Horticulture Magazine

10 Perennial Flowers That Bloom All Summer Long

red coneflowers in a garden

With only a little effort you can bring a panoply of floral shapes in a riotous medley of colours to your garden all summer long – and, indeed, before and after summer! Conical inflorescences, ‘red hot’ spikes, and bona fide multi-petalled flowers, in every colour of the rainbow from the palest tint to the most intense hue, can be grown throughout the United Kingdom.

Let’s admit it. We all love plants that bloom all summer long. Who wouldn’t like to sow and care for just once, and then lie back and revel in lustrous multi-coloured blooms from before June even begins to after the end of August, year after year? What follows is a wonderful ’Top Ten’ assortment of flowering plants that will keep your garden bathed in blooms all summer long. 

We do not toss out vague or sketchy species or flower names but precisely identify series or varieties that, under non-adverse conditions, will bloom clear through summer – yes, that’s 1st June to 31st August. In fact, a good few will begin flowering from April, even more will bloom well into September, and some will do both!

We present species that originate in China and those that are out of Africa; plants that are tallish and others that are dwarfish; blooms that are in pastels and pinks and more that are in vivid vermilion; and flowers that are but tiny florets in panicles and big huge blossoms that are 10 centimetres across. Linking all these richly varied plant properties are two objective facts: our choices are all perennials, be they deciduous or evergreen, and they bloom all summer long! 

1. Gerberas or Gerber Daisies – Gerbera Garvinea

large pink flower Gerbera Garvinea
Gerbera Garvinea ‘Sweet Surprise’

Our Gerbera recommendation covers only Gerbera Garvinea, not Gerbera jamesonii or any other species or series. Gerbera Garvinea is a relatively new series that is more robust and disease-free than other species and series. Most importantly, this series’ varieties typically begin to bloom in spring and wind up in autumn or even later, providing a spectacular floral display for nearly half the year! Choose any of the following: Sylvana (pure white), Orangina (yellow-orange), Sweet Surprise (orchid pink), Sweet Memories (salmon pink), and Fleurie (deep red). All bear drop-dead gorgeous double flowers of about 5 centimetres. What is more, they are prolific bloomers. Simply deadhead regularly to encourage fresh blooms.

Grow Gerbera Garvinea in a loose, very well-drained loam of a Slightly Acidic pH. Direct, full sun in the morning is welcome but afternoon sun should be filtered or indirect. Water well but allow the soil to just dry out between waterings. The root ball should be right at the surface of the soil to guard against root rot. Simply protect these plants from frost; if grown in pots then bring the plants indoors in the winter. Though great in beds, these flowers are a fantastic choice for growing in decorative pots to put on verandahs, parapets, and balconies, and for hanging them off pergolas, beams, and posts. The flowers are equally fantastic for cutting and gifting in a bouquet because of their astonishing vase life. The disk-shaped, many-petalled, vibrant Gerbera has a unique unsubtle and direct charm that brings joy both indoors and outdoors.

2. Lantana Bush (Lantana camara)

Pink Lantana flowers in a garden
Lantana camara ‘Feston Rose’

You’d have to be very unlucky to choose a Lantana variety that does not bloom all through summer. In fact, the odds are that whatever variety you choose, it will start blooming before summer and continue blooming well after summer. Lantana is an evergreen bush that is so strong and fast-spreading that in some regions it is considered an invasive weed! It is beyond us how anyone could use the word ‘weed’ for a bush that has ideally-shaped emerald-green leaves and gorgeous bunches and clusters of florets that are both richly hued and multi-coloured, and are fragrant to boot. Choose from ‘Feston Rose,’ ‘Yellow Sage,’ or any cultivar from the ‘Landmark’ or ‘Lucky’ series. Colours include white, off-white, and pinks, yellows, and oranges from the palest pastel to the most saturated hue. As a bonus, you get bees and butterflies with it.

Lantana is truly easy to grow and just as easy to care for. It does not even need regular watering and flourishes in baking sun! The sole concern is that you will need to protect outdoor plants in winter in many regions of the United Kingdom. If grown outdoors, the root ball and stem should be protected from the cold but it is easier to grow it in a large container and bring it indoors in the winter. Full sun and southern exposure best suit this plant. Though just about any type of soil will do, a balanced loam mix with Slightly Acidic pH will be ideal. Be aware that it is not remotely child-friendly or pet-friendly, being highly poisonous. However, it is very ‘friendly’ to bees and butterflies and will attract these visitors in droves. Lantana’s profusion of sometimes top-heavy floret-clusters will also delight visitors of the human kind.

3. Buddleja aka ‘Butterfly Bush’ – Flutterby Petite Series

a butterfly sat on buddleja bush
Butterfly Bush Inflorescences are a Magnet for Butterflies

Buddleja are deciduous perennials that are indigenous to China. Though quite a number of Buddleja species and varieties have extended flowering seasons, Flutterby Petite Series’s cultivars bloom from the start of summer well into autumn. They are remarkably easy-grow and low-maintenance varieties that are drought-tolerant. The word Petite is not quite accurate because these varieties range from 60 to 90 centimetres in height with a similar spread. Flutterby Petite Buddleja have a habit that is bushy but not dense, with gently arching, swaying stems and stalks. Choose from Tutti Frutti Pink (Magenta-Pink), Blue Heaven (Lilac), and Snow White (snow white!). The first two varieties’ flowers are sweetly fragrant; the third one’s are unscented.

These plants can be grown in any halfway decent soil but preferably a fertile loam of compost, chalk and sand. Soil should be well-drained. What they appreciate more than anything else is full sun. What you will appreciate is that while Buddleja is well-known to be fast-spreading, invasive, and destructive to native ecosystems, the Flutterby Petite Series’ plants are sterile and produce no or few seeds. And what you will appreciate even more are the masses of frothy, conical inflorescences with delightful little florets which will draw every butterfly and hummingbird in the neighbourhood. Hardy through USDA Zones 5 to 10 they can be enjoyed virtually anywhere in the United Kingdom. They are excellent to grow in broad containers, in mixed beds, and as borders for walkways.

4. Creeping Buttercup (Ranunculus repens) 

yellow flowering Ranunculus
Creeping Buttercup’s Arresting Yellow Flowers

It is poisonous. It is invasive. It is a ‘rampant weed.’ It’ll colonise even damp, wet soil! Among all the Buttercups, Creeping Buttercup, Ranunculus repens, has the worst press. It’s also the Buttercup species that will bloom reliably from the beginning of summer – if not earlier – to the end of summer – if not later! We do not say that Creeping Buttercup is ‘easy to grow’ because once it gets into your garden it will grow by itself! Indeed, many gardeners grapple with the question of how easy or difficult it is to control. Nonetheless, this article is about flowers that bloom all summer long and this zero-care deciduous perennial fits the bill to a ’T.’ What’s more, it brings forth masses of delightful little flowers.  

This plant grows on runners and has a prostrate creeping habit, and as the foliage is a brilliant emerald-green it makes for truly attractive ground cover. Creeping Buttercup loves damp soils but is not fussy about soil type or pH. Our Buttercup selection does not provide any choices in varieties or colour; there’s just one colour, but it is the richest, sunniest, cheeriest hue of yellow there can be. Furthermore, it blooms profusely, and its wee-little, simple, five-petalled wildflowers are the exemplar of ‘simple joys.’ Weed or not, you can’t beat this variety for its brand of simple good cheer all summer long. Just be careful not to let it take over your garden; you can do so by surrounding it with inhospitable and non-damp soils and by cutting off the stolons. Also ensure that children and pets do not go near it as it is very toxic.

5. Agastache or Hyssop

Agastache Acapulco Purple blooms in a garden
Two Kinds of Agastache or Hyssop

A garden stunner, an Agastache or Hyssop plant can simply overwhelm the viewer with the incredible profusion of its flowers, the vibrancy of its hues, the gentle graceful swaying in the breeze, and even the wafting fragrance. This plant is very easy to grow and you are virtually assured of summer-long blooms going into autumn if you choose from ‘Blue Boa’ (deep purple), ‘Kudos Ambrosia’ (pink-to-rose), ‘Kudos Gold’ (amber-gold), ‘Kudos Mandarin’ (Mandarin orange), ‘Kudos Silver Blue’ (silvery lilac), and ‘Kudos Yellow’ (bright yellow). And then there’s ‘Little Adder’ (lavender-to-mauve), the long-blooming champion which will begin its show before summer and continue deep into autumn. Because these varieties are of different series, their heights and spreads vary widely with some being taller than wider, and others having a wider spread than height. But all of them bear lots and lots of big, thick, erect spikes with bunches of florets.

Agastache or Hyssop need full sun and very well-drained soil. Other than that they are low-care plants that are generally disease-free and pest-resistant. They will bring bees, butterflies and hummingbirds to your garden like there’s no tomorrow. Because the primary criteria for our selections is all-summer-blooms, the recommended varieties of Agastache turn out to have diverse habits and, as a result, are best suited for different garden purposes. For example, ‘Kudos Silver Blue’ is perfect for edging long paths and walkways and to serve as a companion plant for tall, erect species; on the other hand, ‘Blue Boa’ is just as perfect to plant in the rear of beds, especially against the back of marigolds, and to grow against verandahs and fences.

6. Golden Feverfew (Tanacetum parthenium ‘Aureum’)

lots of white and yellow Golden Feverfew flowers
Golden Feverfew Flowers

Resembling rather a daisy but actually a type of chrysanthemum, Golden Feverfew will just about give you a veritable mat of lovely wildflowers from the start of June until the close of August. However, it brings unexpected ‘extras’ to the garden. To begin with, the pinnate lobed leaves are of a light, bright, almost shiny green that make for awesome foliage. And this foliage emits a fresh, humusy scent that will remind you of the countryside. The plant forms rounded clumps that are wider than they are taller, being 45 to 60 centimetres in spread and 30 to 45 in height. Because of its form it is perfect for the front of beds, for edging walkways, and as groundcover. It can also be grown in containers provided they are kept outdoors in a sunny spot. Though the plant is a perennial, it is a short-lived one so let some flowers go to seed and deadhead most; that way you’ll never be short of blooms and will always have new Feverfew plants.

There’s more to Feverfew than all-summer flowers, though. It is a veritable medicine chest! In centuries past it was considered a remedy for a variety of malaises including depression, headaches, and fevers before ‘modern science’ displaced purported pseudoscience. Well, guess what? Modern science has reconsidered. Now this plant is known to relieve migraines and to have anti-inflammatory and anti-cancer properties courtesy of the chemical Parthenolide. It also contains Pyrethrin so it is a nature-made insect-repellant. But to return to our subject at hand, reminiscent of alpine wildflowers, Golden Feverfew’s happy little blooms are like flat disks with pure white petals emanating from a biggish golden yellow centre. And each plant produces loads and loads of them!

7. Begonia – Nonstop Series

orange begonia flowers
Begonia ‘Nonstop Orange’

A ubiquitous garden favourite on both sides of the Atlantic, Begonia surely makes everyone’s list of all-summer-long flowering plants. Many varieties start blooming in spring and tail off only near the end of autumn. As an ‘easy out’ as well as a sure thing we recommend the Nonstop series of Tuberous Begonias but like as not you can draw a variety name out of a hat and it will give you flowers through summer and perhaps even more. Take ‘Hanging Basket Scarlet’ and ‘Bossa Nova Pure White,’ to throw out two examples. As for the Nonstop series, they bear fully double rose-like flowers that are up to a staggering 10 centimetres across. Moreover, they produce a sea of blooms and do so continuously. We recommend the Nonstop ‘Pink,’ ‘Red,’ ‘Orange,’ and ‘Yellow’ varieties. 

The one concern is that Begonia Nonstops are tender perennials which are ‘hardy’ only to USDA Zones 10 to 11. As such, the tubers will not survive the winter in any region of the United Kingdom and so you have a choice. Grow Nonstops in (largeish) containers and overwinter them indoors or in a heated greenhouse, or dig up the tubers, dry them, and store them for the winter. The only other concern is the possibility of powdery mildew. Other than that these are strong plants that are low-maintenance. They like part sun, part shade, and are best grown in a fertile sandy loam of pH Slightly Acidic. They have a bushy mounding habit with 40 to 60 centimetres spread but only 20 to 30 centimetres in height so we suggest that you grow these terrific plants in a portable planter and set them on the patio and the garden spring through autumn.

8. Geranium – Four A.G.M. Selections

closeup of a blue geranium rozanne flower
A Close-Up of a Single Geranium ‘Rozanne’ Flower

Colourful, low-care, hardy, pest-resistant, disease-free, fairly drought tolerant . . . the virtues of some varieties of Geranium are such as to make them an automatic choice for any British garden. Some varieties are possibly among the easiest and most trouble-free bushes you can grow. You could try any and all of ‘Mavis Simpson’ (light lilac-pink), ‘Orion’ (gentle lavender blue with a pale eye), ‘Ann Folkard’ (vivid magenta with black eye), and ‘Rozanne’ (gradated purple). Let’s not quibble about summer, these babies flower from late spring to mid autumn! The four varieties we have selected range from 30 to 120 centimetres in height and 60 to 120 centimetres in spread. They have a bushy habit that may be clumping or mounding in form. All four are R.H.S. Award of Garden Merit recipients.

In the United Kingdom these Geraniums are best planted in full sun but part shade will be fine too. They are not too particular about soil; all they ask is that it be well-drained and kept moist in the summer. Any reasonable loam mix will work very well. What you need to do is to remove old foliage and flowers to promote fresh growth. Geranium bushes will keep growing, gently, gently, without ever trying to take over your garden. The open, slightly cuppy, happy-go-lucky five-petalled flowers are from 3 to 5 centimetres, and you’ll see scads and scads of them! The broad, sharply serrated, deep green leaves make for very pleasant foliage too. These fuss-free and versatile flowering bushes are ideal for cottage-style gardens, as companion plants to tall specimen plants, mass plantings in beds, and even as groundcover.

9. Kniphofia or Red Hot Poker or Torch Lily

red and yellow Kniphofia uvaria flowers
Kniphofia or Red Hot Poker ‘Incandesce’

Stalks averaging one metre, ramrod straight, bearing spikes of densely-packed tube-shaped florets in vibrant hues in the yellow-vermilion spectrum. And that’s why this floral present from South Africa is called ‘Red Hot Poker.’ Several varieties bloom all through the summer with one or two starting in spring or finishing in autumn, or even both. In order of flowering season, from longest to least long, these varieties are ‘Elvira’ (flame orange), ‘Jenny Bloom’ (cream-orange gradated), ‘Mango Popsicle’ (deep orange), Timothy (peach), and ‘Incandesce’ (deep orange). Because the colour of the spikes fades as they grow and mature, they are gradated with the base being paler and the growing tip of a more vivid hue.

Be aware that Kniphofia guzzles water; at the same time, it cannot stand waterlogged soil! Very well-drained loam mainly of organic compost and sand is ideal. In summer they need frequent watering. They are disease-free and pest-resistant but be sure that the root ball is not deep in the soil. Care is limited to trimming the plants in spring and deadheading in the flowering season but you can allow the plants to self-seed, and be surprised and delighted with nature-made new shades and tints. In most regions of England and Wales the plant’s own withered foliage is sufficient to protect it from frost. The plant as a whole is a spectacular one as the ‘torch’ or ‘poker’-like shafts with their blazing, fiery racemes catch and hold the eye and will make your guests go, “Wow, what’s that plant!” Besides pulling eyes, these out-of-the-ordinary flowers also pull bees and hummingbirds. Red Hot Poker is a brilliant choice for mass plantings, borders of walkways and driveways, and against verandahs, decks, and fences.

10. Azalea – Encore Azaleas

pink Autumn Royalty Encore Azalea flower
An Encore Azalea Bloom

Closing out our list is a googly (or a curveball, depending on your sport and your nationality). That’s because Azaleas are associated with spring, and their flowering season closes before the end of summer. But Encore Azaleas are a different beast altogether. While many Encore Azalea varieties are re-bloomers, some are continuous bloomers, especially if you follow the instructions, and also deadhead. Azaleas are unquestionably among the loveliest of flowers on top of which some varieties, including the Encore series, are profuse bloomers. Nothing could outdo the before-summer to after-summer blooms of Autumn Sunburst ‘Roblet’ (coral pink), Autumn Majesty ‘Roblezd’ (purple), Autumn Bonfire ‘Robleza’ (deep red), Autumn Chiffon ‘Robled’ (pale pink with rose flares and speckles), and Autumn Ivory ‘Roblev’ (white). All varieties are dwarves and their flowers measure 6 centimetres or more!

These Azaleas will do best in a good loam mix with some compost and organic manure. Soil pH should be Slightly Acidic to Moderately Acidic. The top of the root ball should be just above the surface; in no event should it be at all deep in the soil. The soil should be well-drained. The plants should get full sun through the morning and shade or part shade in the afternoons. Water regularly, though not frequently, such that the soil stays moist. If you live in a location that has mild winters, simply mulch the plant when winter arrives. You can delight in Encore Azaleas in the United Kingdom’s northern regions too provided you keep the plants in containers and overwinter them indoors or in a heated greenhouse. Azaleas are awesome anywhere and everywhere, from a small pot on a 0.3-metre windowsill to a mass planting in a 3-metre bed.

Thank you for reading – we hope this article has inspired you to introduce more perennials in your garden!

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