Hydrangeas are perennials and those typically have shorter bloom cycles than annuals. Much of the popularity of hydrangeas are their lush blooms.
As a shrub, the hydrangea is considered to have the longest blooms of all perennials. When they don’t produce flowers, disappointment follows.
To avoid that disappointment, follow along to learn about the tricks of the gardening craft to keep your hydrangeas blooming the longest.
Start with the Right Variety (Or Better – a Mix)
Of the many species, and cultivars (of which there are hundreds), hydrangeas can be drilled down to just two types…
- Those that produce buds on new wood
- Those that produce buds on old wood
To add to the confusion of when hydrangeas bloom, there are varieties that produce flower buds on old and new growth (rebloomers or remontant hydrangeas).
Hydrangeas that bloom earliest grow on old wood. The seeds for flowering are carried over from last year’s growth. New growth that comes in around early spring tend to bloom in the summer then continue through until the fall.
The Annabelle cultivar blooms on new wood only, so this is one type not to prune in early spring. The Endless Summer® (aka “Bigleaf Hydrangea) cultivar does as the name suggests – blooms all summer! And, it blooms on old and new wood.
The Endless Summer® variety has the added advantage of changing color based on the soil acidity.
The Difference for Hydrangeas Growing on Old and/or New Wood
There can be confusion over whether hydrangeas require pruning or not. By pruning, it means cutting it back. It is different from deadheading, which is only pinching off a spent flowerhead.
Hydrangeas that produce growth on new wood only will bloom later in the season with or without pruning. You will get more blooms by not pruning this variety. Deadheading them once the flowers are spent will help them produce more flowers.
Varieties of hydrangeas that flower on old and new growth, known as remontant or reblooming hydrangeas, you can let them grow wild, disregard pruning, and only deadhead when required.
The hydrangea shrubs that bloom the longest are not a single cultivar. They will be a carefully selected curation of multiple species. Some that bloom on new growth, others on old wood, and tended to with pruning adjustments to control the height, shape, size of bloom, or length of time it stays in bloom.
To learn about this, see this hydrangea care and maintenance guide.
- Endless Summer® (this is the original Bigleaf Hydrangea)
- Forever and Ever®
Each has different varieties and colors.
These remontant hydrangeas have the unique ability to flower on old and new growth, which is the simplest way to extend the blooming period. With these hydrangeas, they start blooming in the spring, stop flowering after around two months, then rebloom in late summer for another spell.
A simple way to have hydrangeas blooming from spring to fall is to plant remontant hydrangeas for early and late summer blooming, then a different cultivar to fill the gap. When these begin to fade, summer blooming varieties fill the void.
When Should I Cut the Flowers Off My Hydrangea?
Hydrangeas that produce flower buds on old wood should not be pruned in late summer. A good guideline to stick with is to remove spent flowers just as the color is beginning to fade.
The reason to do this is for the plant to stop pouring energy into a dying flowerhead. The flowers do die, then new blooms replace them. This is natural and different from a hydrangea dying, which is when the bulk of the plant is presenting with problems.
Removing spent flowers helps the plant redistribute energy into seed production, for which it will develop stronger blooms early next season. The more mature the buds are, the longer lasting the blooms will be.
Specialty Pruning Requirements of Hydrangeas
Each type of hydrangea has specific pruning requirements. How you prune it depends on whether buds form on new wood or old wood.
Those that flower on new wood only should be pruned back to 12-inches from ground level right after the blooming season finishes. By removing the old wood, new growth emerges in just enough time for the next blooming cycle.
For varieties of hydrangea that only produce buds on old wood, avoid pruning those. Only deadhead them by removing the flower just below the bud. The only time pruning should be done on these types are to remove dead, damaged, or diseased canes.
If you have mixed things up and planted various types of hydrangeas as shrubs to prolong the blooming period, some old wood growth may be cut back to control height, and promote larger blooms by lessening the amount of energy the shrub puts into each.
Go Easy on the Fertilizer
Be cautious with fertilizers! If the nitrogen content gets too high, you will get a leafy shrub with very few blooms. Phosphorous is the ingredient in fertilizers that promotes blooming. But too much will be detrimental because the green leaves are needed for photosynthesis, which is how the plant gets enough energy to put into blooming.
The other key ingredient in fertilizers is potassium, which helps promote healthy root development.
Hydrangeas need a fine balance of all three ingredients (NPK), which is why a balanced fertilizer, such as a 10-10-10 or 20-20-20 fertilizer is recommended. There are fertilizer ratios for annual bloomers such as 7-22-8, which will not result in long-lasting blooms.
You will get a flurry of flowers, but they will be short-lived and re-blooming could be affected too.
Careful Yet Frequent Watering
Given that the majority of hydrangea varieties require a good amount of full sun, and plenty of afternoon shade, moisture evaporates fast from the soil. Most will need the soil to be watered deeply three times weekly throughout the summer.
Always water the soil because it is the roots that need the most nourishment. Given the weight of the oversized flowerheads, large stems and all the foliage, watering from above will add to the weight, likely causing the hydrangea to droop under the weight of water. Avoid that by watering the soil, not the leaves.
Without sufficient moisture in the soil, the root system will struggle to meet the needs of the plant to produce blooms, let alone keep them alive.
Pair with Shallow Root Plants
Hydrangeas are magnificent on their own, but for continuous colorful florals throughout the season, they are paired with flowering plants at lower heights, or sometimes taller to benefit from afternoon shade.
When planning your garden design, think about what to plant with hydrangeas. Given that these require a lot of nutrients from the soil, the last thing you want is to plant anything that is going to starve out the hydrangeas’ root system from getting the nutrients it needs from the soil.
Lastly, Know that the Blooming Period May Be Entirely Out of Your Control
The weather has a huge impact on garden-grown hydrangeas. Especially rebloomers. When winter temperatures drop below freezing, the extreme frost can kill the buds.
If that happens, the first blooms of the season will fail, then the only blooms that will happen will be later on the new growth. Essentially, without winter protection, regardless of the variety, the hydrangea will only bloom on new growth.
Whether you need winter protection for your hydrangeas depends on the variety you grow. Pay attention to the zone hardiness. The lower the growing zone number is, the harsher a winter the plant can sustain.
As an example, Oakleaf hydrangeas can cope with winters in Zone 4 and 5, but if you’re in zone 3, you will likely need winter protection, such as staking around established shrubs in the fall, wrapping a fabric around it to create a makeshift cage, then adding some winter filler material for insulation such as leaf debris.
The most important thing for the health of hydrangeas is to nourish the soil. The healthier the roots are, the healthier the plant is, and that promotes lush blooms that last the longest. A mix of various types of hydrangeas, including perennials and remontant hydrangeas will ensure blooms all season.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.