Hydrangeas ( Hydrangea spp . ) and rhododendron ( Rhododendron spp . ) are showy , flowering shrubs that , in some case , have evergreen leaves . They also divvy up some preferences in terms of growing weather condition . They are , however , entirely unrelated plants with very distinct show .
Rhododendron Genus
The genusRhododendronincludes the shrubs commonly calledrhododendrons and azaleas . They are blossom shrubs with waxy leaves that may or may not be evergreen , depending on the variety and the mood in which the plant is produce .
In general , the vulgar name azalea is return to those shrub with deciduous parting and funnel - shape flowers . The usual name rhododendron is typically employ to those appendage of the genus with evergreen plant farewell and Vanessa Stephen - shaped flowers . Some azalea areevergreenin warmer climates , however .
Rhododenron cultivars vary in term of theirwinter hardiness . The Williams rhododenron ( Rhododendron williamsianum ) , for model , is hardy only in U.S. Department of Agriculture plant hardiness zone 7 to 9 , while the pinkshell azalea ( Rhododendron vaseyi ) is stout in USDA zones 5 to 7 , and the swamp azalea ( Rhododendron viscosum ) is hardy in USDA zone 4 to 9 .
They also vary considerably insize . The Florida pinxter rhododendron ( Rhododendron canescens ) can reach a elevation of 15 feet , for model , but the " Pleasant White " azalea only grows to about 2 feet high-pitched . Florida pinxter is intrepid in USDA zones 6 through 9 and " Pleasant White " is hardy in USDA zones 5 through 8 .
Hydrangea Types
The hydrangea ( Hydrangea macrophylla ) , also sometimes called theFrench hydrangea , is a flowering bush that ’s dauntless in USDA geographical zone 6 to 10 . It is typically deciduous , but it may be evergreen in warm climates . It most often grows to between 3 and 6 feet in height but may reach 8 feet in prison term under idealistic conditions .
Theoakleaf hydrangea(Hydrangea quercifolia ) is distinguished from the French hydrangea by its lobed leaves and its conical prime clusters , as compared to the rounded heyday clusters of the French hydrangea . The oakleaf hydrangea raise to between 6 and 8 feet in height and is hardy in USDA hardiness zone 5 to 9 .
Soil Acidity
Both rhododendrons and hydrangeas are sensitive to soil pH , andboth grow best in acidulent soilswith a pH level between 5 and 5.5 . Hydrangeas , however , are less sensitive and will stick out soil with a higher pH.
The blossom of Gallic hydrangea will variegate depending on the pH of the soil in which the bush is grow . In acidic soils , the flowers are drear , and in alkaline soils , they turn pink . In inert soil , the flower are clean or pale unripened . The colour of rhododendron flowers is untouched by soil pH.
Growing Conditions
Aside from soil acidity , hydrangea and rhododendron are similar in their other cultural necessity , as well . Both prefer grime that ’s ample in organic topic , and both call for soils that keep a consistent level of wet without being soggy .
Both type of shrub menu best in location that receive eitherfull sunshine or partial shade . Although both rhododendron and hydrangeas can benefit from shelter from direct good afternoon sunlight , neither shrub will grow well or bloom prolifically if grow in a full funny locating .
