Calibrachoa, widely known as Million Bells, are popular flowering plants frequently grown in hanging baskets and various containers. They are celebrated for their abundant, small, bell-shaped blooms that provide continuous color throughout the growing season. This prolific flowering habit necessitates specific nutritional care.
Why Calibrachoa Requires Regular Fertilization
Calibrachoa are “heavy feeders” due to their continuous blooming and rapid growth. In containers, limited soil volume means nutrients are quickly depleted or leached. Consistent fertilization is important for vibrant flowers, healthy foliage, and overall plant vigor from spring until frost. Without nutrients, calibrachoa may exhibit stunted growth and reduced blooming.
Selecting the Right Calibrachoa Fertilizer
Choosing an appropriate fertilizer involves understanding nutrient ratios and types. A balanced, water-soluble fertilizer, such as a 10-10-10 or 20-20-20 NPK (nitrogen, phosphorus, potassium) formula, is often recommended. Some suggest formulas slightly higher in phosphorus and potassium (e.g., 3-3-5 or 20-10-20) to encourage blooming while managing foliage growth. Nitrogen supports leafy growth, phosphorus aids root development and flower production, and potassium contributes to overall plant health and disease resistance.
Calibrachoa also benefits from micronutrients, especially iron. These plants are prone to iron deficiency, often caused by high soil pH which makes iron unavailable. Fertilizers can be liquid soluble for quick uptake and regular feeding, or slow-release granular for sustained nutrition. A combination, with slow-release at planting supplemented by liquid feeds, can be effective.
Fertilizing Calibrachoa: Methods and Timing
Fertilization should begin shortly after planting and continue throughout the active growing and blooming season. For liquid water-soluble fertilizers, apply a diluted solution every one to two weeks, or weekly for hanging baskets where nutrients leach quickly. Dilution rates vary, but a half-strength solution is often suggested to avoid over-fertilization. Always ensure the soil is moist before applying liquid fertilizer to prevent root burn.
If using slow-release granular fertilizer, incorporate it into the potting mix at planting. These provide nutrients for several months, reducing the frequency of liquid feeding. However, for heavy bloomers, supplementing slow-release granules with occasional liquid feeds ensures consistent nutrient supply. Monitoring the plant’s appearance helps adjust feeding, as needs increase during rapid growth or hot weather.
Common Fertilizer Problems and Solutions
Improper fertilization can lead to plant issues. Symptoms of nutrient deficiency include yellowing leaves, stunted growth, or lack of blooms. General yellowing, especially on older leaves, can indicate nitrogen deficiency.
Yellowing on newer leaves with green veins (interveinal chlorosis) often points to iron deficiency, frequently linked to high soil pH. If iron deficiency is suspected, adjusting soil pH to 5.5-5.8 is important. Supplemental iron chelate applications can also help.
Conversely, over-fertilization can cause burnt leaf tips, wilting, or general plant decline. This occurs when excess fertilizer salts build up, damaging roots. If over-fertilization is suspected, flushing the soil with clear water helps leach out excess salts. Monitoring the plant closely and adjusting fertilizer concentration or frequency are key to preventing problems and maintaining healthy, vigorously blooming calibrachoa.