A wide variety of plants make good companions for Knockout Roses, including many perennials and annuals.
In addition, a wide variety of low-growing, easy-care herbs make good choices because they help hide the bare, leggy lower branches of rose bushes.
In this article, we discuss and recommend several excellent choices as Knockout companions.
Companion Plants For Knockout Roses
Try these suggestions for knockout rose companion plants:
Lavender
Lavender is a fragrant, easy-to-grow choice as a Knockout companion.
This herb needs well-draining, slightly alkaline, not too fertile soil and full sun, but in scorching climates, it can benefit from a bit of shade in the afternoon.
Salvias
Salvias of all sorts make good companions for Knockout Roses.
These members of the mint (Lamiaceae) family are easy to grow and produce pretty spikes of colorful, tubular flowers in various shades that attract hummingbirds, butterflies, and other pollinators but are not attractive to rabbits and deer.
Salvias of all sorts do well in a sunny location with well-draining soil and regular soak and dry watering.
Salvia Officinalis
Salvia officinalis is a useful kitchen herb that is especially nice to have in the garden.
It is easy to grow from seed sown directly into prepared garden soil after all danger of frost has passed.
Although it may not bloom in the first year, it will spread and bloom with little or no care in subsequent years. [source]
Mexican Sage
Mexican Sage is a very colorful choice that also does well in slightly alkaline, well-draining soil.
Water deeply, then allow the soil to dry thoroughly before the next watering.
This herb can do well with full sun or partial shade.
Catmint
Catmint is another herb that does very well planted alongside Knockout Roses. These plants like full sun or part shade.
They do best with well-draining soil that has been amended with organic matter, such as compost.
Catmint needs ample water and space during its first year. The plants should be spaced 1′ or 2′ feet apart.
With the right care, they will spread and fill in on their own. Once established, they will do well with a soak and dry watering.
Thyme
Thyme is another herb that does well with wide spacing, bright sun, and well-draining, fertile soil.
This herb likes a pH level of around 7.0. Thyme will also appreciate a regular feeding schedule with good quality water-soluble plant food.
Oregano
Oregano is another sun-loving herb that likes a pH level of between 6 and 7. These plants should be spaced about nine inches apart at planting time.
They do best with soil that has been well amended with rich organic matter such as aged compost.
Marigolds
Marigolds are colorful, fast growers that come in various heights and shades of yellow and orange.
You can sow the seed directly onto the prepared soil in full sun when all danger of frost has passed and expect bright, cheery flowers within a couple of months.
You should keep the soil moist as the seeds germinate and begin growing—established plants by soaking and dry watering.
Larkspur
Larkspur seeds should be kept at cold temperatures of 35° degrees Fahrenheit for a week before planting. This will improve the success of germination.
You can sow Larkspur seed right into well-draining soil in a sunny location early in the spring.
They germinate well in a cool temperature under 55° degrees Fahrenheit soil.
Cover the seed lightly (no more than a quarter-inch deep). Expect flowers in mid-to-late summer or autumn.
You can also sow Larkspur seed just before winter for an early springtime bloom.
Petunias
Petunias do well in fertile, well-draining soil and full sun.
They spread readily and produce blooms in various colors to complement your Knockout Roses.
Be advised that they will not bloom as well in a shady location.
You can sow petunia seeds directly onto prepared garden soil early in the spring or set out young plants in the later months of spring and early summer.
Deadhead frequently for constant bloom.
Lamb’s Ear
Lamb’s Ear (Stachys byzantina) is a pretty, velvety, grayish-green ground cover that grows quickly in bright sun and well-draining, slightly moist soil.
This plant spreads quickly, so you should start with plants between 1’ and 2’ feet apart.
Before you know it, you’ll have a solid ground cover, and you may need to care for them to avoid unwanted, aggressive spread.
In very hot weather, leaves may begin to wither and die off. Simply pick them off. Your plants will rally when the weather cools.
Bellflowers
Bellflowers are a bright purple, drought-tolerant option. These sun-loving plants should be spaced a couple of feet apart, to begin with.
Keep them well-watered until they are established. With time, they will spread.
Easy care, perennial Bellflowers do well with a top dressing of organic compost added in the springtime to help feed the soil, keep it cool and retain moisture.
Delphiniums
Delphiniums need well-draining soil, soak and dry watering and between 6 and 8 hours of sun daily.
It’s best if they can get most of their sun in the morning and have shade in the afternoon heat.
These tall, stately flowers do best in a setting that provides shelter from high winds, which tend to topple them.
Torrential rains will also wreak havoc on Delphiniums.
Heliotrope
Heliotrope is a fragrant, pollinator-friendly, pretty plant in shades of white, blue, and purple that can grow 3′ feet high.
This summer and autumn bloomer loves full sun and well-draining soil and is easy to grow from seed or stem cuttings.
Knockout Rose Conditions Are Ideal For Many Plants And Shrubs
It’s easy to see that your Knockout Roses will be happy standing at the center or back of an herb garden.
In addition to the herbs mentioned here, a wide variety of other choices (e.g., parsley and oregano) can happily share ideal Knockout Rose conditions.
Mix in marigolds and other traditional flower bed annuals. Plant an attractive ground cover.
Keep in mind that other options, such as low-growing shrubs or bulbs, can also do quite well with full sun, well-draining soil, and soak and dry watering.
Let your imagination be your guide.