Window Boxes A practical guide to get the maximum joy for everyone.

Window Boxes

A window box is a joyful and colourful addition to your garden or outside space at any time of the year. They do not have to be big or expensive as window boxes can be used all year round and time and again, providing you care for them.
However, their splash of colour but can make an enormous impact at little cost. Window boxes are ideal for a limited space. Their cheer and vibrancy can stop passersby as they delight in the splash of colour for a moment, but at the same time they increase your privacy as they cannot see past them through your window.
The owners of a house with lots of windows may choose to put a window box in front of each of the windows or just a few of them. They make a greater impact and create the feeling of symmetry if the window boxes are all on one level. For the strongest impact, the window boxes need to be similarly planted.
Most people choose downstairs windows as they are easiest to access for maintenance and they benefit most from the shielding that the growing plants provide.


Window boxes make a fabulous and key component of a balcony garden. Some of them may be filled with salad crops like lettuce and tomatoes to utilize the space. They need to be securely fixed, and care should be taken not to drop things from first floor apartments and above.
How to choose a window box
Once you have decided where to put the window box, measure the width of the window. Aesthetically, you want a smaller width window box for a smaller window and a larger width box for a bigger window.
The recommendation is that a window box should be no more than 20% wider than the window ledge, else it looks too big, out of proportion and unbalanced. You do not want the box to overhang too much as there is a danger of getting knocked off and injuring someone.
Choosing a window box that is at least 20cm (8”) wide means that there is enough space front to back for a variety of plants and plenty of soil to plant a beautiful display. It will look neat on the ledge.
The window box needs to be sturdy enough to bear the weight of the soil and the growing plants. Those plants will need water, which adds to the weight of both. The planter should be at least 20cm (8”) deep for the roots to establish.
Ensure that there are drainage holes in the bottom to prevent root rot. If you cannot drill holes into the bottom, The best window boxes are made of treated hardwood, like cedar wood or redwood as they are naturally waterproof and do not leak water through the sides. They are also unlikely to smash and shatter causing less damage if they were to fall.                                         '                 
How to fix a window box
Firstly, one must consider the legal safety and building regulations of putting a window box, particularly on high up balconies and outside the first floor or above windows to avoid accidents to passersby.
Bear in mind that it would be easy to drop soil, water, and plants on someone below.
Choose a mount that can withstand the weight of the container. The starting point for the ‘green load, capacity and the correct size for the dimensions and that it is bearing, the right dimensions and shape to support the window box. These fixtures and fittings need to be made from a corrosion–resistant material suitable for outdoors, like stainless steel.
Once your window box is in place, it is ready to be planted up. It is worth planting up after it is in place because they become very heavy once they are watered!
Choosing your plants for a window box
Most people only have summer window boxes in this country as they can easily get frosted in the winter killing the plants.
For summer planting, you need to decide on a colour theme and choose different plants within no more than three colours. The foliage plants fill space and add another colour. They are also invaluable for adding texture to your arrangement. Some people choose a riot of vibrant, mixed colours, but this often looks very disjointed and messy. Others prefer to choose one or two colours for their preferred taste. Either way, you need to choose plants that have similar requirements for sunlight, soil, fertilizer, and moisture.
When choosing your plants, you need to balance low growing, uprights, and trailing plants. It is worth spending a few minutes planning where you will put them before you put them in the soil. To begin with, I advise applying using the rule of three that interior designers use to avoid uneven planting. Once you gain confidence, you can plant in odd numbers to create a lovely flow.
You need to be aware of where the sun shines in your garden. If you have a choice, South and East facing windows and walls are the best. They give you the widest choice of plants as they get the most sun
Experienced gardeners recommend choosing different foliages and one or two varieties of ‘main flower’ between ‘filler’ flowers. However, with experience, you may want to experiment with trailing foliage over the front face of the window box too.
The different foliage plants suitable for a window box are the Ivy, Asparagus or foxtail fern, Euonymus, Heuchera, Hosta and Vinca or Periwinkle. They add a lush effect.
Classic ‘main’ colourful flowers include different varieties of Fuchsia Geraniums, Petunias and Begonias. You may want to add some other bright and cheerful ‘accents’ with Marigolds, Salvias, Zinnias and Nasturtiums.
Filler flowers provide other textures and colours in the gaps between the main flowers; you can choose from a variety of good ‘filler’ flowers like Coleus, Pansies and Roses.
If you want the flowers to cascade over the edges, there are many trailing varieties to choose from.
How to plant a window box
Window boxes can be a source of joy and colour all year round. The different seasons require different planting for each season, especially for those who want to grow salad plants.
In the summer, gardeners use annuals to plant a window box. These will double in size by about the middle of the season, from the water and all-purpose feed that you need to give to them. If you choose to put in perennials', check to see how big they grow and plant the planter accordingly.
In the winter, it is difficult to get the same vibrancy as in the summer, however, cyclamens and winter flowering pansies are good choices. The pansies will still need deadheading and do not last if the summer blooms because of the colder conditions. They do not grow as fast, so you need to put the plants a little closer to get the same impact.
Clean out anything left over from the last season.
If you need to create a drainage area because you do not have holes in the bottom, place a 5cm (2”) layer of light non-biodegradable packing material or wine corks and top with a single layer of ‘landscape fabric’ to stop the soil from being washed into it. Try to avoid using stones as this will add to the weight of the window box.
Add fresh soil and compost that is appropriate for your new plants. Fill your planter to about half-way with soil/compost mix and then add the plants. Plant the planter in situ. They are very heavy when they are full and impossible to secure safely.
When you are choosing your plants, do not forget that these plants will grow and there will be little soil showing in a matter of a few weeks. Bigger plants will need more water.
Water the plants and add fertilizer to give them the best possible start in their new home.
How to look after a window box
Your window box will need regular watering and feeding throughout the season as they can easily dry out, especially if the window box is placed in the full sun. There is little soil and a lot of roots in a window box. The plants cannot behave completely naturally by growing deeper roots to get water; the bottom of the window box itself is in the way!
Too little water leads to poor plant growth and less prolific flowering. This can be a bigger problem when it is raining in the winter and the window box is not getting enough water because it is too sheltered or drowning in water because it is too exposed.
However, you can also overwater your window box. If the drainage holes are not big enough, over time, they get clogged up with soil and the water just sits there. The roots can get enough air from the soil to breathe resulting in root rot.  It is easy to detect as there will be the accompanying, distinctive, nasty smell of anaerobic bacteria.
The plants depend on you feeding and watering them! This is time-consuming and will require help when you are away from the house for a few days. The best time to do it is when the sun is not on the window box. For some, that may be in the evening, for others the morning. It is worth getting into a routine that fits into your lifestyle as they need you every day. When it is extremely hot, they may need extra water at the opposite end of the day as well.
The plants should not be crammed into the window box. They need space to grow, and they need air circulation. If the air cannot circulate and the leaves are damp, mildew quickly sets in rotting the leaves and the stems. It is a quick, regular visual check that will help you nip it in the bud, particularly after a few days of rain where the plants have not had a chance to dry out.
Checking for damage is easy to do when you are dead heading your plants. Removing the dying flowers encourages the plant to continue to grow, produces more flowers and keeps your window box looking at its best. The wilting or dying flowers can also damage the plant and invite pests to your window box.
Window boxes are also susceptible to other pests like insect damage and yellowing leaves as well as aphids. Any of these can become quickly out of hand and kill the plants if they are not spotted and dealt with.
It is worth treating your window box each year with a moisture protecting sealant to preserve them as long as possible. Either before or after planting,
In the winter months, some plants may survive the frost because the window box is sheltered by the window, but to be sure, it is worth covering the plants with a layer of bubble wrap.
If you've enjoyed this month's "Window Box" Blog, why not get in touch with us to let us know what subjects you'd like us to chat about or pop into our Charlton Kings shop to discuss ideas so we can help you chose the type best for your windows.