10 Fast-Growing Perennials That Fill Borders at Record Speed

Many amateur gardeners will recognise the situation: you plant with high hopes, wait what feels like forever – yet gaps remain where only weeds really thrive. Fortunately, some perennials not only return every year but also grow at a remarkable pace. They spread quickly, flower for months and provide insects with an abundant feast. These are the “turbo perennials” covered here.

Why fast-growing perennials are a game changer in the garden

Perennials are the long-distance performers of the border: planted once, they return year after year, creating a stable network of roots in the soil. Choosing fast-growing varieties effectively skips the stage when borders look sparse for several years.

“Fast-growing perennials fill gaps, suppress weeds and provide colour for a long time – with considerably less effort than many annuals.”

Most perennials follow a similar pattern: they establish their roots in the first year, spread in the second and have usually claimed their space by the third. With particularly vigorous plants, these stages simply happen much faster, provided the growing conditions are reasonably suitable.

Light is especially important:

• Full sun: around six or more hours of direct sunshine each day
• Partial shade: roughly half that amount, with the remaining time out of direct sun or lightly shaded

Following this simple rule avoids plenty of disappointment – and means you can enjoy dense, healthy borders much sooner.

How to help perennials get off to a fast start

Most fast-growing perennials prefer well-drained soil. Waterlogging slows their growth, while roots can easily rot in heavy ground. It is therefore worth carrying out a quick soil check before planting.

The ideal start in the border

• Remove weeds thoroughly, including their roots
• Loosen the soil with a garden fork, without leaving smooth-sided “pot-shaped” holes
• Work in compost or well-rotted farmyard manure
• Soak perennial root balls before planting until no more air bubbles rise

Using more established potted perennials rather than tiny young plants produces a visual impact sooner. For the first few weeks, water regularly, particularly in sunny or windy weather.

Mulch is another key factor. A layer of composted bark, shredded prunings or straw retains moisture in the soil, holds back weeds and creates a more balanced soil climate. This is a major advantage, especially during the hot summers of recent years.

The 10 perennials that fill borders at record speed

1. Agastache – fragrant perennial and insect magnet

Agastache, often sold as giant hyssop, thrives in sunny, fairly dry positions. It soon forms upright clumps with numerous flower spikes in shades of purple, pink or orange. Its leaves release an aniseed or mint scent when touched, and bees and butterflies are especially drawn to it.

Once established, Agastache copes well with heat and dry spells. A light trim after its first flowering often encourages a second flush.

2. Catmint (Nepeta) – a blue flower carpet for sunny spots

Nepeta is among the most dependable ground-cover plants for sunny borders. It grows in a loose, arching habit, forming dense cushions and often flowering from May into late summer. Its delicate bluish blooms create an almost floating effect in the border.

Cats enjoy the scent, and insects do too. Cut it back firmly once the main flowering period has finished, and the plant will regrow compactly and flower again.

3. Coreopsis – long-flowering in yellow and red

With its daisy-like flowers in yellow, orange or red, Coreopsis brings an instant summer feel to the border. The plants branch strongly, grow with a relaxed upright habit and, with good care, flower at an impressive rate.

Regularly removing faded blooms extends the season considerably. A position in full sun with relatively poor soil is ideal.

4. Gaillardia – a red-and-yellow firework display

Gaillardia loves warmth, drought and full sunshine. Its flowers resemble small fireballs in yellow, red and orange. It flowers for a long, sustained period, even if watering is occasionally forgotten.

As a cut flower, it lasts for several days in a vase. In the border, it quickly fills empty spaces while remaining easy to control.

5. Gaura lindheimeri – floating flowers above the border

Gaura lindheimeri looks almost like a swarm of small butterflies hovering above the border. Its fine, branching stems carry countless small white or pink flowers that dance in the breeze.

It prefers a sunny, light and free-draining site. In severe winters it can die back to some extent, but it usually regrows strongly in spring and quickly fills its space again.

6. Red hot poker (Kniphofia) – exotic bursts of colour

Kniphofia, also known as red hot poker, makes a striking statement with its two-tone flower spikes in yellow, orange or red. The plants form dense clumps fairly quickly.

A full-sun position with well-drained soil keeps it vigorous. In exposed areas, some winter protection around the root zone is advisable.

7. Hardy geraniums – a living carpet at the border edge

Hardy geraniums, not to be confused with bedding pelargoniums, are rightly considered the workhorses of the border. Many varieties grow quickly and widely, cover bare ground and flower from late spring into summer.

They are ideal for underplanting taller perennials or shrubs. Cutting them back hard after flowering rewards you with fresh foliage and often a lighter second flowering.

8. Perennial sage – flower spikes for weeks

Perennial sage adds structure to the border with its upright flower spikes, usually in violet or blue. It quickly grows into compact clumps and flowers over many weeks.

Cutting it back straight after the main flowering period encourages a second flush. Sunny, rather dry soil suits it far better than a permanently damp location.

9. Daylilies – low-maintenance clump-forming perennials with impact

Daylilies form impressively large clumps within only a few years. Although each individual bloom lasts just one day, fresh flowers keep opening, so the overall display remains lush for weeks.

They cope with both sun and light partial shade. Nutrient-rich soil produces particularly large flowers and strong colours.

10. Bee balm (Monarda) – a colourful accent and bee magnet

Monarda spreads relatively quickly through short runners, forming continuous carpets. Its ruffled flower heads in red, pink or purple attract bees, bumblebees and butterflies.

It prefers fresh soil that does not become too dry, and benefits from an airy position because its leaves can otherwise be prone to powdery mildew. Dividing it regularly every few years keeps it vigorous and under control.

How to combine these fast starters cleverly in the border

If you want a garden that not only fills out quickly but also looks harmonious, plan loosely in layers:

• Background: red hot poker, daylilies, tall Agastache varieties
• Middle: Monarda, Coreopsis, Gaillardia, Gaura lindheimeri
• Foreground: catmint, hardy geraniums, low-growing sage varieties

This creates depth and structure without individual plants immediately overwhelming the others. If you prefer a more natural, meadow-like appearance, mix the species more loosely and repeat small groups throughout the planting.

Practical tips for permanently easy maintenance

After a few years, fast-growing perennials can become a little too successful. Regular division and replanting keeps them in shape and prevents competition for space. Early spring or late summer are the best times for this.

Another point is to fertilise sparingly. Too much nitrogen mainly promotes leafy growth, makes plants more likely to flop and leaves them more vulnerable to disease. A thin annual layer of compost is entirely sufficient for most borders.

What terms such as “poor soil” and “well-drained” really mean

Gardening guides often refer to “poor” or “free-draining” soil, which can sound abstract. Put simply, they mean:

• Poor: low in nutrients, generally sandy, with water draining away quickly and weeds growing more slowly
• Well-drained: soil that does not stick together when squeezed in your hand, and where water does not sit for long

If your garden has heavy clay soil, you can improve it with sand, grit and plenty of organic matter. This helps even drought-loving perennials feel more at home and establish themselves much more reliably.

Combined well, these ten turbo perennials take a large share of the gardening work off your hands. They cover bare areas, provide food for pollinators and ensure that, after only a short time, the border looks as though it has “always” been there.