Spectacular flowers make the Hydrangea a landscape favorite. They are also a source of frustration for homeowners when they do not bloom. Improper pruning or winter damage is the primary reason what a Hydrangea may not bloom. The name Hydrangea is from the Greek “Hydro” (water) and “Aggeion” (vessel) referring to the cup shaped seed capsules. There are many species and varieties of Hydrangeas…these are the primary groups:
1. MACROPHYLLA (big-leaf hydrangeas)
Big Leaf with “mophead” flowers. Colorful blue, pink, re-pink, lavender blooms. Highly desired and noted for the ability to alter bloom color by adjustment to the soil pH. (Pink in alkaline soil and blue in acidic soils.) Macrophylla are the most popular for their desired colorful blooms. They are also the source of frustration if pruned improperly (they produce blooms on the previous year’s growth) or if over winterizing buds on the stem are exposed to frozen during the winter or spring. This results in a plant during the spring and summer season with foliage growth but not flowers. Today there are Macrophylla Hydrangeas that bloom on “old” (previous year’s growth) and “new” (this year’s) growth making them more reliable bloomers. An example would be Endless Summer Hydrangeas.
2. SERRATA (saw-tooth hydrangeas)
Also known as Lacecaps, with round “disks” of individual florets. The “disks” can be as large as 4 to 8 inches in diameter. Culture similar to H. Macrophylla. Native to the mountains of Japan and Korea thus adapted to colder climates. Fall color is another feature of this plant.
3. PANICULATA (panicle hydrangeas)
Hardy! Blooms on the same year’s wood so pruning is not a problem and they bloom reliably. White blooms on hardy plants like Peegee, Kyushu, Tardiva, Lime Light and Pink Diamond Hydrangeas. 6 ft. tall blooms July through September. Flowers ideal for cutting and drying.
4. QUERCIFOLIA (oak leaf hydrangeas)
“Oak Leaf” Hydrangeas with large panicles of cone shaped flowers that start white turning to pink. Foliage resembles a large oak leaf with beautiful fall color! Prune only if need to keep size in check as Paniculata Hydrangeas.
5. ABORESCENS (smooth hydrangeas)
The “Annabelle” Hydrangeas. Easy to grow with big and bold snowball flowers. Gradually change from green to pure white. Can be treated like a perennial, cut to the ground from late fall through early spring.
6. ANOMOLA PETIOLARIS (climbing hydrangeas)
Climbing vine Hydrangeas with white flowers and vigorous stems that will cling to walls, trellises or structures. Easy to grow, prune as needed.
Simply put, all one basically needs to know to achieve successful blooming is “does this variety flower on old growth (last years stems), or new growth (this years stems)”.
Hydrangea Macrophylla bloom on previous year’s stems and should not be pruned in fall or spring. They should be planted in a protected area of the landscape. The north side of the house works well. Otherwise protect the plant in winter with burlap screen or fencing mounded with straw, pine needles, bark or oak leaves. Don’t use maple leaves, they mat and suffocate the plant. Remove protection in May. Consider using new varieties like Endless Summer that bloom on both old and new wood.
Hydrangea Arborensens, Petiolaris, Querciolia and Paniculata bloom on the new season’s growth and can be pruned or cut back from late fall into early spring. An exception may be group 4 “Oak Leaf” Hydrangeas. Even though they bloom on new seasons’ growth, you’ll have better success when treated like Hydrangeas in groups 2 and 3. Hydrangeas prefer a cool, moist soil. Don’t let them dry out but provide good drainage. Soil with a high organic content is beneficial, fertile & remains moist while providing drainage. Mulch around the base of the plant is helpful.
Remember their name ”hydra” (water) and “Macrophylla (big leaf) is an indication they do not like to dry out. Standing in poorly drained soil is also a problem. That’s why working in liberal mount of organic material into the soil is a good idea. Good soil is a proper proportion of water, air and minerals for healthy roots.