How to Fertilize Endless Summer Hydrangeas to Boost Their Flower Power
Keep the show going all season long by giving these reblooming shrubs the exact nutrients they need.
Popular bigleaf hydrangeas got a major upgrade in 2004 with the development of Endless Summer, the first reblooming hydrangea variety. Instead of just producing a limited number of flowers on "old wood" that the plant grew the previous year, Endless Summer produces new stems and new flowers continually. And now, the Endless Summer collection includes five unique varieties (the newest is ‘Summer Crush,’ a compact, container-friendly shrub with flowers that can vary from raspberry red to vibrant purple). But all that constant growth and flowering use up a lot of nutrients, so it's important to give your reblooming hydrangeas the fuel they need in the form of an easy-to-use fertilizer, applied at the right times in the season.
Best Fertilizer for Endless Summer Hydrangea
Feeding your reblooming hydrangea begins with the right product. Your local garden center's fertilizer section likely has an overwhelming number of options to choose from, so it's important to know exactly which kind to seek out. “You’re looking for a slow-release granular fertilizer that is labeled ‘bloom boost,’” says Endless Summer expert Ryan McEnaney from Bailey Nurseries. Bloom boost fertilizers such as Flower-tone ($10, Ace Hardware) have a higher level of phosphorus, the nutrient that promotes flower formation. Phosphorus is the middle number in the N-P-K nutrient label.
A slow-release fertilizer is packaged into tiny pellets that slowly break down, supplying nutrients over weeks or months. This product just needs to be sprinkled onto the soil around the base of your plants, then watered lightly. As always, follow package directions when applying fertilizer to make sure you use the correct amount.
When to Fertilize Endless Summer Hydrangea
In general, as soon as your hydrangea bushes start growing again after the winter, it's time to fertilize. “Just like you and I thrive with a shot of caffeine to wake us up in the morning, Endless Summer hydrangeas bloom best with an early spring application of fertilizer,” McEnaney says. Fertilize your plants in spring when you see green foliage begin to emerge from the base of the stems. If your growing region experiences long, cold winters, expect to see green leaves in mid-spring after the soil warms up a bit.
Fertilize Again in Midsummer
After your Endless Summer hydrangeas first bloom in late spring or early summer, you can push them to send up a second flush of flowers with another dose of fertilizer. Wait until the first set of flowers begins to fade, then apply more of the same slow-release bloom-boosting fertilizer you used in spring, according to package directions. Make way for the new flowers by snipping off the faded blossoms, pruning away each flower head down to the first set of leaves.
How to Change Color of Endless Summer Hydrangeas
Like other bigleaf hydrangeas, Endless Summer varieties can bloom in shades of blue or pink, depending on the pH of your soil. Fertilizer alone doesn’t affect the pH of soil enough to change the flower color from blue to pink or from pink to blue, but a couple of commonly available soil amendments can do the job. You'll need garden lime ($5, Lowe's) to raise the pH enough to turn the flowers pink, and a soil acidifier ($11, The Home Depot) to lower pH and turn your hydrangeas blue.