We suggest the use of a quality potting soil or potting mix or, better yet, a 50/50 combination thereof. Make sure the container you are planting in has a drainage hole(s). You can also add 10 to 20 percent perlite or pumice to the soil mix to enhance drainage.
To loosen the soil, mix dehydrated cow manure, garden compost or peat moss (up to 1/3 concentration) into your pile of topsoil. Make sure the peat moss you get is either baled sphagnum or granular peat.
For loamy, compacted soils in particular, you should dig a large hole and then mix the excavated soil with leaf humus at a ratio of at least 1:1. If you don't have any of this, you can also use bark humus. Garden compost, on the other hand, is not ideal for Hydrangeas, because it often has high levels of lime and salt.
The most common way to raise the pH of your soil (make it more alkaline and less acidic) is to add powdered Garden Lime. Dolomitic limestone will also add magnesium to the soil. Apply it in the fall as it takes several months for the effects to be noticeable. Wood ash will also raise soil pH.
Generally speaking, acidic soil, with a pH lower than 6.0, yields blue or lavender-blue hydrangea blooms. Alkaline soil, with a pH above 7.0, promotes pinks and reds. With a pH between 6 and 7, the blooms turn purple or bluish-pink. To lower your pH, add garden sulfur or aluminum sulfate to your soil.
It's best to start adding coffee grounds to the soil months before the blooming season begins, ideally in the late fall. You can repeat the process with your typical fertilizing schedule. With a little caffeine and a lot of patience, your hydrangeas should reward your efforts come spring with the boldest blue globes.
To grow hydrangeas in planting beds, focus on improving the native soil. One simple way to do that is to combine equal parts existing soil and Miracle-Gro® Garden Soil for Trees and Shrubs. In warmer regions (zones 7 and warmer), where winter tends to be mild, you can also grow hydrangeas in containers.
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.
This common household item is surprisingly effective at helping perk up plants and brighten blooms. For hydrangeas specifically, adding baking soda helps the plant retain more moisture in the roots. When this happens, the result is bigger blooms with more vibrant colors that last longer than they would otherwise.
Best Fertilizer For Hydrangeas
Organic, slow-release fertilizers for roses (such as a 15-10-10, or 10-5-5 formula) work well on hydrangeas, giving the plants the nutrients they need to increase the size and quantity of their blooms.
For best results when planting hydrangeas, follow these steps: Create a hole twice as wide as the plant's root system, and about six inches deeper than the plant's pot. Break up the soil a bit before you plant to help the roots easily establish themselves.
After you plant the hydrangea into the amended soil, be sure to add a thick layer of mulch. This will prevent weeds and maintain soil moisture. Then, give the plant a deep watering right after planting.
To give hydrangeas their best chance at success, apply a layer of chunky mulch around the base of the plant. Decorative mulch is helpful but we recommend straw, marsh hay, or fallen leaves.
Start fertilizing the year after planting.
There are several different types of hydrangeas—bigleaf, panicle, smooth, oakleaf, mountain. All these types should be fertilized at least once a season in late winter or early spring, certainly by the time new growth begins to show around the base of the plant.
The best place to plant hydrangeas is in a sheltered location with sunny mornings and shady afternoons. You often find this on the north or south side of your home. Avoid planting directly underneath trees, which can lead to competition for water and nutrients.
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!
You can use vinegar to lower the pH of your soil, but be aware that in order to achieve blue blooms, you will need both an acidic environment and aluminum ions. The acidic environment will also need to be a sustained over a period of time, which could be hard if rainwater is washing the vinegar away.
Keep good air space between the plants; don't crowd them together or against other plants. Don't give bigleaf hydrangeas too much love; if they're too comfortable (water, fertilizer, etc.), they may devote all their foliage to leaves instead of blooms.
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.
Excessive acidic soil can kill or hamper the growth of plants like asparagus fern, Chinese mustard, Italian ryegrass, lavender, orchids, rosemary, tomatoes, and geranium. The roots of these plants are also not potent to absorb the nutrients added by the coffee grounds in the soil.
*We don't recommend oakleaf hydrangeas because they don't often look their best when grown in a container. They flourish when planted in the ground. But if you enjoy the look, go for it!
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.
Using a granular, slow- release fertilizer with high percentages of phosphorus will get you the greatest results. Bone Meal from Espoma is an all-natural, organic source of Nitrogen and Phosphorus ideal for developing a sturdy root system and promoting plant growth. For hydrangeas it's the ideal supplement for blooms.