HYDRANGEA: Caring for your special treasures
by Lesli Peterson
Every time I see a Hydrangea I am taken back to my first encounter with this amazing shrub. The large trusses of blue flowers that seemed to persist for weeks and then dry with amazing ease instantly caught my heart. I had just moved into my first house and inherited four bushes outside the back door. I was new to gardening at the time, and it took me several weeks of research just to determine its name. Once I learned they were Hydrangea macrophylla, my next mission was to learn all I could about how to care for my new treasures.
Based on the feedback gathered by the American Hydrangea Society (AHS) at the 2004 Southeastern Flower Show, I am led to believe there are many other gardeners out there in a similar situation with their first Hydrangea. The large bouquet of flowers captivates them, but they need more information about how to care for this shrub successfully. In fact, AHS reported that most inquiries at the Flower Show were centered on questions of this nature. It is my hope that following tips on growing Hydrangea macrophylla (aka Mophead Hydrangea or French Hydrangea or Lacecaps) will help Hydrangea lovers around the South become confident about growing and caring for these magnificent gifts from Mother Nature.
How can I change the color of my Hydrangea?
In Georgia where glorious Azalea thrive with great ease due to the naturally acidic soil, Hydrangea macrophylla will almost always flower in shades of blue. Gardeners who have their heart set on pink flowers will probably have the most success if they grow their Hydrangea in pots. In this situation, the gardener can control the soil pH. By providing soil that is more alkaline than acidic, the flowers will show themselves as more pink than blue. The color change is actually due to the amount of Aluminum in the soil being made available to the plant. The more acidic the soil, the more Aluminum is available and the more blue the flowers become.
Another option for gardeners seeking pink flowers is to add lime to the soil in which the Hydrangea is planted. For this I recommend dolomitic lime, as it contains Manganese and over-use is less likely to cause toxicity problems with your plant. Also, it is available at most nurseries. Changing the pH with lime will require patience from the gardener, as the affect does not happen over night. Regular and repeated applications over several years will be required to see a color change.
If this seems like too much effort, you might try growing a different Hydrangea species. For example, H. arborescence offers an attractive flower that usually begins as a shade of green and opens to a creamy white. H. quercifolia and H. paniculata are much larger specimens in general. They each have cultivars that produce panicles of white and/or pink blooms.
When do I prune my Hydrangea?
Hydrangea macrophylla (along with H. quercifolia) are shrubs that set buds on old wood. “Old wood” are the stems that have been on the plant for at least nine months. Because of this, pruning Hydrangea in early spring with Nandina, Boxwood, Forsythia and others will remove the buds from the shrub.
Buds are generally formed from September to November, so to be safe any pruning should be done before September and after flowering in mid-summer. This, of course, does not apply to dead wood. At any time that you see dead branches on the shrub they can be removed.
It should be noted as well that, with the exception of removing dead wood, it is not necessary to prune Hydrangea unless you want to control the size and shape of the plant. In my garden I have taken steps to ensure that each Hydrangea I plant has plenty of room to stretch and grow as it desires. This makes my pruning efforts much more manageable -- with my 40+ Hydrangea, I can use all the help I can get.
How do I propagate my Hydrangea?
By far, the fastest method for propagating Hydrangea is to taking cuttings. While this can be done at any time in the season, I personally have the best success in spring and summer. Gardeners each have their own special process for propagating plants; some with water, some in peat pots, others in a sand mixture. The following steps have worked for me time and again:
·Examine the plant for a strong, healthy stem with at least two sets of leaves.
·Using sharp shears, cut the stem on the diagonal about one-half inch below the second pair of leaves. Cutting on the diagonal is a tip I learned from another AHS member: when you are making several cuttings at one time, cutting on the diagonal allows you to know which end is up and which end is down.
·Remove the bottom set of leaves at the node.
·Using sharp shears again, cut off half or more of the top set of leaves. Make this cut across the width of the leaf, not the length.
·If the stem is not a new, soft skin stem then I shave off (using my fingernail or dull knife) the top layer of “skin” on the bottom of the stem.
·Dip the stem into a rooting hormone and shake off the excess powder. The rooting solution I have had the most success with has been Rootone.
·Fill a pot (I start with a 4” pot ) with soil-less potting mixture or the mixture of your choosing.
·Stick a pencil in the mix to form a hole. Then, put the stem into the hole and cover with potting mix making sure to cover the first node (without the leaves) but not the second node. I use the pencil so that the rooting hormone is more likely to remain on the plant as it is potted.
·Keep the soil moist and in indirect sunlight. In as little as a week, sometimes two, roots will begin to form out of the bottom node and new growth will develop on the second node.
·After about six weeks I repot the cutting in a larger pot with a true potting mixture until I am ready to plant it outside.
Another tried and true method for propagating Hydrangea is layering. Again, there are many approaches to layering. If I want to layer a plant, I pull down a branch closest to the ground and pull off the leaves on the nodes closest to the ground. Then I cover the nodes with soil, sit back and wait for the node to take root.
After a substantial number of roots have grown (sometimes I wait an entire year for this) I cut the branch from the mother plant and transplant it to another area.
Why is my Hydrangea not blooming?
The winters in Georgia are typically suitable to the H. macrophylla so cold hardiness is rarely the cause for a Hydrangea not blooming in the South. The three most common reasons for Hydrangea not blooming in Georgia are spring frosts, dense shade and improper pruning.
When warm spring days bring out the Dicentra and Hosta, buds on the Hydrangea are still developing. Spring frosts that occur after these warm sunny days can damage the newly forming blooms. If new leaf growth is rising from the base of the plant rather than on the existing wood branches, a late frost may have harmed your blooms.
If you plant your Hydrangea in too much shade they may not bloom, or may not bloom well. Hydrangea are known as shade plants, but actually prefer a bit of sun. In fact, my first group of Hydrangea was planted in full sun. I recommend that if you are going to grow your shrub in full sun that you begin with a small shrub, allowing it to acclimate while it is young. In the Georgia climate you may find that the leaves wilt in the afternoon and that the need for water is greater, but the flowering will be worth any extra effort.
Lastly, as we discussed above, if pruning is done too late in the season then the chance of removing newly set buds is high. To prevent this, never prune your shrub after November. If possible, try to do so in September or October.
Hydrangea are easy shrubs to grow and can bring much beauty and satisfaction to your yard. I hope that with these few tips you will attempt to grow these treasures in your own garden.
