How To Grow And Care For Panicle Hydrangeas

Some hydrangeas burn to a crisp in August sun. Others die of thirst. Still others won't bloom if you prune them in fall, winter, or spring. For those of you who hate such results, may I kindly suggest you go to your garden center and purchase a panicle hydrangea (Hydrangea paniculata)? This type is easy, easy, easy to grow in USDA Zones 3 to 9A. That's a big chunk of country.

The one you see above in Grumpy's yard is 'Limelight,' by far the most popular selection and among the most widely planted summer-flowering, deciduous shrubs in the USA. It grows 6 to 8 ft. tall and wide and gets its name from large flower clusters borne on the tips of sturdy stems that start off lime green and brighten to white. I highly recommend this fuss-free shrub, but there are many other selections. Keep in mind that hydrangeas are mildly toxic to humans and toxic to dogs and other pets, according to the ASPCA.

Plant Attributes

• Common Name: Panicle hydrangea
• Botanical Name: Hydrangea paniculata
• Family: Hydrangeaceae
• Plant Type: Shrub
• Mature Size: 3 to 12 ft. tall and wide, depending on variety; some eventually reach 15 ft.
• Sun Exposure: Full sun; may appreciate afternoon shade in hot climates
• Soil Type: Tolerant of most soils if well-drained
• Soil pH: Acidic to alkaline
• Bloom Time: Late spring, summer
• Flower Color: White or green; some varieties turn pink as weather cools
• Hardiness Zones: 3-9 (USDA)
• Native Area: Asia

Panicle Hydrangea Care

Mine grows in full sun in soil that's well-drained, but still pretty crummy. It blooms for a good two months or more here in north-central Alabama starting in June and continuing into August. I never spray, fertilize, or fuss over it. It's a keeper. Here's how to care for 'Limelight' and other panicle hydrangeas.

Light

Panicle hydrangeas are more tolerant of sun than most other types of hydrangeas. Plant in a location that receives at least four hours of sun a day for the most prolific flowering. A panicle hydrangea can grow in full sun, but may appreciate afternoon shade in hot climates.

Soil

Panicle hydrangeas tolerate most soils, even clay, as long as they are well-drained. You can plant this shrub in average garden soil, and adding compost or other soil amendments is generally not necessary. Add a layer of mulch to preserve moisture if planting in a dry spot.

Water

Water regularly during the first year after planting to help your shrub get established. Panicle hydrangea is more tolerant of dry conditions than other hydrangeas, but continuing to water in subsequent years (especially during hot, dry spells) will encourage flowering. Too much water or poor drainage can lead to root rot.

Temperature and Humidity

Panicle hydrangeas can be grown throughout most of the country up to a Zone 8 climate. 'Limelight' is noted for its heat-tolerance and can be grown in Zone 9. But 'Limelight' is far from the only panicle hydrangea you can buy. After breeders saw how well it sold, they produced smaller versions, earlier-blooming ones, and selections whose white flowers turn rose and burgundy as they age. This latter feature got people all juiced up, but if you live in the South, temper your fervor. For the color change to happen, nighttime temperatures must drop into the 60s or below. Otherwise, flowers stay white and then gradually dry and turn brown. So don't count on pink flowers in USDA Zones 7B, 8, or 9. In Zones 3 to 7A, enjoy the show.

Fertilizer

These non-fuss plants don't require fertilizer, but if you want your panicle hydrangea to grow faster, apply a granular fertilizer for shrubs in early spring. Too much fertilizer can lead to weak stems, so be wary of overfertilizing and of fertilizing other plants located around them.

Types of Panicle Hydrangeas

• 'Bobo.' Very compact plant, 2 to 3 feet tall and wide, white flowers may turn pink. Good in containers.
• 'Little Lime.' Compact form of 'Limelight,' growing 3 to 5 feet tall and wide. Good in containers. Lime-green flowers turn white and may age to pink.
• 'Little Quick Fire.' Compact shrub, 3 to 5 feet tall and wide. Good in containers. Blooms about a month earlier than other selections. White flowers may age to pink and red.
• 'Moon Dance.' Large, conical clusters of white flowers held upright on strong stems. Great for cut flowers. Grows 6 to 8 feet tall and 4 to 5 feet wide. Makes nice informal hedge.
• 'Pinky Winky.' Very large, conical flower clusters up to 16 inches long age to pink; clusters may be pink and white at same time. Grows 6 to 8 feet tall and wide. Good for informal hedge.
• 'White Wedding.' Large, pillow-shaped clusters of white flowers appear from spring until fall. Grows 4 to 6 feet tall and 3 to 4 feet wide. Good for cut flowers, informal hedges, borders.
• 'Zinfin Doll.' Huge, conical flowers clusters open white, then change to pink from the bottom up. Clusters may be two colors at once. Grows 6 to 8 feet tall and wide. Long bloom season. Superb for cut flowers.

Pruning

Because it blooms on new growth, winter and early spring before the plant leafs out are good times to prune. Pruning is not strictly necessary, but can be used to strengthen stems or reshape the shrub. Remove about 1/3 of the plant's height, as well as any spindly stems or unattractive side branches.

Propagating Panicle Hydrangea

Hydrangeas can be propagated by taking cuttings and rooting them in soil. They are most easily propagated from new growth in late spring or early summer. Cut a 4 to 6 in. length of stem; the bottom should be cut right above a leaf node. Remove all leaves except for the top set. Moisten the bottom of the stem and dip in rooting hormone. Plant immediately in a container of well-moistened, high-quality potting soil about 2 inches deep. Then cover the plant to maintain moisture—a clear plastic bag does a good job of creating a mini-greenhouse for the plant. Keep in bright indirect sunglight, watering to keep soil moist. The cutting is ready to plant once it has rooted and does not come loose with a gentle tug.

You can also propagate this plant with ground layering. Removed the bottom leaves from a low hanging branch and bury it in a shallow trench in the soil. Place a rock or brick over top to hold it in place. After several weeks, the buried section of branch should develop a strong root system. You can remove the branch and replant it in a pot or in a sheltered area of your garden.

How to Grow Panicle Hydrangea from Seed

Most gardeners don't grow hydrangeas from seed, but start with a well-established plant that has been cloned to have desirable traits. Open-pollinated plants can produce seed with different traits from the parent plant and will take longer to reach maturity.

If you would like to grow a hydrangea from seed, press the tiny seeds into the surface of a moist tray of soil in a warm spot and cover with clear plastic. Keep the soil moist and the tray in a bright spot out of direct sunlight. Seeds should sprout after two weeks, and plants can be gradually exposed to the outdoors once a few sets of leaves have formed.

Potting and Repotting Panicle Hydrangea

Panicle hydrangeas can be grown in a container for a least a couple of years (dwarf varieties may do well in a container indefinitely). Use a weather-proof container with drainage holes that is at least 16 inches wide. Fill with potting soil to the bottom of where the plant will sit. Place your hydrangea in the pot, fill in with soil around it, and water well. Add a thin layer of mulch to help preserve moisture.

Your hydrangea will need frequent watering in warm weather; check the container for moisture daily. In winter, check soil moisture every 10 to 14 days. If the plant's leaves become stunted after a time, it's time to move your hydrangea to a larger pot or transplant it into the garden.

Common Pests & Plant Diseases

Panicle hydrangeas are relatively problem-free, but can suffer from fungal leaf spot or powdery mildew in damp conditions. Improve ventiliation around the plant and spray with a fungicide if these problems occur. Sometimes aphids and spider mites can infest hydrangeas; spray them away with a strong blast from the hose.

Unfortunately, deer relish hydrangeas, as my brother and sister-in-law discovered at their home in West Virginia. Deer repellents like Deer Off, Liquid Fence, and Bobbex prevent this but must be reapplied periodically. My brother protects his hydrangeas inside cylindrical wire cages. He tells me after the shrubs get tall enough, flowers pop out of the tops of the cages and the deer pretty much leave them alone.

How to Get Panicle Hydrangea to Bloom

If your panicle hydrangea isn't blooming, it could be that the plant isn't well-established and needs a few seasons to settle in. But there are other reasons a hydrangea might not bloom:

• Pruning at the wrong time: make certain to prune when the plant is dormant or you may unintentionally remove flower buds.
• Deer: use repellant or netting if deer could be nipping off the flower buds.
• Too much shade: shade can affect flowering. Make certain the plant receives at least four hours of direct sun or filtered sun all day.