There is a long-standing debate in the rose community of whether you should plant anything else with your roses. The truth is, in the long run, monoculture is detrimental to your soil and plants. Growing them on their own is an open invitation to any pests and diseases that favor roses. But what plants play well with roses? A plant that is known for not liking others.
First off, small plants or at least ones that will not overshadow. Your rose needs sun, and any companion has to let the rose get the lion’s share of light. They also cannot compete with the rose for resources. That means nothing aggressive or invasive like periwinkle, cover grasses, mint, or sweet alyssum. They should require the same type of resource, water, and care as your roses. For instance, do not plant something that wants acidic or alkaline soil. Roses like a well-balanced ph as do red columbine and false indigo.
Desert plants will not appreciate the extra water or fertilizer. Unless you are planting a California native species rose, avoid putting native plants with them. California poppies are among the few exceptions as they grow in two of our rose gardens, but they can grow like weeds and choke your roses, so pay attention that they do not.
Companions should be planted at least 12 inches from the rose, so its roots are not disturbed and allow sufficient airflow to the bush. If you have wild spreading companions (like the poppies), pull out the seedlings that start growing directly under your rose.
For rose health try Alliums (there is a wide verity of decretive and edible alliums to choose from) these repel aphids, weevils, borers, gophers, and moles. Plant dill nearby if you have spider mites. Geraniums will help repel aphids, Japanese beetles, and other rose beetles.
French marigolds repel harmful Nematodes, such as the root rot nematodes. They can also attract pollinators and predatory insects such as ladybugs, lacewings, hoverflies, parasitic mini-wasps, and others. ‘Tangerine,' ‘Petite Gold, ‘Petite Harmony’, ‘Goldie,’ and ‘Nemagold’ are said to be particularly effective. And of course, the scented foliage of some herbs also helps repel harmful insects. Lavender, thyme, catmint, and sage are all excellent choices.
It would help if you also considered that time of year your roses are not in bloom. With pruning happening in late winter and buds showing up in mid-spring, many bulbs are ready to fill in for the lack of flowers. Anemones, crocus, snowdrops, scillas, narcissi, and grape hyacinths are all excellent choices. Daffodils not so much. (Always give Daffodils extra room if you do not want them killing their neighbors.) Pansies and violas are other options.
Something else to keep in mind when choosing companion plants is texture, color, and form. Small salvias are great at this as they come in a variety of colors, and their spire form is a nice contrast to a roses cupped form. When talking about color, it depends on the effect you want in your garden. Here are some examples;
Analogous: say you have a yellow rose, pick out two other plants, one yellow-orange, and one orange. This works nicely with blends or striped roses.
Monochromatic: Pink rose, pink companions of verifying shade, tint, and hue. Also suitable for striped roses.
Complementary: yellow rose, purple companion. This can be very striking.
Furthermore, the last color scheme you want to look at is Split complementary: that means you are looking at the tertiary colors. So yellow rose with red-violet and blue-violet for the companion plant colors.
Do not forget about the leaves! If your rose has dark foliage, take a look at plants with lighter or silver foliage.This also works in reverse, light or bright green rose leaf? Choose a dark green companion.
Here are some other plants to look at:
Alchemilla mollie (Lady’s Mantle)
Alstroemeria (Peruvian Lily)
Anthemis tinctoria (Golden Marguerite)
Armeria maritimas (Sea thrift)
Brunnera macrophylla (Siberian Bugloss)
Campanula lactiflora (Milky Bellflower)
Campanula persicifolia (Peach-leaved Bellflower)
Centranthus ruber (red valerian)
Digitalis purpurea (Common Foxglove)
Echinops ritro (Globe Thistle)
Erygium x zabelii (Sea holly)
Gypsophila paniculate (Baby’s breath)
Heuchera (Coral Bells)
Kniphofia (Red hot poker)
Liatris spicata (Gayfeather)
Papaver orientale (Oriental poppy)
Perovskia (Russian sage)
Phacelia tanacetfolia (Fiddleneck)
Santola chamaecyparissus (Lavender Cotton)
Stachys byzantine (Lamb’s Ears)
Stipa tenuissima (Mexican Feather Grass)
Hope this helps, if you have any questions leave a comment. Happy gardening!