Window boxes: a beginner's guide

Our beginner's guide to window boxes will help you design and plant out the perfect window garden; there are pretty ideas and practical tips, too

window boxes: RHS antique grey oval trough
(Image credit: RHS)

Window boxes are both the perfect small space gardening solution for urban homes and pretty additions to the windowsills of country cottages with rambling plots. Better still, they're easy to grow, even for beginners to gardening, and you can choose plants – shade-loving or sun-thrivers – that suit your window's orientation. Plus, they needn't be high maintenance. You can of course grow pretty seasonal blooms in window boxes, but frost-proof perennials can look smart, too.

Window boxes themselves come in a wide variety of finishes, but are typically elongated rather than round, to fit onto windowsills. Use our guide below to find out everything you need about window boxes. Then consult our sourcebook of top garden suppliers for all your garden needs. Don't miss our guide to gardening for beginners, too.

1. Window box gardening

The first thing to think about is what you want the look of the window box to be, and to choose plants accordingly. Will the plants you'll be growing in your window boxes be elegant and formal-looking or are you going for a rustic feel with pretty flowers and trailing plants? 

Once you've decided this, you'll want to consider how much maintenance you want to give your window box. Fruit, veg and some herbs, plus seasonal flowers take up more time than perennials, for example. 

Next, consider the shape and scale you'll create with your window box planting. The labels in plant pots or on the back of seed packets will tell you the growing habit of the plants (upright, trailing, etc), as well as their height and spread. Plants that grow very tall and upright won't suit a window box and may need more soil around their roots, so always stick to plants that are described as having a 'compact growing habit' or that can be pruned into a shape and size that is a suitable scale for the window box it's in. 

Finally, choose window boxes that suit the look you're going for. As a general rule, matching, rectangular-shaped troughs create a more formal look, and oval-shaped troughs or mismatched window boxes gives a more relaxed look. 

Read more on choosing plants for your garden.

(Image credit: RHS)

2. Window box planting ideas

Flowers with a compact growing habit or trailing varieties look wonderful in window boxes. Lobellias, petunias, fuchsias, daisies, pansies, and pelargoniums all make for a wonderful window display, but you needn't stick to flowers. Below, we list our favourite, easy to care for window box planting ideas.

3. Growing the best window box flowers

Lavender is one of the easiest plants to grow in window boxes; its compact growing habit will add just enough height without going floppy. Try combining thyme, lavender, and salvias for a fragrant, herbaceous window box that's also perfect for bees.

Find out how to create a bee-friendly garden in our guide. 

Embossed galvanised window trough

(Image credit: Waitrose Garden)

4. Choosing the best window box herbs

Growing herbs in window boxes is one of the most satisfying ways to grow a herb garden. You can easily combine several herbs in one window box: thyme, basil, parsley, and oregano will all happily grow together, although rosemary is probably best left as a border plant, since it can get leggy. Most herbs can be easily raised from seed: just give them two to three weeks to germinate. 

Embossed galvanised window trough

(Image credit: Waitrose Garden)

5. Picking the best window box fruits

Growing strawberries and tomatoes in window boxes is another way to add edible colour to your window garden. Tomatoes are easily raised from seed, but strawberries may be best bought as plug plants. Go for compact, trailing varieties – or, if you feel up for something a little different, consider a climbing strawberry variety, such as Mount Everest. Train it up with a plant support positioned against a wall. 

Interested in growing organic produce? Read our advice on how to grow organic fruit and vegetables.

Strawberry 'Mount Everest'

(Image credit: Waitrose Garden)

6. Planting a window box

Planting window boxes is essentially the same as planting up any garden pot or container (and many people mix pots and window boxes in their window gardens anyway). 

You will need potting compost mix, or any other good quality compost, such as John Innes. Ideally, all your window boxes should have drainage holes in them, but many on the market do not, in which case it's advisable to line the bottom of the window box with gravel, or chips from a broken terracotta pot to prevent water logging in the soil. 

On the other hand, if your window boxes do have drainage, you may have the opposite problem of water evaporating very quickly, a problem that can be resolved by mixing vermiculite into your compost.

Find out more about container gardening for small spaces.

Julian Window Box Planter

(Image credit: Wayfair)

7. How to fix a window box with brackets

If your windowsill isn't wide enough to hold a window box – or you don't have one at all – hanging a window box by fixing it to the exterior of your house will be your best option. Just bear in mind that you will have holes in your brickwork, and, if you live in a flat, your window box may be a safety hazard for the people below, if the brackets ever came loose. 

To fix your window box with brackets, you will need a masonry drill bit, to protect your brick. Watch this handy step-by-step guide that demonstrates how to drill the holes and attach the brackets. 

8. Best window boxes to buy

The best window boxes for your window garden will depend on your preference for materials, but also on how heavy you're prepared for your window boxes to be. Stone and Italian terracotta look amazing, but weigh a lot, so if you don't think you'll be able to move your window boxes, you might be better off with plastic or metal window boxes. Plastic also has the benefit of holding on to water better, which can be a benefit if you won't be able to water your plants regularly. Rattan or wicker window boxes will also be light, but you will need to change them every couple of years, as they will not be weatherproof.

Galvanised window trough from the RHS

(Image credit: RHS)

9. Window box liners

Window box liners can be used to prolong the life of your window boxes. Typically made from plastic or coconut fibre, window box liners create a buffer between your window box and the wet soil, preventing your container from cracking, discolouring, or rotting. Always choose the same size of liners as your window box or trough, and make sure the drainage holes align. 

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