. Choose plants for different bloom times as well as for interesting texture and foliage. Vary heights by using different size pots as well as a mix of annuals, perennials and shrubs. Repeat some plants several times (odd numbers look more natural), to weave the scheme together.

Marie Viljoen

Some plant basics to keep in mind when making selections for your garden:

• Annuals last one growing season and die in winter. They pack punch, and are an excellent seasonal fix for tight spaces.
• Perennials are herbaceous plants that live longer than a year, blooming for two to six weeks.
• Shrubs are woody plants that can be annual or perennial in your zone. Choose them for bloom-time, fruit, and structural interest.
• Climbers expand cramped spaces by taking interest up. They double as green screens. They can be annual or perennial, and they are great for maximizing greenery in a tight space
• Trees (small and medium) perform well in small gardens and require larger containers. Every few years containerized trees benefit from a root-pruning, to prevent girdling.

6. Choose the right containers

You will need them, unless you’re gardening in-ground. Almost anything is a suitable planting container, as long as it has drainage holes. If weight is an issue on a rooftop, go light with plastic, metal, fiberglass or grow bags. Wood, terracotta, and concrete are fine if weight is of no consideration.

Container size depends on the plants. Annuals can thrive in as little as 4" in diameter. Perennials need more room– 10" and upwards. Shrubs, 16" and up. Small trees, 20" and larger. Your local nursery will be invaluable in helping you make the right choices. Keep in mind that if your garden is located on a wind-swept balcony, larger containers are less likely to topple over than many small containers, so consider grouping plants rather than individually potting each one.