Complete Guide to Perennial Plants | BBC Gardeners World Magazine

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Border including salvias, astrantia and fennel

There are perennials to suit every type of garden, for any aspect or soil type, and they range in size from low-growing herbaceous plants for the front of a border, to medium-sized ones for the middle, to giants a couple of metres tall for the back. They establish and grow quickly, with most reaching their full size in a few growing seasons. Many perennials make good cut flowers and the more compact varieties are excellent for growing in pots. Most are flowering plants that are very attractive to pollinators.

The difference between annual and perennial

Most garden plants are either annual or perennial. Annual plants flower, set seed and die within 12 months, while perennials live for several years. Perennials are split into further categories:

Herbaceous perennials – these die back to the ground in autumn and regrow in spring. Examples include Verbena bonariensis, penstemon and ornamental poppies.

Evergreen perennials – these keep their leaves all year round, such as some varieties of heuchera and hosta.

Woody perennials – while most shrubs are referred to as shrubs, some smaller-growing perennials that develop woody stems are described as shrubby or woody perennials. These include lavender and some salvias.

Hardy perennials – hardy plants tolerate low temperatures and can be planted outside all year long. Many of them are herbaceous and die back each autumn, such as cranesbill geraniums and phlox. Some are evergreen and/or shrubby, such as lungwort and lavender.

Half-hardy perennials – Half-hardy perennials are tolerant of winter wet and cold, but are vulnerable to frost. They therefore need protection over winter such as a thick mulch of straw over the roots or can be dug up and brought into an unheated greenhouse for winter. Examples include penstemon and salvias.

Tender perennials – these won't survive winter wet or cold and need digging up in autumn and storing in a frost-free location. They include dahlias and gazanias.

Choosing perennials for your garden

For the greatest success when growing perennials, choose the right plant for the right place. Assess your site, including soil type, and how moisture retentive it is, the amount of sun or shade the area gets, and how exposed it is to the wind. There are perennial plants for absolutely every situation, and matchmaking their growing preferences to your site means they should thrive for many years. Choose a selection that flower at different times of the year and combine with shrubs, ornamental grasses and annuals for a long-lasting display.

Alan Titchmarsh shares his five favourite perennial plants, in this short video from BBC Gardeners' World Magazine.

Here's our list of top 20 perennials to grow, plus advice on how to buy and grow them.

20 top perennial plants to grow

Yarrow, Achillea

Achillea 'Walther Funcke' — Achillea 'Walther Funcke'

Yarrow is an herbaceous perennial and makes a colourful summer display in a sunny spot. It produces large, flat heads made up of many tiny flowers, borne on stems above clumps of feathery leaves which are green or silvery in colour. Yellow varieties predominate and there are reds and oranges too.

Height x Spread: 45-75cm x 45-60cm

Michaelmas daisy, Aster

Lilac flowers of Michaelmas daisy

Michaelmas daisies or asters are an herbaceous stalwart of late summer and autumn borders, bearing masses of ‘daisy’ flowers on sturdy stems in brilliant pinks, mauves, and purples as well as white. An excellent plant for pollinating insects too. Prefers sun.

H x S: 30-75cm x 45cm

Elephant's ears, Bergenia

Bergenia cordifolia 'Purpurea' — Bergenia cordifolia 'Purpurea'

Called elephant's ears for its large, rounded, evergreen leaves, Bergenia is a tough perennial that makes excellent ground cover in sun or shade, and thrives on any reasonable soil. Large clusters of pink, white or purple flowers are borne in late winter and early spring.

H x S: 30-45cm x 45-75cm

Crocosmia

Crocosmia 'Lucifer' — Crocosmia 'Lucifer'

Crocosmia is a herbaceous perennial growing from bulb-like corms. Crocosmias are also known as montbretia, although this tends to refer to the common species Crocosmia x crocosmiiflora. This has naturalised in many areas and is considered to be invasive. It is listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales, meaning it is an offence to plant or otherwise cause to grow this species in the wild. You should stop them spreading from your garden and avoid purchasing or accepting gifts of these species.

The cultivated varieties are less likely to become invasive. They dazzle from early to late summer with orange, red or yellow blooms on slender stems, with the bonus of attractive lance-shaped fresh green leaves too. Great for introducing a vertical element to a border. Grow in sun or part shade, and shelter in cold areas.

H x S: 60-90cm x 30-40cm

Delphinium

Delphinium 'Amadeus' — Delphinium 'Amadeus'

Delphinium bears tall stems clothed with many strikingly beautiful flowers, which open over time from bottom to top so the plant gives colour for many weeks. Blue is the predominant shade, as well as white, pink and mauve. Young stems and the divided leaves are attractive to slugs and snails, which can be protected with barrier granules or an environmentally friendly bait. Grow in sun or part shade.

H x S: 60-90cm x 30-45cm

Sea holly, Eryngium

Eryngium x zabelii 'Jos Eijking' — Eryngium x zabelii 'Jos Eijking'

Sea holly combines handsome, often architecturally shaped or variegated leaves with tall stems of blue flowers in summer that are beloved by bees. Prefers sun and free-draining soil and is ideal in gravel gardens too.

H x S: 45-60 m x 30-45cm

Spurge, Euphorbia

Euphorbia donii — Euphorbia donii

Euphorbias give long-lasting interest with a combination of attractive, architectural foliage and bold heads of ‘flowers’ in colours such as lime, yellow and orange-red. These are papery bracts, not flowers, which is why they last for months rather than weeks. Many varieties keep their foliage and form through winter. This huge and diverse plant group offers something for every garden situation.

H x S: 15-120cm x 45-120cm

Cranesbill, Geranium

Hardy geranium or cranesbill 'Mrs Kendall Clark'

Geranium is an extensive and varied group of plants that are superb for border fronts, raised beds, and underplanting larger plants. Most flower in summer and length of flowering period varies hugely. ‘Rozanne’ is an outstanding variety that blooms for many months. Hardy herbaceous geraniums mustn’t be confused with frost-tender geraniums, correctly known as pelargoniums, widely used for summer pots. Most do best in sun although several species thrive in shade.

H x S: 30-90cm x 30-90cm

Hellebores, Helleborus

Helleborus orientalis — Helleborus orientalis

Hellebores are winter/spring-flowering perennials, including Christmas rose (Helleborus niger) and Lenten rose (Helleborus orientalis). Attractive foliage is mostly evergreen and pretty flowers range in colour from white and green to shades of pink and purple. Many hellebores are happy in shade although a few require sun. Winter-flowering varieties are particularly important for bees emerging early in the year.

H x S: 30-50 cm x 30-40cm

Daylilies, Hemerocallis

Hemerocallis 'Ruby Spider' — Hemerocallis 'Ruby Spider'

Daylilies have colourful, lily-like open trumpet blooms borne in clusters on sturdy stems. The individual blooms last only for a day, hence the name, but are produced in profusion to give a good display over a number of weeks in summer. A wide colour range includes yellow, orange and red. Grow in full sun and fertile, well-drained soil.

H x S: 30-60 cm x 45-60cm

Heuchera

Pink heuchera leaves

Heucheras are renowned for all-year foliage interest, with scalloped-edged leaves in neat clumps and an exceptional choice of colours, including lime-green, yellow, purple, and orange. Slender spires of white flowers appear in summer, but foliage is the big attraction. Grow in sun or part shade.

H x S: 30-45cm x 30-45cm

Hosta

Hosta leaves

Hostas are grown mainly for their bold and handsome leaves in many subtle variations including greens, glaucous blue, and variegated with white or yellow markings. Flowers are also borne in summer, but foliage is the main attraction. Hostas thrive in full or partial shade and prefer moisture-retentive soil. However, they do have the drawback of being attractive to slugs and snails: they eat holes in the leaves and although rarely kill plants, do make the leaves unattractive. Hostas also do well in pots, where it’s easier to protect plants from slugs.

H x S: 30-75 cm x 30-75 cm

Ice plant, Hylotelephium spectabile

Hylotelephium spectabile — Hylotelephium spectabile

Ice plant provides colour in late summer and is attractive to bees and butterflies. It bears large, flat heads composed of many tiny blooms in shades of pink and red. Forms rounded clumps of handsome fleshy-leaved glaucous foliage. Grow in sun and on free-draining soil.

H x S: 30-45 cm x 30-45 cm

Iris

Bearded iris flower

Iris is a huge genus, with species and varieties that offer something for almost every garden situation. Moisture-loving species thrive in boggy soil and at the pond edge, dwarf iris are good in rockeries and raised beds, while sumptuous-flowering bearded iris must have full sun and well drained soil. Most iris bloom in summer.

H x S: 15-90cm x 20-60cm

Japanese anemone, Anemone hupehensis

Anemone hupehensis var. japonica 'Pamina' — Anemone hupehensis var. japonica 'Pamina'

Japanese anemone is easy and reliable for late summer flowers, bearing tall stems of saucer-shaped flowers in white and pink. Happy in sun or shade. It does regrow from pieces of root, so aim to plant in its final position if possible.

H x S: 60-90cm x 45-60cm

Lupin

Lupin 'Gallery Red' with bearded iris 'Black Swan'

Lupin is an old favourite cottage garden flower, renowned for tall vertical flower spikes clad with many little, colourful blooms in summer, above clumps of divided leaves. There’s an extensive colour range including pink, red, blue, yellow and white. The young foliage is attractive to slugs so some protection is recommended in spring when the new leaves appear. Grow in sun and good fertile soil.

H x S: 45-90cm x 45cm

Bee balm, Monarda

Monarda 'Beauty of Cobham' — Monarda 'Beauty of Cobham'

Bee balm bears flowers that are exceptionally rich in nectar, hence its name, as bees and other pollinating insects seem to love its blooms. This bold perennial forms good-sized clumps of sturdy stems topped with showy red or pink flowers in summer. Does best in full sun and good fertile soil.

H x S: 60-75cm x 1m

Oriental poppy, Papaver orientale

Papaver orientale — Papaver orientale

Oriental poppies bear enormous, showy blooms in spring and early summer, followed by decorative seedheads. Colours include pink, red, coral and white, mostly with contrasting black centres. The fern-like fresh green leaves appear very early, with flowers appearing in mid spring. Then the whole plant goes dormant and dies back by summer. Easy to grow, in any reasonable soil and in sun or part shade.

H x S: 60cm x 45-60cm

Primroses, Primula

Primrose, Primula vulgaris — Primrose, Primula vulgaris

Primroses are beloved for their early flowers – prima rosa is Latin for ‘first rose' – and our native primrose starts blooming in winter in mild areas. There’s a huge range of colourful varieties as well as moisture-loving primulas for damp soil.

H x S: 15-60cm x 15-45 cm

Lungwort, Pulmonaria

Purple lungwort flowers

Lungwort sparkles with colour in spring and are both beautiful and useful, tolerating shade as well as sun and forming low spreading clumps that can be planted beneath shrubs and trees. Bees love the blue, white or pink flowers. Some pulmonarias have prettily marbled leaves, too.

H x S: 30cm x 45 cm

When to plant perennials

Perennial plants growing in pots

Autumn is the ideal time to plant hardy perennials, while the soil is still warm, and plants can establish a good root system ready for the following spring.

After autumn, spring is the next best time to plant perennials, as long as plants are watered during dry spells when temperatures increase in summer. This season is best to plant perennials that aren’t reliably hardy, so they have plenty of time to establish before winter.

You can plant perennials in summer, however it’s critical that the plants are kept watered for the rest of the growing season, as there's naturally less moisture in the soil.

In mild areas, hardy perennials can be planted during winter, except when the ground is frozen or waterlogged.

How to plant perennials

Planting perennials in the ground

Prepare ground thoroughly, as some perennials will be there for years. Improve soil with plenty of well-rotted organic matter or soil conditioner, remove large stones and clear all weeds, particularly the roots of perennial weeds.

Dig a hole slightly larger than the plants’ roots or pot, take off the pot and carefully unwind any roots that have spiralled around the rootball. Put the perennial in the ground so the top of the rootball is at soil level, backfill with soil, firm to remove any air pockets, and water thoroughly.

Caring for perennials

Deadheading spent lupin flowers

In early spring, feed your perennials with a general slow-release fertiliser and mulch the bare soil between plants with well-rotted organic matter
In spring or early summer, support tall-growing perennials with stakes such as canes and string, or grow-through plant supports placed over the clump
Through spring and summer, keep the surrounding ground clear of weeds
Remove dead and faded flowers to prolong the flowering season and to keep plants looking good
In autumn, cut back fleshy-leaved perennials as soon as they die back, otherwise the leaves go soggy and rot
Woody-stemmed perennial growth can be left until late winter/spring before cutting back. Frost, mist, and snow transform parchment-coloured stems into a winter wonderland, and during very cold winters, this growth also helps protect the roots from damage by severe frosts. Beneficial insects such as ladybirds hibernate in dead stems
Tidy evergreen perennials from time to time to remove dead or tatty leaves and faded flower stems
After three to five years, perennials tend to form large clumps and performance starts to decline. Lifting, dividing and replanting them will rejuvenate plants and provide you with more plants to grow around the garden

How to propagate perennials

Dividing Aster Novae angliae plant — Dividing Symphyotrichum novae-angliae plant

Perennials are superb for the budget-conscious gardener. Many can be raised cheaply from seed, then, once perennials have formed good-sized clumps, nearly all can be propagated by division, breaking up the clump into good-sized chunks to replant while discarding the old, woody centre.

Advice on buying perennials

Perennials are widely available at nurseries and garden centres, usually in at least two different pot sizes so you have the option of buying more costly plants for instant impact, or smaller ones that take a year or two to grow
Perennials can also be bought by mail order – the best time to buy is autumn to spring, when plant growth is dormant, and they are more easily transported. Bare rooted plants are available whilst dormant, which avoids using plastic pots and is often cheaper
Perennials can also be bought as plug plants, which are small and need growing on in pots before planting in the garden

Where to buy perennials online

Frequently asked questions

Do perennials come back every year?

Yes. Perennials are long-lived plants that come back year after year, although short-lived perennials may come back for just two to three years.

Does perennial mean evergreen?

No. Perennial means it comes back year after year. Some perennials are also evergreen, like hostas and some heucheras, but most perennials are herbaceous, meaning they die back each autumn and regrow in spring.

Is perennial permanent?

Sort of. Perennial plants come back year after year but some are only short-lived so may last only for two to three years.