Best Window Boxes

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Length is the specification to settle first, and it is the one most people guess at. Boxes in this category are sold in fixed sizes, typically 24 or 30 inches, and they are usually bought in twos and fours so a run can be built up along a sill or rail; measure the span you want to fill and divide by those increments rather than ordering a single box and hoping. Leave a finger's width between boxes so they can be lifted out individually. The next decision is construction. Open metal frames fitted with a coco liner drain freely, breathe at the sides and look softer, but the liner dries out fast in wind and needs replacing every year or two. Solid boxes hold moisture much longer and are the better choice on an exposed upper floor, provided they have drainage holes; if they do not, you will be drilling them. Then think about weight, because this is the part that catches people out: wet compost is heavy, and a planted 24-inch box needs brackets or rail hooks rated well beyond the empty weight printed on the listing. Check how the box attaches, whether it clamps to a round or flat rail and whether the clamp adjusts, and add a drip tray or plan the runoff so it does not land on the balcony below. Powder-coat colour is the least important thing here.