The water-soluble formulation should be applied every 7 days throughout the growing season for the biggest, brightest blooms and healthiest plants. Get the Miracle-Gro Performance Organics Blooms Plant Nutrition at Amazon, Lowe's, or The Home Depot (2.5 pounds).
For hydrangeas planted in ground.
For optimal growth, bloom production, and quality, fertilize three times: In early spring when plants are just leafing out. In early May to boost their flower production for summer. In late June/early July to help your plants finish the summer strong.
Miracid by Miracle-Gro: This water-soluble fertilizer is excellent for acid-loving plants like Hydrangeas. The fertilizer is water-soluble, so you can easily dilute the mixture to err on the side of caution. You should apply this quick-release fertilizer to your Hydrangeas once a month.
If you over-fertilize, it can burn the root system of your hydrangea bushes and actually inhibit bloom production. For more tips on fertilizer and how to achieve big, beautiful blooms, please click here. My hydrangeas have brown dry spots on the leaves and brown petals on the bloom.
Select the best fertilizer for hydrangeas.
They also do best with a formulation that encourages flower production. Balanced granular fertilizers such as Espoma Rose Tone and Holly Tone are good choices. Jobes Fertilizer Spikes are another good option. Avoid using fast-release fertilizers in liquid form on hydrangeas.
Hydrangeas should be lightly dressed with fast-release fertilizer in March, May, and July. Be sure to spread it around the drip line of the branches and not the base. Water well. If the fertilizer you choose is a slow-release type, remember to lightly cover it with soil to activate the fertilizer.
But there's one key aspect of ensuring hydrangeas return bigger and better every year: deadheading. The practice of removing spent flowers from a plant, deadheading encourages stronger, more bountiful blooms later on.
A 2-3” layer of mulch around the base will help keep the moisture in as well but remember, no “volcano” mulching (where you pile the mulch higher up next stem). Mulching around your hydrangea will encourage deep roots to develop, adding to winter hardiness. Right now, your hydrangeas should be leafed out.
Avoid feeding hydrangeas after August, especially in regions with cold winters. A slow-release plant food works well. For best results, try Miracle-Gro® Shake 'n Feed® Flowering Trees & Shrubs Plant Food, which feeds for up to 3 months.
Also, when you do water, after a week or 10 days, water with a water soluble fertilizer such as Miracle Grow, Rapid Grow or Peters 20-20-20. Apply this water soluble fertilizer every second or third watering and see if the plant doesn't do better.
Hydrangea Care Tips
Water at a rate of 1 inch per week throughout the growing season. Deeply water 3 times a week to encourage root growth. Bigleaf and smooth hydrangeas require more water, but all varieties benefit from consistent moisture.
Water your hydrangeas in the morning before the heat of the sun is strong enough to quickly evaporate soil moisture. Try to avoid watering at night, which can encourage mold and mildew as the moisture sits through the cool night. Water your hydrangeas through the growing season as well as in late fall.
Hydrangeas need more water than most garden plants and will begin to wilt quickly without it. To ensure that Hydrangeas thrive, water deeply two to three times a week in the summer. Be sure to water in the morning or evening so that water does not evaporate as quickly as it would during the heat of the day.
A pH of 7 is neutral, and household vinegar has a pH of around 2.4 (which is quite acidic). The theory is, applying diluted vinegar to the soil will lower the pH enough to change the color of your hydrangea blooms. This strategy will make the soil more acidic, but not for long!
Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. The coffee grounds make the soil more acidic, allowing the hydrangea to more easily absorb aluminum. In addition, fruit peels, lawn clippings, peat moss and pine needles, are thought to have a similar effect.
Wrap with winter protection.
During the winter, make a DIY A-frame wire cage out of burlap and chicken wire to protect your hydrangea plant. This cage will protect it from winter winds, heavy snowfall, and cold temperatures.
If you don't prune hydrangeas then they can eventually resemble a tangled mass of woody stems, and the flowers will become smaller and less showy.
Though hydrangeas prefer protection from hot direct sun, too much shade can prevent them from forming flower buds. Ideal light conditions for hydrangeas are several hours of direct morning sun with afternoon shade, or dappled shade that allows plenty of bright indirect light.
There are plenty of reasons why your hydrangeas may not be blooming as much as they once did. Conditions like extreme heat, drought, or excessive sun exposure can all impact how many flowers your shrubs produce. Pruning is also an important consideration.