Mid-Summer Fillers

Turbo-boost your summer garden beds with strikingly colourful and easy-to-grow filler plants. These beauties are perfect when you are looking for something bold to fill gaps you might find over the summer season.

1. Physostegia virginiana

The old-fashioned species is a clumping perennial with tall spikes of light purple tubular flowers – and has always been a popular garden cut flower. But, it has a tendency to flop over and stay ‘obediently’ down, and maturing flowers tend to fade to brown too soon. Good breeding has resulted in modern hybrids which are compact and well-branched, producing many non-fading flower spikes.

Common name: Obedience plant.

Plant type: Perennial.

Recommended hybrid: ‘Crystal Peak White’ brings a fresh look with sturdy stems and upright terminal flower spikes of snow-white blooms.

Size: 40cm x 40cm.

Exposure: Full sun to light shade in the afternoon.

Soil type: Slightly acidic, lean soil, enriched with compost. Use pine needles as a mulch.

Aftercare: Regular, but not too much water. Pick the flowers for the vase or deadhead them to keep more blooms coming. Do not over-fertilise these plants.

2. Alternanthera brasiliana

The main job of the old alternantheras we used to plant was to cover the soil as fast as possible with their variegated foliage. Nowadays, we set an even higher premium on colour contrast with stunning foliage and turn to alternanthera again.

Common name: Joseph’s coat or joyweed.

Plant type: Perennial groundcover.

Recommended hybrid: ‘Purple Prince’ is non-invasive with its rich burgundy-purple leaves with their ruby-rose undersides.

Size: 40cm x 50cm.

Exposure: Full sun to light shade.

Soil type: Moist, well-draining, loamy soil.

Aftercare: Water regularly, but be assured that this plant is very heat tolerant.

3. Leucanthemum x superbum

Leucanthemums are favourite summer perennials because they flower non-stop and never give a gardener any hassles. We all know and love the hybrids with single white blooms, but what about a sassy yellow hybrid?

Common name: Shasta daisy.

Plant type: Perennial.

Recommended hybrid: ‘Goldfinch’ is undoubtably yellow with shaggy semi-double flowers which slowly change from bright lemon yellow to ivory white as they age.

Size: 45cm x 60cm.

Exposure: Full sun to light shade in the afternoon.

Soil type: Well-draining soil enriched with ample compost.

Aftercare: Regular, but not too much water. Pick the flowers for the vase or deadhead to keep more blooms coming.

4. Penstemon hartwegii

Amongst good reasons to plant the drought-tolerant penstemons, are their enchanting bell-shaped flowers appearing while early spring-flowering annuals and bulbs are slowly petering out. Penstemons make the transition from early spring into summer seamlessly and add a little nostalgia for the traditional cottage gardens our grandmothers planted.

Common name: Beardtongue.

Plant type: Short-lived herbaceous perennial.

Recommended series: ‘Arabesque’ in a wide choice of colours.

Size: 60cm x 60cm.

Exposure: Full sun.

Soil type: Sandy and lean, but add some compost when planting.

Aftercare: Water sparingly when established and cut off spent flowers to encourage more.

5. Angelonia angustifolia

When looking at the delicate flower spikes of angelonias, it is difficult to believe they can be so tough and resilient against heat and even periods of drought! They flower non-stop during the summer months and are available in many ranges and colours.

Common name: Summer snapdragon.

Plant type: They are perennial in temperate climates, but must be treated as annuals where winters are harsh.

Recommended series: ‘Serenita’ including colours such as white, lavender, pink and purple.

Size: 35cm x 35cm.

Exposure: Full sun to shade in the afternoon.

Soil type: Sandy, well-draining soil enriched with ample compost.

Aftercare: Water sparingly when established and feed with a slow-releasing fertiliser until autumn. Keep on deadheading spent flower spikes.

READ MORE: Take a look at other colourful summer bedding plants.