Geraniums are colorful flowering plants that add interest and improve the vitality of home gardens. When planted as companion plants, geraniums repel many common insect pests from home gardens and the oil produced by the plant helps prevent spider mites, according to Brigham Young University Idaho's "Companion Planting Guide." Geraniums are a versatile garden plant that produce flowers throughout the summer until the first frost.

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Geraniums are attractive flowers.

Companion Planting

Companion planting is a gardening technique that involves planting different species of plants in the same area to increase the productivity of all plants. While there is little scientific research on the benefits of companion planning, a mixed garden environment that has numerous plants with different colors, smells and periods of blooming help confuse pests and are more resilient than monocultures, according to the Cornell University Cooperative Extension. Companion planting is often practiced by trail and error in each growing location. The success or failure often depends on the type of geranium, the companion plant and the local growing environment.

Growing Geraniums

Geraniums grow best in well-drained, fertile soils in full sunlight. Geraniums require at least eight hours of sun to develop healthy, robust flowers. Remove flowers from the plant once they have bloomed and wilted; removing spent flowers -- a process called deadheading -- prevents the plant from producing seeds and will encourage the plant to produce more flowers. Numerous geranium varieties are readily available and common flower colors include red, pink, orange, white, purple as well as bi-color flowers. Flowers last through the summer and will continue to bloom if brought indoors over winter.

Companion Plants for Geraniums

Geraniums are commonly planted along side other varieties of geraniums or flowering plants such as chrysanthemums and coreopsis to create a brilliant maze of colors in flower gardens. Brigham Young University suggests planting geraniums near roses, grape vines and corn due to the flowers' ability to repel cabbage worms. Geraniums are also known to repel earworms, Japanese beetles and leafhoppers and make useful companion plants for vegetable gardens.

Propagation

Once established in your garden, geraniums are easy to propagate and place as companion plants in other locations on your property. Geraniums are simple to propagate by cuttings. Use a sharp knife to remove the top 4 to 5 inches of a stem. Pinch off the lower leaves and place the bottom of the cutting into a root hormone and then plant in a sandy substrate. Cover the geranium cutting with a clear plastic bag to prevent the leaves from desiccating and place in a bright room, but avoid direct sunlight. Keep the soil moist and the cuttings should develop a healthy root system in four to six weeks. Once the roots have developed, you can transplant the geraniums to sunny locations on your property.