The Rhododendron luteum, also known as Azalea pontica, is a yellow flowered azalea with fragrant flowers that is lovely in both spring and autumn with its honeysuckle-like blossom during May and June and crimson foliage in autumn. This is the common yellow azalea that makes quite a substantial shrub in time, since it will reach 2-3m (7-10ft) in both height and spread.
Although no specific mention of toxicity has been seen for this species, it belongs to a genus where many members have poisonous leaves. The pollen of many if not all species of rhododendrons is also probably toxic, being said to cause intoxication when eaten in large quantities. The fragrant yellow azalea ranges from Western Europe to the Caucasus and Lebanon, thriving in rich forests under Fagus, Picea and Abies species. It is also found above the tree line
Like all of the deciduous azaleas, the fragrant yellow species needs moist, well-drained, acidic soil (pH 4.5 to 5.5) that has been well supplemented with peat moss or leaf mold. Azaleas will grow in full sun or light shade, but light shade is preferable in hot areas. Pruning is almost never required. Some deciduous azaleas bloom later than evergreen azaleas.
Do not fertilize yellow azaleas at the time of planting, as this might injure the roots; instead, just water deeply. Plants that have been given a soil mixture rich in organic matter probably will not need feeding for several years. Do not stimulate fast growth because it produces long weak stems and few flowers.
But if a plant seems weak or sickly, use cottonseed meal or a special rhododendron-azalea-camellia-holly fertilizer such as Hollytone dusted on the soil in early spring. Supplemental feeding later is not normally needed, but phosphorus and potassium may be applied any time.
For acidity, flowers of (powdered) sulfur or iron sulfate are best. Do not use aluminum sulfate since aluminum builds up in the soil and is toxic to most plants eventually. For flower bud production and hardiness, super phosphate is best. Around the base of each plant I use a tablespoon of dry sulfur and a tablespoon of dry super phosphate when a plant shows signs of problems. For a general fertilizer for rhododendrons and azaleas, Hollytone is preferred by many growers.
Yellow azaleas are best sown in a greenhouse as soon as it is ripe in the autumn and given artificial light. Alternatively, sow the seed in a lightly shaded part of the warm greenhouse in late winter or in a cold greenhouse in April. Surface-sow the seed and do not allow the compost to become dry. Pot up the seedlings when they are large enough to handle and grow on in a greenhouse for at least the first winter. Layer azaleas in late July. Growth takes 15 – 24 months.