Like many gardeners, I eagerly await garden catalogs mailed each year, hoping to be first in line ordering all those new varieties of my favorite plants.  Interior decorators like to redecorate inside and gardeners like to do the same outside, but there is something to be said for sticking with the tried and true.  Hydrangeas are typically thought of as "that old shrub in the corner of Grandma’s house," but in truth, there are few shrubs that can come close to blooming for as long as a hydrangea will.  Also, if you are one of those who is forever lamenting the few available plants that bloom in shady areas, a hydrangea is the perfect choice.

The most commonly grown type of this woody, deciduous shrub is Hydrangea macrophylla which comes in two types:  Mopheads (which most people are familiar with) and lacecaps.  Mopheads have large, sterile flowers in a dome shape, sometimes reaching 10" in diameter.  Lacecaps have a ring of sterile flowers surrounding very small, BB-like, fertile flowers in a flat cluster.  Both make terrific garden shrubs and both have remontant (reblooming) varieties which can extend the blooming period throughout summer and into fall.  When a hydrangea is labeled as being remontant, it means new blooms will appear after pruning in the same season.  You may have seen the cultivar 'Endless Summer' at your local nursery; if you prune this in May or June, it will rebloom that same summer because it forms flower buds on both old and new wood.  This is unlike most other H. macrophylla hydrangeas which only bloom on old wood from the previous year's growth.
 
There are hundreds of named varieties of H. macrophylla to choose from, but there are other species of hydrangea which are worth planting.  H. quercifolia is the Oakleaf Hydrangea which turns a beautiful bronzy red in the fall; as its name implies, its leaves are similar to those of oak trees.  H. serrata is mostly a lacecap variety and doesn't grow as large as the mopheads.  H. paniculata, commonly called the PeeGee Hydrangea, can grow to 20' and has white flowers; it blooms on new wood.
 
White-flowered hydrangeas stay white no matter what kind of soil you have, but blue or pink flowers are indicative of the amount of aluminum in the soil that can be absorbed by the roots.  If soils are acid, aluminum is available for the roots to absorb and you will have blue flowers.  If, on the other hand, you have pink flowers, the aluminum is not able to be absorbed by the roots due to soil alkalinity.  So, what do you do if you want blue flowers?  The soil acidity has to be raised which can be accomplished by applying aluminum sulfate mixed in water as a soil drench.  You can buy this at your local nursery or garden center in both liquid and powder form; just be sure to read and follow the directions for application carefully.  Azaleas and camellias are both acid-loving plants as well as shade plants, so if you have these and they are thriving, hydrangeas will do well in the same location, plus will tend to be blue in flower color. If you want pink flowers, however, and you know your soil is on the acid side, apply lime to the soil at a rate of 1 lb. for every 10' of surface area once or twice a year.  Remember, more is not better for either treatment and in my experience, it's better to live with the soil you have rather than try to change it.
 
There are a few other points to keep in mind when planting hydrangeas.  They can't tolerate hot afternoon sun, so plant them in a location where they receive morning sun only; east exposure is ideal and north is good too.  They are moisture-lovers and need regular irrigation; however, if the plant seems a bit limp in the afternoon, ignore it until morning.  If at that time of day the leaves still appear limp, then it's time to water, drip irrigation being the best way to do this.  Balanced, slow-release fertilizers are preferred and should be applied in the spring.  High nitrogen fertilizers are not recommended as they tend to produce long, extended shoots that may not set a good quantity of flower buds for the next season.

Pruning hydrangeas is probably the most vexing problem you'll have with this plant.  Except for 'Endless Summer' mentioned previously and some of the H. paniculata varieties, winter pruning is not a good idea unless you want to rejuvenate an old shrub.  Flower buds develop on old (mature) wood of the previous year, opening in the summer of the following year.  Therefore, if you winter prune, you will cut off most of your next summer's blooms.  It is best to prune when the flowers become ratty-looking and unattractive; this will give your plant enough time to develop new flower buds before the first frost.  My hydrangea pruning usually takes place in mid August to September.

Once you plant one hydrangea, I guarantee you'll want more; the problem will be deciding which one.  The Sunset Western Garden Book is an excellent reference book as is Hydrangeas for American Gardens by Michael A. Dirr.  He is a professor of horticulture at the University of Georgia and a self-proclaimed hydrangea lover.

There is no Master Gardener public education class for tomorrow, April 22, but come see us at the El Dorado County Home & Garden Show next weekend; our information booth will be in the Organ Room at the fairgrounds.  We will also hold a class on "Ponds and Water Plants" next Saturday, April 29, beginning at 9 a.m. in the Ag Extension Office at 311 Fair Lane in Placerville.  We can be reached at 621-5512 Monday through Friday, 9 a.m. to noon, or come in to see us; our office is located at the above address.