Category: Hydrangea

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Helping Hydrangeas Turn Blue

TheGardenLady received this question from Cookie:

Is it too late in the season to add aluminum sulfate to my hydrangeas to make them blue?  How much would you add to each plant as I have a row of 29.  The blooms are starting to come in but are very light blue at this point.  Would you recommend something else to add to make them blue.  I am always worried I will kill them by adding too much.

It may be a little late  to get the color Hydrangea you want, but it is never to late to start.

The first thing you should do is to test your soil to find out what the soil pH is. Blue hydrangeas like a soil acidity of between 5.2 and 5.5. You can buy a soil test kit at your local hardware store or get the kit through your Master Gardener office of your local agriculture extension office. This will give you an idea of how much  you want to amend your soil with things that bring up the acid level. You should have this test done every year to be sure your soil is as acid as you need it to be. Before you start amending your soil,   you want to check to see what other flowers are near the hydrangeas to know if they are also acid loving plants.  Here is a list of some acid loving plants.

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People Enjoy Hydrangeas in TheGardenLady’s Garden

hydrangea blooming-01 by kazukichi

TheGardenLady continues to write about some of the flowers in her garden that make people  stop and ooh and aah.  Today she will talk about hydrangeas.

Paz e Esperança by Eduardo Amorim

There are so many different hydrangeas that you can choose from. They have lovely, wonderful and showy flowers and some plants have interesting leaves. They are called the workhorses in the garden because, as this fact sheet says,  “they can be grown in either full sun or partial shade. They are resistant to most insects and diseases. They can be grown in a wide range of soil but prefer a rich, moist soil and should be planted where watering will not be a problem.”

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Climbing Hydrangea

Climbing Hydrangea Vines by beautifulcataya

When the TheGardenLady was asked for the name of a good vine to grow along the wall of a house, my first suggestion was to check the amount of sunlight that side gets. Depending on the amount of sunlight will determine the vine you want to choose. Also, it would be wise to have a soil test of the area where you want to plant anything. The concrete from the base of the house might leach into the soil to change the pH making it very alkaline. This might not affect the plant you want; but it is best to be sure.

My favorite vine for shade is the climbing hydrangea, Hydrangea anomala petiolaris.  See here.   This is a vine that will grow even in a northern exposure though it likes some sun or dappled sun. It grows in zones 4 or 5 and warmer. It will grow in full sun, too but in the Deep South and in western Zones 9 and 10 it needs shade in the afternoon.

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Pruning Hydrangeas


Hydrangea by Eric M Martin

TheGardenLady received this question from Mary.

Last month I planted a hydrangea plant and it has 8 blossoms on it. Can I cut the blossoms off now, and will it affect the growth next year? Or should I leave it alone?

The choice of cutting the blossoms or leaving them on your hydrangea plant is up to you. Either way is fine for the plant. If you decide that you want to cut the blossoms off now, it is ” safest to remove them with very short stems so you won’t disturb any developing bloom buds for next year. As long as you cut above the first set of large leaves, the blooms will be fine. ” Read this good website for pruning hydrangeas. Deadheading, which is what you do when you remove blossoms, is a type of pruning.

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Affecting the Color of Endless Summer Hydrangeas

Endless Summer Hydrangea by geekstogardeners

TheGardenLady received this question from Kathy.

I live in Fenwick, Old Saybrook and have always had a yard full of beautiful, brilliant blue Endless Summer hydrangeas. However, this year is the exception!! I have tried deadheading since the blooms are  overly abundant but the color is still lackluster, pale blue.  I have tried adding hydrangea acid based fertilizer and watering with the hose daily.  Any suggestions?

First of all you should check the pH of the soil where the hydrangea is growing. If your soil is highly alkaline, you will have problems maintaining the blue flower no matter what you do. The pH of the soil should be 5.2 to 5.5.  Sometimes if your hydrangeas are planted near cement, like a sidewalk, the alkaline can leach into your soil. And sometimes your water is alkaline. Get test strips to test the water and the soil, or have the soil in your hydrangea garden tested at your state agricultural extension or through your local Master Gardener office.

If you have the proper pH, next Spring, water the plants really well and then add a solution of 1/2oz (1Tbsp) aluminum sulfate to each 1 1/2 gallons of water and feed this carefully to your plants- it can burn the roots. This should be applied in the spring when you see the buds forming- about 6 weeks before the flowers come.

Readers who have new hydrangea plants should NEVER use aluminum sulfate until your plants are about 3 years old. The addition of the aluminum sulfate seems to be the most reliable method of keeping the hydrangea flower blue.

It is good that you used a hydrangea fertilizer that is high in potassium. But most authorities do not think that this will help change the color.

An excellent site that goes into details of how to keep your hydrangea blue or pink is this.

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Acid for Hydrangeas

TheGardenLady received this question from Martha:

How can I add acid around my hydrangeas?

Because hydrangeas like an acidic soil – especially if you want the blue blooms- you can supplement the fertilizer and add acid.  Know that not all the hydrangeas will change color. Usually it is the pink and blue hydrangeas that can have their flowers change color, not the white or red hydrangeas.

Any of the following will help: aluminum sulfate (1/4 oz. per gal. of water) which can be bought in many garden stores, egg shells, coffee grounds which you can get free, TheGardenLady was told, at places like Starbucks,  ground up orange or grapefruit peels.

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