Helpful information from Whiteflower Farm’s catalog website

In recent years, there has been an explosion of new Hydrangea varieties with a wide range of enticing bloom color, elegant foliage, and extended bloom times. The six main types of Hydrangea include the Big Leaf, commonly known as Mophead or Lacecap types, the Anabelle or Smooth Hydrangea, the Pee Gee Hydrangea, the Oak Leaf Hydrangea, the Mountain Hydrangea, and the Climbing Hydrangea.

Hydrangea macrophylla – Big Leaf Hydrangea

This species was originally cultivated in China and Japan. Many varieties tolerate wind and salt spray. Fortunately for gardeners in colder zones, recent Hydrangea introductions are more likely to flower on new growth as well as year-old stems, which means flowers are guaranteed even after a tough winter. Some older Hydrangea macrophylla varieties flower on old wood, and must carry their flower buds through the winter. Early or late freezes may damage flower buds and prevent them from blooming. For example, in Zone 5, bloom may only succeed 3 years out of 5, but the plant itself is hardy there. Fortunately for gardeners in cooler zones, recent introductions will likely bloom for them, as they flower on new growth as well as year-old stems. Hydrangea macrophylla flowers will come as round blooms, Mophead, or as flat blooms, Lacecap.

Light/Watering: Most varieties tolerate full sun in the North, but benefit from afternoon shade. In the South, plants require afternoon shade with at least 4-6 hours of full sun to have good blooms. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: Fertilize once in spring with a fertilizer designed to encourage blooms (such as 13-13-13). In many H. macrophylla varieties, flower color is determined by the pH of the soil; at low pH (acid soils) flowers will be blue and at higher pH, flowers will be pink. Generally, a pH below 5.0 results in deep, vivid blues and as the pH rises the flowers range from blue to lavender to mauve to a vivid deep pink at pH 7.0 (neutral). The pH determines the availability of aluminum in the soil; this element is more readily available in acid soils, and this availability results in the blue flower color. Since phosphorus ties up aluminum in soils, using a fertilizer low in this nutrient will aid in attaining blue flowers. If pink flowers are desired and your soil is acid, simply add lime to raise the pH and use a balanced fertilizer. Aluminum sulfate will lower pH if blue flowers are desired.

Pests/Diseases: None serious. Occasionally powdery mildew and Cercospora leaf spot will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: If your Hydrangea is growing too large, prune to the desired size by the end of August. In spring, only prune out dead wood once the new growth has emerged. This includes H. m. ‘Big Daddy,’ H. m. Cityline® Mars, H. m. Cityline® Rio, H. m. Cityline® Venice, H. m. Color Fantasy®, H. m. Double Delights™ Star Gazer, H. m. Everlasting™ Amethyst, H. m. ‘Lady in Red,’ H. m. Light-O-Day®, H. m. ‘Nikko Blue,’ H. m. Pink Shira™, and Paraplu®. These varieties bloom on old wood.

For Big Leaf varieties blooming on both old and new wood, by the end of August cut back stems by about half if plants are growing too tall. Remove some of the oldest stems at ground level to thin out the shrub as needed. In spring, only prune out dead wood once the new growth has emerged. This includes H. m. ‘Blushing Bride,’ H. m. Double Delights™ Star Gazer, H. m. Endless Summer®, H. m. Endless Summer® Bloomstruck™, H. m. Everlasting® Revolution, H. m. Let’s Dance® Big Easy, Let’s Dance® Blue Jangles®, H. m. Let’s Dance® Moonlight, Let’s Dance® Rave™, H. m. Let’s Dance® Starlight, H. m. Mystical® Opal, H. m. Nantucket Blue™, H. m. Pistachio, and H. m. Twist-n-Shout™, H.m. For Ever and Ever.

Reflowering: Regularly deadheading the spent blooms of H. macrophylla that bloom on both old and new wood helps encourage repeat bloom on the current year’s growth.

Transplanting: Young plants may be transplanted when dormant in early spring.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi. For gardeners in Zone 5, we recommend covering the stems with a 12″ layer of organic material such as straw or mulched leaves to help preserve the flower buds through the cold winter. In addition, you may wrap your Hydrangea with burlap to protect it from winds and cold temperatures.

Calendar of Care

Mid-Spring: Prune out any dead wood from all varieties. Check soil pH and adjust up or down if needed for desired flower color. Feed plants with a fertilizer high in phosphorus (such as 13-13-13) to encourage blooms. Complete any transplanting before leaves unfurl. Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Fall: Remove and destroy any fallen foliage that was infected by fungus like powdery mildew or Cercospora leaf spot. In Zone 5, cover the stems with a 12″ layer of organic material such as straw or mulched leaves to help flower buds overwinter. You may also wrap your Hydrangea with burlap to protect it from winds and cold temperatures.

Great varieties for your garden: Endless Summer, Blushing Bride, All Summer Beauty, Pink Beauty, Lady In Red, Glowing Embers, For Ever and Ever, Twist and Shout, Let’s Dance Series, Cityline Series, Abracadabra Series

Hydrangea Arborescens – Anabelle Hydrangea

Hydrangea arborescens, the Anabelle or Smooth Hydrangea, is a good choice for colder climates since it flowers on new wood and is not bothered by late spring frosts. It is reported to be winter hardy to -40 F.! Plants tolerate light shade as well.

Light/Watering: Most varieties thrive in full sun in the North, but in the South require afternoon shade. Four to six hours a day in full sun will promote good flowering. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: Fertilize once in spring with a fertilizer designed to encourage blooms (such as 13-13-13). Soils should be moist but well drained, and rich in organic matter.

Pests/Diseases: None serious. Occasionally powdery mildew and Cercospora leaf spot will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: Can be shortened, or pruned back to the ground, either in fall or early spring. Hydrangea arborescens blooms on new wood.

Reflowering: You may cut the first flowering stems of H. arborescens ‘Annabelle’ and hang to dry for arrangements; rebloom may then occur in August or September.

Transplanting: Young plants may be transplanted when dormant in early spring; larger tree-form varieties are difficult to move once established, but it can be done. Prune top growth after transplanting to reduce water loss.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi.

Calendar of Care

Early Spring: Prune as indicated above. Prune out any dead wood from all varieties. Feed plants with a fertilizer high in phosphorus (such as 13-13-13) to encourage blooms. Complete any transplanting before leaves unfurl.

Mid-Spring: Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Summer: Cut flowering stems from H. arborescens ‘Annabelle’ and hang to dry if desired.

Fall: Remove and destroy any fallen foliage that was infected by powdery mildew. If not pruned in spring, plants can be shortened, or pruned back to the ground.

Great varieties for your garden: Anabelle, Invincibelle Spirit, Invincibelle Ruby, Incrediball

Hydrangea Paniculata – Pee Gee Hydrangea

Likely the most cold-hardy Hydrangea of all, Hydrangea paniculata flowers aren’t subject to frost damage since they bloom on new wood. This type of hydrangea is also reported to withstand temps down to -40 F.! Plants generally have large, cone-shaped blooms.

Light/Watering: Most varieties thrive in full sun in the North, but in the South require afternoon shade. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: Fertilize once in spring with a fertilizer designed to encourage blooms (such as 15-30-15). Soils should be moist but well drained, and rich in organic matter.

Pests/Diseases: None serious. Occasionally powdery mildew and Cercospora leaf spot fungus will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: Little pruning is needed beyond removing any dead wood whenever seen. If desired, plants can be cut back as needed in early spring. Hydrangea paniculata blooms on new wood. Tree form Hydrangea paniculata: Prune in early spring, removing lower suckers and up to half the older top growth.

Transplanting: Young plants may be transplanted when dormant in early spring. Prune top growth after transplanting to reduce water loss.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi.

Calendar of Care

Early Spring: If desired, prune as indicated above. Feed plants with a fertilizer high in phosphorus (such as 15-30-15) to encourage blooms. Complete any transplanting before leaves unfurl.

Mid-Spring: Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Summer: As soon as blooms fade, remove old flowering stems.

Fall: Remove and destroy any fallen foliage that was infected by powdery mildew.

Great varieties for your garden: Limelight, Little Lime, Bobo, Quick Fire, Zinfin Doll, Polar Ball, Pinky Winkie, Vanilla Strawberry, White Wedding.

Hydrangea Quercifolia – Oakleaf Hydrangea

Oakleaf Hydrangea is native to the US and has long, cone-shaped flowers. Its large, broadly lobed leaves are very attractive in fall. This hydrangea is hardy only to zone 5, but will bloom on last season’s wood

Light/Watering: Most varieties thrive in full sun in the North, but in the South require afternoon shade. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: Fertilize once in spring with a fertilizer designed to encourage blooms (such as 15-30-15). Soils should be moist but well drained, and rich in organic matter.

Pests/Diseases: None serious. Occasionally powdery mildew and Cercospora leaf spot will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: Little pruning is needed beyond removing any dead wood whenever seen. If desired, plants can be cut back as needed in early spring. Hydrangea quercifolia blooms on last years’ growth.

Transplanting: Young plants may be transplanted when dormant in early spring. Prune top growth after transplanting to reduce water loss.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi.

Calendar of Care

Early Spring: If desired, prune as indicated above. Feed plants with a fertilizer high in phosphorus (such as 15-30-15) to encourage blooms. Complete any transplanting before leaves unfurl.

Mid-Spring: Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Summer: As soon as blooms fade, remove old flowering stems.

Fall: Remove and destroy any fallen foliage that was infected by powdery mildew.

Great varieties for our area: Snow Queen, Alice, Munchkin, Pee Wee, Ruby Slippers, Gatsby Pink, Gatsby Moon and Gatsby Star.

Hydrangea Serrata – Mountain Hydrangea

Native to the mountains of Japan and Korea, this species prefers cooler locations. The flower color in some varieties is affected by soil pH. Mountain Hydrangea is cold hardy to zone 5 and blooms on last season’s wood.

Light/Watering: Most varieties thrive in full sun in the North, but in the South require afternoon shade. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: In some varieties, flower color is determined by the pH of the soil; at low pH (acid soils) flowers will be blue and at higher pH, flowers will be pink. Generally, a pH below 5.0 results in deep, vivid blues and as the pH rises the flowers range from blue to lavender to mauve to a vivid deep pink at pH 7.0 (neutral). The pH determines the availability of aluminum in the soil; this element is more readily available in acid soils, and this availability results in the blue flower color. Since phosphorus ties up aluminum in soils, using a fertilizer low in this nutrient will aid in attaining blue flowers. If pink flowers are desired and your soil is acid, simply add lime to raise the pH and use a balanced fertilizer. Aluminum sulfate will lower pH if blue flowers are desired.

Pests/Diseases: None serious. Occasionally powdery mildew and leaf spot fungus will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: Little pruning is needed, but if shrubs grow too large, cut back stems by about one-third by the end of August. In spring, only prune out dead wood. Most Hydrangea serrata varieties bloom on old wood. H. s. Tuff Stuff™ is a variety that blooms on both old and new wood. If no fall pruning was done, stems can be cut back by one-third in spring if necessary—but this will sacrifice the bloom on the old wood and shrubs will not flower until late summer.

Transplanting: Young plants may be transplanted when dormant in early spring; larger tree-form varieties are difficult to move once established, but it can be done. Prune top growth after transplanting to reduce water loss.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi.

Calendar of Care

Early Spring: Prune out any dead wood from all varieties. Check soil pH and adjust up or down if needed for desired flower color. Feed plants with a fertilizer high in phosphorus (such as 15-30-15) to encourage blooms. Complete any transplanting before leaves unfurl.

Mid-Spring: Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Summer: As soon as blooms fade, remove old flowering stems. If needed, prune as indicated above by the end of August.

Fall: Remove and destroy any fallen foliage that was infected by powdery mildew. If not pruned in spring, plants can be shortened, or pruned back to the ground.

Great varieties for our area: Blue Billow, Tuff Stuff, Ben Gaku

Hydrangea Petiolaris –Climbing Hydrangea

Climbing Hydrangea (H. petiolaris) will grow and flower even in a northern exposure. This large, heavy vine has lateral branches that will grow out as much as 3′ from the supporting structure. It is superb for growing up the trunk of large shade trees, walls, or along a stone wall. The reddish brown, peeling bark is attractive in winter. It is hardy up to zone 4. Although growth is slow the first couple of years after planting, this species is vigorous once established. Blooming usually begins in 3–5 years. It is commonly confused with another climbing plant that looks very similar, the False Climbing Hydrangea, Schizophragma ‘Rose Sensation’.

Light/Watering: Most varieties thrive in full sun in the North, but in the South require afternoon shade. Moist soils that do not dry out are best; do not plant in hot, dry, exposed sites. Mulch to conserve moisture and buffer soil temperatures.

Fertilizer/Soil and pH: Fertilize once in spring with a fertilizer designed to encourage blooms (such as 13-13-13). Soils should be moist but well drained, and rich in organic matter.

Pests/Diseases: None serious. Occasionally powdery mildew and leaf spot will infect the foliage, especially in humid areas with poor air circulation. Treat with an appropriate fungicide if the problem is serious, and be sure to rake up and destroy all fallen foliage in the autumn.

Pruning: Remove any dead wood in early spring. Prune as needed after flowering. Blooms on old wood.

Transplanting: Young plants may be transplanted when dormant in early spring. Prune top growth after transplanting to reduce water loss.

End of Season Care: Rake up and destroy any fallen foliage that was infected by powdery mildew or other fungi.

Calendar of Care

Early Spring: Prune as indicated above. Feed plants with a fertilizer high in phosphorus (such as 13-13-13) to encourage blooms. Complete any transplanting before leaves unfurl.

Mid-Spring: Mulch plants after soil has warmed to conserve moisture and buffer soil temperatures. Watch for powdery mildew and treat as needed.

Fall: Remove and destroy any fallen foliage that was infected by powdery mildew.

5 Reasons Why Your Hydrangea May Not Be Blooming

1. Time - It takes some hydrangeas 2-5 years to begin blooming.

2. Light - Your plant may be not be getting enough light, it needs 4-6 hours per day, preferably morning to early afternoon.

3. Pruning - Improper pruning time can remove bloom buds, so know if the plant bloom on last season or current seasons growth

4. Animals - Deer and other browsers can take away last season’s growth and hence the blooms for the year on certain types.

5. Winter Cold - Tender plants subjected to late freezes or hard early freezes may not bloom due to die back.

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