With the right perennials, you can make that happen much faster than you might expect. There are tough, long-lived plants that create dense mats, tall clouds of flowers and a real burst of colour after just one or two seasons. They grow quickly, return every year and give weeds very little room to settle in.
Why fast-growing perennials are so popular
Perennials are the marathon runners of the border: once planted, they put out fresh growth again year after year. Unlike annual summer flowers, they do not need replacing every season. Focusing on quick-growing varieties saves time, money and effort, while still delivering a generous, full planting.
The usual pattern is this: year one for establishing, year two for spreading, year three for taking over the space - fast starters shorten that timeline dramatically.
Many of these perennials are also excellent for wildlife. They provide plenty of pollen and nectar for bees, bumblebees and butterflies. As a result, a garden does not just look full and colourful; it also feels wonderfully alive with buzzing and fluttering activity.
Site and care: how to get these plants moving quickly
Most rapid growers share a few key requirements. If those are right, they soon get going and put on impressive growth.
- Well-drained soil: they dislike waterlogged conditions, but love open, airy soil.
- Count the hours of sun: full sun means roughly six hours of direct light each day.
- Use partial shade wisely: for more light-sensitive species, about half that exposure is enough.
- Give them a strong start: remove weeds before planting, loosen the soil and work in some compost.
- Water properly: keep them evenly moist during the first season; after that, many become remarkably undemanding.
Larger container-grown plants that are already well rooted fill gaps faster than tiny young plants. They may cost a bit more, but they can easily save one or two years of waiting.
A sensible layer of mulch after planting can also help young perennials get established by reducing evaporation and keeping the soil temperature more stable. That matters most in the first few months, when new roots are still exploring the surrounding soil.
10 perennials that really fill borders fast
1. Anise hyssop (Agastache) – scented flower spires for sunny spots
Agastache, often called anise hyssop, thrives in sunny, fairly dry positions. It quickly grows into upright clumps with long flower spikes that bring colour to the border from midsummer into autumn.
The leaves release a light scent of anise or mint when touched. Bees and butterflies are irresistibly drawn to it. Planting several together in loose groups creates a tall, lively floral backdrop in next to no time.
2. Catmint (Nepeta) – a blue flower cushion with no fuss
Nepeta forms broad, gently arching mounds in a short space of time. Its countless small flowers in blue or violet shades produce an almost continuous carpet of colour from late spring well into summer.
The plant copes easily with heat, drought and the occasional grumpy gardener. Cutting it back after the first flush of bloom often encourages a second show. At the front of borders or along paths, it closes gaps extremely quickly.
3. Tickseed (Coreopsis) – a long-flowering favourite in yellow and red
Coreopsis grows bushy, branches well and covers itself in daisy-like flowers through summer. Depending on the variety, the blooms can be yellow, orange, red or bicoloured.
These plants cope with poor soil, as long as it is not constantly wet. Deadheading regularly extends the flowering period and keeps the clumps neat and compact. In sunny borders, several plants together look like a bright carpet of colour.
4. Blanket flower (Gaillardia) – sunshine for lean soil
Gaillardia is one of the quickest plants for bringing colour into a border. It forms substantial clumps in its first year and flowers for weeks in warm red, yellow and orange tones.
The best part is that it enjoys free-draining, rather dry soil and is equally at home in a rock garden or a sandy bed. Combined with ornamental grasses, it creates modern, drought-tolerant planting in very little time.
5. Gaura – a delicate-looking cloud of flowers on repeat
Gaura may look fragile at first glance, but it is surprisingly tough in the border. Long, slender stems rise from the base, carrying countless small, butterfly-like flowers that seem to dance in the air.
It flowers from early summer right through to autumn. Because of its airy habit, it fills space without crowding out neighbouring plants. It is ideal for borders that should look light and graceful while still becoming dense quickly.
6. Red hot poker (Kniphofia) – exotic accents with pace
Kniphofia brings a touch of the exotic to the garden with its upright flower spikes. The torch-like blooms in yellow, orange or red stand clearly above the foliage and catch the eye from a long way off.
When planted in full sun and kept out of excessively wet ground, this perennial forms larger clumps quickly. Used with grasses or as a focal point near a terrace, it provides structure and height in a short time.
7. Hardy geraniums – a living ground cover that beats weeds
The creeping types of hardy geraniums are superb as fast-growing ground cover. They spread rapidly, cover bare soil and therefore suppress unwanted growth.
Depending on the variety, the flowers appear in pink, violet, blue or white, usually from late spring into summer. Under shrubs, along the edge of a border or between taller perennials, they do an excellent job.
8. Perennial salvia – violet flower spikes with extra appeal for bees
Perennial salvia forms dense clumps with upright flower spikes in violet, pink or blue tones. It stays compact, yet spreads quickly when given sun and free-draining soil.
A cut back after the main flowering period often triggers a second burst of blooms. Hardly any other perennial attracts so many insects; it is a real magnet in the garden.
9. Day lily – tough clumps with fresh flowers every day
Day lilies are classic gap-fillers that tolerate almost any position, provided they are not left in boggy ground. Their grass-like leaves develop into strong clumps that soon occupy plenty of space.
Each individual flower lasts only a day, but new buds keep opening all the time. That means weeks of rich colour in yellow, orange, red or even darker shades.
10. Bee balm (Monarda) – colourful clusters for slightly damper spots
Bee balm spreads by short runners and can form dense stands within a few years. It prefers soil that does not dry out completely and enjoys sunny to partly shaded positions.
Its striking flower heads in red, pink or violet are a magnet for bumblebees and butterflies. In a perennial border, bee balm quickly forms thick groups that usually sit at mid-height.
Fast-growing perennials: how to combine the quick starters
If you are creating a new border or refreshing an old one, a good mix of heights and flowering times makes a huge difference. A simple starting plan would be:
- Back of the border: anise hyssop, red hot poker, tall gaura
- Middle layer: bee balm, day lily, taller coreopsis
- Front of the border: hardy geraniums, catmint, low blanket flower, low perennial salvia
Planting in groups of three to five of each kind gives a much faster impression of a cohesive, well-planned border than scattering single plants here and there.
Another useful approach is to repeat the same plant several times through the border. That creates rhythm and helps even a newly planted space look more established from the start.
Typical mistakes and how to avoid them
Many fast starters can cope with dry conditions, but not in their first year. Insufficient watering at this stage is one of the most common reasons perennials seem to stall.
Another issue is space. Some plants, such as bee balm or vigorous hardy geraniums, spread more than their pot size suggests at the garden centre. Allowing for that from the outset saves you the trouble of dividing and moving them later.
What terms like “poor soil” and “well-drained” really mean
These phrases are used all the time in gardening, but they are not always fully understood. “Poor soil” means ground with few nutrients and without a thick layer of humus. In that kind of soil, many perennials grow more compactly and stand more firmly. “Well-drained” means that water runs through quickly rather than sitting in the root zone for days.
If you are unsure, dig a small test hole after a heavy rain. If water is still sitting there two days later, the position will be problematic for many of the perennials listed above. In that case, adding sand or fine gravel to the upper layers of soil can help - or you can deliberately choose plants that prefer a little more moisture, such as bee balm or certain day lilies.
Many of these plants also benefit from a light tidy-up rather than heavy intervention. Removing faded flowers, cutting back after the main bloom, and dividing overgrown clumps every few years will help keep the border vigorous, floriferous and full of energy.
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