What Size Window Boxes Should You Use?

A home with several window boxes

A good rule of thumb: Match the width of the flower box to the width of the window. Use smaller flower boxes on smaller windows, and larger ones on larger windows.

Matching the right window box to your home can add curb appeal, but there are many things to consider before making a final decision. What materials should the box be made of? How big should the box be? What size and depth is best for the plants that you want to pair with your home?

A flower box beneath a window with shutters

For windows with shutters, consider using a flower box wider than the window.


Window Box Length Tips

Once you’ve settled on a flower box material and style, deciding how long your new window boxes should be is the next big decision. In general, window boxes look best if they are the same width as the window, but there are exceptions to the rule. For example, if your home has shutters or wide exterior trim pieces, you may want your window boxes to run under these architectural features or sit slightly inside. Since many windows are around three feet long, almost every window box style is available in 30″ and 36″ lengths.

When placing a window box on a deck or porch railing, it should fill the space without making the railing unusable. Leave several inches between the end of the window box and any steps so that your growing plants don’t make these spaces unsafe. Use a cardboard cut-out or chalk outline to help yourself visualize the perfect window box for your space if you’re unsure of the right size.

an eight foot long window box under a window

This 96″ long window box was custom made for a homeowner who wanted something impressive! Very long flower boxes look stately.

For a very long window, railing, or fence, you can either mount several small window boxes or one large one. Most Hooks & Lattice window boxes can be purchased in 60″ and 72″ lengths, and many can be manufactured in even larger custom sizes. We’ve built flower boxes over 100″ inches long! Long window boxes look dramatic and impressive; just remember that you’ll probably need some serious help to lift and mount them.

An XL window box

This extra-wide, extra-deep window box has lots of room for plants and their roots.


Window Box Depth & Width

Window box suppliers like Hooks & Lattice usually offer our most popular boxes with standard dimensions and extra-large boxes that are wider and deeper than usual. Standard boxes are a good fit for many homes, but sometimes the extra-large flower boxes are more appropriate. Organic Gardening magazine recommends measuring the height of your windows before settling on a size. A box that is 20 to 25 percent of the height of your window feels adequately robust on most homes. If you choose very large brackets for your flower boxes, consider their visual impact in your decision as well.

Bigger boxes have a practical benefit: Because they hold more soil, they won’t dry out as quickly, and so they will allow you to plant less drought-tolerant plants. For this reason, we recommend that gardeners in hot climates use XL hayrack window boxes instead of hayrack planters in normal sizes. Deep flower boxes also work better for perennial plants, which tend to root more deeply than annuals. Extra-large boxes are more flexible to plant, even allowing multiple rows of small annuals if you want to create layers of colors.

This cedar flower box is just 6" deep, so your flowers will draw most of the attention.

This cedar flower box is just 6″ deep, so your flowers will draw most of the attention.

On the other hand, shallow boxes look nice on homes with delicate features, since the smaller box and brackets won’t overwhelm the home’s architectural details. Small window boxes won’t stand out in an obvious fashion, instead providing a subtle space for gardening. Our Tapered Cedar Window Box is just 6″ high, putting the spotlight on your plants. These smaller boxes are great for annuals, herbs and artificial plants. Because they hold less soil, they’ll weigh less, making them easier to lift and mount.

As with any décor decision, you should be aware of these design suggestions but ultimately choose whatever looks best to you. Don’t be afraid to defy convention! With some skill, almost anything can look great. Above all, window box gardening should be a fun and relaxing way to express your creativity. Experiment with different options and find the one that suits your style. Need flower box sizing advice? Comment below and we’ll let you know what we think!

26 replies
  1. Deborah
    Deborah says:

    I have a plain ranch home with clay colored vinyl siding and white shutters with 36″ windows. Should the window boxes sit just under the window or should they go from shutter to shutter (outside)?

    Thank you!

    • Andrea Satterfield
      Andrea Satterfield says:

      Excellent question! There is no exact way to measure for a window box as it is solely up to personal preference but for a general rule of thumb, go at least the length of your window, no more than 4″ outside of either side unless you have shutters – then you can go as far as the halfway point of each panel. And since you do have shutters, make sure that when you install a window box, that is be under the window sill, not on the frame, so if your shutters are operable, they can close over the window opening. I hope I was able to answer your questions 🙂

  2. Rebekah
    Rebekah says:

    My house is stucco and very tall and narrow. I am trying to add some depth and width to the house by adding window boxes under three front windows measuring 90 inches long. How wide or deep should the window boxes be and should I break it up into 3 separate window boxes or just one long box?


    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Rebekah!

      Excellent question – we get this one often. If you have three windows right next to each other, the preference is really your own personal style. As you mentioned, the two best options are to:

      1. Purchase three window boxes that are ~30″ long to break it up equally.
      2. Purchase one long custom ~90″ window box

      The depth and height of the window planters isn’t that important – most boxes you find will be around 8-10″, which is more than enough planting space and large enough to see the architectural detail of the window boxes. In my experience, this is also the most common practice – plus, 30″ is a standard size for us so you save money by avoiding customization fees and oversized shipping costs. You’ll likely be able to receive your window boxes faster if they are not made-to-order.

      My personal preference, and this is due to planter maintenance and my own personal style, is to purchase three smaller boxes. Seasonal plantings are easy and I just think a window box under each pane looks ideal.

      Here are a couple of links my past clients have sent me that will hopefully help with your decision.

      Kathy’s Fiberglass Window Boxes
      Allan’s Fiberglass Window Boxes >>
      Sandi’s Second Story Windows
      Scott chose to go with two planters under three windows, Click Here >>

      We’re here Monday-Friday to help you choose the right size. Feel free to give us a call at 1-800-896-0978 between 7am and 5pm PST.


    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Nicole,

      Yes, tall windows need window box love too! Just be sure to measure prior to placing your order to be sure that the height of the planter will fit in the 2-foot space you mentioned. Window boxes should be installed snugly under windows (not to the trim itself). Most of our window planters are 6-10″H, fitting well within the space you have. We also do custom sizes should you need.


  3. Janine
    Janine says:

    I have a large house that has many double hung windows with no shutters. I was going to put flower boxes on every window. Is there a rule of thumb on just putting them on the first floor or second floor only? Or sporatically?

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:


      First off, EVERY window can benefit from a window box! 🙂

      More often than not, homeowners will opt to do one floor at a time, or will focus on more prominent windows first if they don’t outfit the entire floor at once. Most people start with the ground floor and work their way up to the second and third stories, then balcony railings.

      We do have a very talented design team that would be happy to take a look at a photo of your home and make more specific recommendations. Email us: Sales@HooksandLattice.com

      Additionally, we offer discounts for orders of 10+ of the same item. If you need 10+ of the same size and style window box we will give you 10% off! Call: 800-896-0978 to get the discount.


  4. Nilusca
    Nilusca says:

    Where I live it is summer year around, and I mean a lot of sun and really hot. Which material is the best for this kind of weather?

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Nilusca,

      You are wise to search for a material that can withstand high heat without damaging your plants, thanks for your question!

      You’ll mainly just want to avoid metal planters if you are concerned with heat and full sun. Cellular PVC composite is an option for your location, but do keep in mind that PVC is a flexible material – even the solid 1/2-inch thick stuff we use to make them. We have seen PVC window boxes bow in locations with full sun and high temperates, but ONLY when the boxes were painted a dark color (especially black and dark green hues). That said, a cellular PVC planter would work well for your plants, but I recommend leaving it as it comes (white) or opting for a lighter paint color.

      Fiberglass is an ideal material choice for both hot and cold locations, and what’s great about fiberglass is that it can even mimic wood! Imagine a world where your planters look like wood but never rot and never need refinishing. These window boxes come in many styles, and most have the option to add a self-watering reservoir to give your plants an extra helping hand — even when it gets into those triple digits! We’re located in a coastal desert climate, and fiberglass window boxes with reservoirs are our #1 pick for containers: http://www.hooksandlattice.com/windowbox56.html


  5. Alicia
    Alicia says:

    I have a bungalow with concrete built in brackets to the brick. I want to purchase a metal box but am unsure of how far past the brackets is safe for the box without compromising the shape of the metal box. a 60″ goes about 3″ out on either side of brackets and a 72″ goes around 10″ out on each side. I prefer the larger, but don’t want to make the wrong purchase and ruin the box. Whatcha think?

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Alicia,

      If I’m understanding correctly, you’re trying to choose between a 60″ or a 72″ box, based on bracket spacing and overhang consideration. Large window boxes like this can become very heavy once filled with soil, plants and water. With our window boxes, we recommend using 1 pair of brackets for boxes up to 48″. Longer boxes like the 60″ and 72″ would require the use of at least 2 pairs of brackets to sufficiently support its weight.

      However, there are ways around this should you only want to see 1 pair of brackets. Purchase one of our wrought iron cage and liner combinations and install it using the built-in channel mounting system on the back. You can do this using 1/4″ diameter bolts and the pre-drilled holes in the back of the cage. Once secure, you are free to add any number of brackets for aesthetic purposes.

      Hopefully this helps, but let me know if you come up with any more questions or I didn’t understand your question.

      Thanks! 🙂

  6. Kimberley
    Kimberley says:

    My windows have wide trim all the way around them. Should the box be on top of the trim and snug to the window or should it be under the trim and snug to the trim. The trim is like 8 -10 inches wide.

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Kimberley,

      Great question! I have seen window box planters installed both on and under the trim, depending on the width and the personal preference of the homeowner. I normally would not recommend bolting the box right to the trim, but since you’re working with 8-10″ of it, it makes sense.

      Our line of PVC window boxes are all roughly that height; if you were to install one of them right under the window itself it would cover the trim and look pleasing to the eye. Many of them also have cleat mounting systems that make it incredibly easy to install and remove whenever replanting or cleaning is desired. Here is a link to the collection of the no-rot planter boxes I’m talking about: http://www.hooksandlattice.com/windowbox25.html

      They’re also fully customizable!

  7. Audrey
    Audrey says:

    I would like to instal a window box but my windows all open outwards. Should I instal them 10-12″ lower than the actual window to allow for growth?

  8. Cathy
    Cathy says:

    I have a different question but need some help I have 6 windows across the front of my house do I do window boxes on all 6? Seems like over kill but I’m afraid if I don’t then it will look like I skimped I’m open to everyone to give an opinion

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Cathy!
      While I have not seen your home’s windows, I will tell you that a flower box on each window is not overkill. In fact, it’s downright gorgeous! We provided flower boxes for a brick house in VA with multiple windows. You can view their photo here: http://www.hooksandlattice.com/frpaonbr.html
      We’d love it if you would reach out to our San Diego-based design team. We can work with you to find just the right look for your home!
      Call/email at your convenience: 800-896-0978 / Sales@HooksandLattice.com

  9. Julie
    Julie says:

    Hi there,

    We have a 1950s little California ranch house with horizontal wooden siding and stucco and are wondering what style window boxes to use. Our windows are original, one diamond payne and one regular, and are 6 1/2 feet long. It seems hard to find anything that long that is not over $300. I’d love any advice from you, thank you!!


  10. Sam
    Sam says:

    I am putting boxes on several old, small windows. The window glass is 24″w, if I measure trim to trim, it’s ~30″, and if I measure the thin sil that sticks out a little more they are 33-36″. I’m wavering between 24″ and 30″. What would you suggest? Thank you!

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Sam, I recommend going with a 30 inch window box. The general rule of thumb is to get a window planter that is at least the width of your window glass and protruding no more than 4″ past either edge. A 30 inch planter will look more appealing than a 24 inch will with your window trim. Thanks!

  11. Tara
    Tara says:

    Hi Lindsey,

    I am so glad I found your page! I have been going back and forth on how to add a window box to our large, 82 inch picture window for years. Would you suggest one large custom box or two smaller ones? Also, what depth would you suggest? It is a smaller cape with one large window and black shutters, if that helps at all. Thank you!!!

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Tara…I’m glad you found us too! 🙂

      Both methods will give you a gorgeous display, but I have a few tips that might help you make your decision.

      For the technically “perfect” installation, you’ll want to order a custom window box that’s between 82″ and 90″ long. While this will look absolutely amazing it can also be cost prohibitive, depending on the window box style chosen and how far you live from our shipping warehouse. My personal recommendation is to order 2 of our standard 42″ long boxes. They will look just a beautiful, and – you can often hide the seam between the two boxes using trailing flowers or vines – giving you the same aesthetic of a tailored window box while saving you a considerable amount of money and time.

      For depth, I recommend something that’s at least 9″H. Most of our window boxes fall in this range, including all of our wrought iron boxes here: http://www.hooksandlattice.com/windowbox42.html and our XL series of no-rot PVC boxes here: http://www.hooksandlattice.com/windowboxes25.html

      For a custom quote or more information, give us a call at 1-800-896-0978. Thanks!

  12. Ed
    Ed says:

    Hi Lindsay. We have an English 2 story brick home. I have two double hung windows in front, measuring 39″ and 70″, respectively. Window boxes need to be black. Sun exposure is mornings only (facing east). I’m thinking fiberglass boxes might be the best, but would appreciate any recommendations you have, considering the need to mount to the brick and other factors. Note both windows have a ‘sill’ of turned bricks that extends 2″past the wall of the house, so we would mount below those.

    • Lindsey Pfeiffer
      Lindsey Pfeiffer says:

      Hi Ed,

      You are wise to consider fiberglass as a material. Its lightweight durability and no-rot properties make it my #1 pick for overall value and versatility! Plus, we can customize nearly every aspect, should the need arise.

      I recommend sticking with standard sizes for your windows. A 42″ size will fit your 39″ window, and the 72″ size will fit your 70″ window nicely. Don’t worry that the 42″ box is 3″ larger and the 72″ box is only 2″ larger than the windows. Once the window boxes are centered the only person who will know is you – especially if you plant trailing varieties on either end of the box.

      All of our fiberglass window boxes come with brackets and bolts for installation into wood/stucco. Be sure to pick up lag shields to protect your masonry and securely install. We offer bolt/lag shield packages made specifically for brick/masonry installations, but you can also find common pieces like this at your local hardware store.

      My top recommendations for black fiberglass window boxes are the Laguna or the Brickton (new for 2017).

      Give us a call for a quote on custom pricing or additional consultation, we’re happy to help! 1-800-896-0978


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