Hydrangeas
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Hydrangea macrophylla, panniculata, and arborescens
Hydrangeas are such a summer favorite with their huge flower clusters on big, lush shrubs. They have the advantage of blooming in the middle of summer and their colorful blooms can last through to winter.
Their attention getting colors range from white to pink, and on to brilliant blue and some purples. You can even control the color of some hydrangea flowers by adjusting the pH of the soil. (See that in the how to grow section.)
Hydrangeas are quite easy to grow, as long as they are in the correct zones and sun. They need enough water in dry areas. They are NOT deer resistant. And you must prune them properly. For cut flowers there are a few treatments to know about. And pick them at the right time and they’re good for drying.
I’ll go through the three best hydrangea species for cutting and drying, the bigleaf hydrangea (Hydrangea macrophylla), panicle hydrangea (H. panniculata), and smooth hydrangea (H. arborescens). There are several other species that are great landscape shrubs, one is a vine. The flowers of all can be treated the same way for cutting. Some may not dry as nicely as the ones I mention here.
What Hydrangea Flowers are Like
Bigleaf hydrangeas:
Also known as mopheads. They have big round flower clusters. Some of these are lacecap types that have a starry-like cluster of small fertile flowers surrounded by large flowers.
It’s the regular mopheads that are best for cut flowers, and for drying.
The flowers are white, blue, purple, pink, or red. For the blue or pink ones, the colors can depend on the soil pH and aluminum content. Blue color occurs in strongly acid soils, a pH of 5.5 or less, with aluminum present.
Here’s how to change the flower color:
- To get blue flowers from a plant that’s producing pink flowers, add aluminum sulfate to the soil. The blue comes from aluminum in the soil, and the sulfate lowers the pH for the aluminum to be absorbed. Add about 1 Tbsp of aluminum sulfate per gallon of water that drenches the soil right after planting and throughout the growing season. Apply only to well-watered soil.
- If you have a blue-flowered hydrangea you want to turn to pink, you want to raise the pH to 6.0-6.2. No higher than that or they can suffer from an iron deficiency. To do this add dolomitic lime to the soil several times a year. Using a high phosphorous fertilizer helps.
- The flowers will not necessarily change the first year, you may need to wait till the second year for full results. Meanwhile you’ll get a range of purples in your flowers while it changes.
- You’ll need to maintain this color changing ritual for as long as you desire the new color. To make it easier, consider growing your mophead hydrangea in a large container where there is less soil to treat.
White mopheads stay white no matter what.
Pannicle Hydrangeas:
I love these hydrangeas. The flowers are dense clusters along a stem forming a cone shape. They come in white, creamy ivory tinged with reds and pinks, and a greenish white.
The greenish white flowers are on a nice variety called ‘Limelight’. They start out greenish-white, get whiter, then turn to ivory with a pink blush by the end on summer. Most of these flowers age with nice rosy-tawny color at the end of the season.
Smooth Hydrangeas:
These are native American hydrangeas and most grow to around 10 ft. Some varieties are much shorter and produce nice flowers.
The flowers on smooth hydrangeas last up to four weeks in the vase! What great cut flowers.
Varieties include ‘Incrediball’, ‘Incrediball Blush’, and ‘White Dome’. All feature large domed flower clusters in white or pinks, on shorter plants, around 5 ft. tall and wide.
What the Plants are Like
They all are deciduous, woody shrubs. Many have nice fall color.
How to Grow Hydrangea Plants
Bigleaf Hydrangea:
Zones: 5-9, sun – pt. sun, afternoon shade in hot areas; generally morning sun to afternoon shade, full sun in cool areas. Plants are 4- 8 ft. tall and wide.
They need adequate moisture throughout their growing season. Mulch the soil with compost.
To prune: Most bigleaf hydrangeas bloom on old wood, so you need to be sure you don’t prune the wood too far. Some new varieties are repeat bloomers and they bloom on new wood also, later in the season. But their main bloom is on the old wood. Cut stems back by about a third, cut at the nodes. Throughout the summer growing season next year’s flower buds form. Prune during the dormant season.
For biggest flower clusters, thin to fewer stems. For smaller flower clusters do not thin, or thin less.
If your zone is lower than 5 you risk having the wood freeze to the ground, which kills off next season’s blooms. Take measure to protect the plants from too much freezing.
Pannicle Hydrangea:
Zones: 3-8, 4-9 depending on variety; sun – pt. sun, afternoon shade in hot areas, generally morning sun to afternoon shade
These are more drought tolerant than the bigleaf hydrangeas. Mulch the soil with compost. These are typically taller, varying with variety.
To prune: Prune during the dormant season, prune to shape
Smooth Hydrangea:
Zones 5-8, varies with variety, part sun
These are more drought tolerant than bigleaf hydrangeas; give them deep and infrequent irrigation if you need to, mulch the soil with compost. Their size varies with variety. Flowers are typically in huge clusters.
To prune: as in the panicle hydrangea.
How to Harvest Hydrangea Flowers
Since hydrangeas are woody shrubs, the stems need help in getting water into them.
1. One way is to have a clean bucket of warm water ready, cut the stem just above a node, at a 45 degree angle. If it’s a woody part of the stem, carefully, take the blade and make a slit in the middle up the stem for about an inch, or less. It it’s a thick stem you can make an x at the bottom of the stem so you have another slit at right angles to the first slit. This allows more surface area of the water conducting vessels to have access to that water.
Here are two other techniques I found from the people at greatgardenplants.com:
2. Dip the cut stem in alum powder. Alum should be available in the baking section or pharmacy. Then place into room temperature water.
3. Have a pot of just boiled water handy. Dip the stems into the water for 15-30 seconds, then place into room temperature water.
These latter two are to prevent sap from clogging the water conducting tissues in the stems.
I find greater success in keeping hydrangea flowers from wilting when I wait to harvest the flowers when they are quite mature.
How to Dry Hydrangea Flowers
Once the flowers are quite mature and have been in water, or just picked, when you remove the stems from water they don’t wilt. If they do leave them in water, or on the plant, for a little longer. They harden up with time. They can stand upright in a vase until you arrange them…or just leave them as is. They work very nicely in wreaths, either wired in or inserted with glue on the stem tip.
My Favorite Varieties
‘Limelight’ panniculata hydrangea is my favorite. I like all the colors it goes through and it’s been so easy for me to use fresh and dried.
The blue hydrangeas are blue naturally where I live so there’s never any forcing. And I usually like to pick them in the fall for making dried arrangements.
I haven’t tried a smooth hydrangea, but it’s on my list.
Sources for Hydrangea Plants
I strongly recommend you go to your local nursery in the spring and summer to find a variety that is suited to your area. They’re always there in the season. Plus, I believe it’s so important to support local merchants. Local purchases benefit local economies.
But if you want to see what’s available, there are lots of online nurseries that have excellent selections. Here are two:
Flowers to Go With Hydrangeas
I think hydrangea flowers are perfect all on their own.
But here are a few flowers that bloom in the late summer when you may be picking your hardened hydrangeas: