With their arresting beauty, enchanting fragrance and numerous color, size and shape variations, roses are the darling of any garden. However, they are also highly sensitive plants, requiring specific conditions and constant upkeep.
Therefore, plant breeders have been trying to produce roses that are easier to grow. In 2000, rose breeder William Radler introduced to the U.S. his Knock Out Rose. Since then, this breed has become extremely popular among gardeners of all skill levels. Knock Out Roses grow easily when supplied with full sun and fertile, well-drained soil.
Wondering what to plant with knockout roses to really make their beauty come alive? Find our list below.
9 Perfect Companion Plants for Knockout Roses
Knock Out Roses grow well with many annual and perennial flowers. Here are 9 of the best companion plants to knockout roses.
Scientific Name: Hemerocallis lilioasphodelus
Genus: Hemerocallis L.
Just like knockout roses, daylilies also thrive in full sun. These are hardy, adaptable perennials which don’t require a lot of upkeep; in fact, sometimes they don’t need any care whatsoever. Furthermore, the flowers seem to be virtually immune to disease or pests.
Yellow to orange in color, daylilies grow from 1 to 4 feet high and make a great backdrop to other plants. If you’re using your knockout roses for your perennial flower border, daylilies are a great companion.
Scientific Name: Lavandula angustifolia
Genus: Lavandula L.
Of all of the various knockout roses available, only Sunny is fragrant. So unless you’re planting Sunnies, it might be a good idea to plant lavenders to add fragrance. The gorgeous purple-blue lavenders are hardy flowers, blooming from late spring and throughout the summer.
The most fragrant variety of lavender is Grosso, which usually grows up to 2.5 feet. The flower readily attracts bees, butterflies and other pollinators. Grosso lavenders might even repeat their summer blooming cycle in the early fall or late summer.
3. Mexican Blue Sage
Scientific Name: Salvia chamaedryoides
Species: S. chamaedryoides
Mexican blue sage (Salvia chamaedryoides), or Germander as they are called sometimes, are small sky-blue flowers that grow prolifically.
Mexican blue sage is hardy in USDA zones 7 through 11 and starts blooming in early summer, lasting until the fall. Mexican blue sage will readily bring in butterflies and hummingbirds. This is a low-maintenance plant requiring routine care and will thrive nicely alongside your knockout roses.
Scientific Name: Tagetes erecta
Genus: Tagetes L.
Marigolds are another breed of flower that warmly welcome the glow of full sunlight. Their crepe-like golden blooms make wonderful companions to knockout roses with their warmth and texture. Another reason to love marigolds beside knockout roses is their high draw of pollinators. Plus, they make it easy to prevent pests.
And, since marigolds are hardy in USDA zones 2 through 11, they can easily produce summer blooms in many areas. As far as maintenance goes, marigolds require full sun and weekly watering during the growing season.
5. Creeping Thyme
Scientific Name: Thymus serpyllum
Species: T. serpyllum
Creeping thyme is perennial in USDA zones 5 through 9. In these areas, the plant works perfectly as a complementary ground cover for your knockout roses. The plant also naturally resists pests like aphids and Japanese beetles.
The hardy plant basks in full sun, just like knockout roses, and produces delicate blooms which attract pollinators, as well.
Scientific Name: Allium sativum
Genus: Allium L.
When we say alliums, we mean the beloved kitchen ingredients such as chive, onions, shallots, scallions, garlic and leek.
You might be confused as to how the pungent smell of these plants pairs with knockout roses, but in reality they easily prevent rose diseases like black spot disease and ward off pests like aphids.
If planted in well-drained soil and exposed to full sun, alliums do wonderfully, and what’s more, they’ll also give you wonderful e that look gorgeous beside knockout roses.
Scientific Name: Verbena bonariensis
Genus: Verbena L
Low-growing plants and flowers are the ideal companions of knockout roses, and of these, the verbena is a great choice. They do well in USDA zones 5 through 10, and easily hide the leggy lower branches of knockout roses.
Their beautiful purple and blue blooms last all throughout summer, and look great beside summer and spring Knock Out roses. Well-drained soil and full sun, once again, are the friends of verbenas, so they’re primed to be the perfect companion of your knockout roses.
Scientific Name: Zinnia flower
Genus: Zinnia L.
Another highly prolific bloomer is the zinnia. This flowering plant is popular in annual gardens, as they thrive in full sun and when planted in well-drained soil. They attract pollinators very easily, especially butterflies.
They come in various shapes and sizes, from tall to bushy or to having a singular stalk. They are also available in multiple colors, such as pink, red and yellow, so no matter the shade of your knockout roses, you’re likely to find a zinnia companion for them!
Scientific Name: Petunia exserta
Genus: Petunia Juss.
One of our most favorite companions for knockout roses are petunias. These amazing flowers are vividly colored and bright, lighting up any garden in which they are planted.
Like roses, they love full sun, and rarely need much maintenance except weekly watering. They’re easy to grow and come in seemingly endless colors, so you’ll have a wide range to choose from!
What Not to Plant Near Knock Out Roses
So now you know what flowers to plant with your knockout roses. But what plants should you avoid? This is an important distinction to make. Although knockout roses resist disease more easily than other rose species, they do need some special conditions in order to grow and thrive.
To begin with, knockout roses need a lot of space, so you should avoid planting them beside aggressive growers like wildflowers. Next, although roses love being deeply watered in the summer, they are still sensitive to wet feet. So don’t place them beside plants with moisture-retentive soil. You should also never plant them beside vegetables, as they will most definitely compete for moisture.
With all that in mind, here are some plants not to plant beside your knockout roses.
The blue-and-purple beauty of hydrangeas may seem like a perfect visual companion to roses. However, because they need lots of moist soil, they will compete with your roses. Not to mention, hydrangeas love shade, and roses love sun!
With their lively hanging blooms, fuchsias are undeniably beautiful. However, fuschias, like hydrangeas, require a lot of moisture and shade. And so, they’re incompatible companions for roses.
Shrubs and Large Trees
We love a healthy garden with shrubs and trees. They look welcoming, and undeniably add dimension to any garden. However, shrubs and large trees require large amounts of water and nutrients, and planting them near knockout roses is a sure-fire way to keep them in the shade.
Instead, consider growing a compact hedge like boxwood shrubs. These can make your knockout roses look very elegant indeed.