August is the month when late-season plants start to flower in earnest and here are ten of the best to give your flower borders a burst of glorious late-summer colour and interest.

1. Dahlia ‘Spartacus’ Senior (Dahlia)

If you’re looking for an impact plant, ‘Spartacus’ Senior certainly fits the bill.  Large, yellow-green buds open to reveal huge deep maroon flowers up to 20cm across, known as dinner-plate blooms!  The flowers often fade to a rich, velvet red as they mature. And they are certain to be a talking point amongst visitors to your garden.

dahlia spartacus
  • Flowers from July to October
  • Hardy
  • Grows to 120cm tall and 60cm wide
  • Rich, moist but well-drained soil
  • Full sun
  • Exposed

Top Tip

To ensure your flowers grow bigger, remove the side buds once the terminal bud is developed. If you don’t mind about size, leave the side buds, your blooms will just be a little smaller.

2. Crocosmia x crocosmiiflora ‘Emberglow’ (Montbretia)

These easy-to-grow plants provide a lovely splash of late-summer colour with long sprays of small, red flowers appearing above pleated green leaves.  The seed heads look wonderful when added to a vase of cut or dried flowers.

crocosmia x crocosmiiflora
  • Flowers from July to September
  • Hardy
  • Grows to 90cm tall and 75cm wide
  • Well-drained soil
  • Sun
  • Exposed

Fun Fact

This lovely plant attracts a very particular bird. If you would like to see more hummingbirds in your garden, if they live in your area, this is the plant for you.

3. Clerodendrum trichotomum ‘Purple Blaze’ (Glory Bower)

This wonderful, tall, deciduous shrub produces white, scented flowers in August, followed by bright blue berries surrounded by vivid red outer ‘petals’ which light up an autumn flower border!  It will grow best in a sheltered spot and, if you’re looking for a feature shrub, some plant nurseries sell it grown as a standard tree.

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  • Flowers in August
  • Hardy
  • Grows to 450cm tall and 350cm wide
  • Well-drained, fertile soil
  • Sun to part shade
  • Sheltered

Fun Fact

This unique and interesting-looking plant is actually a member of the Mint family, Lamiaceae!

4. Rudbeckia laciniata ‘Herbstonne’ (Black-eyed Susan)

Another easy-to-grow perennial which needs no staking; this cultivar produces citrus-yellow flowers with green centres on extremely long stems for many weeks and is perfect placed at the back of the flower border.

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  • Flowers from August to September
  • Hardy
  • Grows to 180cm tall and 100cm wide
  • Well-drained soil
  • Sun
  • Exposed

Top Tip

The name ‘Herbstonne’ is actually German, so you may see this plant labelled with its English counterpart. Herbstonne is German for ‘Autumn Sun’, so look out for that name at the garden centre.

5. Ceratostigma plumbaginoides (Hardy plumbago)

This delightful plant produces the most intense, bright blue flowers in late summer, which appear from in between bright green leaves on long, thin red stems.  Those leaves turn fantastic shades of red before falling in the autumn making this a great late summer choice for front of a border.

ceratostigma plumbaginoides
  • Flowers from July to August
  • Hardy
  • Grows to 80cm tall and 50cm wide
  • Well-drained soil
  • Sun to part shade
  • Exposed

Fun Fact

Not only is this plant striking in the garden, but it is good for the local wildlife too! The RHS have acknowledged it as a great Plant for Pollinators. In addition, it has the RHS Award of Garden Merit!

6. Sorbus aucuparia (Rowan)

Rowans are conical shape trees that cope extremely well with harsh conditions, hence their other common name of ‘Mountain Ash’.  At this time of year, the berries turn a bright shade of orange/red and are much loved by birds making this an ideal choice for a wildlife-friendly garden.

sorbus aucuparia rowan
  • Flowers from April to May
  • Hardy
  • Grows to 12m tall and 5m wide
  • Well-drained soil
  • Sun to part shade
  • Exposed

Fun Fact

Rowan trees have quite a mystical history! They have been grown historically near houses thanks to their suspected protection against witches. This was because the colour red was thought the best for protection against evil.

7. Hydrangea arborescens ‘Ruby Annabelle’ (Hydrangea)

This is a more compact form of the other ‘Annabelle’ hydrangeas and is covered in clusters of deep pink flowers at this time of year.  It can be grown in a large container or planted mid-border. It has the added advantage of being happy growing in the sun as well as light shade.

hydrangea arborescens ruby annabelle
  • Flowers from July to September
  • Hardy
  • Grows to 120cm tall and 120cm wide
  • Moist but well-drained, rich soil
  • Sun to part shade
  • Exposed

Top Tip

Hydrangeas generally don’t like drying out. Water well and regularly to help your Hydrangea to look its best.

8. Buddleja ‘Little Purple’ (Butterfly bush)

Unlike most buddleja, this cultivar is an extremely compact size. This makes it ideal for people with a small growing space who want to attract pollinating insects.  It produces clusters of high-in-nectar, rich purple flowers which butterflies find irresistible!

Buddleja little purple
  • Flowers from July to September
  • Hardy
  • Grows to 80cm tall and 80cm wide
  • Moist, well-drained, moderately fertile soil
  • Full sun
  • Exposed

Fun Fact

Unsurprisingly, this plant is popular with butterflies. So popular, in fact, that naturalist Richard Mabey saw 50 individual butterflies on his Buddleja at the same time in August.

9. Miscanthus sinensis ‘Flamingo’ (Silver grass)

Late summer is the time of the year when Many grasses start to flower and ‘Flamingo’ is no exception, producing arching plumes of tan-pink flowers above clumps of narrow, arching, mid-green colour leaves.  Very hardy and long-lived, it’s a great choice for back of a border.

Miscanthus sinensis flamingo
  • Flowers from August to September
  • Hardy
  • Grows to 120cm tall and 75cm wide
  • Well-drained soil
  • Sun to part shade
  • Exposed

Top Tip

Silver grass is a great choice for many garden styles. Particularly, they are perfect for coastal gardens, city gardens, cottage gardens, or prairie planting!

10. Phlox x arendsii ‘Hesperis’ (Phlox)

This is one of the last phlox to come into flower making it a great choice for the August flower garden as it will continue flowering well into September!  It produces tall clusters of heavily scented, small, lilac flowers on strong stems that rarely need staking.

phlox x arendsii hesperis
  • Flowers from July to September
  • Hardy
  • Grows to 80cm tall and 50cm wide
  • Well-drained soil
  • Sun to part shade
  • Exposed

Top Tip

The blooms of Phlox are particularly wildlife friendly. Pollinators love them, thanks to the flowers providing easy access. Plus, this variety being purple makes the especially attractive to bees, as they see purple better than any other colour.

These wonderful plants will perfectly brighten up your garden this August.

Find out about some more of my favourite and most interesting plants:

12 beautiful but harmful plants inspired by This Morning The Poison Garden

Or check out my Pinterest board for more ideas: