Friday, March 1, 2013

What's The Right Hydrangea For Your New England Garden(Part 1)?

Part 1 - Species, Flower Forms, Cultural Requirements and Problems


Hydrangea arborescens 'Incrediball' or Soccer Ball ©BDG
This is a bit of a trick question since it really depends upon where you live in New England(zones 4, 5, 6 or 7) for some species.  However, recent horticultural developments in the creation of new Hydrangea hybrids have made location less important and the color choices more dynamic.  Hydrangea is the quintessential, old-fashioned cottage garden plant, and with new plant introductions there is renewed interest in this prolific and outrageous bloomer.

Hydrangeas in bloom(and after) are some of the most beautiful and impactful shrubs in the New England garden.  I believe every garden would benefit from one or one hundred of these flowering stalwarts.  You just need to know which ones will perform in your garden and need some basic knowledge for proper care.

In general, all hydrangeas require moist, not boggy, soil with plenty of organic matter (for feeding and moisture retention).  Most require some sun, though there is quite a range with the arborescens tolerating shade and the paniculatas tolerating full sun.

[Reed stepping onto soapbox] This is one of several plants that I feel the nursery trade has been irresponsible in marketing and selling over the years.  Each summer, nurseries will have beautiful plants in full bloom with big blue or pink flowers (grown in warmer climates and protected spaces), and, since Hydrangeas are often reasonably priced, people snatch them up and plant them in their gardens.  Unfortunately, in subsequent years the plants may have few or no flowers at all and people get frustrated.  This happens with the most common macrophylla species where the plants are hardy in our area, but many will not reliably flower.

Following is a summary of the major Hydrangea species available in New England:

Hydrangea macrophylla - Cornell Woody Plants Database
These are the most common hydrangeas available in the trade, and the ones that cause the most headaches and challenges.  They are wonderfully lush foliage plants that range from 2-6', depending upon the specific plant.  Their flower heads are Mophead (round inflorescenses with smaller flowers forming a ball) or Lace-Cap (flattened, two-dimensional inflorescences).  The colors come in blue, purple, red, pink, magenta, blush and many in between.

These beautiful plants do best with some sun but not full sun.  They will tolerate shade, but that will decrease their flowering and weaken the stems, making them flop more easily under the weight of the flower heads and water. An ideal location would be in sun but protected from strong afternoon sun.  They like some moisture since their big leaves can lose a lot during a hot day through transpiration.

Mophead Flower ©BDG 
The plants are mostly hardy to zone 5 (flowers to zone 6/7), but the real problem lies in the flower buds that can break dormancy during warm days in late winter and then get killed with a cold snap even in zone 6.  This species of Hydrangea sets its flower buds during the previous growing season, and if the buds don't survive the winter and spring, the plant will not flower and it will not produce new flowers during the season.  People who live on the Cape or by the sea (with ocean moderated temperatures) tend not to have these spring cold snaps and the macrophyllas perform beautifully on the coast in zone 7.  It is hard to believe the difference in performance with this plant from the suburbs of Boston to Cape Cod and the Islands.

Twist'n Shout Lace-cap Flower ©BDG
Within the past decade, a new macrophylla has become available called Endless Summer.  These are offspring of a particularly sturdy plant that is hardy to zone 4 (way up in New Hampshire and Vermont).  The original Endless Summer is a blue mophead and then a subsequent offering called Blushing Bride is a white to blush mophead.  More recently, Twist 'n Shout is a lace-cap with pinks and blues. All of these plants bloom continuously throughout the summer by flowering on this season's wood(new wood) and last season's wood (old wood), so they are not as susceptible to late frosts.

Hydrangea arborescens - Cornell Woody Plants Database
This one of the native Hydrangeas in New England and it grows to 4' and spreads even wider.  Hardy to zone 4, it doesn't have the same flowering issues of the macrophylla since it flowers on this season's growth(new wood).  It reliably flowers every year with big white mophead infloresences.  Also, this is the one hydrangea that will flower reliably in shade.  To keep them neat and smaller, you cut cut them back hard each year.

The only downfall to this species is that the big flowers will flop over with rain and moisture.  In a natural garden this may not be a big issue, and several new cultivars of arborescens have stronger stems and are more resilient.  An exciting new Endless Summer introduction, called 'Bella Anna' of the arborescens species has a pink flower and reblooms...not bad for the shade.  I have not used this plant yet, but it apparently has stronger stems to hold the flowers too.


Hydrangea paniculata - Cornell Woody Plants Database
This is a large group of generally bigger hydrangeas that like the sun and are distinctive with their cone to pyramidal shaped flower heads (panicles).  The Pee Gee Hydrangea(Hydrangea paniculata 'Grandiflora') is the old-fashioned hydrangea that people see throughout New England.  These shrubs can get 10-15' tall and wide, and they are covered in big white flowers in mid-summer that age to red, rust and bronze in the fall.

Most of this species are hardy to zone 3, which is north of Maine, Vermont and New Hampshire.  They flower reliably on new wood if not a little late in the season, and their flower heads are persistent throughout fall and winter.  In full bloom, the flowers can be so heavy has to make the shrubs droop.  Light pruning can help to keep the branches shorter and stronger to resist this problem.

This plant can be grown as a shrub or as a tree as is often seen in the trade.  The only downside to the tree-form is that it requires some pruning to keep its shape which removes some of the nice aging flower heads, and if the pruning is not done at the proper time, you risk losing  flowers.  However, this species has had so many cultivars with different flowers and shrub sizes, you are sure to find a paniculata to meet your needs.  Many new plants in the trade are making this an interesting plant again for the garden.


Hydrangea quercifolia - Cornell Woody Plants Database
This plant, more commonly known as the Oak-Leaf Hydrangea, is also a native and a fantastic addition to the shrub border for its flowers and big leaves, that have fantastic fall color.  The species is hardy to zone 5 and will flower reliably here in southern New England provided they get some sun.  Like the macrophylla, it too flowers on old wood, but doesn't seem to be as fickle in flowering.

The flower is pryamidal shaped, similar to the paniculata, but overall I don't think the display is quite as outrageous.  Still, it is a beautiful plant whose large oak-leaf leaves add to the dramatic impact.

I love this plant for its leaves and flowers, but it is not the best looking shrub late in the year and winter, so it is not the best choice by the front door.  With the exception of the few dwarf varieties, these plants can get up to 8'tall and wide, so give them the space to do their thing.  Some of the dwarf varieties can be maintained easily and kept in borders like the macrophylla species.



I started this post not realizing how much it would take to cover the topic, so I am splitting it into two posts.  Next week I will cover specific plants that I like, how to get the best color out of your hydrangeas, pruning and proper care (hint: don't love them too much).



Here is the link to Part 2:  Hydrangeas - Color, Care and Varieties

5 comments:

  1. Good post! I have several aroborescens, which we really enjoy. Our neighbor has a quercifolia right along the fence so we get to enjoy it too. I am perfectly happy with white hydrangea flowers and feel no need for blue or pink, in fact I prefer white hydrangea flowers.

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  2. This is an excellent and very informative post. I had to give away my Endless Summer hydrangeas last year because they were getting fried by reflected light off my windows every morning. They spent all morning wilting and all afternoon recovering. They had tons of foliage but very few flowers. I think the stress reduced flowering. I'm adding a tiny Cityline Venice hydrangea to a pot in a shady spot in my garden this spring. I really missed having them in my garden.

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  3. Very informative and useful. I have learned that the native are the only true reliables in my garden...the others are a gamble even Endless Summer although it is usually reliable for some blooms if we don't have a freezing April like last year.

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  4. Reed, Thanks for this. I have long wanted to grow hydrangea, but I think the real problem is my "well-drained" (understatement of the century!) sandy soil. On the other hand, there is a beautiful pee-gee hydrangea growing in my neighborhood, so maybe I could grow one if I prepared the conditions for it properly and gave it a good start. I know it doesn't make sense to wish for a hydrangea that doesn't need much moisture; they're not called hydrangea for nothing. -Jean

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  5. Gardeners expect a lushness and floriferousness in their hydrangeas that the Endless Summer series does not provide as reliably as other varieties do.

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