Azaleas, one of the most popular spring bloomers and often called the "The Royalty of Flowers," are hardy plants that grow well even with little help from gardeners. They prefer moist (but not wet) slightly acidic soil, eastern exposure, and filtered shade. They come in evergreen and deciduous varieties; azaleas bloom between early March through late June, also depending upon the variety. Azaleas do best if fertilised when new growth begins appearing in the spring, then monthly through early July.
Select a slow-release fertiliser designed specifically for acid-loving plants like azaleas, rhododendrons, and camellias. Good choices include Miracle Grow Miracid, Monrovia Organic Azalea Food, Holly-Tone, Osmocote Azalea, or Schultz Spectrum Azalea Food. Never use a general plant fertiliser on azaleas, as it may kill them.
Read the product packaging so you know exactly how much fertiliser to use. Each product is different and should be used according to manufacturer instructions.
Spray liquid fertiliser or shake pellet fertiliser onto the soil near the azaleas. Do not dig or scrape the fertiliser into the soil, since azaleas have surface roots that could be destroyed by doing this.
Water the fertiliser in.
Lay a one inch layer of mulch over the fertiliser. Good choices include compost, pine straw, bark mulch, or shredded leaves. Mulching helps control weeds, conserves water, and lowers the soil temperature throughout spring and summer.
Apply fertiliser again at the end of summer, since this helps make new growth hardier, and increases root development so that plants are more abundant in the spring. Also apply a new layer of mulch to help protect azalea roots from frost, ice, and snow.
Fertilising after early July encourages new growth that will die during the cold winter months. This may weaken--or even kill--the plant. If your azaleas are producing plenty of blooms, you can skip fertilising altogether. Well producing plants that are fertilised may develop lots of new foliage, which can attract pests like aphids. If your azalea leaves look yellow, they are probably lacking iron. Purchase chelated iron at a gardening supply centre and spray it on the plant. Then, after testing your soil, amend it so the earth isn't so alkaline.