What are the causes of azalea death or bud drop
The azalea has a graceful tree form and brilliant flowers, and is one of China's traditional top ten famous flowers; it is a commonly used flower for landscaping, indoor potted cultivation and bonsai making. There are many causes of azalea bud drop or death, mainly:
Soil. Azaleas are suited to growing in acidic sandy loam rich in humus, with strong permeability and a pH of 5.0 to 6.5, and dislike alkaline soil and clay soil. If the planting site is alkaline or highly clayey with poor aeration, it easily causes poor plant growth, bud drop, and even death.
Fertilizing. Too high a fertilizer concentration or applying unrotted raw fertilizer will both cause "root burn", leading to bud drop and plant death.
Watering. Azalea roots are extremely fine and fear waterlogging. Too much watering causes a lack of air in the soil, leading to bud drop, leaf drop and plant death.
Temperature. The optimal growing temperature for azaleas is 12°C to 25°C; below 5°C or above 35°C both easily cause damage.
Pests and diseases. Azaleas have many pests and diseases, mainly leaf gall disease, Stephanitis takeyai (azalea lace bug), and brevipalpus mites.
Repotting. Not repotting for many years leaves the plant short of nutrients; repotting at the wrong time, such as in severe winter cold, when it blooms in spring, or during the high-temperature period in summer; improper potting soil preparation, such as high alkalinity and poor permeability, will all cause bud drop and plant death.
In response to the above causes, the following technical measures should be taken.
Soil selection. Plant in acidic, well-drained soil rich in humus. If the soil is slightly alkaline, it can be improved: apply 1000 to 1200 kg of rotted farmyard manure (such as pig manure or cow dung) per mu, then turn and sun the soil; after one year the alkali in the soil will be neutralized by the fertilizer containing large amounts of humic acid. For soil that is heavy in clay and poor in aeration, this can be solved by mixing in river sand or sawdust, burying green manure, or applying organic fertilizer. For potted cultivation, the growing medium can be made up of 45% leaf mold, 45% peat soil, 5% sawdust, and 5% bone meal or rotted cake fertilizer.
Fertilizing. Azaleas stay green with foliage all year and bloom profusely, consuming a lot of nutrients, so their fertilizer requirement is also large. But to prevent "root burn", you must follow the principle of "light fertilizer, applied frequently", using rotted, dilute fertilizer. In early winter, apply 500 to 700 kg of rotted farmyard manure per mu as a base fertilizer, which can raise soil temperature, help azaleas grow in winter and strengthen their ability to withstand cold and overwinter. In February before spring flowering, apply 1 to 2 times a light fertilizer mainly of phosphorus fertilizer combined with nitrogen and phosphorus, to promote brilliant flowers and green leaves. After the flowers fade, apply liquid fertilizer mainly of nitrogen fertilizer 2 to 3 times, with an interval of 10 days each time, to promote the growth of many new branches and tender leaves. During flower bud differentiation, apply rotted cake fertilizer once, plus an appropriate amount of potassium dihydrogen phosphate, to promote flower bud differentiation and the formation of flower buds. To maintain the acidity of the potting soil, water once every 1 to 2 months with a 0.2% ferrous phosphate aqueous solution.
Watering. The azalea's root system is a shallow, fine root mass, fearing both drought and waterlogging, so watering must be done in moderation, and the planting site must always be kept in a semi-moist state. Water in drought conditions, and drain or irrigate in waterlogged conditions. During the spring bud and flowering period, water demand is high; water thoroughly 2 to 3 times a week to meet the needs of growth and flowering, which can effectively prevent wilting of leaves and tender branches, a shortened flowering period, and flowers fading early. In summer, temperatures are high and water evaporates quickly, and it is also the period of vigorous growth of azalea branches and leaves, so water demand is even greater; besides watering once each morning and evening, also spray water on the leaf surfaces and around the flower pots to raise air humidity. In autumn and winter, water less, keeping the potting soil slightly moist. At any time, if there is standing water in the planting pot, pour it out promptly, and loosen the soil and let it dry. For those suffering especially severe waterlogging damage, repot and change the soil.
Light. Azaleas are highly shade-tolerant and suited to growing in a semi-shaded environment; they cannot endure intense summer sunlight. Therefore, when choosing a planting site, a relatively shaded, moist place with scattered light, such as under a large tree, is preferable. If potted, in summer the potted flowers should be placed under a large tree to avoid intense light.
Repotting. For potted azaleas, because their root system is well developed, their sprouting ability is strong, their flowering is abundant, and they consume many nutrients, they must be repotted and have their soil changed once every 1 to 2 years. Prepare the potting soil according to the method described in item one above; the specific repotting time is best after spring flowering or before bud formation in autumn. The procedure is: water thoroughly 1 to 2 days before repotting, so the potting soil swells and loosens; when the potting soil is slightly dry, first tap the sides of the flower pot with your hand to separate the potting soil from the pot wall; use a bamboo stick or other sharp object to pry loose the soil in the pot, and gently lift out the plant; remove the soil along the outer roots and the topsoil, keeping only 1/3 of the old soil; cut off rotten roots, damaged roots, overly long roots and thin, weak roots; change to a pot one size larger, refill with soil and repot; then water thoroughly again, and place it in a semi-shaded place for care.