Best railing planters for balconies: no-drill picks by railing type

Measure before you read any further

Almost every one-star review of a railing planter says the same thing: it did not fit. Planters are built around a railing profile, and the profiles vary more than people expect. Before buying anything, measure three things:

• Width of the top rail. A round steel tube is often 1.5 to 2 inches. A square aluminum rail is usually 2 to 3 inches. A flat wooden cap is 3.5 inches (a 2x4) or 5.5 inches (a 2x6). Masonry parapets can be 8 inches or more.
• Shape. Round, square or flat. A bracket molded for a flat board will rock on a tube; a hook sized for a tube will not reach around a board.
• What is under the rail. Straddle planters need clear space on both sides of the rail. A rail set into a solid panel or a wall only takes hook-over or bracket designs on the open side.

With those three numbers, most of the choices below sort themselves.

The four designs

Straddle (saddle) planters have a base shaped to sit over the rail with the weight balanced on both sides, usually with sliding or clamping brackets that adjust to the rail width. They fit the widest range of rails, they stay put in wind because the load is centered, and they need no fixings. They lose an inch or two of planting depth to the saddle.

Hook-over planters hang from the rail on a pair of molded hooks or a notch, with the trough on one side. They are cheap, simple and quick to remove, and they suit flat wooden rails well. On a round or narrow rail, the hooks can rock, and a single-sided load catches wind.

Bracket planters use metal brackets that clip or screw to the rail and hold a liner or trough. Coco-lined steel ones look the best of the group and suit flowers and light herbs. Screw-on versions need holes in the rail, which rules them out for most renters and most metal railings.

Hanging pots hook individually over the rail and hold one plant each. They are flexible and cheap, suit narrow rails, and are the easiest way to add a few herbs. They dry out fastest and hold the least.

Wind, weight and the balcony below

A 24-inch trough full of wet potting mix weighs around 25 to 30 pounds and presents a broad face to the wind. Two things keep it where it belongs.

Balance the load over the rail. A straddle planter with equal weight on both sides is very hard to tip. A single-sided planter hanging off the outside of the rail is a lever, and a gust lifts it. If you must use a single-sided design, hang it on the inside of the rail, over the balcony floor, and add a tie.

Keep it low and dense. Compact, bushy plants catch less wind than tall ones. Herbs, lettuce, trailing tomatoes, nasturtiums and strawberries all suit a railing; a 4-foot pepper plant does not.

Drainage is the other neighbor problem. Water running out of a railing planter lands on whoever is below, and in many buildings that is the fastest way to a complaint. Choose a planter with a built-in tray or reservoir, water slowly until the tray is just wet rather than overflowing, and if the planter has open holes, add a drip tray or a liner with a few inches of reservoir at the bottom.

Lease and building rules

Most leases and many building rules allow freestanding containers and forbid anything fixed to the structure. All three picks above are no-drill and lift off in seconds, which keeps you inside those rules and leaves no mark when you move out. It is worth checking whether your building has a rule about planters on the outside of the rail; some require everything to hang inward, and a straddle planter satisfies either rule.

What to grow in a railing planter

A 24-inch planter holds about 3 gallons of mix, which is plenty for herbs and salad and enough for a couple of compact fruiting plants.

Water daily in summer. Railing planters are exposed on every side and dry faster than a pot on the floor, which is why the self-watering option is worth its price on a sunny balcony.

Setting one up

1. Measure the rail and check the planter's stated range before ordering.
2. Fit the planter to the rail empty, adjust the brackets until it sits level and does not rock, and tighten.
3. Put a layer of landscape fabric over any drainage holes so mix does not wash out onto the balcony below.
4. Fill with potting mix to an inch below the rim, mixing in a little slow-release fertilizer.
5. Plant, water gently until the tray is just wet, and check the next morning that nothing has dripped.

1. Adjustable straddle railing planter, 24 in — best overall

A saddle-shaped base with sliding brackets that clamp to the rail width, so the planter sits balanced over the top with no screws and no marks. Balanced load on both sides is what survives wind. Fits more railing types than any other design. Best for round, square or flat rails from about 2 to 6 inches wide, rented or owned.

2. Bloem Deck Rail Planter, 24 in — best for flat rails

A molded notch on the underside drops over a standard flat rail and sits level with nothing to adjust. Deep enough for herbs and lettuce, with a drainage tray. The simplest option if your rail is a flat board. Best for wooden deck and balcony rails with a flat 2x4 or 2x6 cap.

3. Self-watering railing planter with reservoir, 24 in — best self-watering

A false floor over a water reservoir wicks moisture up to the roots and stretches watering to every few days even in summer. On an exposed balcony, that is the difference between a railing of herbs and a railing of dry sticks. Best for hot, windy balconies where a trough dries out in a day.

Ones I wouldn't recommend

Single-sided screw-on brackets hang the full weight of a wet trough off one side of the rail and need screws into it, which most leases forbid and most railings are not meant for. The same bracket that holds a dry planter in May is the one that works loose under 30 pounds of wet mix in a July gust. A straddle design carries the load over the rail and needs no fixings; it is safer for the rail, the planter, and whoever is underneath.

Common questions