Flowers in August: the best plants this month

Wondering what flowers look great in August? Here are a few choices, including two richly coloured gladioli, a delicate sunflower and strong-growing, pale-blue ipomoea, from Tom Brown’s top picks for this month. Read our piece on where's best to catch them in full bloom here. 

For more inspiration for flowers over the summer months, try our summer flowers article, alongside 60 plants from early to late summer. Don't miss our gardens to visit in August,  and make sure you're doing the right gardening jobs for the month. 

The best flowers for the month of August

Tithonia rotundifolia ‘Torch’

Tall, vibrant and blisteringly bright-orange flowers appear on this Mexican sunflower as the summer warms up and throughout August. Grow as an annual and plant in full sun in reasonable garden soil to achieve a strong two metres of growth. Tithonias will keep flowering until the frosts (don’t forget to collect the seed). This is a strong cultivar with consistent dark-orange flowers that are hard to beat in mixed and exotic plantings. They detest the cold so resist planting them out until June.

Ipomoea ‘Caprice’

I have trialled several morning glories and they were surprisingly variable in their performance, but this has been one of the best blues. Strong growth covered my 2m-high obelisk in foliage and pale-blue flowers erupted all over this plant. It was quite a spectacle, especially alongside some of the less floriferous forms. Avoid over feeding or you’ll end up with lots of leaf and only a few flowers, but other than that, in a sunny position in August, ipomoeas will provide lots of colour and interest well into the summer and cover up some of those less attractive fences.

Gladiolus ‘Bimbo’

If you enjoy the increasingly popular trend of combining creams, dusky pinks and apricot hues, then this August and summer corm will make a great addition to your planting schemes. There is an antique, coppery quality to its tones that really makes it stand out from the crowd. As with most gladioli, you should plant from April onwards, in clumps where the plants are to flower, and staggered planting will give a longer flowering period. To ensure perenniality, lift the corms after the first cold spell and store in a dry, frost-free place until the following growing season.  

Helianthus debilis ‘Vanilla Ice’

Sunflowers can be troublesome when  it comes to their heavy flowerheads and can demand strong staking techniques to see them through the latter part of the summer. ‘Vanilla Ice’ is a more delicate, multi-branched individual, and as such is far less demanding.  I grow this highly floriferous cultivar for cut flowers. The stems are wiry  and the flowers are very useful in arrangements with other summer and August flowers, such as yellow zinnias and blue statice. Here's our feature on perfect sunflowers. 

Galtonia candicans

Galtonias are widely available but as with a number of summer-flowering bulbs, they’re not used quite as often as they should be. I generally start these bulbs off in pots at the beginning of the year and plant out a strong specimen in the spring. Spikes of tiered, bell-shaped, white flowers appear in the summer and give a boost of colour and elegance to mixed borders and containers. Galtonias work well when planted in small clumps throughout a planting scheme to give an effortless and natural feel to your plantings. They’re also great for containers in August. AGM.

Vernonia arkansana ‘Mammuth’

Tall border plants can be hard to get right. They need to provide that essential, back-of-the-border, top tier, while also offering prime flowering performance. Vernonias provide both. I’ve discovered them only recently, and was immediately entranced by these sophisticated and intriguing late-summer stars. With their dark-purple flowers, carried on tall, stately stems, they offer a late burst of August colour to a border.

Gladiolus ‘Sylvia’

It’s tricky to associate most gladioli with other garden flowers. The exotic blooms scream for attention and dominate their companions. ‘Sylvia’, in common with a number of other dwarf cultivars, is the exception to this rule. I use these little flowers in clumps throughout my herbaceous borders, providing a colourful pick-me-up through the latter part of the season. I’ve started to view them as a summer tulip. Plant them around 100 days before you want them to flower and enjoy a burst of colour in August when much of the garden is a little tired from the summer heat.

Canna ‘Erebus

There aren’t many of these water cannas around and this cultivar of Canna glauca is one of the best in terms of reliable, flowering performance in August. You can grow it in water margins or water-logged containers, submerging the roots throughout the summer. But it is equally happy flowering in a fertile garden soil. Treat it like any other canna, by allowing the first frost to slightly blacken the foliage and then bring it into a frost-free place for the winter. I have learned not to cut the foliage down until new growth emerges in spring. AGM.

Zinnia elegans ‘Benary’s Giant Wine’

I grew a number of taller-stemmed zinnias in 2017, and the ones that stood out head and shoulders above all the others were those from the wonderfully consistent Benary’s range. They are available in a variety of colours, with one to suit almost every taste. This one from the Benary’s Giant Series is a classy plant, with sultry mulberry-coloured flowers. It is perfect grown as a cut flower, but will also have a strong presence in your borders from July, to August and until the first frosts.

Dahlia ‘Black Jack’

I’d be more than happy to grow this dahlia for its foliage alone. Its strong architectural, glaucous foliage appears in the early summer and complements a number of garden plants. I’ve grown it alongside the earlier performing Potentilla ‘Gibson’s Scarlet’ to act as a foil to the fiery red blooms. As the year rolls on into August, very large and rich cactus flowers of the darkest maroon appear on very strong stems. Almost shrub like in its habit, this dahlia works on many levels as a garden plant – a welcome cutting flower too. Don't miss our guide on how to grow dahlias. 

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