Balcony gardening: sun, weight, wind, containers and rules

At a glance

1. Measure the sun before buying plants

Light decides what a balcony can grow. University of Tennessee Extension's small-space guide says balconies see light changes similar to porches and patios, that porch roofs can block considerable sunlight, and that light should be assessed through the day and the year. The Master Gardeners of Northern Virginia, a Virginia Cooperative Extension program, suggest photographing the balcony every hour or two from sunrise to sunset (or sketching it), and repeating that as the seasons change.

Nebraska Extension notes a trade-off: the greater a crop's light requirement, the greater its potential for moisture stress, which on a sunny, windy balcony means more watering.

2. Weight: a question for the building, not the gardener

Balcony load limits come from building codes, and the figures differ by code edition, place and building type. Three examples from pages opened for this guide:

• MGNV writes that most building safety codes require balconies to support 60 pounds per square foot.
• Minnesota's residential code rule as published in 2014 (Table R301.5, "minimum uniformly distributed live loads") lists 60 psf for exterior balconies and 40 psf for decks.
• California's 2017 emergency building standards (Building Standards Bulletin 17-01, attached to San Francisco's Information Sheet S-10) set balconies and decks at 1.5 times the live load of the area they serve, not required to exceed 100 psf, for residential buildings including apartment buildings.

These are design minimums written into a code for construction under that code. They are not a rating of any particular balcony, and this site gives no structural advice. Only the landlord, building manager or association, with a qualified professional where needed, can say what a given balcony may carry.

What a gardener can control is the load itself. MGNV suggests smaller pots and plastic containers rather than clay or ceramic. Water is heavy: the U.S. Geological Survey uses 8.34 pounds per gallon, so every gallon held in the mix or standing in a saucer adds that much. UF/IFAS notes that a window box filled with moist soil and plants weighs considerably more than the empty box. Going too light has a cost, too: Nebraska Extension warns that very light media such as 100 percent peat moss may be too light, and that lightweight containers in lightweight mix may tip over in wind.

3. Containers: size and material

Size rules are the same as anywhere else. University of Maryland Extension gives 1–3 gallons and 4–6 inches of depth for herbs, radishes, scallions and salad greens; 4–6 gallons and 8–12 inches for dwarf tomatoes, peppers and eggplant, beans, beets, chard and carrots; and 8–10 gallons and 12–16 inches, one plant per container, for full-size tomatoes, peppers, eggplant and cucumbers. The container size table lists 25 crops. Every container needs a drainage hole (MGNV; UW–Madison), and UMD warns that dark containers can get hot enough to injure young roots.

4. Wind and water

UT Extension calls wind speed a risk on balconies and suggests windbreaks where needed; MGNV adds that strong wind dries plants out, so plants can be moved to a sheltered spot or protected with a wind screen. Nebraska Extension notes that wind and light exposure both raise watering needs.

1. Check moisture by pushing a finger into the mix to the second knuckle; if it is dry, water until water drains out the bottom (MGNV).
2. Expect to water daily once plants are large and fruiting (UW–Madison), and up to twice a day on hot summer days in sun or wind (MGNV).
3. Water in the morning or evening, when temperatures are mild (UT Extension).
4. Protect the balcony below: set a saucer under each pot and empty it after a few minutes, which also limits salt buildup and mosquito larvae (MGNV). UT Extension describes bottom watering from a tray as possibly essential with neighbors below, as long as the pot does not sit in water continually.

5. Railing planters, hooks and towers

MGNV lists hanging hooks, railing flower boxes, plant towers and floor containers as ways to grow vertically on a balcony, and notes that designs may need to stay within the railing height or use items not attached to the building. UF/IFAS Gardening Solutions, writing about window boxes, says a box filled with moist soil and plants weighs considerably more, so the right hardware matters, and that herbs are a good choice for boxes. Match plants to the box's depth (UF/IFAS): a shallow box suits UMD's small class of herbs and salad greens. In buildings with fire escapes, a New York City residential fire safety notice published on nyc.gov tells occupants to keep all doorways and windows leading to fire escapes free of obstructions.

6. Leases, condos and HOAs

MGNV's first step is to check with the condo association or apartment manager. As one example of how narrow tenant protections can be, California's AB 2561 (2014) added Civil Code §1940.10, which requires landlords to allow personal agriculture in landlord-approved portable containers, but only in a ground-level backyard "private area" and only on properties with buildings of no more than two units. Even there, the landlord may decide where containers go and may prohibit synthetic pesticides and herbicides. The same bill added §4750, limiting how far homeowner associations can restrict personal agriculture in a homeowner's backyard. Neither section covers a typical upper-floor apartment balcony. This is a general pointer, not legal advice; read the lease and ask the manager in writing.

Balcony checklist

• Ask the landlord, manager or association what is allowed: containers, railing boxes, anything attached, and how much weight.
• Log direct sun hours for a full day, and again as the season changes.
• Choose crops by sun hours: fruiting crops at 6+ hours, greens and some roots at 4–6.
• Prefer smaller and plastic containers where weight matters; every pot gets a drainage hole and a saucer.
• Plan for wind: a screen or sheltered corner, and nothing light enough to blow over.
• Keep fire-escape doors and windows clear.
• Check moisture daily in summer; never let runoff reach the balcony below.

For crop-by-crop pot sizes see the container size table; for a fruiting crop that suits a sunny balcony, see growing tomatoes in containers; for timing, use your frost dates and the planting calendar.