How to create the perfect window box (2024)

FAQs

What is the rule of thumb for window boxes? ›

As to height of the box, a rule of thumb is 20 to 25% of the height of the windows. If windows are very large and tall, adding brackets can help with proportion. Simple hooks hold a long box below the rail, resting against spindles. Long and large window boxes will be very heavy once filled with soil and plants.

Selecting Materials

I know that even the best materials would cost me less than two large custom sized window boxes from a retailer. I chose to go with Cypress lumber and plastic trim. This can get pretty pricey, but I would suggest going with a higher quality and durable wood like Cypress or Cedar wood.

A minimum of 8 inches in depth and 8 inches from front to back is required to have enough room for a selection of plants. Larger–say a foot in depth and width–is even better, particularly if you want to include a lot of plants and want them to fill out enough to overflow the box.

Always make sure your window box has drainage holes. To aid drainage, place 2 inches of nonbiodegradable packing peanuts or old wine corks in the bottom of the box, and then cover with landscape fabric to prevent soil from seeping out. Next, fill the box halfway with potting soil, and add your plants.

Place your box planter on the mounting brackets with the front side facing outward. Use your tape measure to make sure each side of the window box overhangs each mounting bracket by the same measurements. This confirms your window box is centered and ready to install.

However, lining a planter has lots of benefits for both your plants and the durability of your planter. A lined planter is less likely to rot from the inside, which is especially important with wood planters that are less robust than, for example, stone planters and terracotta planters.

Proper drainage is key for plants to thrive in windowbox planters. Some come with holes in the bottom to allow excess water to run out and some don't. You'll need to drill holes in the ones that don't. Use a drill with a one-inch paddle bit to make several holes spaced six inches apart in the bottom of the windowbox.

For the most visually appealing and balanced look, select a window box as wide as the window frame. If you have shutters, you can go a bit longer — add 4” to 6” to the length. Anything narrower than the window frame will look too small and out of proportion.

Window Box Substitute–No Mounting Required

If you've always wanted beautiful window boxes but were afraid of the installation, planter boxes are a DIY-friendly alternative. They're easy to build, and can be decorated seasonally …

What kind of soil should I use in window boxes? ›

Avoid heavy clay soil from the ground, says Shoemaker: “Water can't drain through it, and your plants will drown.” Instead, choose a potting mix that's already blended with slow-release fertilizer to decrease the amount of maintenance required. Soil-less peat-based planting mix is another option.

Since many traditional-style uPVC windows are around three feet long, almost every window box style is available in 30-inch and 36-inch lengths. Window boxes generally look best if they are the same width as your window, but there are exceptions to the rule.

If your home has double-hung or sliding windows, measure down 1 inch from the underside of the windowsill directly below one side of the window frame and make a pencil mark to locate the top of the bracket. For an out-swinging window, measure down 6 to 8 inches.

Secure the window box to the brackets with a drill and 2.5 inch (6.4 cm) screws. You will need to fasten the box to the brackets, or it will easily fall off. Use the drill to insert galvanized decking screws that are 2.5 inches (6.4 cm) into the upper back of the box and the top of the mounting brackets.

Sue recommends using 5 to 7 plants in a 24” window box, depending on the varieties you select. 2) Variations on a theme: Play with a single variety or color. “Great looking planters can be created using a single variety of plants, such as petunias, in one or more colors,” says Sue.

It's essential to consider the size when choosing the appropriate window boxes. A good rule of thumb is to match your flower box's width to your window's width, use smaller flower boxes on smaller windows, and opt for larger boxes on oversized windows.