In the garden
BY CELESTE CASH - Second Nature Seed & Garden Texas A&M Horticulturist
June 13, 2012 at 1:13 a.m.
Why is it that we are always craving what we don't have? When it comes to hydrangeas we usually desire the blue colored flowers if we have pink, and if we have blue, we want to do whatever is required to have pink colored blooms.
Not all hydrangeas can be manipulated to change color. Hydrangea blooms that are naturally white will remain white regardless of soil pH or what type of soil they are grown in. Most other Hydrangea blooms will change color somewhat as they mature, but plants with naturally pink or blue flowers can be manipulated.
Blue blooms are present on plants with an acidic soil. These can be changed to pink by making the soil more alkaline. Likewise, plants with a pink bloom are in a more basic soil and can be changed to blue by increasing the acidity of the soil. It has been found that it is much easier to change a hydrangea bloom with a pink color to blue than it is to change from a blue color to pink. And, remember it is easier to manage the pH of a plant that is in a container than one that is placed in the garden. The premise is that it is easier to change the pH of a small container than to change the pH of the soil in a flowerbed.
Aluminum sulfate is a handy tool to help lower the pH of the soil and help the bloom develop a blue color. The presence of aluminum in the soil will make a hydrangea bloom blue. As with all fertilizer products be cautious about the amount you are applying. Too much aluminum sulfate will burn the roots and cause plant damage. A good rule of thumb is to apply one tablespoon of aluminum sulfate per gallon of water. Do not attempt to do this on newly established plants, but do not hesitate to try this on well established plants that have been in the garden for a couple of years. Always thoroughly wet the surrounding soil before applying the fertilizer solution. You must apply the solution throughout the growing season to continue to have the blue blooms.
If you have an acidic soil and would like to have pink blooms you must raise the soil pH to between 6.0 and 6.2. This can be accomplished by using lime to make the soil more alkaline or basic. To be able to enjoy pink blooms you must raise the pH to a point where the plant can no longer take up aluminum. Always be cautious not to raise the pH above 6.4 or the plant will not be able to take up iron and will suffer. A fertilizer high in phosphorous will also block the plant's ability to take up aluminum from the soil , resulting in a more pink bloom. Also, hydrangeas planted near concrete sidewalks or driveways are likely to produce pink blooms. The lime in the concrete can leach just enough to keep the pH high enough so the plant will not produce blue blooms.
Hydrangeas will make an excellent cut flower. They can be used in arrangements and the dried blooms add an incredible beauty. The biggest problem is when to cut the flowers for drying.
Hydrangeas cannot be cut at the height of the flower color. They do not dry well. Rather, wait until the flowers start to dry somewhat on the plant before cutting them. The best time to harvest the flowers for drying is after the flower has started to change colors and is drying on the plant just a bit in late summer or early fall. After collecting the blooms, place them in a dry, airy room out of direct sunlight until they are completely dry. They may be left in a dry vase or hung upside down to dry. Each method works well. The method is not nearly as important as the timing.