The Grumpy Gardener's Guide to Hydrangeas

1. How many kinds of hydrangeas are there?

There are too many to discuss here. But garden centers typically carry named selections of the following five species: French (aka bigleaf) hydrangea (Hydrangea macrophylla), the most popular kind; smooth hydrangea (H. arborescens), the type 'Annabelle' belongs to; oakleaf hydrangea (H. quercifolia), the state wildflower of Alabama; panicle hydrangea (H. paniculata), the group that includes 'Limelight'; and mountain hydrangea (H. serrata), which resembles a smaller French hydrangea. But don't freak out! You don't have to plant them all right this minute.

2. What are "mophead" and "lacecap" flowers?

There are two different bloom forms exhibited by French and mountain hydrangeas. A mophead flower consists of a large, rounded or conical cluster of showy, sterile blooms that conceal the tiny, seed-producing flowers beneath them. A lacecap displays flattened clusters of small, seed-producing flowers ringed by large, showy sterile blooms—and its two types of blossoms may be different colors depending upon soil conditions. Mophead types are more popular, although lacecaps are considered more graceful by the cognoscenti.

3. In what order do different hydrangeas bloom?

Oakleaf hydrangeas bloom in the spring and summer, as do the French hydrangeas; mountain and smooth hydrangeas bloom in the summer; and panicle hydrangeas bloom from summer into the fall. If you plant with this in mind, you can have hydrangeas in bloom for a long time.

4. How can I change a hydrangea's color?

The blooms of some hydrangeas change color naturally, most notably panicle hydrangea, which goes from white to pink as it ages. Mountain and French hydrangeas are the most common types on which the flower color can be altered. For many other kinds of hydrangeas the color cannot be changed. The bloom hue indicates the pH of the soil. In very acidic soil (pH 5.5 or below), flowers turn blue. In alkaline soil (pH 6 or above), flowers turn pink or even red. In slightly acidic or neutral soil (pH between 5.5 and 6), blooms may be purple or a mix of blue and pink on a single shrub. Keep in mind that selections vary in their sensitivity to pH. For example, 'Ami Pasquier' stays crimson in all but the most acid soil. To make soil more acidic, work sulfur to the soil. To make it more alkaline do the same with lime. This chart can help you determine how much sulfur or lime you need, depending on your desired pH. Endless Summer's Color Me Pink and Color Me Blue products supply pelletized lime and sulfur respectively. Depending on the size of your plant and your soil conditions, you may need to adjust it several times. Be patient; results may take months.

5. Will white French and Mountain hydrangeas change color?

Sorry, they stay white regardless of the soil pH.

6. What's the deal with reblooming hydrangeas?

This concerns the French hydrangea, which in times past bloomed only on the previous year's growth. This meant that if a cold winter damaged the growth or some nincompoop pruned the shrub in late fall or winter, you'd be lucky to get any blooms. However, some French hydrangeas bloom on both last year's growth and the current year's growth. Thus, even if you cut them to the ground in winter, they'll still bloom. Rebloomers include the Endless Summer series, the Forever & Ever series, the Let's Dance series, 'Big Daddy,' 'LA Dreamin,' 'Penny Mac,' 'Mini Penny,' and 'All Summer Beauty.'

7. When is the right time to prune my hydrangeas?

What is it with you people who always want to chop on things? Hydrangeas need little pruning other than removing any dead wood or shortening a wayward branch. And as I said before, if you prune certain types at the wrong time, you won't get any flowers. So pay attention. Here are the best times to prune hydrangeas:

• Once-blooming French hydrangea: summer
• Reblooming French hydrangea: summer or winter
• Oakleaf hydrangea: summer or spring
• Smooth hydrangea: winter
• Panicle hydrangea: winter or spring
• Mountain hydrangea: summer.

8. How can I control powdery mildew and leaf spot on French hydrangea?

First, don't water your hydrangeas with sprinklers. The splashing drops will spread the disease. Second, pick up and throw away any diseased leaves that have fallen. Third, spray the healthy foliage (before any diseases show up) with Daconil or Immunox according to the label directions.

9. Do any hydrangeas have pretty autumn foliage?

Yes. Oakleaf hydrangea turns scarlet and crimson, mountain hydrangea turns burgundy, and panicle hydrangea turns light yellow in fall.

10. How can I get cut hydrangea blooms to keep their color?

Plunge the cut stems in cool water immediately after trimming. Pour about 1 inch of boiling water into a container, and let it cool for a minute or two. Cut the stems to the lengths you want for your arrangement. Hold the bottom inch of the stems in the hot water for about 30 seconds. Then transfer the stems to cool water. Let the water evaporate slowly.