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How to Plant Window Boxes

Do you have spring fever yet? I have been on a planting frenzy around here. I purchased new window boxes and filled them with beautiful plants. Do you feel lost when it comes to window boxes? What to plant? How to plant them? I have several tips and will cover how to plant window boxes in this post!

Window Box Tips

Choose a Color Palette

The color palette depends of your home, your setting, and most importantly, your preferences. For me, I prefer a simple white, green, and purple color palette. It mirrors our landscape perfectly. I’ve used bright and vibrant flowers in the past, but I grew tired of them quickly. You have free reign here, so select colors that make you happy!

Know Your Zone

One of the most important things you will need to know when selecting plants for your window boxes is your plant hardiness zone. You can find your zone HERE. What grows well in Charleston, SC might not thrive in Asheville, NC. The plant hardiness zone is based on minimum temperatures. When selecting your plants, you will also find all of the information you will need on the back of the insert for the ideal planting zone.

Determine Lighting

You will need to determine the location of the window boxes and what lighting they will have throughout the day. It’s really important to note how many hours of sunlight they will receive. For us, we have several different window boxes and they all receive different sunlight, with one box getting a mixture of partial shade and full shade.

Spacing – Plan to pack the window box

This is highly debated and you will find mixed reviews on this. I know, I know, why would you pack the plants and not give their roots room to grow? The prettiest window boxes are full of plants. Our 5′ window boxes have a ton of space to fill and they’re finally filling out a few weeks after planting. Trust me, the roots will be fine and you’ll have controlled growth.

Thrillers, fillers, and spillers

When selecting plants for your window boxes, follow the “thrillers, fillers, and spillers” method. Thrillers are typically the tallest plant and a focal point. They’re eye-catching, like the flax lillis seen here. Fillers are the middle layer and spread out while filling the space above the soil. These are often flowers and plants with various shapes like the coral bells see here. Finally, spillers are trailing plants that will flow over the containers. With a smaller container, you can select 1-2 of each category. For extra large planters like ours, I selected several different plants. I will dive more into that in my next post, with a complete list of the plants that I used.

Designing window boxes with tall plants, filling plants, and vines thats pillow over.

Drainage

Do not skip this step, you must ensure that you have proper drainage. Our window boxes have a water chamber and drainage holes below. If you do not have drainage, the roots will sit in water and your plants will be diseased.

Steps for planting Window Boxes

You’ve followed the tips above, now it’s time to plant your window box. Window boxes come in several forms, just make sure it’s secured properly. Adding soil, plants, and water will weigh it down.

1 – design

Set your plants out like they’re going in the window box. Move them around and play with groupings. If it is a long box, consider spacing several thrillers. For smaller boxes, use one thriller in the middle. Don’t worry about making them perfect here, you will be able to move them around, even after planted. Our window boxes are exposed on both sides, so I like to mirror the front and back of the boxes. If these are on a window or house, you will start with taller plants in the back.

window box arrangement with green, purple, and white plants

2 – Add Soil

First, make sure you select proper soil for containers. Regular soil will not have the nutrients needed to help your plants thrive. Some gardeners recommend mixing soil with perlite and peat. I’ve had great luck with Potting Mix Moisture Control. While our boxes have special drainage built in, you can also add gravel to the bottom of your window box before adding soil. Just note, this will make them heavy.

3 – Add Plants

Gently remove the plants from their containers. Break up the sides and bottom of the roots. They are often attached to the container and don’t worry if roots break when pulling the plant from the container. Tip: if your plant is difficult to remove, place the container on it’s side and gently tap on each side of the container until it wiggles free. Add plants per your design above. I prefer tipping the spillers to where they will pour out of the window box. Give each plant breathing room but do remember to pack those plants close enough to look full!

Breaking up the roots in window boxes

4 – Fill with Soil

Top the plants with soil. I like to use one of the plant containers as a scoop and to spread the soil. Finish with a thin layer of moss or mulch. This will help keep the soil moist. Make sure you leave at least one inch at the top of the window box so soil does not spill over with each water.

Spillers, thrillers, and fillers in window box
Flax Lillies, coleus, and geranium

You did it! Don’t forget to water the plants thoroughly after planting. Remember to make sure the soil doesn’t dry out between watering and keep them fed with fertilizer! Finally, deadhead (remove dead flowers) frequently to encourage new growth. If the plants start looking “leggy,” don’t be afraid to trim them back. They will thank you with beautiful and luscious new growth.

Happy Planting!

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2 Comments

    1. Hi, we attached them with heavy duty decking screws and the brackets that came with the boxes. They’re linked in the post above. Thank you!

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