What to Plant With Knockout Roses and What to Avoid

As lovely as the blooms are, roses can be very tricky for you to grow, and this is why you want to be very careful with companion planting around these delicate flowers. You may also wonder what to plant with knockout roses to ensure that the companion plants don’t deplete the resources. Even though knockout roses are hardy, you want your plants to coexist and thrive when you plant them, and this is why we’re going to touch on several great plants to put amongst your knockout roses, and we’ll also talk about which ones to avoid.

Defining Knockout Roses

William Radler introduced Knockout roses in 2000 to the general market. SInce then, it’s been the go-to plant throughout North America. Even though roses have a reputation for being very high maintenance, Knockout roses are an easy-growing choice. They produce stunning flowers from spring until late fall, and they are hardy in zones four to nine. They’re also not prone to the problems traditional roses have.

You’ll get a very compact growth habit at three to four feet tall at full maturity, and it’s a low-maintenance choice that is resistant to diseases and pests. It thrives when you plant it in full sun, and it can tolerate moderate drought. You’ll want to fertilize it once a month to encourage long-lasting blooms, and you don’t have to deadhead them. In the early spring or late summer months, take time to prune the bush to shape it.

Additionally, there is now an entire family of this hybrid shrub rose on the market, and they offer a range of sizes and colors. Although some people say that this rose lacks the classic rose smell, they will give you a very fruity, sweet, and soft fragrance. When you’re considering what to plant with knockout roses and which cultivars you should pick out, keep the following in mind:

• Blushing Knockout (R. ‘Radyod’) — 3 to 4 inches in a  light pink
• Coral Knockout (R. ‘Radral’) — 4 ½ inches in brick orange and coral
• Double Knockout (R. ‘Radtko’) — 3 to 4 inches in cherry red
• Knockout (Rosa ‘Radrazz’) — 3 to 4 inches in cherry red and hot pink
• Peachy Knockout (R. ‘Radgor’) — 3 inches in shell pink with a yellow center
• Petite Knockout (R. ‘Meibenbino’) — 1 ½ inches in fire engine red
• Pink Double Knockout (R. ‘Radtkopink’) — 3 to 4 in pink
• Pink Knockout (R. ‘Radcon’) — 3 to 4 inches in bright pink
• Rainbow Knockout (R. ‘Radcor’) — 3 to 4 inches in coral pink with a yellow center
• Sunny Knockout (R. ‘Radsunny’) — 3 to 4 inches in cream and yellow
• White Knockout (R. ‘Radwhite’) — 3 ½ inches in white

How to Plant Rose Companions

When you plant companion flowers with your knockout roses, make sure you keep them at least a foot away from the roses so they don’t disturb the root system. You may want to have a thicker pair of gloves handy when you work with these roses. Getting a pair of thorn-resistant kidskin leather will make sure they mold to your hands and stress points at the fingertips and thumbs are reinforced to make them last longer.

Use good pruning practices to create a healthy open structure around your flowers, and always make a point to keep good air circulation around the plants to prevent disease or pest issues. With proper care, you’ll learn what to plant with knockout roses and how to make them all thrive well into the fall months.

What to Plant with Knockout Roses – 15 Options

Though Knockout roses are hardy, they benefit from companion planting. First, there’s the matter of aesthetics to fill out a rose garden — while roses look great on their own, they look even more gorgeous in the right company. Plus, suitable companion plants also deter pests and share similar watering and sunlight needs with healthy rose blooms. Here are a few great companion plants for Knockout roses.

1. Alliums

Allums are full sun perennials that encompass a large range of popular culinary plants like scallions, chives, onions, shallots, garlic, and leeks. They produce a pungent smell that wards away many pests, especially aphids that can cause huge amounts of damage to your roses. They can also work to prevent black spot disease from taking hold. LIke roses, allums thrive when planted in full sun in a soil that drains well. On top of all of these good properties, the more delicate blooms on allium plants pair well with knockout roses.

2. Alyssum

The low-growing nature of this plant creates a beautiful but dense carpet of soft-colored flowers. So, if you’re wondering what to plant with knockout roses, this is a great choice. It grows best in zones five to nine, just like lavender. It also enjoys soil that drains well but is very rich. This plant isn’t a huge fan of being in full sun though, especially when the climate is much hotter. They make a great choice for any gardener who lives in hotter climates and they want to add something under their roses bushes in shady areas. They have a very honey-like scent, and when you pair them with your roses, they draw pollinators in.

3. Baby’s Breath

You’ll typically see baby’s breath used in floral arrangements or bouquets. It offers soft pink or white clouds of flowers that look very nice in gardens, especially when you pair them with darker pink or orange roses. Baby’s breath is a great choice when you’re wondering what to plant with knockout roses because it allows you to create a floral feature in your garden with very little effort. You’ll need good drainage in the soil to keep them happy, but this hardy perennial doesn’t need much to thrive.

Baby’s breath does require being in a full sun location, and it doesn’t need a lot of water. It’s very drought-tolerant, so it handles dry climates much better than humid ones in zones three to nine. Baby’s breath and roses make a great pair, and they complement each other in the garden and in bouquets.

4. Creeping Thyme

Creeping Thyme is a practical and pretty ground cover flower. It works as a complementary ground cover under your roses, especially when you plant it in zones five to nine. While Knockout roses have a natural pest resistance to them, creeping thyme will deter pests even more, including aphids and Japanese beetles. It’s hardy and can tolerate being in full sun, and it produces very delicate flowers that attract bees.

5. Foxgloves

Tall plants look very nice planted next to roses, especially when they’re foxgloves. When you plant them together, they create a very striking pair along pathways or borders. The tubular flowers these plants produce tend to bloom late in the summer, and they can be purple, pink, yellow, white, or a variety of colors that can complement any rose. They enjoy growing in a range of light conditions, including full sun or partial shade. The climate will dictate the amount of light these plants get. In cooler areas, they enjoy more sun, but they prefer shade in hotter climates. They grow well in zones five to nine, but they are very sensitive to prolonged higher temperatures. Having soil that drains well will keep this plant vibrant and tall.

6. Lady’s Mantle

If you want a traditional cottage garden and you’re wondering what to plant with knockout roses, this is a great pick. It’s slightly shorter, and it forms a ground cover with smaller yellow blooms. It also makes a very interesting plant to have in a border because it’ll cover the stems on your taller roses to create a full, lush look. It enjoys different light conditions, but it does best when planted in partial shade. You can plant it in full sun, but you have to monitor it for sunscald. It’s not too picky about the soil you put it in as long as it drains well because it won’t tolerate waterlogged soil. It will adapt nicely to various temperature changes, but it’ll need more shade if it’s hotter out. Plant it in zones three to seven for the best results.

7. Lamb’s Ear

As the name suggests, this plant is a velvety, pretty, greenish-gray groundcover that grows very quickly when you plant it in well-draining soil that is slightly moist and bright sun. This plant spreads very quickly, so you want to start them one or two feet from your roses. Before you know it, you’ll get a solid groundcover. However, you will have to clip it back to keep it in check. In very hot conditions, the leaves will start to die and wither, but all you have to do is pick them off as the plant will rally when the temperature drops again.

8. Lavenders

Roses and lavender are a classic pairing, and it’s common to plant them side by side. Lavender’s short purple spires offset the plant’s tall stems and the rose’s cupped blooms nicely. Also, they both grow very well in the same conditions. Certain roses, like floribunda and shrub roses, love soils that drain quickly, just like lavender. The full sun conditions that allow lavender to grow so nicely is also favored by knockout roses.

Lavender also offers other benefits. For example, it’s known to be a great repellent for rabbits and deer, and it attracts bees. They also make a good host plant for aphids to keep them out of your roses. It’s also very easy to maintain and care for once you get it established, and it requires very little water to thrive. It grows best planted in zones five to nine, and as long as there is full sun, they’ll take off.

9. Marigolds

Marigolds are seen as one of the best options when you’re wondering what to plant with knockout roses. This isn’t just because they share similar growing conditions and look good either. They also attract a host of beneficial pollinators to your space. If you’re growing vegetables nearby, you won’t regret adding this plant to your garden. They deter hornworms from around your tomatoes, and they’re also good for preventing the root-knot nematodes from taking over. Marigolds also strengthen your roses’ growth and attract pollinators.

The orange, yellow, and golden hues marigolds offer add life to your rose beds and brighten up your area. They can also thrive in virtually any climate, and this makes them very popular with beginner gardeners. They grow in zones 2 to 11 without an issue, and they love full sun conditions with water once a week once they establish.

10. Parsley

When you’re considering what to plant with knockout roses, parsley may be the furthest thing from your mind. However, they go surprisingly well together, and parsley offers several great benefits for your roses. It works well to deter unwanted insects from your plants, including rose beetles and aphids. Even better, this herb can help enhance how your roses smell. It grows in a broad range of climates from zones 2 to 11, and humidity won’t impact it. It enjoys being in a well-draining but consistently moist soil, and it’s easy to care for if you can get the watering schedule correct.

11. Pincushions

Pincushion flowers are interesting but small, and they can add a little interest around your rose bases. If you’re someone who likes to pick flowers and show them off at home and  you’re wondering what to plant with knockout roses, don’t sleep on this choice. It comes in many colors that will pop along the lower half of your roses.

This plant is very easy to maintain, and it thrives when you plant it in temperate climates. Extreme cold, heat, or higher humidity levels are things this plant can’t tolerate, and it grows best in zones three to seven. They’re sun lovers, and they’ll require plenty of light to give you pretty blooms. In warmer climates, you may need to provide them with shade in the afternoon to prevent scorching. Once established, this plant can go without water for a long period, and this is why it’s a great companion plant for the no-fuss knockout roses.

12. Sage

Sage is another herb you can put on the list when you’re considering what to grow with knockout roses. It’s a great deterrent for beetles and aphids to stop them from attacking your plants. They also work to fill in any gaps created by the longer rose stems while ensuring your roses stay bright. Sage is best planted in full sun and it needs a well-drained, dry soil. It’s drought-tolerant, and it won’t thrive if you water it too much.

Along with working to deter pests, this plant also attracts beneficial insects to the area. Bees, butterflies, and hummingbirds are sure to make an appearance around it. If you’re not 100% sure where to plant your sage, put it as a border plant. It also works well woven between your roses.

13. Shasta Daisy

Shastas daisies, just like knockout roses, are a classic plant to have in the garden, and they produce pretty white flowers with bright yellow centers. This plant’s more simple look pairs very well with the more intricate look of roses in any shade. Shasta daisies will thrive in zones five to nine when you plant them in full sun and soil that drains very well. Exposure to longer periods of extreme temperatures, either cold or hot, can stress out this plant. As long as you have a stable temperature, they are easy to care for, and they need very little water once they establish.

14. Snapdragons

Snapdragons are a favorite plant for spring, for both bees and gardens. It offers long, snout-shaped blooms that contrast well with the rose shape. They help to fill in the gaps to create a bright flower display. They come in virtually any color, and you want to give them plenty of sun with partial shade during the hottest point of the day. Snapdragons thrive when you plant them in cooler climates, but they can grow in zones 7 to 11. Due to the different flowering times, you most likely won’t see them bloom at the same times, but they’ll keep their flowers when roses go dormant in the fall. They also require slightly more water than other perennials.

15. Verbenas

Finally, we have verbenas to round out what to plant with knockout roses. They grow well in zones 5 to 10, and they complement your rose plants because they’re a lower-growing cultivar that hides the leggy lower branches. Verbena offers long-lasting flowers that come in shades of purple and blue, and they bloom at the same time as knockout roses. They are also very tolerant to heat, and they do very well when you plant them in well-draining soil in full sun.

What to Avoid Planting Around Knockout Roses

Even though knockout roses are less prone to diseases, they still benefit from the basic care you’d give any type of rose. They love full sun, and any plant that covers them or does best in full shade will be a problem. They also need space, so any plants that grow aggressively aren’t great companion plants. And although they also like deeper watering sessions during the summer, roses are very sensitive to wet feet, so they won’t do well if the companion plants require soil that retains moisture.

We’ve gone over 15 options if you’re wondering what to plant with knockout roses, but now we’re going to touch on plants to avoid. If you want to grow these plants still, you can put them in separate containers and set them amongst your roses so they’re not competing for space or nutrients.

1. Fuchsias

Fuchsias are very pretty summer plants with bold, colorful hanging blooms. They have a drooping growth habit that can complement the cup shape the rose blooms have. However, they require a higher amount of moisture and shade, and this makes them a bad companion plant for roses.

2. Hydrangeas

Even though the pretty purple and blue hues the hydrangea bushes produce can work nicely with rose colors, they’re not the best pick to plant next to them. The papery flowers conflict with what your rose plants need because they require a lot of shade and constantly moist soil to do well.

3. Large Shrubs or Trees

Shrubs and trees can easily add dimension to your garden, you should be careful about planting them around your knockout roses. They can compete for water and nutrients, and they will eventually block out the light. You can grow a more compact hedge like boxwood by your roses without a problem.

Landscaping With Knockout Roses – Six Ideas

One of the best things about having knockout roses is that you can grow them virtually anywhere. They prefer to be in full sun, but they can tolerate being in partial shade as long as they get between six and eight hours of sunlight a day. You should plant them at least three feet apart to allow for good airflow and give them room to grow.

1. Borders

Knockout roses are fantastic border plants, and they work to brighten up the edges with their pretty blooms from spring until the first frost. You can plant them along a fence or around your island beds, or you can use them to add color to a naturalized border where the woodlands meet the edge of your yard. The middle or back of a sunny, mixed border is also a great spot.

2. Containers

These roses also grow great in containers. The container should ideally be two sizes bigger than the nursery pot you get the rose in, and it should have decent drainage holes. If you set up a thriller-spiller-filler arrangement, these roses play the thriller aspect very well.

3. Cottage Gardens

These versatile and pretty shrubs are the perfect addition to cottage gardens, and they offer a touch of formality to the space without adding a lot of maintenance. You can let your knockout roses grow unattended or you can prune them to maintain a specific shape and size. They work well with coneflowers, delphinium, Shasta daisies and other classic cottage garden plants with this setup.

4. Foundation Plantings

Instead of having your usual evergreen shrubs as your foundation plantings, try knockout roses around the house. They look very inviting when you plant them on either side of an entryway, and they add a stunning beauty below your windows or next to any stairs or pathways. Lighter shades will help to brighten up a dark brick or siding, and vibrant colors will give a pop of interest against white walls. You can plant a row of low-growing plants in front of them to help define the bed.

5. Hedges

A mass planting of these roses makes a very striking hedge that is covered in ruffled, lovely blooms from spring until late fall. Using a single color will help you make a bold statement, and you can pair them with boxwoods to make it more private and beautiful. You can welcome visitors to the property by planting a rose hedge around the perimeter, like around a patio or your garden.

6. Perennial Beds

Mix knockout roses into a perennial flower bed where you would otherwise have gaps between the spring and summer-blooming plants. They also add color in early fall when most plants are fading. Pick several cultivars to ensure you get a range of colors throughout the growing season, or stick to one or two main shades if you want a more simple look. They fit into virtually any garden style without an issue, from pollinator gardens to more formal beds. Pruning isn’t necessarily required to keep them healthy, but it can  help keep them a pleasing shape.

Bottom Line

No matter if you’re just learning about these low-maintenance plants or you have been growing them for years, now you know what to plant with knockout roses to give your garden a very full and lush look. You’ll get colorful blossoms from spring until fall, and garden beds that your neighbors will be envious over.