Geraniums are popular flowering plants that bring vibrant color to gardens, containers, and hanging baskets. To ensure these plants thrive and produce abundant blooms throughout the growing season, providing them with proper nutrition through fertilization is important.
Why Geraniums Need Fertilization
Geraniums require a consistent supply of nutrients to support their robust growth and continuous flowering. They primarily need macronutrients: Nitrogen (N) for foliage, Phosphorus (P) for root development and flower production, and Potassium (K) for water regulation and disease resistance. Geraniums also benefit from micronutrients like iron, magnesium, and calcium. While potting mixes offer initial nutrients, these are quickly depleted, especially in containers. Supplemental feeding is necessary to sustain vigorous growth and continuous blooming.
Determining Fertilization Frequency
The frequency of fertilizing geraniums depends on several factors, but a general guideline for established plants during their active growing season is every two to four weeks. This period typically spans from mid-May through early autumn. Consistency in feeding supports continuous bloom production.
The growth stage significantly influences nutrient demand; geraniums require more frequent feeding during active growth and heavy flowering, and less as they approach dormancy or winter. For geraniums grown in pots, more frequent fertilization is often needed compared to those in garden beds because nutrients leach out of containers more readily. Fast-draining potting mixes can also necessitate more frequent applications.
The type of fertilizer also dictates the schedule. Liquid, water-soluble fertilizers are absorbed quickly and typically applied every one to four weeks. In contrast, slow-release granular fertilizers provide nutrients over several months, reducing the need for frequent applications, often requiring only one or two applications per season. Environmental factors like high light and warmth promote faster growth, increasing the plant’s demand for nutrients and potentially requiring more frequent feeding.
Choosing the Right Geranium Fertilizer
Selecting an appropriate fertilizer is important for encouraging healthy geranium growth and abundant blooms. Fertilizers are labeled with three numbers, representing the NPK ratio (Nitrogen, Phosphorus, Potassium).
For flowering plants like geraniums, a balanced formula such as 10-10-10 or 20-20-20 is often recommended for general feeding. Some experts suggest switching to a fertilizer with a slightly higher phosphorus content, like 15-30-15, once flowering begins to encourage bloom production.
Both liquid (water-soluble) and slow-release granular fertilizers are suitable for geraniums. Liquid fertilizers offer immediate nutrient availability and are easy to apply for regular feeding. Slow-release granules provide a steady supply of nutrients over an extended period, which can be convenient for less frequent applications. Regardless of the type, ensuring the fertilizer contains essential micronutrients is beneficial for overall plant health. Many fertilizers are specifically formulated for flowering plants or geraniums, simplifying the selection process.
How to Fertilize Geraniums
Proper application techniques prevent issues like root burn and ensure optimal nutrient uptake.
When using liquid fertilizers, dilute them appropriately, often to half or quarter strength, especially for potted geraniums. This dilution helps prevent salt buildup and protects the plant’s roots. Always follow the specific instructions on the fertilizer product label.
Apply liquid fertilizer directly to the soil around the base of the plant, avoiding contact with the foliage and flowers. For granular fertilizers, incorporate them into the top layer of the soil as directed by the manufacturer.
Before fertilizing, thoroughly water the geranium until the soil is moist; this prevents root burn and aids in nutrient absorption. The best time to fertilize is during the cooler parts of the day, such as early morning or late afternoon, to reduce stress on the plant.
Recognizing Fertilization Issues
Observing your geraniums closely can help identify issues related to improper fertilization, whether it’s a deficiency or an excess of nutrients.
Signs of under-fertilization, or nutrient deficiency, often include yellowing leaves (particularly older ones, indicating a lack of nitrogen), stunted growth, and sparse flowering.
Conversely, over-fertilization can cause significant harm to geraniums. Symptoms often appear as brown leaf tips or edges, general wilting, and a crust of white salts on the soil surface. This condition, sometimes referred to as “fertilizer burn,” occurs when excessive salts draw moisture away from the plant’s roots. In severe cases, over-fertilization can lead to root damage and plant decline.
If these issues arise, reducing fertilization frequency, flushing the soil with plain water to remove excess salts, or adjusting the fertilizer type can help the plant recover.