How to Build a Window Planter Box and What to Plant in it

By   | Last Updated :   October 14, 2021 | Filed In :   Garden Accessory Ideas

Who hasn’t admired the view of a flower box-adorned Mediterranean street whilst on holiday? Many urban areas are adding foliage to their buildings, balconies and roof gardens, helping them remain cooler in hot weather and providing a welcome burst of colour to passers-by.

Window box planters offer home and business owners an opportunity to display their green fingers to a world outside their windows and are a wonderful way to bring joy and colour to everybody’s daily life.

Window planters provide a beautiful focal point both inside and outside the house.  This article will guide you through the plants that can survive outdoors and those you need to cosset indoors!  I’ve included plans to make your own wooden window planter, ideas for how to fill it and what to plant in each season, as well as a brief history of community window planter boxes. Let’s start with that.

how to build a window box planter

Brighten someone’s day with a beautiful flower box. Credit: Shutterstock

Community window boxes

The therapeutic benefits of growing plants are well documented. The innovative ‘Veg Your Ledge‘ community initiative in Forth, Scotland, has given local residents the opportunity to grow their own produce on their window sills. They receive a free upcycled window sill planter compost, vegetable seeds and bags of information and encouragement.

Plans to help you build a window sill planter box

Follow our guide to making a simple wooden window flower box that can be used indoors or out and watch this handy video guide.

Grow your own

If you’re keen to grow your own produce or flowers from your window sill, you’ll need to consider a few things first:

  1. Shade or sun? Consider if the planter box will be in the shade or full sunlight. Wonderful exotic plants like orchids will thrive on a warm windowsill but will shrivel up if the nighttime temperature drops significantly.
  2. Soil. You will also need to check that the type of soil you fill your planter box with will provide the right mix for all the plants you want to add. One way to do this is to provide different layers within the box. You can place a small plant into a brick or pot then fill the area with soil to cover the pot, this allows other plants to take advantage of the deeper or different soil.
  3. Season. Is this planter box for summer only? You are spoiled for choice with all the beautiful annual summer blooms available. However, when the cooler autumn air arrives, you will need to remove annuals that have reached the end of their lives then add perennial or evergreen plants, which will provide foliage and colour all year round. Read on for more details.

Seasonal window sill planter boxes

Here are some suggestions for what to plant each season so your window sill box is always filled with life.

Spring

Indoors

The trick with an indoor window planter box is to make sure most plants have separate pots which you can place into the planter, then remove after they flower.

Amaryllis will provide one spectacular bloom each year but needs warmth all year round. Allow it to dry out completely after flowering, then remove the whole pot for its dormant phase once the flower has died back.

flowers of amaryllis

Amaryllis blooms once a year but needs warmth all the time. Credit: Shutterstock

Hyacinths are a fantastic choice for planter boxes because the scent of their gorgeous flower head remains for weeks in the room where they are placed. These need to germinate in darkness so cover the pot and transplant them into your window sill when the first bud appears. Once they have flowered, you can leave them in the planter box and they should continue to flower year after year.

Blooming spring hyacinth flowers on windowsill at home

Don’t put hyacinths on your window sill until the first bud appears. Credit: Shutterstock

Cyclamen offer delicate flowers from December to spring.

Wilted colorful variegated white and pink cyclamen flowers on windowsill

Cyclamen will keep your window pretty the whole winter. Credit: Shutterstock

Busy Lizzie is an old favourite of mine, a flower loved in cottage gardens for centuries. Easy to propagate, they enjoy being in a warm sunny place and a window box is perfect. Just make sure you prune your busy Lizzie if it starts to get leggy or overshadow other plants.

a row of hanging baskets filled with busy lizzies

Easy to grow and care for, busy Lizzies are a gardener’s favourite.

Outdoors

Summer

summer sunset

Credit: Shutterstock

Indoors:

Any plants which can be moved outdoors for summer will reward you with abundant growth and I recommend this. The plants below all need summer sunshine and will grow well indoors.

potted spider plant with babies

@crazy.plantlady_tessa

Dwarf tomato plant in a pot with ripe and unripe tomatoes

Good enough to eat! Grow tomatoes in an indoor or outdoor planter box. Credit: Shutterstock

There are plenty of shade loving indoor plants too so don’t despair if your window sill is not so bright.

Different beautiful ferns in pots on white window sill

Ferns are great for windows lacking sunlight. Credit: Shutterstock

Potted Sansevieria plant near window at home

Sansevieria is a low maintenance plant for a window sill planter box. Credit: Shutterstock

summer savory herb plant

Credit: Shutterstock

Outdoors: 

Cover up your spring bulbs with fresh compost and get ready for abundant foliage and flowers! It’s a good time to add a dahlia or a sedum to your window box, which will flower later in the year.

Pelargonium and geraniums in flower pots on the windowsill of a rural house outside

Credit: Shutterstock

Nasturtiums climbing vines

Credit: Siena Scarff

Autumn

beautiful autumn landscape with yellow trees and sun

Credit: Shutterstock

As the evenings draw in and the temperature cools, it’s time to start moving delicate plants indoors.

Indoors:

Ornate Planter with Home Grown Organic Herbs (Tarragon, Chamomile and Oregano)

Credit: Shutterstock

Rosemary (Salvia rosmarinus) and Thyme (Thymus vulgaris) Herbs Growing in a Metal Planter

Credit: Shutterstock

close up of woman potting geranium flowers

Credit: Shutterstock

Outdoors:

Winter

Window sills are not the most hospitable of environments in winter. Indoor plants have to contend with heating and outdoor plants may become frozen. You can protect some plants by covering them up if extreme weather is forecast.

protecting plants from winter

Cover up plants to protect them from harsh weather. Credit: Shutterstock

Bubble wrap, old blankets and even cling film may save delicate window-box perennials.

Indoors:

Beautiful poinsettia in flowerpot. Red christmas flower on the windowsill

Add a festive touch to your home with a red ponsettia. Credit: Shutterstock

Outdoors:

Tina’s tips:

Before you buy a new window sill planter box, see if you can find one here:

https://knowhow.ncvo.org.uk/how-to/how-to-set-up-a-community-garden

http://www.forthenvironmentlink.org/latest-news/community-groups-dig-window-box-growing

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