The vibrant blooms of hydrangea are prized.You might not know that it is possible to change the color of pink and blue varieties of hydrangeas by changing the pH of the soil.Pink flowers can be turned lustrous, silvery blue with the use of aluminum sulfate.If you want to change your hydrangeas from blue to pink, you can spread limestone over the soil to lower the acidity.
Step 1: Take a sample of the soil where your hydrangeas are planted.
Head out to your garden and use a hand trowel to dig 4-5 small holes to a depth of 6–8 inches (15-20 cm) each in the area around your hydrangea.Remove a layer of soil from the side of each hole.To keep the soil fresh, combine your samples in a large container.Storage of soil samples can be done with plastic and glass containers.These materials are free of chemicals that can ruin a sample.It's a good idea to take a sample from each area of your garden, as soil composition can vary quite a bit in just a few feet.
Step 2: Send your soil sample to the USDA lab.
If your collection container is not properly sealed, place it inside a plastic bag.If you live in the United States, you can search for the USDA co-op research and extension office closest to you and send your sample for analysis.They will tell you everything you need to know about your soil.A small fee may be charged by your local extension office for running soil exams.Some plant nurseries and gardening centers may be able to perform soil tests.
Step 3: You can test your soil with a commercial kit.
To use your test kit, fill your sample with distilled water and burrow a hole in it.Wait for the amount of time specified in the instructions to insert the included test probe or strip into the muddy water.At the end of this time, you can use the number on the probe or the color of the strip to determine the pH level of your soil.Your soil is acidic if you see a number lower than 7.It is either basic or alkaline if it is higher than 7.A neutral pH is determined by a reading of exactly 7.A soil testing kit can be purchased at any gardening store or home improvement center.Many of the kits have enough probes for multiple tests.If you want to test your soil at home, you should use distilled water.Since it has a neutral pH, you won't have to worry about it throwing off your results.
Step 4: It's possible to run a quick test.
If you don't feel like going to the trouble of sending off for a detailed soil analysis or using a home testing kit, there's a clever trick you can try right away in your own kitchen.Put distilled white vinegar over the soil by pouring 1–2 fluid ounces (30–59 mL) into your collection container.If the soil's pH is high, it means that the vinegar is bad.If your soil has a neutral or acidic pH, the vinegar won't react.The test is only useful if you want to identify highly alkaline soil.
Step 5: Don't experiment with your hydrangeas until they are strong.
If you want to change the color of your hydrangeas, wait until they are at least 2 years old.They will have a chance to recover from the initial shock of planting.It is not a good idea to mess with the soil's pH.Even if they're well-established, changing the color of your hydrangeas could affect their health.
Step 6: Buy a package of aluminum sulfate.
This naturally-occurring salt can be used to raise the acidity of basic soil.At most gardening supply stores, as well as the lawn and garden section of various supercenters, aluminum sulfate is available.A 4lb (1,800 g) box will run you around $12-15.If you don't want to spend money on pure aluminum sulfate, you can save your old coffee grounds, egg shells, and citrus peels in a covered container.The compounds that can drive up soil pH can be released when these materials are allowed to degrade for a few days.
Step 7: Take 4 ounce of aluminum sulfate with 1 gallon of water.
Take the salt out of the watering can and put it in the water.Shake or stir the mixture to get the salt out of it.The amounts should only be used as a rough guideline.Follow the manufacturer's instructions on the label of the specific product you're working with to make sure you use a safe concentration.
Step 8: The solution should be applied liberally to the soil.
When the liquid just begins to pool, stop the application by rinsing the soil around the base of the plant thoroughly.If you want to treat each hydrangea, do this.There is no need to wet the leaves or flowers.The plant will spread the aluminum sulfate through the roots to the foliage.If you decide to use coffee grounds, egg shells, or other organic materials, you can simply work them below the surface of the soil and water the plant as usual.
Step 9: Continue treating your hydrangeas for up to half a year.
The change of color will take some time.It may take weeks or even months before you notice a difference.Scale your aluminum sulfate applications back in the fall and winter when the plant is not active.Ideally, your soil's pH should be between 5.2 and 5.5.If you introduce aluminum sulfate to your hydrangeas, it could cause them to die off in the spring.If your plants appear to be in poor health, stop your applications.The species you're working with, as well as the specific conditions of your growing soil, may have an impact on the final color of the hydrangeas.It is possible for a flower with a deep pink or reddish cast to be more purple than delicate blue.
Step 10: Pick up a bag of gardening lime.
You can find this type of lime at any gardening center, along with hardware stores and online retailers.Depending on how much you buy and where you get your lime, it can be as little as $2-8 per pound.There are various sizes of bags for gardening lime, ranging from 1–50 pounds.It will be used to condition your hydrangeas for up to 6 months at a time, so make sure you buy enough.Lime serves to raise the pH of your planting soil, which in turn causes pale blue hydrangeas to become rosy pink.
Step 11: At the base of your plants, spread the lime evenly.
Sprinkle the lime on using a measuring cup or gloved hand, or transfer it to a garden spreader.To avoid overloading the soil, gardening experts recommend applying a ratio of 4 pounds (1,800 g) per 100 square feet.Lime can be applied before or between waterings.It makes direct contact with the soil.Don't put too much lime at one time.If you inject your soil with magnesium, it will result in sickly, discolored leaves or dead hydrangeas.
Step 12: The lime can be applied every 3-4 weeks.
During the spring and summer months, continue conditioning your hydrangeas.After several weeks or months, you should begin to see a gradual change in color.The effects will be amazing when you do.Don't apply lime more than once in a 3-4 week period.You will get more pronounced and immediate results if you turn blue hydrangeas pink.As the chemical levels of the surrounding soil return to normal, your hydrangeas may reverting to their original color if you fail to keep up with your lime applications.At the beginning of the next growing season, you can resume your applications.
Step 13: In the late spring or fall, you can feed your plants with a 25-10-10Fertilizer.
At the end of the growing season, apply a layer of phosphorus-richfertilizer to all of your plants.Be sure to follow the manufacturer's instructions for your climate and soil type.If you want to resume regular lime applications, wait until the following spring.It is important to use afertilizer with high levels of phosphorus in order to prevent aluminum from entering the soil.Adding magnesium to the lime will harm your hydrangeas, so fertilization will restore vital nutrients to your growing soil.