Hydrangea – Hydrangea macrophylla

Common Name: Hydrangea

Botanical Name: Hydrangea macrophylla, hy-DRAN-jee-a mac-ro-FY-la

Decorative Life: About 15-20 days for the flowers and the rest of the plant since both vegetative and reproductive parts last similar amounts of time.

Flower Color: Blue, Pink, White

Availability: Spring

Harvest when at least 75% of the flowers are open. We have always been taught that flower color is determined by the concentration of aluminum in the cells. Specifically, that low pH growing media allowed more aluminum to be taken up by plants resulting in blue flowers whereas high pH media and low aluminum levels favored pink flowers. The problem is that aluminum levels in pink and blue flowers were found to be essentially the same (Wallace and Wieland, 1980). In another series of tests, Blom and Piott (1992) showed that there was a relationship between the aluminum levels in the two upper leaves and flower blueness. While no one doubts that flower color can be controlled by soil pH, the question remains how in light of these findings? On another subject, research confirmed hat flower quality is greatly influenced by the cold treatment period and it is also very cultivar specific.

• Member of the Hydrangeaceae (hydrangea family). Formerly included in the Saxifragaceae (saxifrage family).
• Native to Japan and Korea.
• Relatives include Astilbe, Heuchera, currant, Philadelphus and Viburnum.

• Has small, flat flowers in dense, round clusters up to 6 inches in diameter at stem ends.
• Stems with several large leaves, 16-20 inches long.
• For the most part flowers are not fragrant.

Can be shipped at 34F for 4 days with no or little loss in postharvest life. Longer storage or shipping times significantly reduced shelf life.

• The scientific name is from the Greek words “hydro” (water) and “aggos” (a jar) and refers to the fruits of the plant, which are cup-shaped.
• The showy parts of the flowers are sepals, not petals. The American Academy of Allergy, Asthma and Immunology list this species as an allergy-safe pollen producing plant.
• Requires high light levels (>200 ft-c.) under interior conditions.
• Ethylene is sometimes used by growers to force mother plants into premature leaf fall such that the plants can be subsequently forced into flower sooner.

Using ‘Leuchtfeuer’, Yeh and Chiang (2001) showed that flower initiation is maximum when all leaves are present (especially the upper ones) and plant development is enhanced when root restriction is prevented.