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One of the most interesting aspects of growing Bigleaf hydrangeas is the ability to change their color. It isn't easy and it doesn't happen overnight, but if the beautiful pink or blue hydrangea you brought home from the nursery has started to look a little muddy and pale, you can restore its color (or change it) by adjusting the pH of your soil.
The pH scale runs from 1.0 (strongly acid) to 14.0 (strongly alkaline), 7 being neutral. In general, plants grow best in soil with a pH of 6.5-6.8. This range makes for happy worms and microorganisms and generally supports an abundance of readily available soil nutrients. Bigleaf hydrangeas, however, prefer moderately acidic soil with a pH range of 5.0 to 6.4. A soil pH toward the acidic end of the scale (5.0) will change the color of their flowers to blue. On the other hand, a soil pH toward the neutral end of the scale (6.5) will change their flowers to pink. Tip: It takes about 5 pounds of lime per 100 square feet to raise soil pH by 1 point and 2 to 3 pounds of sulfur per 100 square feet to lower soil pH 1 point.
To get a baseline measurement of the pH in your soil, you're going to need a soil test. Inexpensive test kits are available at garden centers, although you'll get more accurate results if you send a sample to a soil testing lab (ask your county extension office). If you decide to send your sample out for testing, be sure to request organic recommendations for adjusting your pH and ask for an explanation of what each amendment will do. These tests and recommendations can be important because different types of soil (e.g. sandy or clay) will change pH at different rates. If you change the pH too abruptly, plants and soil organisms won't have time to adjust.
If you're just trying to intensify a color you already have, a soil test may not be necessary. You simply need to make your soil more neutral to darken your pinks or more acidic to intensify your blues. The best time to amend your soil is in the fall after the plants go dormant.
Mother nature intended for white hydrangeas to stay white and no amount of soil amendments can change that. If your hydrangeas are white, enjoy them. They are going to stay that way. Sometimes as white plants age the flowers take on a pinkish tint, but that is about as colorful as white hydrangeas will ever get. The blue and pink Bigleaf hydrangeas like Mophead hydrangeas ( Hydrangea macrophylla) and Lacecap hydrangeas (Hydrangea macrophylla normalis) are what you need to grow if you want to change colors.
For a hydrangea to go from pink to blue, aluminum needs to be present in the soil. In one respect, this sounds easy, because you're adding something to the soil instead of taking something away. Most experts recommend applying it in liquid form by dissolving _ oz (1 Tbsp) of aluminum sulfate in a gallon of water. Plants should be watered well with regular water before applying this solution to avoid possible root burn.
Hydrangeas take up aluminum best in acidic soil, so before you apply aluminum sulfate the pH of your soil should needs to be in the 5.2 to 5.5 range. The aluminum sulfate will then work to lower the soil's pH even further. Organic amendments used to lower soil pH include coffee grounds, fruit peels, lawn clippings, peat moss and pine needles. Fertilizers can change soil pH, too. Bone meal, as well as fertilizers high in phosphorus, should be avoided. Instead, use a fertilizer high in potassium.
If you're starting with blue hydrangeas, your soil naturally contains aluminum and your soil is already more acidic. To change your hydrangeas to pink, you'll need to keep aluminum from becoming available to the plant. One way to do this is to raise the soil's pH by adding dolomitic lime or wood ash several times a year to edge up the scale toward 6.0-6.3. The higher pH will make it more difficult for the hydrangeas to take up any aluminum that is present. Fertilizers high in phosphorus will also help prevent hydrangeas from taking up aluminum.
You may be able to change the color of your hydrangeas, but a pale blue will never turn into a deep red. Intensity is somewhat predetermined by genetics, so if you want to change your pink color to a blue color, expect it to be as pale or intense as the original color.
One of the advantages to growing in containers is that you have complete control over the chemistry of the soil because it's contained. If you have naturally alkaline soil and want to grow blue hydrangeas, you can lower the pH of the soil in a container without negatively affecting nearby plants that prefer more alkaline soil. If you live in an area where blue hydrangeas grow naturally, you may want to consider growing pink hydrangeas in containers in order to easily control the amount of aluminum in the soil.
Weather can also play a role in color intensity, as can plant stress or environmental variables like nearby concrete walls or paths leeching lime. Don't try to change the pH of your soil dramatically over one season. Doing it over the course of several seasons will give beneficial soil organisms time to adapt and you'll get to experience the many shades of color in between your starting point and end results!
By Ellen Brown
My dad puts dill pickle juice on his hydrangea roots to make them turn purple and pink instead of just white. They are very pretty.
Hardiness Zone: 4b
Helenw from Ontario Canada
If you're growing Hydrangea Marcrophylla (French hydrangea) you can turn it from pink to blue by lowering the pH level of your soil. The color is determined by the amount of aluminum available to the plant. Add 3 to 4 tablespoons of aluminum sulfate to a gallon of water. Apply it 2 times, 2 weeks apart, for 4 to 6 months prior to blooming. You can also add coffee grounds, eggshells or ground-up citrus peel to the soil. You're shooting for a pH of 5-6.
On a similar note, blue hydrangeas can be changed to pink by adding 3-8 cups (depending on the size of the plant) of dolomic lime around the base of the hydrangea. Do this 2 or 3 times between the blooming seasons. As an alternative, you can also try a bit of superphosphate around the base of the plant. Shoot for a pH of 6.8-7.2.
The color change doesn't happen overnight so be patient. It can take as long as a year or two to see the results. The white varieties of hydrangeas (such as PeeGee, Silver Leaf, Hills of Snow, etc.) cannot be changed. They remain while regardless of tampering with the pH of the soil.
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Here are questions related to Changing the Color of Hydrangeas.
I started out with pink and blue hydrangeas in pots and they have now turned green. What can I do to get them colorful again?
Ii brought a red hydrangea on my holiday in Daylsford. I brought it home and sat it on my bench in its original pot and watered it the very next day. It turned purple why?
By Jess D.
By Catherine 02/25/2013
The change of shade is natural but traveling is not something plants really enjoy so maybe it aged the flower a bit quicker than usual. Anyway with maturity the red flowers of hydrangea fade to shades of purple. They always do.
All you have to do now is wait for a new flower and check how long its red shade will last. This changing of shade is what makes hydrangeas so interesting if you cut them and make dry bouquets.
Hope this help!
How do I turn a pink or white hydrangea blue?
By Cheryl 08/23/2012
An easy and no cost way to get highly acidic soil is to simply save your coffee grounds. You don't have to do fancy stuff like mixing the grounds into the soil; just dump them on top in early to mid spring.
I have a hydrangea I got from my daughter last year for Mother's Day. It's taking root, but I need to know how to add the ash and in what quantity, and where to place it. Dry on earth? Dilute in water in root area? Teaspoons or tablespoon? Thanks ahead of time.
By April 06/11/2012
Why are you adding ash? Are you trying to change the color of the bloom? The color of the bloom is determined by the ph of the soil, and you would have to first test the ph, then determine what color you wanted the bloom to be to know how much ash to add...BUT, add to much and you will kill your plant.
http://www.gardeners.com/Growing-Bl ... geas/hydrangealp%2Cdefault%2Cpg.html
I had some hydrangeas that were blue, and now they are pink. What can I do to make them blue again? My grandmother used to dump her coffee grounds on them, but I'm not sure that's what kept them blue.
By Mara from Seattle, WA
By looneylulu 05/06/2011
Acid content of soil is deciding factor in making Hydrangea blue or pink. Just forget whether it's high or low acid content.
How do you get blue hydrangeas?
Hardiness Zone: 8a
By tf1 from GA
By Cheryl 07/20/2011
Hydrangea blue or purple blooms come from highly acidic soil. You don't need to buy some chemical additive; you can get acidic soil by dumping your used coffee grounds on top of the soil.
There is a purple hydrangea bush in our neighborhood. How was that effect achieved?
Hardiness Zone: 8a
Nana from Hattiesburg, MS
By Mary 05/30/2007
maybe one of these links will help
How do hydrangeas get their color?
Hardiness Zone: 8a
Martha from Cherryville, NC
By Mandy 04/20/2007
I think I read somewhere that they get their color based on how acidic the soil is. If the soil is more acidic, the flowers are more pink in color. If it's more basic they are more purple in color. I think I read about it in Better Homes & Gardens. They have an excellent website where you may be able to find further info. Good luck!
Thrifty Fun has been around so long that many of our pages have been reset several times. Archives are older versions of the page and the feedback that was provided then.
By Charlotte Harris
Do you have a blue mophead hydrangea that you would like to be pink? Or, do you have a pink hydrangea that you want to turn blue?
Hydrangea Macrophylla, also known as French Hydrangea, or Mopheads because of their large clusters of flowers, are beautiful and easy to grow, and you can "play with" their colors.
You can change the color of their blossoms by changing the acidity of the soil in which they are growing. The color is actually determined by the availability of the aluminum in the soil to the plant. If the pH is low (pH 5-6, acidic) the blooms will be blue. If the pH is high (pH 6.8-7.2, alkaline) the blooms will be pink. If your hydrangea has both pink and blue flowers at the same time, the soil is at, or near neutral.
So how do you change the pH of the soil?
For pink blooms:
For blue blooms:
Be patient. It sometimes takes a year or two to see the results, and you will need to continue the treatment, or the plant will revert back to the color it was.
Have fun with your hydrangeas. The white varieties, such as Peegee, Silver Leaf, and Hills of Snow, DON'T respond to the pH change, they stay white.
About The Author: Charlotte Harris is the author of "Charlotte's Garden", a Monthly Gardening website. For more information about growing Hydrangeas and other flowers visit her site at http://www.charlotteswebb.biz