The Art of Creating Beautiful Window Boxes

Windows are one of the most the important architectural features of any
house. And windowsills are for many London flat dwellers the only piece
of garden they can cultivate. In this blog we look at the art of creating
beautiful window boxes.

Why bother? Firstly, if as Shakespeare wrote, ‘the eyes are the window to
your soul’, then windows are the eyes to the soul of your home and deserve
beautiful window boxes. Secondly, cultivating beautiful window boxes allows
you to express your individuality and offer your visitors a cheery welcome.
Finally, it’s a great way for budding gardeners to get started.

Setting up your window box

1. Location

Window boxes can be placed on sills or supported on brackets beneath the
window.
Expert tip: Why not double up your growing space with boxes on the
sills and on brackets under the windows?

2. Styles

At Capital Gardens there are many materials and colours of window boxes
to choose from. Unglazed terracotta and reconstituted stone look
traditional but are heavy and more expensive. However, they are more
likely to stay put during sudden gusts of wind. Remember, always ensure
your window boxes are well secured!
We also stock wooden, metal and plastic window boxes in a range of styles,
colours and sizes. Check instore for availability.
Examples of our boxes: Venetian terracotta window box, 82cm; £24.99.
Hidcote wooden trough planter, 57cm, £29.99; Plastic Millennium trough,
79cm, £49.99; Elho recycled plastic window box, 50cm, £16.99.

Expert tips 

a) Plain window boxes are okay; you can always screen them with tumbling
plants such as ivy. But if you invest in good quality decorative window boxes
then you can show them off by leaving the sides clear.

b) Super-Size Me. Purchase the biggest window boxes you can fit on your
windowsills. Firstly, big boxes hold more soil and therefore more plants.
Also, a larger window box will dry out less quickly than a small one. Finally,
window boxes need to be bold to be noticed.

3) Preparation – Before you plant you need to get the basics right.

To re-use an old window box, first take it down and empty the contents. Then
save any plants you want, and throw away the rest. You only have limited
space in a window box – don’t waste it on poorly performing plants.

Throw away the old soil. Wash and scrub the window box to keep it free of
pests and diseases. Now it is ready to use.

Cover drainage holes with crocks (broken shards of terracotta pot) to stop the
earth compacting around the hole.

Consider investing in window boxes with built in reservoirs if regular watering
is an issue.

Always fill your window boxes with new multipurpose compost to ensure your
plants have the correct mix of nutrients and there are no weed seeds or pests
and diseases in the soil.

Mix pre-soaked water retaining granules in with the compost – it will help even
out any watering issues. Grow-it water gel crystals, £3.99 for 125g, can reduce
the need for watering by up to 4 times.

Add a slow-release fertiliser to your compost.

Arrange your plants in the box before planting them, to see how best to place
them.

When planting in your window box firm the compost around the plants to make
sure they are well planted.

Finally, after planting up, add a dressing (mulch) to the top of the compost. This
could be grit, gravel, pebbles or glass beads. This top layer not only gives the
boxes a professional finish, but it prevents the soil from splashing out when you
are watering. It also helps cut water loss by evaporation and reduces wind and
bird carried weed seeds from germinating.

Make sure there is a 4cm gap from the top of the window box to the dressing so
that the water soaks in and doesn’t spill over the sides when you are watering.

Expert tip

Terracotta window boxes dry out faster than plastic ones. Line terracotta boxes
with a plastic bag to reduce water loss by evaporation – but be sure to cut holes
on the base so the water can still drain!

Choosing the plants

The art of creating beautiful window boxes for a summer display is in the planting.

New gardeners often like to go for the ‘Queen Vic look’ – and there is nothing
wrong with this. If you want to bring colour to your street and happiness to your
neighbours and passers I say, ‘go for it’!

Many pubs display vibrant window boxes that bring great pleasure to all. This year
pubs and restaurants will be decorating their outside side areas with renewed
vigour as outside drinking and dining is possible again now Covid-19 rules are
being relaxed.

Oscar Wilde said, ‘nothing succeeds like excess’, and that applies here. To ‘style
the look’ pack your boxes with as much colour as possible. For example, picture
a mixture of colourful Petunias, brilliant Begonias and Pelargoniums
(aka Geraniums), blue Felicia, yellow Bidens, and rivers of Lobelia spilling down
the sides. You will find all these plants and more in the bedding area of your
local Capital Gardens garden centre.

Basic window box planting design

Even a kaleidoscope of colour can be improved by following a basic garden design
rule. This is where we add the ‘art’.

The key to an aesthetically pleasing window box is ‘Thriller, Filler & Spiller’. This
design hack creates a 3-D structure that looks rich, mature and right.

Follow this rule and you will avoid window boxes that look like a dog’s dinner:

Firstly, the ‘Thriller’. A tall plant that gives impact through its colour and shape.
Window box ‘thrillers’ include Canna lily, large begonias, Cordyline, Cosmos,
Salvia and Dahlia.

Then the ‘Filler’. A mound forming plant that will fill the lower space, hiding the
soil and the base of the ‘thriller’.

Good ‘fillers’ include Ageratum, bedding Begonia, Coleus, blue Festuca grass,
Gerbera, Gazania, Helichrysum, Heliotrope, bush Lobelia, Lantana, black Ophiopogon,
Petunia and Pelargonium.

Finally, the ‘Spiller’. A trailing or tumbling plant that blurs the edges of the planting
and container.

My go to ‘spillers’ are Alyssum, trailing Begonia, Bacopa, Calibrachoa, Ivy, trailing
Lobelia, Nemesia, Nasturtium, Surfinia Petunia, and Sweet potato vine.

‘Thrillers’ work best when planted in low numbers. Plant them as a single specimen,
or group of 3 at the centre of your design. The ‘fillers’ and ‘spillers’ are planted in
multiples of 3 or 5 depending on the size of your window box.

Expert tips

1. The key to beautiful window boxes is generous planting. Don’t worry about
   cramming bedding plants together, they will have plenty of fresh compost to
   grow into, and you won’t have long wait before you have a brilliant display.
2. Move beyond the basic by thinking about your use of colour. Instead of a
   rainbow go for a theme. It could be red, white and blue for the patriotic
   gardener, or pastels and purples for an artistic look, or mainly whites and
   greens for a sophisticated Sissinghurst feel.

Keep it simple

I don’t like mixing lots of plants in window boxes. A mass planting of a single variety
can make a much greater impact than a smorgasbord of different plants.

If you are lucky enough to have a sunny aspect your window, then few plants will give
you as much continuous bloom for the minimum amount of effort as pelargoniums.
Whether you prefer the Mediterranean feel of brick red Geranium flowers or the
Tyrolean feel of pink tumbling ivy-leaved geraniums you can’t go wrong with this
classic planting. A window box full of Mexican fleabane (Erigeron karvinskianas)
will provide a gentle profusion of pink and white daisy flowers well into autumn.

Basement bargains

London has many basement flats that are dark and dingy with little to cheer them
up. But where even a small amount of light penetrates there is scope for the urban
gardener.

If your walls are painted white to reflect the light, then this creates the perfect
backdrop to display a variety of bedding plants in window boxes. Bedding and
tuberous Begonias, Coleus, Fuchsia, Hydrangea, Impatiens (busy Lizzie), Lobelia,
and Pelargonium will thrive in this situation – just remember ‘Thriller, Filler,
Spiller’. For a greener feel, choose shade lovers such as ivy, hart’s tongue ferns
Heuchera and Tiarella.

Succulent silver

If you are looking for something different (and low water, low maintenance) then
consider planting up your boxes with

succulents. Silvery plants remain cool and refreshing on even the hottest of days.
Easy growers such as the ‘burro’s tail’ and the ‘ghost plant’ are easy to establish in
window boxes. Tall Aeoniums with their plate like rosettes of purple leaves or large
cacti act as ‘thrillers’ in these types of arrangements. Sempervivums (houseleeks)
make great ‘fillers.’ Have a look in the houseplant and alpine sections of your local
Capital Gardens and choose some succulents for that sunny window box. Come
autumn, you can bring them indoors as houseplants.

The incredible, edible window box

If your real passion is growing vegetables and cooking, then why not use your
window boxes for this?

Choose the biggest window box you can because vegetables need space. Select
small growing versions of vegetables because they will need less room.

To learn more about growing vegetables in small spaces:
https://www.bbc.co.uk/news/uk-52844039

Lettuce, spinach, radish, chillies and small fruited tomatoes such as ‘Tumbler’
and ‘Red Profusion F1’ can be easily grown in a large window box. If you want
to grow fruits, then strawberries are ideal as the plants and flowers are just as
beautiful to look at as the fruit.

Many herbs thrive in window boxes. Basil, Mint, Coriander Thyme and Chives
are my top 5 choices for window box cultivation.

Remember, some flowers are edible too:
https://www.capitalgardens.co.uk/blog/creating-your-own-edible-flower-garden/

If you wish to grow vegetables and herbs, remember the boxes will need to be
easily accessible for watering and harvesting. Growing vegetables in a window
box requires daily watering in the summer months.

In conclusion

Window boxes are great for budding gardeners to start learning. Window boxes
look good from the inside too. Window boxes provide outdoor growing space for
flats without gardens.

Be imaginative with your window box placing – they don’t just have to be on
windowsills! You can place window boxes on balconies and use the ones with
brackets to hang from fences and railings.

There are plant combinations to suit every type of gardener. Remember, ‘Thriller,
Filler, Spiller’ when buying your plants, and use it to create a more artistic display.
But, above all, have fun!

If you enjoyed this blog, why not check out our tips for entertaining in a small
garden?
https://www.capitalgardens.co.uk/blog/category/garden-tips-and-ideas/

Blog by Ali Barwani, Capital Gardens