Mother’s Day is May 12th! Shop window boxes and planters in time for the special day at Hooks & Lattice. Use code CONTAINS15 to save 15% off your purchase! #hooksandlatticepartner

For many of us, Mother’s Day kicks off the container gardening season. The threat of frost is likely behind us, but we have a few more weeks before Memorial Day and the official start to Summer. Retail garden centers are overflowing with colorful annuals to ring in the season. The time is right to start planting!

If you caught my recent post, Window Boxes 101, you learned my tips for selecting the right style and size window boxes to fit your space. Here, in Window Boxes 201, I share more design tips and guide you step-by-step through the planting process. I want to help you plant your new window boxes like a pro!

DESIGNING A WINDOW BOX

LIGHTING CONDITIONS

Before selecting plants for your design, consider your sun exposure. Every environment is unique, but you’ll generally fall into one of three categories: Shade (0-3 hours of sunlight daily), Partial Shade/Partial Sun (3-6 hours of sunlight daily), or Full Sun (6 or more hours of sunlight daily). If you aren’t already familiar with the plants that will thrive in your outdoor space, or if you simply want to try something new, read the tags on plants you like and ask a pro at your local garden center if those are good choices for your environment.

COLOR PALETTE

Once you know your lighting conditions, consider your desired color palette. For a sophisticated design, or for anyone just beginning to experiment with container gardens and flower boxes in general, I recommend a base of green and white plants with a pop of one feature color. If there’s room to repeat that same color across several plants, or incorporate multiple shades of the feature color…even better! I chose to feature a joyful yellow in this design.

POSITIONING

There are two ways I like to position plants in window boxes. The first method involves using one central Thriller, then surrounding it with mid-tier Fillers and trailing Spillers as you work your way out to the front and sides of the box. You can read more about that style and find a sample planting diagram in  Window Boxes 101.

The second method is what I call the “Suspension Bridge” approach, where three Thrillers (“T” in the diagram below) are positioned equidistant from each other to create the peaks of the “bridge”, then Fillers (“F”) and Spillers (“S”) are added to fill the valleys between the peaks. This technique creates a nice up-and-down rhythm to your arrangement and is especially valuable in filling very long window boxes where you want to break up the length with more height and movement.

Imagine using Thrillers (the tallest plants in your arrangement) to mimic the peaks of a suspension bridge, with Fillers and Spillers tucked in the valleys.

PLANTING A WINDOW BOX

Once you’ve chosen Thrillers, Fillers, and Spillers, follow these steps to planting a window box using my Suspension Bridge method. This is a 36-inch, no-rot Laguna window box from Hooks & Lattice and I filled it with shade-tolerant plants. This space is a covered porch that enjoys about one hour of early morning sun.

STEP 1 — PREPARE YOUR FOUNDATION

After your window box is mounted securely beneath your window, add drainage discs to cover the drainage holes. This will help prevent clogs, allow excess water to escape freely, and minimize the amount of debris that might escape and create a mess on the surface below the box. Then fill your window box with fresh potting mix to a level about two inches from the rim. I often use Miracle-Gro potting mix because it already includes slow-releaser fertilizer to help feed the plants for a while…plus, it drains well.

STEP 2 — LAY OUT THE PLANTS

It’s helpful to lay out your plants beneath the window box to make sure you’re pleased with the positioning, particularly if you’ll be planting while standing on a ladder. This is also a great time to give them a really thorough soak if the soil is dry. I started with three ‘Jester’s Crown’ Ferns to serve as Thrillers, or the peaks of the bridge. Then I began to fill in the valleys between the ferns with my first Fillers, the ‘Magnum White’ New Guinea Impatiens. My second Fillers, ‘Amstel Blitz’ Rieger Begonias, are positioned more toward the front of the box so their happy color can be enjoyed on day one. Next, I placed my third Fillers, ‘Diamond Frost’ Euphorbia, next to the Begonias. I love how the lacy airiness of the Euphorbia contrasts with the rich colors and lightens the mix of plants. Lastly, I placed two different types of Spillers along the front edge of the box: Needlepoint Ivy went to the outside corners and center; ‘Jade Frost’ Lamium, with its subtly variegated leaves, filled in the gaps between the fern fronds and the ivy.

STEP 3 – START PLANTING

Follow the same order I used in laying out my plants — Thrillers, Fillers, then Spillers. The Thrillers (the ferns in this example) set the framework for the arrangement and should be placed in the center, then evenly spaced to the right and the left. Remove plants from their nursery pots, give the roots a gentle massage, and tap them to release any loose dirt. Then nestle each one into the potting mix in the box. Add more potting mix to surround the root balls if necessary, and gently pat down any loose soil. Next, move on to the first Fillers (New Guinea Impatiens). Then, add the remaining Fillers (Begonias and Euphorbia). Lastly, add the Spillers (Ivy and Lamium) to their designated spots.

STEP 4 — FINE TUNE

This step is important. Do one final check to tuck in each individual root ball and fill any gaps with potting mix. Then, double check all the way around the interior perimeter of the box — on all four sides — to really pat that potting mix down so that it’s a good two inches beneath the rim. This not only helps protect roots, but also prevents excess water from overflowing and taking the potting mix with it. Once you’re confident the potting mix is tucked in, use garden snips or scissors to trim off any broken stems or unsightly leaves.

STEP 5 — CLEAN UP

Bringing water into your planting area at this point will probably create a muddy mess. I recommend removing as much plant debris and spilled potting mix as possible with a broom or gentle leaf blower, before you water. A dry paint brush is a great way to remove dirt from the edges of the window box and even the window sill!

STEP 6 — WATER

Water gently and target the base of each individual plant to help the fresh potting mix settle around the roots. Your potting mix will probably be a little loose for a week or so, until several waterings have occurred. Any smudges of dirt on the window box can easily be removed with a clean, damp microfiber cloth.

STEP 7 — MAINTAIN

Your window boxes and container gardens will be most successful if watered consistently, fertilized occasionally, and deadheaded as needed. Most mixes of annuals prefer their soil to stay evenly moist, so test the soil every few days to make sure it hasn’t dried out. Conversely, please don’t overwater — signs of which are yellowing leaves or even the stinky smell of rotting roots. Apply water-soluble fertilizers according to instructions and use either a Blossom Booster for flower-forward designs, or an All Purpose solution for foliage-heavy arrangements.

How Can I Help You?

I hope these two blog posts, Window Boxes 101 and 201, have given you the confidence and inspiration to add window boxes this year…whether you’re treating yourself or a special mom in your life! If you have questions, need additional guidance, or simply want to share what you think, please leave a comment below.

Hooks & Lattice is just as excited as I am to help you get started, and they’ve extended their 15% sitewide discount for my readers for a limited time! Shop Hooks & Lattice for all the window boxes and accessories you need to get started, and use code CONTAINS15 at checkout to save 15% off your entire purchase!

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Wishing all of the moms and mother figures out there a very Happy Mother’s Day! I hope to hear from you soon!

All the best,

Steph

PS: I’m so grateful to Hooks & Lattice for sponsoring this post! I hope you’ll visit hooksandlattice.com to see the beautiful window boxes, railing planters, hanging baskets, and self-watering systems they offer to help YOU create elegant container gardens with ease!