Discover The Pleasure of Hydrangea Plants
Native to China and Japan the Hydrangea has been celebrated for centuries. The Hydrangea
most commonly known is Hydrangea macrophylla. Hydrangea macrophylla’s rich history includes an identity crisis of sort. Included among its many past names are Hydrangea hortensis, and Hydrangea opuloides. While hybridizing has been somewhat limited in the past what work has been done with this plant has been significant commercially. In the U.S., the variety ‘Merritt’s Supreme’ was developed and is currently the most popular variety among Hydrangea growers. Hydrangeas are currently being bred in the U.S., Japan, Germany and France.
Maintaining Hydrangea as a Flowering Potted Plant
Temperature - Keep plants in a cool location, from 65° to 75°F (18° to 24°C).
Location - Place plants near a window that provides high light levels. Avoid direct sunlight so that plants don’t dry out rapidly.
Irrigation - Water plants frequently to avoid wilting of leaves and flowers. Hydrangeas can be damaged by overwatering, so it’s important to maintain a moist medium without applying water so frequently that overwatering becomes a problem.
Grooming - Remove individual leaves and flowers as needed to keep the plant attractive.
Hydrangea macrophylla plants are winter hardy even in colder climates like Minnesota. However, in colder areas like Zone 4 they are not always reliably bud hardy. In this case the plant will come back but they may not flower. Therefore, some type of over-wintering protection is needed. The older the plant, the better your chances are for summer blooming. Abscised leaves from large plants falling in between the branches, affords some bud protection. Additional protection can be given by placing the plant near foundations, and using natural materials such as straw, leaves or mulch for insulation. Plants may die down to soil level in extreme cases but they come back again as the weather warms like all perennials. There are considerable differences between varieties as far as cold tolerance and consistent blooming. Recently there has been some attention given to varieties which supposedly bloom on new wood. Such blooming is not uncommon, all varieties can bloom on new wood if the winter has not been too severe. Until now, claims for varieties blooming consistently on new wood, have not been sustained. However, new breeding shows that there will be introductions of varieties which reliably bloom on new wood. Until then, winter protection is the best answer for summer blooming pleasure.
As H. macrophylla change color readily, below is a list of results that one can expect. The left column is for plants growing in soil with a low pH 4.5 – 5.0 to which aluminum sulfate has been added at the rate of ¾ lbs. per 5 gallons of H2O (not on foliage soil only). Two to three applications at 2 week intervals will give the best results. The right column is for plants growing in a limed soil (pH 6.0), with high phosphorous.
Low pH - Slightly Blue, Purple, Brilliant Blue, Blue Bicolor & Purple Bicolor
Middle pH - White
High pH - Slightly Pink, Red, Pink, Pink Bicolor, & Red bicolor
There are many variations of the above. We have seen white flowers which turn green after
blooming which has a unique look. In general, we have found that light pink varieties tend to
make the best blues.
Hydrangeas require a well-drained media high in organic matter. They cannot stand wet feet.
Aeration and good drainage is very important in overall plant performance.
While Hydrangeas have a large leaf surface; they do not require large amounts of fertilizer.
Rather they should be fertilized often at low rates. Plants can easily be harmed if fertilized too
heavily when the leaf growth is not active. When transplanting, it is best to transplant into a
media where little or no fertility is present. Such a poor start will encourage rooting and then
plants can be fertilized.
Any pruning should be done before July 1st. In fact, most hydrangeas as garden plants should
not be pruned at all. Late pruning can result in flower buds for the next season being cut off.
Planting in Garden
Any Hydrangea received during the cold months cannot be immediately planted outdoors.
Movement to the outdoors should be done after the danger of frost. The plants will then have
the summer and fall to acclimate for the next winter.
Cut Flower / or Foliage
Growth Rate in the Garden
Season of Interest (Flowering)
Late Spring / Early Summer
Soil Moisture Needs
The best pictorial reference which we have found is the Hydrangea book called, “Encyclopedia of Hydrangea” by CJ &DM Van Gelderen of the Netherlands. Published by Timber Press. The Father-Son team, who collaborated on this book, have extensive experience with Hydrangeas both growing them and visiting many of the world’s leading Hydrangea collections.