Plant a Window Box – Tips and Best Container Plants for Planting Your Window Garden

Plant a window box following these instructions and you will have plants blooming for the entire growing season. Nothing does more to add color and character to a home than colorful, beautifully blooming window boxes. Even new container gardeners can get spectacular results from their efforts the first time around by following these simple guidelines:

Choosing Your Container

The is no shortage of choices when it comes to window boxes. This is the number one favorite for container gardeners and the garden stores reflect this popularity. When debating about size, there should be a minimum of 1″ between the window ledge and the box.

Consider the weight of the container and the condition of the sill when you plant a window box. Once you plant the box, it could be quite heavy even if you use soil-less potting mixtures. Plastic, resin or fiberglass would be a good choice for a container. If you are an environmentalist, wood is good, but it eventually rots and has to be replaced.

Match the window box to the style of your home. Is your home style modern or traditional? Do you have a log cabin or a southwestern home made of stucco and adobe? Choose the color of your window box to match or complement your house trim or shutters.

For more info on the types of containers available, check out Choosing Garden Containers.

Preparing the Window Box

Be sure your planting container is clean and sterilized. Check to make sure your window box has an adequate amount of drainage holes drilled in the bottom of the box. Three-to-four holes should be enough. Drill more holes if necessary.

Cover the holes with metal mesh or styrofoam peanuts. You can also cut up styrofoam trays or any other type of styrofoam packing material you have around. Use styrofoam to reduce the weight of the window box. Once a window box is filled with soil and fully planted, it is very heavy and the use of styrofoam for drainage, rather than rocks or terra cotta pot shards will help reduce its weight.

For excellent drainage, insert wicks going from the soil through the drainage holes. Cut the wick about 2″ long from the outside bottom of the box.

10 Most Popular Plants for Window Boxes

Any top 10 list is subjective, but you will find at least 3-4 of these varieties in most window boxes.

  • petunias
  • geraniums
  • begonias
  • coleus
  • alyssum
  • lobelia
  • ivy
  • asparagus fern
  • impatiens
  • verbena


Create a Lush Window Box

If you are one of those gardeners who wait impatiently for your newly planted vining plants to spill over the edge of your window box, this tip is for you.

When you plant a window box, before filling your box with soil, drill some holes in the front of your window box about 2 inches apart in a random pattern about halfway up from the bottom. As you fill your box with potting mix, tuck plants into the drilled holes and firm soil around the roots of the plants. Annuals such as alyssum, lobelia, and petunias will grow quickly, covering the sides of the window box. When your plants reach full growth, your window box will look positively voluptuous and be overflowing with beautiful blooming flowers.

How to Plant a Window Box

No matter what type of container or potting mix you use, the basic procedure for planting a container is the same. Follow the Basics of Planting a Container Garden. Be sure to water all your plants before you start your planting using the basic method described on the page “Basics of Planting a Garden Container”.

Fill the container 1/2 full with potting soil. If you are using polymer crystals when you plant a window box, now is the time to add them to the soil. These non-toxic crystals absorb up to 200 times their weight in water, then release it gradually as plants need it. And because it contains potassium-based polymers instead of sodium-based, it breaks down into fertilizer instead of soil-damaging salts. Add 1 tbsp polymer crystals per gallon of soil, no more! These crystals absorb 200 times their weight in water so if you add too many, you may find your plants and soil pushed right out of the pots if you’re not careful. (Did you ever read the Dr. Seuss book-“A Fish Out of Water”? Same principle!)

You can also use water-absorbing hydro mats cut to the size of your window box and placed at the bottom under the soil if you wish. These mats work the same way as the crystals.

Leave your plants in the pots they came in and place them in the window box. Move them around and play with them until you like the arrangement. It’s usually a good idea to plant the tallest plants in back and center, with smaller ones in front and on the sides. Hanging and drooping plants are planted around the edges.

Once you are happy with your arrangement, follow the techniques outlined in Basics of Planting a Garden Container.

Setting out Your Window Box

When you plant a window box, this can be a great addition to your home, but be sure you realize that the weight of a window box is quite substantial. You need to be able to secure the window box and at the same time prevent mold and mildew from accumulating on your sills. Allow a gap of 1/2″ to 1 ” between your window box and sill to allow air to flow and water to drain.

If this is the first time you are going to plant a window box, it’s a good idea to fill the box with soil and water it well. Then as you lift it into place, you will have an idea of the actual weight of the window box. This will also be of help when you go to buy supporting brackets as you will have some idea of the weight of your box and will be able to buy the correct brackets.

When your box is planted and watered, set it on your window sill if it is large enough. Even if the sill is wide enough to hold your window box, it’s a good idea to anchor it down with a chain or other support. Those summer winds can get really blustery on some of those blustery summer storms.

If the box doesn’t fit on the sill, there is an array of brackets and hardware kits available for attaching boxes to windows and railings. Check out your local hardware, garden supply stores, and home improvement stores to find a solution that will fit your conditions.

Maintain Your Window Box

Because a window box is elevated, it will dry out more quickly than containers located at ground level. Be sure to check your box at least once and often twice a day in hot weather. When you water, consider using a weak solution of fertilizer on a regular basis.

Dead-head (remove dead flowers) to keep the window boxes looking their best. The ultimate purpose of a flower is to make seeds for the survival of the species. Once the seed is made, the plants die. To keep your plants blooming and looking their best, it is necessary to remove dead flowers as soon as you see them.

If one or more of your plants is not doing well, don’t hesitate to remove it and plant a window box with new stock to keep your container from looking ragged and developing bare spaces.

You’ve done the hard work. Now sit back, smell the flowers, and enjoy the day.

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