There are many different kinds of Hydrangeas, from vines, to shrubs, to small trees. The following list encompasses the species that we carry at Natureworks with information about their growth habits and pruning techniques.
Hydrangea arborescens - Hills of Snow Hydrangea, Smooth Hydrangea
These are the old fashioned farm yard hydrangeas with white snowball flowers on 4-5’ plants. They are hardy to zone 4 and bloom on current year’s growth. They can be pruned back hard in late fall or spring. They spread rapidly to form
huge clumps and can be divided when they become too large. Hills of Snow Hydrangeas tolerate deep shade and will also grow in full sun! Their flowers dry a greenish-cream color. If you are planting a pollinator garden, use only the straight species Hydrangea arborescens or fertile, lacecap-type varieties such as ‘Pinky Pollen Ring’ or H. radiata varieites, or H. arborescens ‘Haas Halo’. Double forms such as ‘Annabelle’ do not support pollinators.
H. a. Haas Halo’- single white flowers, top pollinator variety in the Mt. Cuba trials.
H.a. ‘Invincibelle Spirit’; ‘Bella Anna’- These are soft pink forms of Hills of Snow! A true breakthrough.
Hydrangea macrophylla (excluding Endless Summer types) - Big Leaf, Snowball, or House Hydrangea
These are the most common types with large, rounded flower heads appearing in July and August. The tops are hardy to ZONE 6 which means that they may suffer damage in a severe winter in Ct., the roots are hardy to zone 5. This
hydrangea will bloom on new shoots growing off last year's wood. DO NOT cut them to the ground in the fall or spring. In the spring, remove some of the older, thicker canes to the base to thin the plant out. Wait for the new growth to
sprout and then trim the tops of the canes to encourage branching. In midsummer, cut new vigorous shoots to a spot lower than the height of the old wood so they will branch and won’t hide the flowers. If they continuously don't bloom well for you, the tender one-year-old shoots may be getting winter killed. Move to a protected spot or wrap the plant each winter OR replace them with repeat blooming varieties that bloom on both old and new wood.
You can adjust the flower color of Hydrangea macrophylla plant. Their flowers are pink if the soil is alkaline (i.e. PH 7.0+). Add aluminum sulfate to change the color to blue and make the soil more acidic. Their flowers are blue if the soil is
acidic (i.e. PH 5.5-6.0). Add lime if you want to change the color to pink and make the soil more alkaline. This species prefers a rich, compost-enriched soil that retains moisture. Plant in morning sun or dappled shade. If in full sun, be sure
that the soil does not dry out. A thick organic mulch helps keep the soil moist. Deep shade may reduce flowering. There are MANY varieties, too many to list. Here are some classics:
H. m. ‘Nikko Blue’ The standard blue hydrangea in the trade. Enormous round blue heads. Grows 5’ x 5’.
H. m. ‘Cityline Series’ (‘Paris’, ‘Mars’, ‘Vienna’, ‘Rio’ are examples)
Wonderful dwarf varieties with incredible blooming power. Large blossoms on 2-3’ plants. Because they are so compact, leaves piled around the base of the plants (or good snow cover) will protect the one year old wood. Developed in Germany.
H. m. ‘Wedding Gown’ Double flowers start out pure white and transform to brilliant red in the fall. Compact habit, growing only 2-3’ tall.
Blooms on old wood with some reblooming later in the season. Exceptionally hardy. Bred by Ball Horticulture, part of the Double Delights series.
Hydrangea macrophylla (Endless Summer types) – Reblooming Big Leaf Hydrangeas
Hydrangea macrophylla ‘Endless Summer’ was a breakthrough in plant breeding. This plant produces flowers off of old wood AND new wood! That means that even if the old wood is pruned or killed to the ground, you will still have flowers! Prune the same as any H. macrophylla types. If old wood dies in winter, cut it to the ground and the current year’s wood will replace it with flowers beginning later in the summer.
H. m. ‘Endless Summer’ , ‘Bloomstruck’
These plants bloom on both old and new wood! That means they flower EVERY year, even if we have a hard winter. Grow to 5’ tall. ‘Bloomstruck’ is an improved ‘Endless Summer’ with deeper blue, larger flowers. There are MANY new varieties of repeat blooming Hydrangeas that flower on current year’s wood being introduced each year. Examples include ‘Penny Mac’, Let’s Dance series, Revolution series, and more.
Hydrangea serrata – Mountain Hydrangea
A very hardy species. Roots and stems are zone 5 hardy, making them reliable bloomers in CT even after a hard winter. Flowers are slightly smaller than mophead types. Leaves and stems turn burgundy red in the fall.
H. s. ‘Acuminata Precioza’ - Pink Beauty Hydrangea
Flowers are rosy pink deepening to almost red in the fall. Grows 4’ x 4’.
H. s. ‘Bluebird’, ‘Blue Billow’ Two exceptionally hardy varieties of lacecap hydrangeas with profuse blue flowers covering the plant. Grow to 5’ tall and wide with an excellent dense habit making it a real asset to the foundation planting or the perennial border. Flower interest begins in late June and continues until October.
H. s. Tuff Stuff series- Dwarf, very hardy, lacecap flowers.
Hydrangea quercifolia - Oakleaf Hydrangea
Oakleaf Hydrangeas have beautiful, striking foliage that resembles giant oak leaves. The leaves alone make this plant a true garden asset. They turn a rich red in the fall. The flowers are pure white pointed panicles up to 10” long and appear
in July. Oakleaf Hydrangeas can tolerate quite a bit of shade or will grow in full sun. They are hardy to zone 5 and bloom on the TIPS of last year’s wood. Pruning involves opening up the plant and creating an architectural, picturesque form. The bark is exfoliating (peeling) and a good winter feature. If you want to reduce the height, prune immediately after flowering. An invaluable shade shrub growing 5-6 feet tall. Native.
H. q. ‘Snow Queen, ‘Ruby Slippers‘, ‘Alice’ Excellent varieties of classic oakleaf hydrangeas.
H. q. ‘Snowflake’ A beautiful double flowering form, very sought after for exceptional flowers.
H. q. ‘Munchkin’ A dwarf form reaching only 3-4’ tall.
Hydrangea petiolaris - Climbing Hydrangea
This is a vine which attaches itself by holdfasts. It will climb on walls, chimneys, tree trunks, fences, or any surface. Although they grow slowly at first, after 2-3 years they begin to grow rapidly and cover a tremendous area in one year,
eventually growing to 25’ long! The flowers are creamy white lacecap types, 6-10” in diameter. They are hardy to zone 4 and can tolerate deep shade or sun.
Hydrangea paniculata ‘Grandiflora’ - P. G. Hydrangea, Tree Hydrangea
P. G. Hydrangeas have enormous panicles of creamy white flowers in the summer which gradually fade to creamy pink as the fall progresses. They are the most popular for drying. Standard varieties will grow 12-15' tall; the new dwarf reach 6-8’. All can be trained as a tree by selecting out strong trunks at an early age. They bloom on current year's growth and should be pruned back hard each spring to develop a strong, woody framework to support the huge, heavy flowers. They need full sun or dappled shade. Hardy to zone 4. There are MANY new varieties available.
H. p. ‘Little Quickfire’, ‘Pinky Winky’ Dwarf forms of “P.G.”, start blooming earlier, usually early July, starting white, quickly fading to pink or deep rose.. Great for smaller gardens and yards.
H. p. ‘Limelight’ Late blooming with pure white, upright, pointed flowers that are much longer than “P.G.”; flowers and do not hang down! A definitely different variety that adds a distinctive, dramatic look to the fall garden; grows 8’
tall, up to 10’ wide.
Visit our friend Lorraine Balloto’s website and buy her book to learn a LOT more about hydrangeas.
In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.