Greetings, discerning gardener. We, the hydrangeas, are known for our grand, showy blooms and lush foliage. To achieve this magnificent display, we require specific nourishment tailored to our growth cycle. Providing the right fertilizer at the right time is the key to unlocking our full potential.
Our primary requirements are consistent with most flowering plants: Nitrogen (N) for vigorous leaf and stem growth, Phosphorus (P) for strong root development and prolific blooming, and Potassium (K) for overall plant health and disease resistance. However, our unique trait is the ability for many species to change bloom color based on soil pH, which is influenced by aluminum availability. This is where our nutritional story becomes specialized. For blue flowers, we need aluminum available in acidic soil (pH 5.2-5.5). For pink flowers, we need aluminum to be locked up in more alkaline soil (pH 6.0-6.2).
A balanced, slow-release granular fertilizer is often ideal. Look for a formulation labeled for acid-loving plants, such as 10-10-10 or 12-4-8. The "slow-release" property is crucial, as it provides a steady supply of nutrients over several months, preventing a surge of growth that can be tender and susceptible to cold damage or that can prioritize leaves over flowers. For those seeking to enhance blue blooms, a fertilizer supplemented with additional sulfur can help maintain the required acidity. To encourage pink blooms, a fertilizer with added lime will help raise the soil pH. Organic options like well-composted manure, coffee grounds, or commercial organic blends for acid-loving plants are also excellent, as they feed the soil ecosystem which in turn feeds us gently and sustainably.
Timing is everything. Feed us when we are actively growing and can best use the energy.
Early Spring: As new growth emerges from our stems and the soil warms, apply the first and most important feeding of the year. This gives us the nutrients needed to support the rapid development of leaves and the formation of that season's flower buds.
Late Spring / Early Summer: A second, lighter application can be made just as our flower buds begin to swell and show color. This supports the enormous energy expenditure of flowering.
Important: Cease fertilization by mid-summer. Fertilizing too late in the season encourages tender new growth that will not have time to harden off before the first frost, making it vulnerable to winter kill. It can also interfere with the natural process of us beginning to set buds for next year's flowers.
If we are newly planted, wait until we have established ourselves in our new home before fertilizing. Allow us to focus our energy on root production first. For those of us living in containers, our nutrient supply is limited to the pot's soil. We will benefit from a diluted, liquid fertilizer for acid-loving plants applied more frequently (every 4-6 weeks) during the growing season, as nutrients can leach out quickly with regular watering.
