To ensure tree peonies produce an abundance of large, magnificent blooms, fertilization is key. The core principle is “three fertilizations per year,” applied specifically before flowering, after flowering, and before the onset of winter.
First Application: Pre-Flowering Fertilizer (Promoting Blooms)
Timing: Currently (late March to early April)—approximately 15 to 25 days after the Paeonia suffruticosa buds emerge but before the flowers open.
Objective: To replenish the nutrients required for flowering, resulting in fuller buds and more vibrant flower colors.
Fertilizer Choice: Primarily phosphorus and potassium fertilizers.
Recommended: Use monopotassium phosphate diluted to a 1:1000 solution (i.e., 1 gram of fertilizer per 1 kilogram of water) for foliar spraying. Apply once every 10 days for a total of two applications. Alternatively, the solution can be applied by watering along the rim of the pot or around the base of the plant.
Optional: Supplement with well-rotted organic fertilizers—such as oilseed cake—to provide longer-lasting nutrient release.
Second Application: Post-Flowering Fertilizer (Revitalization)
Timing: June to July—within two weeks after the tree peony flowers have faded and withered.
Objective: To replenish the substantial nutrients depleted during the rockii tree peony flowering process, help the plant regain its vitality, and lay the foundation for the differentiation of next year’s flower buds.
Fertilizer Choice: Primarily balanced compound fertilizers (containing nitrogen, phosphorus, and potassium) or well-rotted organic fertilizers.
Recommended: Broadcast 20–30 grams of a balanced compound fertilizer (e.g., 15-15-15 NPK ratio) around each plant, then cover with a layer of soil.
Optional: Apply well-rotted sheep manure, oilseed cake, or similar organic fertilizers, which also serve to effectively improve soil structure.
Third Application: Winterizing Fertilizer (Nutrient Storage)
Timing: October to November—before the onset of winter and prior to the arrival of the first frost.
Objective: To build up a reserve of nutrients required for the plant to survive the winter and to enhance its cold resistance. This step is particularly crucial for rockii tree peonies grown in the Lanzhou region.
Fertilizer Choice: Primarily slow-release organic fertilizers.
Recommended: Apply bone meal, well-rotted oilseed cake, or compost. For ground-planted tree peonies, dig a circular trench (15–20 cm deep) around the plant to bury the fertilizer; for potted chinese tree peonies, bury it shallowly along the rim of the pot.
Function: These types of fertilizers decompose slowly; they not only provide a steady supply of nutrients but also create an insulating layer around the root zone, helping the tree peonies safely survive the winter months. Fertilization Guidelines
• Apply Dilute Fertilizer Frequently: It is preferable to use a lower concentration applied multiple times rather than applying a highly concentrated dose all at once; failure to do so can easily lead to “root burn.”
• Avoid High Temperatures: Fertilization should be performed on sunny days—ideally in the morning or late afternoon—to avoid working during the high heat of midday.
• Combine with Watering: Water the plants thoroughly immediately after fertilizing. This aids in dissolving the fertilizer, facilitates better absorption by the root system, and simultaneously dilutes the fertilizer concentration to minimize the risk of fertilizer damage.
• Suspend Fertilization in Summer: During the high temperatures of summer (typically July and August), when tree peonies grow slowly or enter a semi-dormant state, fertilization should be suspended.
