Hydrangeas are one of the most beautiful blooms, and we tend to get many questions around their care. Today we are providing answers to the two most common questions we get! If you have other questions about your hydrangeas, get in touch and we'll happily help!
The most common question we get about hydrangeas is “How do I change the color of my hydrangea blooms?”
Many varieties of hydrangea blooms change color because of the acidity of the soil (more acid generates more blue hues and more alkaline generates more pink hues). That means you can change the color of your hydrangeas by changing the acidity of your soil! But before attempting to change the color, it is important to note a few things:
- White hydrangeas cannot be changed to pink or blue, although a slight coloration will show as blooms age.
- There are no ‘true red’ hydrangeas, so no matter how convincing those pictures in the catalogs are or how much lime is added to the soil, at best you'll achieve a very dark pink.
- The intensity of a bloom's color (how deep or pale the color is) develops for a number of reasons including plant heredity, weather conditions, health of the plant and other natural factors. A regular fertilizer program is one way you can help create a more intense color.
- A few varieties of hydrangeas have color that is extremely difficult to change, such as Pia, which wants to stay pink. The way to change the color to these more complicated varieties is to alter the soil chemistry. These soil additives should be applied four to six months before blooming begins.
- If your soil is alkaline (more common in Contra Costa), then the color will naturally be pink/lavender. To change the color to blue, add Master Nursery HYDRA BLUE Aluminum Sulfate. Hydra Blue should be applied at a rate of 1 Tbsp. to ¼ cup, depending on the age and size of the plant. Make three applications, starting late fall, and going through winter (December, January and February).
- If your soil is acidic, the color will naturally be blue. To change the color to pink, add Dolomitic Lime (or Superphosphate where available). Dolomitic Lime should be applied two to three times during late fall and winter. Sprinkle 3-4 cups around the base of a large shrub. It is almost impossible to add too much lime, but too little will give disappointing results. It is common for blooms on a hydrangea shrub to be several colors – from pink to lavender to blue. This is especially true the first year the hydrangea is planted and after the soil chemistry is altered.
The second most common question we get is "Why won’t my hydrangeas bloom?"
Timing is everything when it comes to pruning hydrangeas! The most common reason that hydrangeas don’t bloom is that the shrub was pruned at the wrong time of year. While it is fine to cut off blooms for arrangements or just to neaten the plant at any time, unless a hydrangea is quite old and the blooms have become small, it is not necessary to prune a hydrangea to maintain good health. If pruning is necessary to revitalize the plant or reduce its size, the following guidelines should be considered:
- For pruning purposes, hydrangeas can be placed into two categories: those that bloom on new wood (‘new wood’ are the branches that emerged on the shrub in the spring of the current year) and those that bloom on old wood (‘old wood’ are the branches that have been on the shrub throughout at least one summer and winter before spring bloom).
- If a hydrangea blooms on new wood, it can be pruned almost any time of the year, as close to the ground as one wishes. It will still bloom at its normal time since blooms form on the current new growth.
- Two popular hydrangeas that bloom on new wood are ‘Annabelle’ and ‘Pee Gee’ hydrangeas. Both bloom creamy white and can be pruned regularly. Other Hydrangea paniculata varieties would also fall into this category.
- Most commonly grown hydrangeas bloom on old wood (last year’s branches). Hydrangeas that bloom on old wood set their flower buds in late summer or early fall to bloom the following spring. It is important that this type be pruned before the end of July to assure abundant blooms the following spring. Do not prune ‘old wood’ types in the fall, winter or early spring because most of the flower buds will be removed and few blooms will appear.
- The best known species in this category is Hydrangea macrophylla. This group includes the commonly grown ‘mophead’ varieties with blooms of pink, blue and occasionally white. There are also many lovely lacecaps in this category. In addition, the following are ‘old wood’ bloomers: H. quercifolia (Oakleaf hydrangea), H. aspera, H. serrata (such as ‘Grayswood’ and ‘Preziosa’), H. petiolaris and some other lesser known species.