What is the thriller filler spiller method?

Thriller filler spiller is the most reliable container planting formula. The thriller is one tall structural plant in the centre or back (50-90cm tall, e.g. Stipa gigantea, dahlia, cordyline). The fillers are 3-4 mid-height plants (20-40cm, e.g. heuchera, salvia, geranium) that fill the bulk of the pot. The spillers are 1-2 trailing plants (helichrysum, trailing ivy, bidens) that drape over the rim.

How big should a container be for a mixed planting?

For a thriller-filler-spiller combination with 5-6 plants, use a pot 40-60cm diameter and at least 35cm deep. Smaller pots starve the plants and need watering twice a day in summer. Larger pots (60cm+) hold moisture better and look more proportional in most UK gardens. Three plants in one 60cm pot beats six plants in three 30cm pots.

What plants work for year-round container interest?

For 12-month structure: Heuchera (any colour), Hakonechloa macra Aureola (golden hakone grass), Ophiopogon planiscapus Nigrescens (black mondo grass), small evergreen ferns (Dryopteris), and Carex testacea (orange sedge). Add seasonal fillers - tulips and primroses in spring, salvias and verbena in summer, ornamental kale in autumn, hellebores in winter.

How often do I water a container combination?

From May to September, water large UK containers daily during dry spells; smaller pots need watering twice a day in heatwaves. October to April, water once a week if the compost looks dry. The rule: stick a finger 5cm into the compost; if dry, water until liquid runs from the drainage holes. A container saucer holds water for slow uptake but never let pots stand in water in winter.

Do I need to feed container plants?

Yes. Container compost has 6-8 weeks of nutrients; after that you must feed weekly during the growing season. Use a balanced liquid feed (Tomorite, Maxicrop) at half strength every week from May to September. For year-round perennial pots, add slow-release fertiliser pellets in early April. Underfeeding is the second-biggest cause of container failure after underwatering.

Modern Container Combinations for UK Gardens

Modern container combinations for UK gardens have moved a long way from the bedding-plant troughs of 1995. Editorial pot design now draws on the same plant palette as the best mixed borders - ornamental grasses, structural perennials, and foliage-led pairings that hold their look for 9 months of the year. This guide covers the classic thriller-filler-spiller formula that still anchors most professional designs, the modern plant choices that have replaced the old standards, and the grouping rules that turn a single pot into an editorial focal point.

The advice draws on 30+ container designs across client gardens in the West Midlands and Cotswolds since 2019. The modern container movement runs through Gardens Illustrated and the major Chelsea show garden plantings, where ornamental grasses now appear in roughly two-thirds of designed pot combinations.

The thriller filler spiller framework

Every container combination in this guide uses the same underlying structure. One tall structural plant. Three to four mid-height fillers. One to two trailing plants. The proportions matter more than the specific plant choices.

Layer	Height	Role	Modern plant choices
Thriller	50-90cm	Tall focal point, one plant	Stipa gigantea, dahlia, cordyline, miscanthus, foxglove
Filler	20-40cm	Bulk of the pot, 3-4 plants	Heuchera, salvia, geranium, hardy fuchsia, dianthus
Spiller	Trailing 30-50cm	Soften the rim, 1-2 plants	Helichrysum, trailing ivy, bidens, bacopa, lobelia trailing

A 50cm pot fits one thriller, three fillers and two spillers. Plant the thriller dead centre, arrange fillers in a triangle around it, slot spillers into the gaps near the rim. Press the rootballs firmly together - container plants grow into each other’s space, not separate.

Tall ornamental grass Stipa gigantea as the thriller centrepiece in a UK container combination surrounded by mid-height perennials and trailing plants A Stipa gigantea thriller (back) with heuchera and salvia fillers and a trailing helichrysum spiller. Stipa replaces canna in most modern UK container designs because it works in shade as well as sun.

Foliage-led grouping

The biggest shift in modern UK container design is the move from flower-led to foliage-led planting. A pot full of brilliant flowers looks spectacular for six weeks and forgettable for ten months. A pot of well-chosen foliage looks structured every day of the year, with flowers appearing as bonus events when the season is right.

The foliage palette to plant from:

Heuchera - the year-round backbone. Available in deep purple (Obsidian, Palace Purple), lime green (Lime Marmalade), bronze (Caramel) and burgundy (Plum Pudding). Hardy to -15C, evergreen, mounding 20-30cm.
Hakonechloa macra Aureola - golden hakone grass. Soft mound of bright gold leaves, turns copper in autumn. The single best filler for shaded pots.
Ophiopogon planiscapus Nigrescens - black mondo grass. Almost black strap-like leaves, evergreen, 15-25cm. Pairs with anything pale.
Carex testacea - orange sedge. Bronze-orange leaves catching light, evergreen, 30-40cm. Underrated.
Dryopteris erythrosora - autumn fern. Coppery new fronds turning green, semi-evergreen, 40-50cm. Brilliant in shaded pots.
Stachys byzantina - lambs ear. Silvery-white woolly leaves, mat-forming. Read as silver in any combination.

Foliage-led UK container combination featuring heuchera black mondo grass and silver senecio in a stone planter with contemporary design A foliage-led pot in the contemporary style. Black mondo grass, deep purple heuchera and silver senecio combine with no flowers at all - the pot reads beautifully through 12 months of the year.

Grouping pots: 3 or 5, never 1

A single pot looks isolated unless it is genuinely enormous (90cm+ and architectural in its own right). Three or five pots grouped at varying heights look intentional and editorial.

The grouping rule:

Three pots at heights of 45cm, 60cm and 80cm
Or five pots at heights of 30cm, 45cm, 60cm, 75cm and 90cm
Always odd numbers - three or five, never two or four
Coordinated material - all terracotta, or all glazed ceramic, or all stone-effect; mixing materials reads as messy

For more on garden design fundamentals that apply to container grouping see our guide on garden design principles for beginners and using colour in garden design.

Three UK terracotta containers grouped at varying heights on a paved patio with coordinated planting in pinks and silvers featuring lavender salvia and stachys Three terracotta pots at 45cm, 60cm and 80cm grouped on a paved patio. Coordinated planting in pinks and silvers (lavender, Salvia nemorosa, stachys) ties the group together visually.

Five proven combinations

Five combinations I have planted in client gardens that hold their look for 18+ months:

1. The Mediterranean

For a sunny south-facing patio. Drought-tolerant, sweet-scented, low maintenance.

Thriller: Stipa tenuissima (60cm)
Fillers: Lavender ‘Hidcote’ x 2, Salvia nemorosa ‘Caradonna’ x 1
Spiller: Helichrysum petiolare (silver)

2. The Shade Garden

For a north-east facing courtyard. Cool, structural, surprisingly bright in winter.

Thriller: Dryopteris erythrosora (40cm)
Fillers: Heuchera ‘Obsidian’ x 2, Hakonechloa macra Aureola x 1
Spiller: Tradescantia ‘Sweet Kate’ (golden)

3. The Modern Black-and-Gold

For a contemporary patio. Architectural, monochromatic, evergreen.

Thriller: Carex testacea (40cm)
Fillers: Ophiopogon nigrescens x 2, Heuchera ‘Caramel’ x 1
Spiller: Lysimachia nummularia ‘Aurea’ (golden creeping jenny)

4. The Cottage Pot

For a country garden. Traditional, romantic, full of bees.

Thriller: Foxglove ‘Camelot Cream’ (90cm)
Fillers: Hardy geranium ‘Rozanne’, Salvia ‘Caradonna’, Dianthus ‘Mrs Sinkins’
Spiller: Bacopa ‘Snowflake’

5. The Autumn Statement

For September to November interest. Late-season colour and seedheads.

Thriller: Miscanthus sinensis ‘Morning Light’ (90cm)
Fillers: Sedum ‘Autumn Joy’, Aster ‘Mönch’, Ornamental kale ‘Rainbow’
Spiller: Heuchera ‘Marmalade’ (orange-bronze)

Seasonal swap-outs

The professional approach: keep the perennial backbone in the pot for 2-3 years, swap out one or two plants seasonally for fresh impact.

Spring (March-May): Tulips and primroses replace summer fillers
Summer (June-August): Salvia, dahlia, verbena - peak season
Autumn (September-November): Heuchera, ornamental kale, asters, Stipa
Winter (December-February): Skimmia, ivy, hellebore, snowdrops

A 60cm container with a hakonechloa thriller and heuchera fillers can host all four seasonal swap-outs in different filler positions. The base plants stay; the seasonal interest rotates.

Autumn UK container combination featuring ornamental kale heuchera and asters in a glazed pot on a paved patio with warm autumn daylight An autumn swap-out using the same hakonechloa-and-heuchera base from summer with ornamental kale and asters added for September-November interest. The base plants live in the pot; the autumn fillers were a £15 swap.

The compost rules

Container compost is not the same as garden border soil. Three rules:

Use peat-free multipurpose with added John Innes No 3. A 50:50 mix gives free-draining structure plus longer-lasting nutrients than peat-free alone.
Refresh the top 5cm annually. Container compost loses nutrients and structure fast. Scrape off the top 5cm in March, top up with fresh compost mixed with slow-release fertiliser pellets.
Replace the full compost every 2-3 years. After 3 years even fed compost is exhausted and compacted. Tip out the pot, divide perennials, repot in fresh compost.

Pot material and frost rating

Match the pot to the climate:

Frost-rated stoneware or terracotta - reliable to -15C, the right choice for permanent perennial pots
Cheap unglazed terracotta - usually shatters in hard frost; bring indoors or accept replacement
Glazed ceramic - hit-and-miss; the cheap glazed pots crack from inside, premium ones (Gascon, Vasque) last 10+ years
Recycled plastic - lightweight, frost-proof, often the right choice for large containers in exposed gardens
Oak half-barrel - rustic, lasts 7-10 years before rotting, brilliant for vegetables and herbs

For broader UK garden style and trends that pair with container design see garden design trends UK and modern mixed border design. For courtyard and balcony container ideas where pot grouping does the work of borders see courtyard garden ideas UK and balcony gardening ideas UK.

Common container mistakes

Single pot syndrome. One pot on a patio looks lost. Add two more.
Flowers without foliage. Six weeks of brilliance, ten months of nothing.
Pot too small for the plant. Roots circle, plant stunts, watering becomes a daily chore.
Saucer left full of water in winter. Roots rot, terracotta cracks. Drain saucers in October.
Forgetting to feed. Six weeks of nutrients in fresh compost, then nothing. Feed weekly from May.