Hydrangeas are one of the most popular landscape plants around.  They are known, grown and loved worldwide and continue to gain popularity every year.  While one species may be more popular than another, they all bring ornamental value to the garden for months of enjoyment each growing season. From groundcovers and vines to large shrubs or small trees, there is definitely a Hydrangea for every garden.

Hydrangea

 

 

 

 

 

 

Here on Long Island the most common species of Hydrangeas are:

  • Climbing HydrangeaH. anomala subsp. petiolaris
  • Smooth HydrangeaH. arborescens
  • Big Leaf HydrangeaH. macrophylla
  • Panicle HydrangeaH. paniculata
  • Oakleaf HydrangeaH. quercifolia
  • Mountain HydrangeaH. serrata

Climbing Hydrangea is a vine or groundcover that can grow upwards of 40’ (provided it has something to climb on).  The creamy white lace-cap flowers occur in late spring/early summer.  Moist, well-drained, organic rich soil is best.  Climbing Hydrangea will grow well from full sun to deep shade, but will do best in a bright, filtered light, that is protected from the hot afternoon sun.

Smooth Hydrangea is a mounding shrub growing 3-5’ tall and wide.  The abundant summer flowers are borne from the current season’s growth, and are available in creamy white or light pink.  Moist, well-drained, organic rich soil is best.  Best grown in partial shade, but is considered the most shade tolerant Hydrangea available.  Avoid direct, hot afternoon sun.

Big Leaf Hydrangea is considered the most popular Hydrangea on the market.  With many cultivars (hundreds) available ranging in size of 2’ to 6’+.  Flowers can be mop head or lace cap and the colors range from white to pink, purple, and blue and are the result of soil chemistry paired with the particular cultivar.   Filtered light is best and a moist, well-drained, organic soil will produce the best results.

Panicle Hydrangea is also comprised of many cultivars ranging in size from 3’ to 12’.  This large shrub also makes a great candidate as small tree with some formative pruning.  The mostly creamy white flowers peak later in summer and most varieties fade russet pink before completely drying.  This species can handle full sun to part shade, and will also perform best in a moist, well-drained, organic rich soil.

Oakleaf Hydrangea features large foliage that resembles the might Oak, and large panicles of creamy white flowers that fade russet pink providing visual excitement all summer long.  The rich green foliage turns to magnificent tones of wine-red, orange and yellow in fall.  Oakleaf Hydrangeas will handle sun or shade and prefer a moist, well-drained, organic rich soil.

Mountain or Serrated Hydrangeas are very similar to the Big Leaf Hydrangea in size, form, habit and have very similar cultural requirements as well.  The foliage tends to be smaller and is more deeply serrated.  Most varieties are lace cap, but ‘Preziosa’ is a mop head type that is almost always pink regardless of soil chemistry.

HYDRANGEA CULTURE

LIGHT

  • Partial shade or filtered light is best – particularly shade from hot afternoon sun.
  • Too much shade leads to:
    • Weak or no flowers.
    • Poor growth – stretched or leggy habits.
    • H. arborescens & H. quercifolia tolerant the most shade.
  • Too much sun without adequate soil moisture leads to:
    • Burning/scorching of leaves and flowers.
    • Washed out colors.
    • White and Pink flowers do better in more sun.
  • H. paniculata & H.quercifolia tolerant the most sun.
SOIL
A consistently moist, well-drained, preferably acid soil, abundantly enriched with organic matter is best for all species of Hydrangea.
  • —  Enrich the soil before planting, mulch right after.
  • —  Amend sandy soils by incorporating compost.
  • —  Amend clay soils by breaking up (rototiller) while incorporating gypsum and compost.
  • —  Add compost yearly and replenish mulch as needed.
  •  Higher pH soils (over 6.5) —  Iron chlorosis and nutrient deficiencies can occur.
MOISTURE
Hydrangeas will signal when drought stressed, with drooping leaves.  Please note that drooping will also occur in extremely warm temps (over 85 degrees) regardless of moisture availability.
—  In ideal soil conditions, one inch of water per week in spring/fall, and one inch twice a week in summer should be sufficient.
—  AVOID over-head sprinklers – it’s best to water the soil only by using drip or soaker hoses.
FLOWER COLOR
For H. macrophylla and H. serrata, the nonwhite flower colors are based on the soil chemistry in conjunction with the specific cultivar (the cultivar tends to dictate the richness of the colors, as in pale blue or deep blue).  The chart below displays the relationship between soil acidity, aluminum availability, and the resulting color.  A low pH, or acidic soil, tends to have the most aluminum available for uptake into the plant resulting in a blue flower.  It is possible to have multiple colors on the same plant

 

COLOR:
PINK  <—————————————PURPLE———————————-> BLUE
 
 SOIL pH:
7.5  <—————————————————————————————–> 4.5
Alkaline                                                                                                                                       Acidic
 
ALUMINUM AVAILABILITY:
Low <—————————————————————————————–> High

 

FERTILIZATION AND SOIL AMENDMENTS

  • All Hydrangeas will benefit from organic,  soil-release, balanced fertilizers like Dr. Earth and Espoma
  • Top dressing the soil with compost and   mulch yearly is highly recommended
  • For BLUER Hydrangeas, add Aluminum Sulfate to amend the soil, and apply a fertilizer with an NPK ratio high in N & K, but low P is best.     Ex: 5-3-5
  • For PINKER Hydrangeas, add Lime to amend the soil, and apply  a fertilizer with a NPK ratio with a higher P than N & K.           Ex: 3-5-3

PRUNING

  • H. quercifolia and H. petiolaris produce flowers on the previous season’s growth.  Prune right after flowering (mid-summer) to control size and shape (only remove up to 1/3)
  • H. arborescens and H. paniculata produce flowers on the current season’s growth and respond very well to both a hard pruning and light pruning.  Prune late winter/early spring before new growth
  • H. macrophylla and H. serrata produce flowers on the previous season’s growth.  Therefore pruning hard typically results in little to no flowers.  Selectively prune in early spring just before bud break – removing weak, broken, dead or crossing branches, and trimming stems lightly, distinguishing flower buds from foliage buds.  LOOK FOR THE BUDS!  They are much larger than non-flower producing buds, and generally set most abundantly on the top third of branches.  Remontant or re-blooming varieties will also bloom on the current season’s growth to extend the floral display late into the summer and early fall, or serve as back up to      early season flower buds that may be compromised due to winter kill, late frosts, or improper pruning.

 

HICKS PICKS for 2015
Hydrangea anomala subsp. Petiolaris – Climbing Hydrangea
Hydrangea arboresecens – Smooth Hydrangea
Hydrangea macrophylla – Big Leaf Hydrangea
Hydrangea paniculata – Panicle Hydrangea
Hydrangea quercifolia – Oakleaf Hydrangea
Hydrangea serrata – Mountain Hydrangea