Get bigger, better blooms from these summer shrubs by feeding them correctly.

When it comes to fertilization, azaleas often have significantly different requirements when compared to other summer shrubs. Ultimately, they don't always need the added boost to produce the best blooms. Oftentimes, using an organic mixture with mulch, pine straw, and similar additions is sufficient. However, not everyone has the access (or the desire) to create their own mix, which is when store bought brands can come in handy. Ahead, everything you need to know about feeding these seasonal stunners.

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Before you purchase fertilizer, Jim Putnam, a consulting expert for Encore Azalea and the founder of HortTube, says to first learn more about the condition of your soil; this will prevent over-feeding. "A soil test will tell you what kind of nutrients your soil needs in order for your azaleas to do their best—or whether or not they need to be fertilized at all," he says. "Once you've determined that fertilizing is the best way forward, you'll want to use an azalea-specific formula."

Azaleas thrive in acidic soils, which create the ideal environment for nutrient absorption, says Fidel Perez, the horticulture manager at Bellagio Resort & Casino in Las Vegas. "An acidic fertilizer will help to maintain the right pH so that the plant can uptake nutrients," he shares. This is exactly why the fertilizers Putnam's team uses contain a soil acidifier. As for why acid is the key? "Azaleas are heavy iron feeders and iron is more readily available in soils with a lower pH (or more acidic)," he says. If your soil's pH comes back between 4.5 and 6.5, it's likely already acidic enough—and you can opt for a regular slow-release fertilizer that you would use with other plants.

Putnam recommends a granular azalea and rhododendron fertilizer or a premium slow-release formula: "Look for a mix that is well-balanced. The three numbers on the packaging should be the same or similar. These numbers represent nitrogen to promote new growth and foliage; phosphorus to promote plant blooms; and potassium to strengthen roots and stems." Some of his favorites include Espoma's Holly Tone ($10, amazon.com) if the soil pH is over 6.5 and Plant Tone ($14.77, amazon.com) if it is lower.

If you'd rather skip the soil test, Perez says you may be able to tell whether or not your azalea is getting enough acid just by looking at it. "If your azaleas look healthy and have flowers in the summer, then you have done your job as a gardener and created the ideal soil conditions. It is very unlikely that you will need fertilizer," he says. Lackluster shrubs that have seen a decline in bloom might need some help. In this case, timing is key: "Apply the granules to the soil around the azalea and cover it with mulch at the beginning of spring and the nutrients should be released into the soil as the temperature increases," he says, noting that the formula should only be applied in early spring or after their first flowering. He prefers Miracle Grow's Azalea, Camellia, and Rhododendron Plant Food ($14.99, amazon.com) which is slow-release and granular.