Geraniums are actually Pelargonium hybrids, typically grown as annuals in temperate climates for their impressive, long-lasting blooms. Combining these robust flowering plants with other varieties in containers creates a layered, visually dynamic arrangement. Companion planting requires selecting species that offer aesthetic contrast and share identical environmental needs, ensuring all plants in the shared pot can thrive.
Understanding Geranium Growing Requirements
Successful mixed container gardening requires recognizing the specific environmental needs of the Pelargonium. Geraniums are sun-loving plants that need a minimum of six to eight hours of direct sunlight daily to produce dense flower heads. This high light requirement narrows the field of compatible companion plants to those that also flourish in full sun.
The next major consideration is the soil and water balance, which is particularly important in the confines of a container. Geraniums demand a well-draining potting mix; they perform poorly in soggy conditions that can lead to root rot. Allow the top inch of soil to dry out completely between waterings, rather than keeping the soil constantly damp. Therefore, any companion plant chosen must be tolerant of these slightly drier conditions. The container itself must have adequate drainage holes to prevent waterlogging and ensure the roots of all plants remain healthy.
Recommended Trailing and Spiller Companions
Trailing plants, or “spillers,” cascade over the container rim, softening the edges and adding a flowing dimension that contrasts with the geranium’s upright habit. The geranium’s deep green foliage provides an excellent backdrop for the bright colors and varied textures of these spillers.
The Sweet Potato Vine (Ipomoea batatas) is an excellent choice, providing dramatic, large leaves in shades ranging from chartreuse green to deep purple-black, offering strong color and textural contrast. For a finer texture, Dichondra argentea ‘Silver Falls’ creates a long, flowing curtain of tiny, silvery-gray leaves that trails significantly over the pot’s edge. Creeping Jenny (Lysimachia nummularia) offers bright, coin-shaped, chartreuse foliage that provides a sunny contrast to the geranium flowers.
For flowering spillers, Calibrachoa (Million Bells) produces small, petunia-like blooms that tolerate high heat and full sun, and do not require deadheading. Lobularia maritima (Sweet Alyssum) is another option, forming a dense, low-growing carpet of tiny white or purple flowers that attract pollinators. These flowering options add a secondary layer of color to the arrangement.
Recommended Upright and Filler Companions
Upright plants, or “thrillers,” provide vertical interest and height. “Fillers” are mounding plants that bulk up the mid-section of the pot between the geranium and the spiller. The goal is to introduce different leaf shapes and vertical lines that break up the rounded form of the geranium.
For a strong vertical element, the spikey foliage of Dracaena indivisa (Spike) or ornamental grasses creates a dramatic focal point. The sharp, linear leaves of these plants contrast effectively with the geranium’s broad, rounded foliage. Annual Salvia varieties, like Salvia splendens, offer tall, colorful flower spikes in shades of blue or purple that add height and a structural shape different from the geranium’s blooms.
As fillers, sun-tolerant Coleus varieties, such as ‘Wasabi’ or ‘Ruffles Copper,’ provide continuous color through their richly patterned leaves. The silvery, lobed foliage of Dusty Miller (Centaurea cineraria) adds a cool, silvery-gray tone that makes the bright geranium flowers stand out. Celosia is another excellent filler, whose spiky or plume-like flowers introduce a different texture and shape, filling the space between the upright and trailing plants.
Designing and Ongoing Care for Mixed Containers
The visual success of a mixed container relies on the “Thriller, Filler, Spiller” design principle, which ensures a balanced and full composition. The thriller is positioned in the center or back of the pot, with geraniums typically serving as the main filler or a secondary, shorter thriller. Fillers are placed around the central plant to create mass, and spillers are planted near the edge to trail over the sides.
Proper spacing is necessary to allow for growth and ensure good air circulation, which helps prevent fungal issues. Consistent care is paramount for the long-term health of all the plants once planted. Regular fertilization is necessary because geraniums are heavy feeders, and multiple plants rapidly deplete the nutrients in the potting mix.
A balanced, water-soluble fertilizer applied every two to three weeks supports continuous blooming and vigorous companion growth. Consistent watering involves soaking the container thoroughly until water drains from the bottom, then allowing the top layer of soil to dry out before the next watering. Deadheading spent geranium flowers encourages new buds. Occasionally pruning back enthusiastic spillers maintains the intended shape and prevents them from overwhelming other plants.