How to Build a Window Box Planter in 5 Steps

DIY Window Boxes to Add Curb Appeal

When the weather is warm and nice, there’s no place I’d rather be than on the patio.

Jamie was just making fun of me the other day because I was SO excited about the warm weather and eating dinner outside he goes, “What is it with you girls and patios?” I laughed so hard.

But seriously it made me think about why I LOVE them so much. I don’t understand what’s to not love about patios?!

Who doesn’t love a good patio?!

Related Reading: Concrete Patio Makeover Ideas and How to Add Ambiance to Your Patio

Beautiful weather, smiling faces, the sun, ambience…smell of fresh flowers…beautiful planters…

But seriously- once Minnesota hits 70 degrees, you can find me picking out my favorite flower blooms to start decorating our spaces outside- ya betchya- to enjoy that patio! And there is nothing more that I love to plant than window boxes.

Window flower boxes are a design you rarely see sketched up within a new design plan. Homeowners typically request them.

You have to have a specific taste to appreciate a good window box. But they can add so much to the overall look of your home, sprucing up those window frames quickly!

Window box planters provide a unique perspective to your home, adding colors and textures and something you can change with the seasons. Don’t ever leave your window boxes empty.

Related Reading: DIY Cottage Style Cedar Window Box

And just because they’re called window boxes, doesn’t mean you have to only put them under you windows.

Window boxes look great along banisters of a front porch, railings, and any other flat and boring surface you want to spruce up! They even look great just sitting along your sidewalk or edges of your deck.

So today- we are so excited to share with you a full tutorial on how you can build your very own window boxes for as little as $20!

How to Build a Window Box Planter

by Jamie and Morgan from construction2style

This post contains affiliate links. See our full disclosure policy here.

Materials

Tools

1. Design

The first step to any good build is a design plan. And I’m not talking about a full design layout here, just know exactly what style you want.

Window Box Style

Do you want just a simple four sided flat box, or angled ends, curves, bevelled edges and molding? There are so many well designed window boxes out there it’s hard to choose which one to go with!

You can make simple boxed window boxes for as little as $20 or you can go big with high quality material and high design for as much as $300. And if you hire it out you’re looking at $500+.

Window Box Size

If you are using a window box liner, it’s simple to build around the liner. Or if you’re like us and want to create your very own waterproofing liner within, your options are endless.

We always like to keep it classic, creating a simple rectangular box and trim work with decorative support corbels below.

Depending on where you’re going to place your flower boxes will also depend on your design plan.

If it’s under a window, measure the width of the window and cut to your specific window dimensions. We made our window boxes very large! A good general dimension for the depth and height is 11″ deep and 8 ” high.

2. Measure & Cut

Once you’ve decided on your design plan the next step is to get to work- measure and cut! Measure the width of the window and cut to your specific window dimensions.

We made our window boxes very large! A general rule we follow for window box dimensions is the width of the window by 11″ deep and 8 ” high.

Use the width of your cedar boards to save having to rip boards to width on a table saw.

Just remember that once full of plants and soil a window box can be extremely heavy, so you need to make sure you have support to drill into so it doesn’t tear your siding off.

Within these window boxes that we made, they held 160 pounds of dirt into each planter. So for that amount of weight we secured them with 5 large lag bolts. We also made wooden brackets to support the weight of the boxes.

If you’re adding trim pieces like shown, cut them to the fit the length and depth of the window box planter. Cut corbels from thicker 2×10 (or whatever depth) material, or use this method to combine thinner boards to create a vintage carved corbel style.

Related Reading: DIY Craftsman Corbels

3. Assemble

When securing and assembling your window boxes, make sure you place them on a flat surface.

Clamp the front and back boards onto the table and against the bottom window box board to hold securely into place while you drill the front and the back boards onto the bottom board. Repeat for the side boards.

For more information and photos about assembling a window box planter, see this cottage window box tutorial. 

Add Window Box Trim

Adding trim provides a clean and finished look to your window boxes.

To add trim, cut four pieces the length and height of your box for each side of your window box. Secure into place with a nail gun or nails. Either before your woodwork or after your woodwork is assembled make sure to sand you work of art down to give it a nice soft finished look.

Once assembled, make sure you drill holes within the bottom of the planters to create drainage. This is as simple as drilling small holes straight through the bottom of the window boxes, roughly around every 6 inches.

Add Corbel Support

You can attach the corbels directly to the window planter box, or attach them to the house to act as additional support when installing.

Related Reading: Vintage Corbel Tutorial and Template

4. Prime and Paint

Before you get to the fun, make sure to fill in any nails holes with some wood filler, let dry, and sand.

Once sanded down it’s time for the fun, apply the paint primer to the window boxes. I typically like to use a 2″ brush, but any paint brush will do.

As soon as the primer is dry add you fun window box color! And by fun- we mean white. Just kidding. Add any fun color you want.

We like to stay with white because we like to add the fun within the flowers we plant. That way when it’s spring, fall or winter I can add just about any color I want without it clashing.

Simple neutral colors are sometimes the way to go when you like to spruce it up with the decor!

5. Hang & Plant Your DIY Window Box

If you aren’t placing such large window boxes like we did, you can place with screws and nails and secure with a 2×4 block behind the window box and below the window for support.

But being these were so large we wanted to make sure they weren’t going anywhere so we secured with 5 large lag bolts. Jamie even hung from them to make sure they were going to sell with the home!

For another method of hanging window boxes, see this cedar window box planter tutorial. 

Planting a Window Box

If you’re using a liner, place it inside. If not, you can line your planter box with landscape fabric to protect the wood and prevent soil drainage.

Once your planter boxes are hung and you’re ready to plant, it helps to add an inch or so of gravel prior to adding in the dirt to allow for excess water to drain. You can then cover gravel with potting soil and add the beautiful flowers and water!

Related Reading: Tips for Planting Beautiful Flower Pots and Planters

And let me fill you in on a little secret…these flowers are fake! Aren’t they gorgeous?!

Sometimes when you can’t manage the upkeep you can just settle for some beautiful fake flowers. You’ll have everyone fooled.

Saves money year after year, creates a beautiful outdoor space, and you can have decorative flowers throughout the season…even the summertime! Because who wants to be gardening when they can be out on the lake?! Well, maybe me and especially my mom… haha!

Tell us in the comments what you think of these beautiful window box planters?!

Read about more ways to add curb appeal here and with these ideas:

Questions and Answers:

What size should a window planter box be?

The size of a window planter box can vary depending on personal preference, the size of the window, and the type of plants you wish to grow. Here are some general guidelines to consider when determining the size of a window planter box:

1. Length: The length of the planter box should be determined by the width of the window.  It will look good if it is approximately equal to the width of the window or slightly smaller. This allows the planter to fit nicely underneath the window and provides a balanced look.

2. Depth: The depth of the planter box should be at least 8-10 inches (20-25 cm) to provide enough space for proper root growth and moisture retention. Some plants, such as vegetables or larger flowering plants, may require deeper planters.  (If you choose to go artificial this will not matter quite as much)

4. Width: The width of the planter box depends on the available space and your aesthetic preference. However, a width of around 8-12 inches (20-30 cm) is often suitable for most windows. Keep in mind that wider planters may require additional support brackets to prevent sagging.

Remember to consider the weight of the planter box when choosing its size. Make sure it can be properly supported by the window frame or additional brackets if needed. Additionally, ensure the planter box has drainage holes to prevent waterlogging and promote healthy plant growth.

What kind of flowers to you put in a window box?  What plants grow well in planter boxes?

When selecting flowers for a window box, you have a wide range of options depending on your desired aesthetic, sunlight conditions, and personal preferences. Here are some suggestions that might be fun to try or consider:

1. Pansies: Pansies are colorful flowers that can thrive in both full sun and partial shade conditions. They come in various vibrant hues such as purple, yellow, red, blue, pinks, orange, white and even black.   They can add a cheerful touch to your window box.
2. Foliage Plants: Foliage plants like ivy, ferns, and coleus can provide a lush and green backdrop for your window box. They add texture and interest with their different leaf shapes, sizes, and colors.
3. Petunias: Petunias are popular annual flowers that bloom profusely throughout the summer. They come in a wide range of colors including white, red, yellow, purple and pink. They are well-suited for full sun conditions. They can create a cascade of colorful blooms in your window box.
4. Geraniums: Geraniums are classic and hardy flowering plants that are available in various colors. They are tolerant of both sun and shade, making them versatile for window boxes. Geraniums can add a vibrant splash of color to your display.
5. Sweet Potato Vine: Sweet potato vine is a trailing plant with attractive, heart-shaped leaves that come in shades of green or purple. It is a great choice for adding a cascading or trailing element to your window box. It thrives in full sun and can be combined with other flowers or foliage plants.
6. Verbena: Verbena is a low-maintenance annual flower that produces clusters of small, colorful blooms. It thrives in full sun and can create a beautiful carpet of flowers in your window box.
7. Impatiens: Impatiens are shade-loving plants that come in a variety of colors. They are great for window boxes that receive limited sunlight.
8. Herbs: Incorporate edibles right outside your kitchen window!  Fresh herbs like parsley, mint, basil, and oregano in your window box. They add fragrance, texture, and can be used for cooking. The aroma may also attract bees and butterflies.
9. Vines: Vines like the Jenny vine or other climbing plants can be trained to grow vertically along the sides of your window box. They can create a beautiful cascading effect and add a touch of elegance to your display.
10. Spillers: Consider using trailing or cascading plants like asparagus fern, vines, sweet potato vine, and purple fountain grass as “spillers” to create a layered and visually appealing arrangement.

Remember to consider the specific light requirements of each plant and ensure they are compatible with the sunlight conditions your window receives. Also, consider the overall design and color scheme you want to achieve, balancing different flower shapes, colors, and foliage to create an eye-catching window box.

Do the flowers in window boxes need watering?

Depending on what you choose to put in your planter they may or may not need to be watered.  If you choose live plants then yes, they will need to be watered often (maybe even daily)- depending on the amount of sun they receive and the heat in your area.

But you can always try fake plants and follow this tutorial for how we made artificial plants for outdoors planter that looks incredibly realistic.- simply make it fit in the window box instead of a pot. Also, I think the addition of solar lights would look great in a flower box too!

If you would like flowers and not just greenery, I would even suggest trying out the dollar store, in spring, they often have a huge supply of inexpensive but great looking pansy style flowers, like we put in this planter a few years ago.

Remember you can even decorate your window boxes in the winter with evergreen cut branches or dry bare branches.

What is an alternative to a window flower box?

If you’re looking for an alternative to a window flower box, here are a few options to consider:

1. Hanging Baskets: Hanging baskets are a popular alternative and can add a touch of color and greenery to your windows. They are suspended from hooks or brackets and typically come with a built-in hanger. You can plant a variety of flowers or trailing plants in these baskets.
2. Wall-Mounted Planters: Wall-mounted planters are another great alternative that can be affixed directly to the wall beside or below your window. These planters come in various shapes and sizes and can be made of materials like metal, plastic pocket, or ceramic. They provide a vertical gardening option and can create a beautiful living wall effect. You can build your own monogram planter too, with these plans.
3. Freestanding Planters: If you have space near your windows, you can consider using freestanding planters or plant stands. These can be placed on the ground or on elevated platforms and provide flexibility in terms of size and style. They can accommodate a wider variety of plants and are not limited to the size of the window.
4. Window Shelves: Window shelves or ledges can be an excellent alternative for displaying plants. These shelves are installed directly inside the window frame, allowing you to place potted plants or small planters on them. They provide a compact and minimalist way to showcase your plants while utilizing the space efficiently.
5. Vertical Garden Systems: Vertical garden systems are innovative alternatives that allow you to grow plants vertically on a wall or frame structure. These systems often feature modular panels or pockets where you can plant flowers, herbs, or even vegetables.

These alternatives offer a range of options to suit different styles, space availability, and plant preferences. Consider your specific requirements and the aesthetic you want to achieve to select the best alternative for your windows.

Published 30 July 2016 // 24 Sept 2020 // updated 20 June 2023

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