The blue evergreen hydrangea (Hydrangea febrifuga*)* is a beautiful shrub that can serve as an accent or hedge in your garden landscape. The plant attracts wildlife such as birds and butterflies. Its specific epithet is derived from the Latin words ‘febris’ and ‘fugare ‘which mean ‘fever’ and ‘to expel,’ as this plant is a widely known traditional medicine in Asia.
I. Appearance and Characteristics
Dichroa febrifuga or Hydrangea febrifuga is a flowering plant in the family Hydrangeaceae.
National names
- Chinese: Chinese: 常山; pinyin: chángshānⓘ)
- Indonesian language: gigil, alternatively tataruman
- Sundanese: ramram
- Papua: Hom dong (ฮอมดง):
- Thai: Yai khlang yai (ยายคลังใหญ่), in Nakhon Sri Thammarat, Yai Krang (ยายกรัง) in the South, and Hom Kham (ฮอมคำ) in Lanna (Northern Thai).
II. How to Grow and Care
Sunlight
The native environment of blue evergreen hydrangea is under sparse forest, so it is adaptable to partial shade. Too little sunlight will reduce the flower number or even produce no flowers, and too much sunlight may cause sunburn to flowers. In gardens, the best place to plant blue evergreen hydrangea is a place where it can fully receive the morning sunlight while being partially shaded in the afternoon. The colder the climate, the longer sunlight exposure is needed. In the coldest hardiness zone, it requires at least 6 hours of sunlight a day. In the warm areas where it is best adapted, 3 hours of sunlight a day is enough.
Temperature
Blue evergreen hydrangea likes cool and moist environments with relatively small seasonal and day-night temperature differences. The best temperature for it is 18 to 29 ℃ and winter temperatures should not be lower than -1 ℃. The differentiation of flower buds requires temperatures of 4 to 7 ℃ for 6-8 weeks. Blooming can be promoted under 19 ℃. The flowers fade faster under high temperatures above 30 ℃. Blue evergreen hydrangea has relatively strict requirements for soil, which should be moist, permeable, and free of accumulated water.
Watering
Blue evergreen hydrangea is a plant that thrives in moist environments, often found in tropical rainforests where humidity levels are high. It has a preference for regular watering, striking a balance between dry and wet conditions. Watering every week is essential to maintain its health and vigor. As an evergreen plant, blue evergreen hydrangea retains water well throughout the year, making it an excellent choice for indoor gardening where controlled humidity can be maintained.
Soil
Blue evergreen hydrangea requires soil that is rich in humus and well-drained. It likes moist soil but is not resistant to waterlogging. If the soil is heavy, coarse sand or organic fertilizer can be added to improve drainage and permeability. This can also increase the organic matter content. If the soil easily dries out, cover it with organic mulch to keep it moist while maintaining ventilation.
The soil pH will affect flower colors of some varieties of bigleaf hydrangea. Blue evergreen hydrangea growing in acidic and aluminum-rich soils will bloom in blue, while in alkaline soils they bloom in pink. An appropriate amount of aluminum sulfate or lime can be added to the soil to adjust the pH if you want to control the flower color.
Fertilizing
For blue evergreen hydrangea, a balanced nutrition fertilizer is ideal, promoting robust growth and prolific blooms. Apply a granular, slow-release formula in spring and again mid-summer, adhering to package instructions for dosage, typically 1 cup per square yard of soil. Avoid over-fertilization which can hinder flowering. Seasonal adjustments are key: increase feeding during active growth and reduce in fall to prepare blue evergreen hydrangea for dormancy. Complement with liquid feed for a mid-season boost. Always water blue evergreen hydrangea well post-fertilization to aid nutrient absorption and prevent root burn.
Planting Instructions
The ideal planting time for blue evergreen hydrangea is early spring or late autumn. A very high survival rate can be obtained by transplanting blue evergreen hydrangea after it has gone completely dormant. Additionally, it can also be planted in late spring and early summer, but make sure the soil is always moist and well-draining. During the initial stage of transplanting, pay attention to shading. Proper shading will reduce the evaporation rate and prevent sunburn.
For transplanting, dig a pit 61 cm wider than the diameter of, and as deep as, the plant’s root ball. Cover the pit with soil and pile up a small soil mound aboveground to help with water drainage. If planting in a flowerpot, make sure the diameter of the pot is at least twice as big as the root ball.
Pruning
Hydrangeas pruning methods can be divided into two types, based on their different blossoming modes.
The first pruning method is suitable for bigleaf hydrangea (excluding ‘Endless Summer’, a variety that blooms on both old and new branches) and oakleaf hydrangea. These two hydrangeas bloom on old branches and have relatively strict requirements on pruning time, usually only in early summer, and no later than late summer. In late spring, they are blooming or going to bloom, and flower buds start to form or develop from late summer to the following spring. Daily pruning is required to cut off withered flowers and dead, weak, and inward-growing branches.
These hydrangeas have a distinctive feature: new branches will form on two buds adjacent to a cut. Buds that are lower then become almost undeveloped or grow poorly due to the lack of apical dominance. Therefore, pay attention to whether there are buds under the cut, as well as the height of branches and directions of buds. They have opposite branches, so the directions of reserved buds should be decided by the specific shape of the plant. Additionally, when plants are too large, they can be pruned heavily in summer. The part above the ground should be kept at about 15 cm high. This way, there will be a new, small plant at the end of the year, and it will not affect blooming next year.
The new branches of ‘Endless Summer’ bigleaf hydrangeas will bloom. Therefore, there are no strict requirements on pruning time; just avoid pruning in spring when buds are formed. Pruning during the rest of the year does not affect flowering, and plants are usually pruned in winter after the leaves fall.
The second pruning method is suitable for smooth hydrangea and panicle hydrangea. These two hydrangeas bloom on new branches grown that year, so there is a large window for pruning. Blooming will not be affected by pruning in all seasons except during spring budding. The only existing smooth hydrangea is the Annabelle series. After its leaves fall in winter, the parts of Annabelle above the ground can be completely cut off.
However, this results in one disadvantage: the flowerhead of smooth hydrangea is very large and attaches to the annual branch, which is top-heavy, so support is required. Therefore, several main branches and primary side branches should be specially trained during pruning to prevent lodging during blooming.
Propagation
This evergreen shrub is known for its stunning blue flowers and glossy leaves, thriving in partial shade with moist, well-drained soil. Proper propagation begins by selecting healthy semi-hardwood stems for cutting. Make clean cuts, apply rooting hormone, and plant them in a mixture of peat and perlite. Consistent moisture and warmth facilitate root development, so ensuring high humidity and stable temperatures is beneficial. Once rooted, blue evergreen hydrangea should be transferred to individual pots with appropriate potting mix to continue growth until it’s ready for planting out.
III. Uses and Benefits
- Traditional Chinese medicine
Dichroa febrifuga is an important herb in traditional Chinese medicine, where it is considered one of the 50 fundamental herbs. The alkaloids febrifugine and isofebrifugine are believed to be responsible for its antimalarial effects. In traditional preparations, it is used in conjunction with other plants such as Glycyrrhiza glabra (licorice), Ziziphus jujuba and Zingiber officinale (ginger).
IV. Harvesting and Storage
Blue evergreen hydrangea inflorescences can be divided into two categories according to their shapes: Lacecap and Mophead. Both can be used as cut flowers. The inflorescences can be cut with sharp scissors as soon as they fully bloom. The best time to pick flowers is early morning, which helps avoid the effects of evaporation. The stem should be cut at a 45-degree angle and soaked in cool water as soon as possible to prevent moisture loss.