Ensure Your Hydrangeas Impress All Season Long With These Spring Fertilizing Tips

Hydrangeas, with their iconic puffy balls of flowers, feature showy blooms every spring. But the key to ensuring those lovely flowers is in fertilizing them properly each spring. There are several species in the genus hydrangea, including bigleaf hydrangea (Hydrangea macrophylla), mountain hydrangea (Hydrangea serrata), and smooth hydrangea (hydrangea arborescens). The different cultivars of these species are very popular across the U.S., with notable color variations that attract gardeners. By keeping your hydrangea happy, with the right nutrients, you can help this deciduous shrub live up to 50 years.

Provided the right soil conditions, either nutrient-rich clay or loam, hydrangeas do not require an overabundance of added fertilizer. The ideal amendment is a modest one completed once a year right after pruning in mid-April to early May. However, bigleaf hydrangea does well with a few light applications of 10-10-10 fertilizer during its growing season. After utilizing top tips to care for your hydrangeas in the winter, make sure to move forward confidently in the spring with fertilization.

After you find the optimal spot in your garden to plant hydrangeas, you want to carefully manage the pH levels of the soil at the site. Depending on your soil, your hydrangeas may require a higher or lower pH than what they're currently planted in. To raise the pH of your soil, add a limestone fertilizer. Follow the instructions from the bag to ensure your safety and the best results. With some hydrangea species, including bigleaf hydrangea (Hydrangea macrophylla), a higher pH will lead to pink blooms. 

To lower the pH, you will need to find an acidic fertilizer. Acidic fertilizers, such as wettable sulphur or aluminum sulfate, make the soil more acidic. The more acidic your soil (between 5.2 to 5.6), the more likely that you will see bright blue flowers on your hydrangea bush instead of pink. Hydrangeas planted near concrete structures may require more fertilizer, as concrete can pull lime from the soil. Bigleaf hydrangeas and mountain hydrangeas are typically the two species that respond this way to a change in soil acidity. Check which cultivar you are growing before attempting to change the color of the flowers. Some cultivars are more likely to end up blue, like Hydrangea macrophylla 'Blaumeise' and Hydrangea macrophylla 'Nikko'.

Too much fertilizer can be detrimental instead of helpful to a plant. Instead of amending the soil too far or guessing what your plants need, test your soil to know what to do next. You can help your plants a lot by amending the soil slowly at first without putting too much at any one time. You can also tell if your hydrangea has too much of one amendment by its appearance. Using too much lime will yellow new growth because of a lack of iron.

Additionally, using too much of one type of fertilizer can negatively impact your hydrangea. High-phosphorus fertilizer can impact the color of blue cultivars by limiting the plant's uptake of aluminum. Don't make this mistake beginning gardeners make way too often, and monitor how often you feed your hydrangeas. Although blue cultivars of bigleaf and mountain hydrangeas do well with modest fertilization in the spring, follow package instructions carefully for other hydrangea species, like smooth and climbing. Although you want to ensure more acidic soil, these hydrangeas will not react as seriously to pH when it comes to blooming.