Garden enthusiasts know that the right plant pairings can make all the difference between a so-so garden and one that truly dazzles. Summer phlox, with its sweetly scented blooms and tall, stately presence, benefits tremendously from thoughtful companion planting.
I’ve experimented with dozens of combinations over the years, and honestly, some pairings worked better than others. The right neighbors can deter pests, provide structural support, or create stunning color combinations that make those phlox blooms really pop.
From my experience, these seventeen companion plants have consistently helped my phlox patches grow stronger, bloom longer, and generally look their best throughout the summer season. Each brings something special to the garden party!
1. Shasta Daisies
The classic white blooms create a perfect backdrop for colorful phlox varieties. Their sturdy stems grow at similar heights, creating a cohesive look while their strong roots help prevent soil erosion around your phlox patch.
I planted a row of these beauties behind my pink phlox last season, and the contrast was absolutely stunning. The timing works out perfectly too – both plants peak at roughly the same time in midsummer.
Another benefit is their ability to attract beneficial insects that help keep aphids and other phlox pests in check. They’re drought-tolerant once established, meaning they won’t compete with phlox for water.
2. Russian Sage
Airy purple-blue spires provide gorgeous contrast when planted near bright phlox varieties. The silvery foliage adds textural interest even before flowering begins, and the wispy growth habit won’t overshadow your phlox plants.
What makes this combo work especially well is timing – Russian sage hits its stride just as some phlox varieties begin to fade. My garden maintains visual interest well into September because of this strategic pairing.
Russian sage also tolerates poor soil conditions that might stress other plants, acting as a buffer zone for your more particular phlox. Its strong scent naturally deters many common garden pests that might otherwise target your phlox.
3. Coreopsis
Sunny yellow blooms create a cheerful contrast against the cooler hues of most phlox varieties. The two plants share similar sunlight and water requirements, making them naturally compatible garden companions.
Last summer, I tucked several ‘Moonbeam’ coreopsis plants around the base of my taller phlox, and the effect was magical – like the phlox were floating above a golden cloud. Their different heights work together to create visual interest in the garden bed.
Coreopsis attracts butterflies and beneficial insects that help with pollination. They’re also relatively disease-resistant, which means they won’t introduce problems to your precious phlox plants.
4. Ornamental Grasses
Feathery plumes and architectural shapes provide structural contrast to the rounded flower heads of phlox. I’ve found that placing ornamental grasses strategically around phlox clumps helps prevent the sometimes floppy stems from sprawling too much.
The movement of grasses in the breeze adds kinetic energy to an otherwise static planting. My favorite combination is purple phlox with the golden seedheads of Northern sea oats – they practically glow when backlit by the afternoon sun.
Many ornamental grasses also help draw excess moisture from heavy soils, potentially reducing the powdery mildew issues that sometimes plague phlox in humid conditions. Their deep root systems help break up compacted soil too.
5. Butterfly Weed
The brilliant orange flowers create a striking color contrast with pink, purple, or white phlox varieties. Both plants attract pollinators, turning your garden into a buzzing hub of beneficial insect activity during peak summer months.
Butterfly weed’s drought-tolerant nature means it won’t compete with phlox for water resources. I noticed that after adding butterfly weed near my phlox border, the number of monarch butterflies visiting doubled – they’d feed on both plants during their daily rounds.
As a native plant, butterfly weed adapts well to local conditions and requires minimal care once established. Its deep taproot also helps break up clay soils, improving drainage for nearby phlox plants that prefer well-drained growing conditions.
6. Black-Eyed Susans
Golden daisy-like flowers create a warm contrast with cool-toned phlox blooms. Their different bloom shapes – flat and daisy-like versus clustered and rounded – create interesting textural diversity in the garden bed.
Black-eyed Susans have a slightly different bloom time, often peaking just as phlox begins to fade. This extends the visual interest of your garden through late summer. When I added a drift of these sunny flowers near my phlox collection, the garden seemed to gain an extra month of color.
They’re also remarkably unfussy plants that can handle less-than-ideal conditions, taking pressure off your phlox by filling in spots where other plants might struggle. Their presence attracts goldfinches who love their seeds.
7. Bee Balm
Spiky, crown-like flowers in shades of red, pink or purple create fascinating textural contrast next to the rounded flower heads of phlox. Both plants enjoy similar growing conditions, making them natural garden companions.
The slightly staggered blooming times help extend the overall flowering season in your garden. I’ve noticed that hummingbirds frequently visit my garden when both plants are in bloom – they seem particularly drawn to this combination.
Bee balm’s minty fragrance helps mask the scent of phlox from certain pests. Both plants benefit from good air circulation, so they encourage proper spacing practices that reduce disease issues like powdery mildew. Their similar height creates a cohesive look in the middle of perennial borders.
8. Salvia
Spiky blue or purple flower spires create beautiful architectural contrast when planted among the rounded flower heads of phlox. Their vertical growth habit helps break up the sometimes mounding appearance of phlox clusters.
Salvias tend to be extremely drought-tolerant once established, making them undemanding neighbors that won’t compete for moisture. I’ve found that the deep blue varieties like ‘May Night’ look particularly striking against pale pink phlox – it’s been one of my most photographed garden combinations.
Many salvias bloom earlier than phlox and often rebloom if deadheaded, creating waves of color throughout the growing season. Their aromatic foliage naturally repels many common garden pests that might otherwise be attracted to your phlox.
9. Yarrow
Flat-topped flower clusters in shades of yellow, pink, or white create interesting structural contrast with the rounded phlox blooms. Yarrow’s ferny, aromatic foliage adds textural interest even when the plants aren’t flowering.
Drought-tolerant yarrow won’t compete with phlox for water once established. I’ve found that yarrow actually helps draw beneficial insects that prey on aphids – a common phlox pest. The first year I planted them together, my phlox had noticeably fewer pest problems.
Yarrow’s strong stems can also provide a bit of support for taller phlox varieties that might otherwise flop after heavy rain. Both plants appreciate good air circulation, so they naturally encourage proper spacing that reduces disease issues in humid conditions.
10. Catmint
Soft lavender-blue flower spikes create a misty, romantic look when planted in front of taller phlox varieties. The gray-green foliage offers subtle color contrast even before the flowers appear.
Catmint’s spreading habit makes it excellent for suppressing weeds around the base of phlox plants. After adding a border of ‘Walker’s Low’ catmint around my phlox bed, I noticed I spent much less time pulling unwanted seedlings throughout the season.
Bees absolutely adore catmint, which means more pollinators visit your garden and help ensure good seed set on your phlox if you’re saving seeds. Its aromatic foliage naturally deters many garden pests, creating a protective barrier around more susceptible plants.
11. Veronica
Slender spikes of blue, pink, or white flowers create vertical accents among the more rounded phlox blooms. Their different flower shapes complement each other beautifully in mixed perennial borders.
Many veronica varieties bloom slightly earlier than phlox, creating a seamless succession of color throughout the summer. I’ve had great success with ‘Royal Candles’ veronica planted in groups around my white phlox – the deep blue spikes seem to make the white phlox look even brighter.
Veronica’s compact growth habit means it won’t overshadow or compete with your phlox. Both plants attract butterflies and beneficial insects, turning your garden into a pollinator paradise during the height of summer.
12. Agastache
Tubular flowers in shades of orange, blue, or pink attract hummingbirds and create beautiful color echoes with similarly-hued phlox varieties. The anise-scented foliage adds an extra sensory dimension to your garden experience.
Agastache’s upright growth habit complements the sometimes sprawling nature of phlox. I’ve found that ‘Blue Fortune’ agastache planted behind shorter phlox varieties creates a lovely layered effect that adds depth to the garden.
Extremely drought-tolerant once established, agastache won’t compete with your phlox for water resources. Many varieties bloom from midsummer until frost, extending the season of interest well beyond the phlox’s flowering period. Their aromatic foliage naturally deters many common garden pests.
13. Coneflowers
Daisy-like blooms with distinctive central cones create both color and textural contrast with phlox flowers. Their sturdy stems and drought tolerance make them undemanding garden companions that won’t compete for resources.
Coneflowers tend to bloom slightly later than phlox, extending the overall flowering season in your garden. When I interplanted purple coneflowers with my white phlox, the garden maintained interest well into September, long after many other perennials had finished.
Goldfinches and other seed-eating birds are attracted to the seedheads in fall and winter. The deep root systems of coneflowers help break up heavy clay soils, improving drainage for nearby phlox plants that prefer well-drained growing conditions.
14. Lavender
Fragrant purple flower spikes and silvery foliage create beautiful contrast with the broader leaves and rounded flower heads of phlox. The combination appeals to multiple senses – visual beauty and wonderful fragrance.
Lavender’s drought-tolerant nature means it won’t compete with phlox for water. I’ve found that planting English lavender varieties like ‘Hidcote’ or ‘Munstead’ in front of taller phlox creates a lovely layered effect that shows off both plants to advantage.
The strong scent of lavender helps mask the smell of phlox from certain pests, potentially reducing pest problems. Both plants attract beneficial insects, creating a healthy garden ecosystem. Lavender’s compact habit also helps suppress weeds that might otherwise compete with your phlox.
15. Hardy Geraniums
Low-growing mounds covered in delicate flowers create a beautiful groundcover beneath taller phlox stems. Their spreading habit helps suppress weeds that might otherwise compete with your phlox for nutrients and water.
Hardy geraniums come in shades that complement most phlox colors – from cool blues and purples to warm pinks. After planting ‘Rozanne’ geraniums around the base of my phlox collection, I noticed the garden looked much more polished and professional, with no bare soil visible.
Many varieties bloom for months, providing color even after phlox has finished flowering. Their shallow root systems don’t compete with the deeper roots of phlox plants. The textural contrast between their small, rounded leaves and the larger, more pointed phlox foliage adds visual interest.
16. Astilbe
Feathery plumes in shades of pink, red, or white create beautiful textural contrast with the more rounded phlox flower heads. Their fern-like foliage adds interest even before the flowers appear.
Astilbe appreciates similar soil conditions to phlox – rich, moist, but well-drained. I’ve had great success pairing pink astilbe with white phlox in a partially shaded corner of my garden where many other plants struggle. The combination seems to glow in the dappled light.
Their slightly different bloom times help extend the flowering season. The presence of astilbe can also help indicate when your phlox might need watering, as astilbe leaves will droop slightly when soil moisture is getting low, giving you an early warning system.
17. Sedum
Succulent foliage and late-season flower clusters provide season-long interest when paired with summer-blooming phlox. The fleshy leaves create a strong textural contrast with the more traditional foliage of phlox plants.
Tall sedum varieties like ‘Autumn Joy’ begin developing their flower heads just as phlox blooms start to fade. I’ve positioned several sedum clumps throughout my phlox border specifically to maintain visual interest into fall – the strategy works beautifully to extend the garden’s peak season.
Extremely drought-tolerant once established, sedums won’t compete with your phlox for water resources. Their shallow root systems also mean they won’t interfere with the deeper roots of phlox plants. The seedheads persist well into winter, adding structural interest during the dormant season.
18. Allium
Globe-shaped flower heads on tall, slender stems create architectural interest among the more billowy phlox plants. Spring-blooming alliums finish flowering just as phlox begins to develop, creating a seamless succession of bloom.
Even after the flowers fade, the dried seedheads of alliums provide structural interest throughout summer. I’ve planted purple alliums throughout my phlox bed, and their spherical forms echo the rounded flower clusters of the phlox in a pleasing way.
Alliums naturally repel many garden pests with their mild onion scent, creating a protective barrier around more susceptible plants like phlox. Their bulbs don’t compete for resources with the fibrous roots of phlox, making them compatible companions despite growing in the same space.