Window boxes and troughs are the perfect way to dress your house, but you can’t simply plant them up and forget about them. Even before you start planting, it’s worth thinking about the practicalities, and if you can’t easily and regularly water your plants, consider installing an irrigation system or buying self-watering window boxes (try lechuza.co.uk). Choice of compost is also important, as many multi-purpose composts are too light and will dry out in a flash, so choose a soil-based compost such as John Innes No. 3 or make your own mix from top-soil and multi-purpose compost.
In terms of planting, first consider where your window boxes are. If they are on a north-facing wall the range of plants available to you will be restricted; in full sun or partial shade the choice will be much wider. Next think about whether you want seasonal displays using annuals and bulbs, perhaps changing them two or three times a year, or whether you’d prefer evergreen or perennial displays that are more permanent. A combination of structural evergreens or perennials padded out with annuals is often the best solution. You may even want to try fruit, vegetables or herbs. Whatever you decide, it’s best to choose low maintenance plants that hold their colour or structure for as long as possible.
In terms of design, work out what effect you want, whether traditional and symmetrical or loose and naturalistic, and think about plant heights carefully. You’ll need one or two slightly taller plants to create visual interest, but don’t choose excessively tall plants that will obscure the view from the window. Choose a range of plants that will give you different shapes and textures for maximum impact, making sure that you have several from the following categories:
These are the flowers that are going to be the show-stoppers of your container, and if your window box is in a sunny spot, there will be plenty of plants to consider, from flamboyant pelargoniums to colourful cosmos, and you can choose different plants to shine in each season.
The fillers are light, airy plants that provide softness to counteract the more flamboyant plants in the container. Examples include Gypsophila elegans, Gaura lindheimeri and Gilenia trifoliata and they typically have small, floaty flowers that can be dotted throughout the container to provide continuity. You can also use soft grasses such as Stipa tenuissima or Melica uniflora.
Adding a few trailing plants will soften the edges of your window boxes and create a lusher, more flower-filled look. Choose plants such as trailing ivy, Erigeron karvinskianus and annual lobelias or petunias.
If you want an elegant, low-maintenance minimalist look, these are the plants that provide evergreen structure throughout the year. Box balls are a classic choice but can be risky due to blight and box moth. Good alternatives include Euonymus japonicus ‘Jean Hugues’, dwarf hebes, or lavender. If you prefer a more exotic look you could try a cordyline such as C. obtecta ‘Superstar’ as a central focal point.
Shady Green & White Perennials
- Skimmia japonica ‘White Dwarf’ (evergreen structural)
- Melica uniflora (perennial grass filler)
- Hedera helix ‘Eva’ (trailing)
- Astrantia major ‘Shaggy’ (focal point perennial for summer)
- Anemone x hybrida ‘Honorine Jobert’ (focal point perennial for autumn)
- Helleborus x ericsmithii ‘Winter Moonbeam’ (focal point perennial for winter)
Sunny Silver & White for Summer
- Euphorbia characias ‘Silver Swan’ (evergreen structural)
- Stipa tenuissima (perennial grass filler)
- Verbena ‘Quartz XP Silver’ (annual filler)
- Helychrysum petiolare (annual trailing for summer)
- Cosmos bipinnatus ‘Sonata White’ (annual focal point for summer)
- Osteospermum ‘Akila White Purple Eye’ (annual focal point for summer)
Sunny Naturalistic for Summer
- Lavandula angustifolia ‘Hidcote’ (evergreen structural)
- Pennisetum alopecuroides ‘Hameln’ (perennial grass filler)
- Erigeron karvinskianus (perennial trailing for summer)
- Orlaya grandiflora (annual filler summer)
- Echinacea purpurea ‘Green Jewel’ (perennial focal point for summer)
- Symphyotrichum ‘Little Carlow’ (perennial focal point for autumn)
Formal Green & White with Bulbs
- Buxus sempervirens or Taxus baccata balls (evergreen structural)
- Tulipa ‘Spring Green’ (focal point bulb for spring)
- Allium nigrum (focal point bulb for summer)
- Acidanthera murielae (focal point bulb for late summer)
Edible & Ornamental
- Rainbow chard (structural)
- Purple sage (structural)
- Cherry tomatoes (trailing varieties)
- Flat leaf parsley (filler)
- Basil (filler)
- Nasturtiums (trailing)