Most gardeners plant a hydrangea shrub for one reason: Those big, showy flowers. But how do you make sure your hydrangea flowers bloom? The right amount of water, light, and fertilizer are key, but it's also vital to know what type of hydrangea you're growing as each has slightly different preferences. Follow these general care recommendations as well as tips for the most popular hydrangea varieties—panicle, smooth, and bigleaf—and get ready to watch your hydrangea flowers bloom and multiply.
Tips for Planting Hydrangeas
Setting your hydrangea shrub up for success at planting time will encourage a healthy, well-blooming plant. Site it based on your particular hydrangea's light preferences—depending on the variety, they can handle part shade to full sun. In a spot with well-draining soil, dig a hole that's twice as wide and about as deep as your hydrangea's nursery pot; amend with compost for a nutritional boost and cover soil with mulch to retain water. When planting your hydrangea, it's best to water it at least three times a week to establish a strong root system.
How Often to Water Hydrangeas
Regardless of the variety, all hydrangeas love water. (Their name comes from the Greek hydra meaning "water.") But how much water do hydrangeas need? You'll know by looking at the leaves. Hydrangea leaves droop when the plant is too dry, telling you they need water. The leaves also go limp in the midday heat, so wait until evening to see if they recover before you water them. Be sure to keep the soil moist but not soggy.
Fertilizing Hydrangeas
Fertilizing hydrangeas can be a tricky task. Most hydrangeas don't need much, but woody plant authority Michael Dirr, a retired University of Georgia horticulture professor, says the best fertilizer for hydrangeas is an all-purpose plant food applied in late winter or early spring before hydrangea start producing flowers (depending on the variety, most hydrangeas start blooming in June or July). Be careful when applying hydrangea fertilizer: If you give your plants too much, you might get more leaves than blooms. Too much nitrogen also produces long stems that might not set flower buds.
Panicle Hydrangea
Producing huge, cone-shaped hydrangea flower clusters, panicles (Hydrangea paniculata) generally have white blooms, but the flowers of several varieties will blush to pink as they age. Some of the most popular varieties of this type of hydrangea include 'Limelight' (flowers have a greenish tinge) and 'Vanilla Strawberry' (beloved for its pink and white two-tone flowers).
Blooms will begin appearing in July, continuing into the fall. The plants do best in full sun and well-drained soil and are hardy in Zones 3-8. A panicle hydrangea might suit you if you want big hydrangea flowers and plants that grow up to 10 feet tall.
How to Get More Panicle Hydrangea Flowers:
- Plant panicle hydrangeas in all-day sun or afternoon sun.
- Water them during a drought, especially if you notice wilting.
- Add plenty of organic matter (such as compost) around the plant.
- Limit any drastic pruning to early spring, just before new growth emerges.
Smooth Hydrangea
Named for the texture of their large leaves, smooth hydrangeas (Hydrangea arborescens) are better known for their enormous, spherical, white flower heads. The best-known variety, 'Annabelle' (sometimes called Snowball Bush), was discovered by a horticulture professor in the 1960s and traced to Anna, Illinois. 'Annabelle' hydrangea shows off big blooms that are initially pure white but gradually fade to green. Invincibelle Spirit is a newer variety that blooms pink instead of the typical white.
Native to areas of North America, smooth hydrangea begins blooming in late June and continues to bloom intermittently throughout the summer. It grows in sunny or partly shady conditions in Zones 4-9.
How to Get More Smooth Hydrangea Flowers:
- Plant smooth hydrangeas in full sun if the soil stays moist. (Partial shade is better in spots that dry out from time to time.)
- Water them during times of drought, especially during the heat of summer.
- Amend the soil with organic matter (such as compost).
- Prune stems back in early spring, just before new growth emerges.
Bigleaf Hydrangea
The bigleaf group of hydrangeas (Hydrangea macrophylla) and its cousins, the oakleaf hydrangea (H. quercifolia), climbing hydrangea (H. anomala ssp. petiolaris), and serrate hydrangea (H. serrata), can present the biggest challenge when it comes to getting more flowers. These hydrangea flowers primarily bloom on the previous year's stems (sometimes called "last year's wood"). If you prune the stems one year, you are likely cutting off the following year's flowers. It's OK to remove any dead stems in spring. If you want to prune for shape, do it by early August because the following year's flower buds are set when temperatures drop.
In cool summer climates with abundant summer moisture, bigleaf hydrangeas can be grown in full sun. Where summers are hotter or dry, though, these hydrangeas appreciate morning sun and afternoon shade. Growing these in too much shade will result in fewer hydrangea flowers or none at all.
Bigleaf hydrangeas can be especially touchy when grown in Northern states. Although some varieties are hardy in Zones 4 or 5, many are only reliable in Zones 6-9. In cold regions, flowering can be affected by early-fall frost, late-spring frost, or super-cold winter temperatures. If you wish, you can cover bigleaf hydrangeas with 12-18 inches of mulch after the first frost, removing the mulch as soon as the threat of frost passes in spring.
Consider growing one of the many new hydrangeas that bloom on old and new wood. They're often called rebloomers, but they're technically remontant, meaning they flower more than once a season. Or enjoy bigleaf hydrangeas only for their leaf colors; some varieties sport green-and-white variegated leaves or lemon-lime hues. These plants' coarse leaves add texture and fantastic fall color to the garden. Common varieties with variegated foliage include Guilded Gold, 'Lemon Wave', and Light-O-Day.
How to Get More Bigleaf Hydrangea Flowers:
- Plant bigleaf hydrangeas in half-day sun in average soil; full sun in areas with cool summers and consistently moist soil.
- Water them well in spring and early summer; it's okay to let them be a bit drier from late summer to early autumn.
- Amend the soil with organic matter (such as compost) every year.
- Don't prune unless necessary (except to cut out dead/diseased branches). Limit pruning of varieties that bloom on only old wood to late June and early August.
- Give the stems extra winter protection by wrapping them in burlap and insulating with shredded leaves.
- 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.