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    Home » Gardening & Outdoors » Planters / Containers

    Petunia Window Boxes

    Published: Mar 8, 2024 · Modified: Mar 8, 2024 by Susan Moncrieff · This post may contain affiliate links · 3 Comments

    Craving vibrant colors for your windows? Look no further than petunias! This post explores the beauty and ease of planting petunias in window boxes with the addition of trailing sweet potato vine. Learn key tips for about planting techniques, and ongoing care to ensure a cascade of blooms that will transform your home's exterior all season long.

    How to plant your window flower boxes

    window box with petunias and sweet potato vines

    Not sure how to take care of your petunias when they start getting long and leggy? Here is the info you need in the post called Pinching Back your Petunias.

    Table of contents

    • How to plant your window flower boxes
    • Preparing the window box
    • Removing old soil and adding new
    • Fertilizing
    • Do I plant traditional thriller, filler, and spiller plants?
    • Watering
    • Popular Planter Posts

    Preparing the window box

    Make sure there are drainage holes at the bottom of the planter.   Plants don't do well if their roots stay soggy.  If the roots are wet all the time and don't dry between watering, they can suffer from root rot. If you have a window box attached to the house, use a liner to protect the wooden boxes from damage.  In this example today, there are plastic window box pots that get inserted and then there is also a plastic liner to protect the wood from damage from all the water.

    The bottom of the plastic planter container is lined with plastic so that the water doesn't run out and damage the wooden planter boxes.  The planters need to be watered about once a day (twice during those hot days).  Don't plant petunia flower boxes if you can't commit to the regular watering!!

    Removing old soil and adding new

    Each spring, about ⅓ of the soil from the previous year is taken out and replaced.  There were some seriously strong recommendations for Miracle Grow potting soil with moisture control (I love the stuff too!!). When you have window boxes, make sure you use potting oil (not top soil, or ground soil etc.). It does make a difference.

    planter box

    Fertilizing

    And the magic to make these beautiful window boxes grow so beautifully?  These petunia and sweet potato vine window box plants get watered in with a weak mixture of Miracle Grow after they are planted.  After that, they get fertilized roughly every second week (diluted to ½ of the manufacturer's recommendation).  There isn't a lot of soil in the containers and the plants need all the help they can get!

    window box

    Do I plant traditional thriller, filler, and spiller plants?

    The thriller, filler and spiller plant formula is a traditional combination of plants that looks great in a planter. If these terms are a mystery to you, I've described them in detail in my post called
    31 Outdoor Planters for Ideas and Inspiration
    If the window box is under a window, I often don't put in a tall thriller type plant. In some cases the window box looks better when the plants and flowers are the same height across the planter and flowers or interesting leafy plants trail down.  In this example the petunias and potato vine will grow to roughly the same height and will trail down the window frame.

    window planter boxes

    Watering

    Plan to water daily! When it's hot and sunny, you may have to water twice daily. Often the plants start to droop. Stick your finger a couple of inches into the soil and if it's dry, you need to water.

    It often takes a couple of weeks for the plants to establish themselves.

    window box
    Then they thrive! You will definitely know when they are happy!!

    Yes, I think I love the idea of a built-in window box under my front windows.  Hmmmm, I'll have a long winter to give it some thought!

    As promised, here is the window box planter a little later in the summer!  Didn't it fill in nicely?  I love the bright pink petunia and the spikey green sweet potato vine.  Such a bright and fun contrast in colors!

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    window box with pink petunias and sweet potato vines

    Later in the summer, here is a whole-house view of the house with a beautiful window planter box under most windows. I love this look and think it has a European flair. Petunias have such long seasonal blooms that they last the whole summer and even into the fall. Unfortunately, a hard frost marks the end of the season for these guys!

    house with pink and green window boxes on each window.

    Popular Planter Posts

    • planters in front of garage
      Planters in Front of a Garage
    • using a white watering can to water plants
      Tips for watering your plants.
    • petunias sticking out the side of the planter
      Pinching Petunias back
    • hanging planter with red and purple plants
      Watering hanging baskets

    **Originally published June 2015.

    More Planters / Containers

    • Over 20 flower planter ideas from my neighborhood!
      31 Planter Ideas and Inspiration
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      How to Find Cheap Planters (and Repurpose What You Already Have)
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      What Is a Flower Frog? (Antique & Vintage Examples)
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      Wall-Mounted Mason Jar Vase

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    1. Britnee

      July 11, 2021 at 11:08 pm

      Thank you so much for the window box tips. This is my 1st year planting window boxes. I love my flower garden. I would love to be able to share my pictures of my window boxes if possible?

      Reply
      • momcrieff

        July 28, 2021 at 6:28 pm

        Unfortunately, the pictures of your windowboxes can't be shared in the comments. But, I would LOVE to see them. Please send them to me at susan@momcrieff.com .

        Reply
    2. Beverly

      April 26, 2018 at 7:20 am

      Love the names of flowers used. Not allowed to put flowers in ground only in pots, love the colors and blooms.

      Reply

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    I'm Susan! I love sharing easy recipes, especially those that take less than 30 minutes and have less than 5 ingredients. I'm passionate about gardening and creating flower planters. My home is 100 years old and sometimes you will see it in my posts! It was a true fixer upper and I love it!

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