Bigleaf Hydrangea Care

Here are the main care requirements for growing a bigleaf hydrangea:

• Plant in a location with dappled or partial sun and rich, well-drained soil.
• Water whenever the top layer of soil feels dry.
• Fertilize once a year in the spring.
• Prune only moderately, and do it promptly after flowering.
• Mulch around the base to insulate the roots against winter cold.

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Planting

Plant in summer or fall when the weather is cooler. Dig a hole about twice the width of the nursery container and just deep enough to fit the root ball so the plant sits at the same level or a bit higher than in the container. Backfill with soil and tamp down the soil. Water deeply to get rid of any air pockets. If you plant more than one, space the hydrangeas about five feet apart. 

Light

The warmer your climate, the more protection your hydrangea needs from the sun. Dappled sunlight or partial shade—preferably with morning sun and afternoon shade—are ideal. Deep shade, on the other hand, is not advisable, as it leads to weak stems and reduced bloom.

Soil

The soil should be organically rich and moist but well-drained. The soil pH determines the flower color, and it is possible to amend the soil pH to obtain the desired flower color.

 Water

If the top few inches of soil feel dry, water slowly and deeply. Always water the shrub at its base, not from overhead.

Temperature and Humidity

The hardiness of bigleaf hydrangeas varies; some, such as endless summer hydrangeas, have excellent winter hardiness and withstand winter temperatures as low as -30°F. Generally, bigleaf hydrangeas are better suited for moderately warm climates with average humidity than for hot, arid climates. 

Fertilizer

Fertilize bigleaf hydrangea only in the spring just as new growth starts with a slow-release, balanced fertilizer.

Pruning

Bigleaf hydrangea does not need much pruning, only to remove dead or diseased stems or to improve the airflow inside the plant, which prevents the spread of fungal diseases.

The key to correctly pruning hydrangeas is to know if they bloom on this year’s growth (new wood) or last year’s growth (old wood). Most bigleaf hydrangeas bloom on old wood, but some varieties, such as Penny Mac hydrangeas, bloom on both old and new wood. Pruning should be done immediately after flowering.

Propagating Bigleaf Hydrangea

The plants are easy to propagate by rooting stem cuttings or layering. Either method is best done in the spring or early summer so the cutting has time to root and can be planted in the fall. 

Rooting Stem Cuttings

1. Take a 6- to 8-inch cutting without any flowers and at least one growth node. Strip off all the leaves from the lower half of the cutting.
2. Dip the end of the cutting into rooting hormone.
3. Fill a four-inch pot with moist potting mix. Poke a hole in the soil with a pencil and insert the cutting in the soil deep enough so that the growth node is buried in the soil. Tamp down the soil around the stem.
4. Place the pot in a bright, warm location away from direct sunlight. Keep the soil evenly moist until roots form.

Layering a Stem

1. Find a stem that is bent or grows as close to the ground as possible.
2. Look for a node or nodes on that stem and scrape off a little of the bark around each node without damaging the node.
3. Dig a trench about 2 inches deep and place the stem into it so that the node area sits in the trench but the end of the stem sticks out of the soil.
4. Cover the stem about 2 inches deep with soil so that the nodes are fully covered. Secure the stem with a brick or a garden staple so it remains buried.
5. Keep the area moist. Once the stem has grown into a vigorous little plant with plenty of roots (carefully check to make sure), cut the stem off the mother plant and move it to a new location or pot it up.

Potting and Repotting Bigleaf Hydrangea

For potting, select a dwarf variety such as ‘Wee Bit Grumpy,’ which only grows 24 inches tall and 30 inches wide at maturity. Bigleaf hydrangeas need containers with large drainage holes and well-draining potting mix.

When the roots emerge from the drain holes or the plant becomes root-bound, repot it in a container one size up with fresh potting mix.

Overwintering

If planted in their hardiness range, winter protection is not required. However, a thick layer of mulch around the base helps to insulate the roots against the winter cold.

How to Get Bigleaf Hydrangea to Bloom

Failure of hydrangeas to bloom is often due to too much shade, accidentally removing flower buds by pruning at the wrong time of year, or a late spring frost after a period of warm weather that kills the flower buds.

Additional fertilizer does not encourage more blooming. Instead, make sure that the plant is grown in suitable conditions.

Aside from pruning promptly after the bloom is over, there is no other care necessary after blooming.

Common Pests and Plant Diseases

Bigleaf hydrangeas are prone to fungal and other diseases, including powdery mildew, bacterial wilt, blight, and leaf spot. If powdery mildew is an issue in your location, select a resistant variety, such as Bloomstruck.

Several pests, including aphids, black vine weevils, four-lined plant bugs, Japanese beetles, and spider mites, are attracted to hydrangeas. Many of these pests can be managed with insecticidal soap.

Common Problems

If the leaves of your bigleaf hydrangea turn yellow, the cause may be overwatering, underwatering, or too much fertilizer. Other issues are drooping leaves in hot weather and browning leaves, which could indicate excess fertilizer or a fungal or bacterial disease.