Geraniums are a popular choice for gardens and containers, known for their abundant and colorful flowers. When they don’t bloom, it can be frustrating. Understanding the factors that influence flowering can help encourage a profusion of blooms.
Light Conditions
Adequate sunlight is essential for geraniums to flower. They thrive in full sun, meaning at least six hours of direct sunlight daily. Some varieties, like ivy geraniums, tolerate light shade, and all geraniums benefit from afternoon shade in very hot regions. Insufficient light is a common reason for poor blooms, as the plant prioritizes foliage growth. If leaves turn yellow and flowering is slow, increasing sun exposure often helps.
Watering Practices
Both overwatering and underwatering stress geraniums, negatively impacting blooming. Geraniums prefer well-drained soil and do not tolerate soggy conditions, which can lead to root rot. Root rot damages the root system, impairing nutrient uptake and flower production. Allow the top one to two inches of soil to dry out between waterings, then water deeply until it drains from the pot. Container-grown geraniums need more frequent watering than those in the ground, possibly daily in hot weather. Watering in the morning is recommended to allow foliage to dry before nightfall, preventing fungal diseases. While established geraniums are drought-tolerant, consistent moisture (without waterlogging) promotes continuous blooming. Yellowing lower leaves can indicate overwatering.
Nutrient Balance and Fertilization
The balance of nitrogen (N), phosphorus (P), and potassium (K) affects geranium blooming. Nitrogen promotes foliage growth; excess nitrogen leads to lush leaves but few flowers. Phosphorus encourages flower production and root development. Potassium helps regulate water balance and strengthens plant tissues, also contributing to blooming. To encourage flowering, use a fertilizer balanced or higher in phosphorus and potassium. Apply liquid fertilizer every one to two weeks during the growing season, or use slow-release fertilizers. If using liquid fertilizer, water the plant first if the soil is very dry to avoid root damage and ensure better absorption.
Pruning and Deadheading
Regular pruning and deadheading encourage continuous flower production. Deadheading involves removing spent flowers, preventing the plant from expending energy on seed production. This redirects energy towards new buds and blooms, and maintains a tidy appearance. To deadhead, remove the entire flower stem as close to the main stem as possible, either by snapping it off or using clean shears. Check for spent blooms weekly to ensure continuous flowering. Pruning leggy growth (long stems with sparse leaves) helps the plant become bushier and directs energy into new growth and blooms. For perennial geraniums, a significant cut back in late summer or fall can encourage a fresh flush of blooms.
Other Environmental and Stress Factors
Several other factors can inhibit geranium blooming.
Temperature
Extreme temperatures, both too hot and too cold, stress the plant and reduce flower production. Geraniums prefer warm temperatures, ideally 55°F (13°C) at night and 65-70°F (18-21°C) during the day. Prolonged intense heat causes stress.
Root Bound Plants
Root-bound plants may struggle to bloom. While geraniums tolerate being snug, severely root-bound plants lack space for root development and nutrient uptake. Repotting into a slightly larger container (one to two inches wider) can alleviate this.
Pests and Diseases
Pests and diseases also divert the plant’s energy from blooming. Common pests include aphids, spider mites, and whiteflies; diseases include powdery mildew, botrytis, and rust. Regularly inspecting plants and addressing issues promptly maintains vigor.
Plant Age
Very young plants may lack the established root system for extensive blooming, while very old, woody plants might have reduced vigor.