Whether to fertilise is a touchy question with hydrangeas. Most hydrangeas don't need much extra fertiliser, but woody plant guru Michael Dirr, a retired University of Georgia horticulture professor, says you can apply a balanced slow-release fertiliser in late winter to early spring. Be careful: If you apply too much fertiliser, you might get more leaves than blooms. Too much nitrogen also produces long stems that might not set flower buds. Stop fertilising in late summer to let the plant go into winter dormancy.
The key to getting more hydrangea flowers is to understand which hydrangea you're growing. Each type has slightly different requirements.
Panicle Hydrangea
Panicle hydrangeas, with their big cones of flower clusters, need sunlight for best flowering.
Common varieties include 'Grandiflora', Limelight, and Vanilla Strawberry.
How to Get More Flowers:
- Plant panicle hydrangeas in all-day sun or afternoon sun.
- Water them during times of drought.
- Amend the soil liberally with organic matter (such as compost)
- Limit hard pruning to early spring, just before new growth emerges.
- Deadhead blooms as they fade.
Smooth-Leaf ('Annabelle') Hydrangea
Smooth hydrangeas, named for their large, smooth leaves. The best known, 'Annabelle', was discovered by a horticulture professor in the 1960s and traced to Anna, Illinois. There are many types of smooth hydrangeas on the market today, including two varieties that bloom pink instead of the typical white. You can cut smooth hydrangeas to the ground each in spring and they will still produce flowers.
Common varieties include 'Annabelle', Endless Summer Bella Anna, and Invincibelle Spirit.
How to Get More Flowers:
- Plant smooth-leaf 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.
- 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 (Hydrangea macrophylla) and its cousins, the oakleaf (H. quercifolia), climbing (H. anomala), and serrate (H. serrata) hydrangeas, can present the biggest challenge when it comes to getting more flowers. These hydrangeas all primarily bloom on the previous year's stems (sometimes referred to as "last year's wood"). If you prune the stems one year, you are likely cutting off the next year's flowers. It's fine to remove any dead stems in spring.
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 bright morning sun and afternoon shade. Growing these -- or any type of hydrangea -- in too much shade will result in fewer blooms or none at all.
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 in a season. Or enjoy bigleaf hydrangeas only for their leaf colours; some varieties sport green-and-white variegated leaves or lemon-lime hues.
Common varieties with variegated foliage include Guilded Gold, 'Lemon Wave', and Light-O-Day.
How to Get More 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) on a yearly basis.
- 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 in winter 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.
