From time to time I get calls from gardeners about growing hydrangeas.

Unfortunately, the hydrangea that gardeners crave is the bigleaf hydrangea (Hydrangea macrophylla), also known as French or garden hydrangea.

There are two types of bigleaf hydrangea. There is the lacecap (Hydrangea macrophylla var. normalis) type that have a flower head with a circle of large flowers around the outside edge with smaller flowers at the center forming a "lacecap."

Most popular is the Hortensia type (Hydrangea macrophylla var. macrophylla) with large, showy blowsy mophead flowers in white, pink or blue. The "true" blue flowers are a color gardeners aren't often able to achieve in the garden, making them particularly attractive and remarkable. They're very pretty, but these shrubs don't fare particularly well in our climate. It's rated as winter hardy in USDA Zone 6, but is subject to winter injury from severe cold and sudden freezes in the spring. It also isn't well adapted to our region and becomes very stressed in extremely hot dry summer weather.

If gardeners want to attempt to grow bigleaf hydrangea here, they need a protected area where the shrubs will be shaded from the summer's afternoon sun. Like most woody plants, they prefer moist, well-drained soil. In our climate, it's advisable to mulch them with an organic material, such as bark or compost, and provide them with enough water to keep them from experiencing drought stress.

As noted, some Hortensia flowers can be pink or blue. The pink to blue shift is dependent on the amount of aluminum in the soil. Without aluminum, the flowers stay pink. In most gardens here the soil is alkaline, above a pH of 8. For aluminum to be readily available, the soil must have a pH of 5.2 to 5.5. While gardeners can add sulfur and organic matter to the soil, it's likely they won't be particularly successful in turning their hydrangea from pink to blue and keeping it there.

Gardeners wanting blue hydrangeas should consider creating raised beds with amended soil. Aluminum can be provided by adding 1 tablespoon of aluminum sulfate per gallon of water and applying it to the root zone of established (2- to 3-year-old plants.) One gardener suggests trying to grow them in large pots with an organic, acidic planting mix. This could go awry if the irrigation water is alkaline.

Even if you're not seeking blue flowers, alkaline soils may cause you problems. Bigleaf hydrangea is subject to iron chlorosis where the youngest leaves turn yellow to white between the veins and fail to grow well. Adding organic matter and sulfur to the soil before planting, mulching with organic mulches and fertilizing with acidifying fertilizers can help.

Another common complaint gardeners have when growing bigleaf hydrangeas is a lack of flowers. This could be because of a lack of adequate light. While they benefit from some shade, too much shade can lead to a lack of flowers. Injury from severely cold weather or late freezes also can damage potential flower buds.

Another reason for a lack of flowers may be directly in the gardener's hands: pruning. Bigleaf hydrangeas flower on the previous year's growth. There is often a tendency to try to hedge them into submission in the spring, because they can grow large. Unfortunately, this removes the parts of the shrub that would have flowered. The recommended way to prune bigleaf hydrangea is to remove one-third of the oldest stems at the base each winter. If a shorter shrub is desired, the time to prune for height or flower removal is right after flowering.

If you're a gardener who likes hydrangea flowers but you don't crave the true blue ones, you might want to consider the newest cultivars of hardy panicled hydrangea (Hydrangea paniculata) -- more about them next time.

* Marianne C. Ophardt is a horticulturist for the Washington State University Extension Office in Benton County.