Growing Tips: Hydrangeas, Color and Fertilizing (2024)

FAQs

What fertilizer is best for hydrangeas? ›

Use a fertilizer low in phosphorous (the middle number in the content analysis) such as 12‐4‐8 to encourage production of blue flowers. For other types of hydrangeas, use a general purpose fertilizer, at recommended rates on the package. Incorporate dry fertilizer into top 2” – 3” of soil and water thoroughly.

Color morphing of these species depends on the soil pH. To change the color of hydrangea flowers, add small amounts of sulfur or lime to the fertilizer. Treat hydrangeas with sulfur, a soil acidifier, to lower the pH so flowers remain or become blue.

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.

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.

If you've been trying to get your hydrangeas to become big and blue, then we might just have the tip for you. Hydrangeas color is based on how acidic your soil is—the more acidic the soil you plant your hydrangeas in, the more blue. We've found that adding a few coffee grounds to your soil can do just the trick.

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!

There is one more trick up the apple cider vinegar sleeve: You can actually change the color of hydrangea flowers from pink to blue. Hydrangea flowers will be pink in alkaline soil, but change to blue in acidic soil. So, mix up some apple cider vinegar and water, and give all the acid-loving plants a treat.

Multiply the number of bold, bright blooms on your woody hydrangea shrubs by making sure your plants have the right amount of sunlight and soil, a fertilizer designed to increase bloom quantity, and a pruning and deadheading routine that keeps them flowering all season long.

The increased acidity from coffee grounds makes it easier for the plant to absorb naturally occurring aluminum in the dirt, resulting in beautiful blue flowers. To use coffee grounds as fertilizer, simply work the grounds into the soil around your plants (a great use for stale coffee).

Acidic soil changes some hydrangeas so they grow blue flowers. Alkaline soil changes hydrangeas to pink. Neutral soil, on the other hand, will allow your hydrangea to revert to a color in the middle. If you want to know how to change your hydrangeas to purple, neutral soil is the answer.

How to make hydrangeas pink? ›

Pink Hydrangeas Need a Higher pH

Pink-and-red hydrangeas, however, perk up their color in a soil with a higher pH—one that's less acidic and more alkaline—of about six. To lower the aluminum or acid content in your soil, spread wood ashes or limestone over the ground and use a hoe or tiller to work it into the soil.

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.

Epsom salt, or magnesium sulfate, is popular among hydrangea growers for its supposed benefits, from boosting flowering to deterring pests.

It's hard to beat hydrangeas for flower power in the summer landscape. That said, to get the most out of your hydrangeas will require proper fertilization and watering. Fertilize too much and you'll get more foliage and diminished bloom. By adjusting soil pH you can change the colors of some types of hydrangeas.