Growing Hydrangeas is extremely rewarding. For relatively little effort, you can enjoy bushes filled with show-stopping blooms all summer. But will your yard or flower beds be the ideal home for these beauties? What kind of soil do Hydrangeas need to thrive?
Hydrangeas prefer well-draining, loam and sandy-loam soils. However, they can tolerate clay soil or sandy soil if it is amended with compost, peat moss, or other organic material. Hydrangeas cannot survive in soils with a pH below 5.0 or above 8.0. Within this range, Hydrangeas do better when the soil has a pH of at least 5.5.
Hydrangeas will grow in most locations and soil types. They can even grow in more acidic or ericaceous soils than other favorite garden plants can tolerate. The reason that gardeners talk about Hydrangeas and soil so much is that different pH levels in the soil can cause Bigleaf Hydrangeas to shift the color of their blooms. Keep reading to find out the specifics.
Are Hydrangeas Picky About Their Soil?
Several different elements are involved with creating the proper soil mixture for shrubs, including composition, drainage, and pH levels. Hydrangeas have specific needs in some ways but can tolerate more variations in others.
When it comes to drainage, Hydrangeas get a little bit fussy. If the soil is too heavy, causing water to stand at the surface, Hydrangeas’s roots may begin to rot. On the other hand, if the soil does not hold on to moisture well, Hydrangeas will dry out too quickly. Rich, loose soil is just right for Hydrangeas’ needs.
Hydrangeas are not as specific about soil pH as they are about water retention unless you want to change the blooms of a variety that can have either pink or blue blooms. Some Bigleaf varieties change colors depending on the pH of the soil they are planted in.
Most popular plants for homes and gardens do best in soil with a pH level of between 6.0-7.0. Hydrangeas can survive in soils with pH levels between 5.0-8.0, so if you can grow other plants in an area with well-draining soil, you will likely be able to grow Hydrangeas without concern.
What Soil is Best for Hydrangeas?
All Hydrangeas need soil that drains well but still retains moisture, preferably a loam or sandy-loam soil. Different types of Hydrangeas have somewhat different needs for the amount of drainage that they require. Below is a list of the most popular types of Hydrangeas, along with a note about their ideal soil composition.
- Bigleaf Hydrangeas (Mophead and Lacecap) need soil that retains moisture but drains well. The pH level can be a factor in the color of blooms in this type of Hydrangea.
- Mountain Hydrangeas need soil that retains moisture but drains well.
- Oakleaf Hydrangeas can handle soil that dries more quickly. This type does better in sandy soil than other types of Hydrangeas. But Oakleafs are more susceptible to root rot if the soil stays wet for even a short period.
- Smooth Hydrangeas need soil that drains well, but unlike Bigleaf and Mountain Hydrangeas, this type does not require soil that retains as much moisture.
- Panicle Hydrangeas, like most other types, require soil that retains moisture and drains well.
- Climbing Hydrangeas also need soil that retains moisture and drains well.
Do Hydrangeas Prefer Alkaline or Acidic Soil?
Once you have found an area with well-draining soil for your Hydrangeas, the next step is to consider the pH of the soil there. Hydrangeas can grow in both alkaline and acidic soil. If other typical garden plants are able to grow in an area, you can feel fairly certain that Hydrangeas will be able to grow there as well. The pH range that Hydrangeas can tolerate goes from 5.0 to 8.0, although they do better between 5.5 and 7.5.
You may have thought that Hydrangeas were pickier about having either alkaline or acidic soil because many gardeners talk about amending the soil around Hydrangeas frequently. This is done to change the color of certain varieties of Hydrangeas that produce blue blooms in acidic soil and pink blooms in soil that is less acidic.
So while there is a reason to pay attention to the pH of the soil when growing specific varieties of Hydrangeas, as long as the soil is not on the extreme ends of alkaline or acidic, then your Hydrangea will happily grow without you having to worry too much.
How Does pH Affect Hydrangea Blooms?
Many people amend the soil around their shrubs to change their Hydrangea blooms from pink to blue or vice versa. This does not work for all types of Hydrangeas, but it is possible for varieties of Bigleaf Hydrangeas (which includes Mophead and Lacecap). But note, if your Bigleaf Hydrangea produces white blooms, then the color won’t change regardless of the pH level of the soil.
Bigleaf Hydrangeas produce blue flowers when the pH of the soil is 6.5 or below (in acidic/ericaceous soil). They produce pink flowers when the pH of the soil is above 6.5 (in slightly acidic, neutral, or alkaline soil). You can amend your soil to raise or lower the pH to cause your Bigleaf Hydrangeas to have different color blooms. If the soil has different pH levels in different portions of your growing area, you may even get multiple shades of blooms on the same plant.
This shift in flower color occurs because the pH level of the soil affects the amount of aluminum that the plant can absorb from the soil. In acidic soil, also know as ericaceous soil, Hydrangeas take up aluminum more efficiently, resulting in blue flowers. In neutral or alkaline soil, Hydrangeas cannot take up aluminum resulting in pink flowers.
How to Adjust Your Soil for Hydrangeas
Now that you know how pH affects Hydrangea colors, let’s talk about what you need to do if you want to adjust your soil to change your Hydrangea’s blooms.
First of all, it is easiest to control the soil that your Hydrangea encounters if you grow your Hydrangeas in containers. You’ll be more likely to get the results that you want quickly using containers.
In my opinion, a container of Hydrangeas on the front porch is lovely. However, most of us (myself included) have our Hydrangeas planted in the ground instead. This means that we have to work harder to slowly change the soil’s pH around our Hydrangeas to alter their bloom color.
If you want to change the pH level of your soil to alter your Hydrangeas’ colors, begin by testing the pH level of your soil. You can buy a pH testing kit to use at home (like this one) or a soil meter (like this one). But for the most accurate data, consider collecting a soil sample and having it tested at your local extension office.
Remember that Bigleaf Hydrangeas produce pink blooms when the pH is above 6.5 and blue blooms when the pH is 6.5 or below. If you want to switch your blooms’ color, think about how far away the pH of your soil is from 6.5. For pH levels that are one to two points away from your ideal level, know that it will take more work and time to significantly alter your soil.
To make flowers turn blue, you need to make the soil more acidic. The simplest way to do this is to add ericaceous compost, which has a pH level of 5.5, to the soil around the Hydrangea. You can do this by mixing the compost in with mulch or digging up the Hydrangea in the winter while it is dormant and amending the soil before returning the Hydrangea to its place. You can either buy a compost marked as ericaceous or create your own at home (more information on that here).
The other option is to use a soil amendment like aluminum sulfate or a soil acidifier. With soil amendments, be cautious and follow the directions on the package carefully. Too much aluminum sulfate can burn Hydrangea roots and cause damage to the plant.
This process will occur gradually, so do not expect your Hydrangea blooms to change to blue overnight. It may take an entire year before your Hydrangeas shift their colors. You should also continue adding acidic amendments throughout the growing season to keep your Hydrangeas producing blue blooms.
To make flowers turn pink, you need to make the soil more alkaline. Do this by adding garden lime to raise the pH of the soil around your Hydrangea. Follow the directions on the package. Begin adding lime to the soil in the fall and continue every 3-4 weeks throughout the growing season. Again, this process will take time, so do not expect to see pink Hydrangea blooms right away.
A less common option than using garden lime is to use wood ash to raise the pH level around Hydrangeas. Wood ash affects pH faster than garden lime, so Hydrangeas’ color changes more rapidly. However, wood ash can easily damage Hydrangeas. Most gardeners prefer using garden lime instead. If you choose to use wood ash, apply it in the winter and reapply every 2-3 years.
For more of a sure thing, you can pick a variety of Hydrangea that is not affected by the soil’s acidity. This will give you the color you want, regardless of changes in the soil, and avoid the constant upkeep and soil amending that comes with keeping your blooms the color you desire.
Will Hydrangeas Grow in Sandy Soil?
Hydrangeas grow best in soil that is a rich loam with equal parts sand and silt. The sand is important for Hydrangeas because it allows water to drain rather than pooling up around the roots. However, do note that very sandy soil is not ideal for Hydrangeas because it does not hold onto enough of the moisture that Hydrangeas need-when it comes to sand, balance is necessary.
If your soil is too sandy to be ideal, you have two options. You can add peat moss to your sandy soil to allow the soil to retain more moisture. Or, you can choose a variety of Oakleaf Hydrangea to grow instead. Oakleaf Hydrangeas survive better in dry conditions than other types of Hydrangeas do. Oakleaf Hydrangeas only produce white flowers, but they are just as beautiful as other Hydrangeas and require less care.
Will Hydrangeas Grow in Clay Soil?
Hydrangeas need soil that drains water well; otherwise, their roots will start to rot. Because most clay soil will cause water to pool up rather than draining quickly, soil with too much clay is not the best choice for Hydrangeas. Hydrangeas thrive in rich, loamy soil.
That being said, if you want to grow Hydrangeas in clay soil, try out Smooth Hydrangeas. As long as the area does not sit in water for extended periods of time, Smooth Hydrangeas can handle soil with clay better than other types of Hydrangeas.
To grow types of Hydrangeas besides Smooth Hydrangeas in clay soil, amend the soil with peat moss and sand. This will help with drainage issues as well as allow the soil to retain moisture. Pay careful attention when you water Hydrangeas in clay soil because you can easily over-water them.
Do Hydrangeas Like Peat Moss?
Hydrangeas need soil that does not allow water to pool at the surface and retains moisture well. Adding peat moss to your soil can loosen the soil allowing for better drainage, which is good for Hydrangeas. If you have sandy soil or clay soil, you should add peat moss to your soil before planting your Hydrangeas to help them thrive.
But peat moss lowers the pH of the soil, so if you are trying to keep your Bigleaf Hydrangeas pink, which requires a higher pH level, adding peat moss will have the opposite effect. You can balance out the change in pH by adding additional lime to the soil. However, you might decide that using peat moss is not worth the effort if you want pink Bigleaf Hydrangeas.
As an alternative to peat moss, you can add coco coir to the soil before planting Hydrangeas. Coco coir comes from fibers on the outside of coconut shells. Like peat moss, coco coir loosens the soil and helps to retain moisture. Unlike peat moss, coco coir has a more neutral pH and won’t interfere with pink Bigleaf Hydrangeas. As an added bonus, coco coir is a renewable resource, while peat moss takes thousands of years to form.
How Much Room Do Hydrangeas Need to Grow?
A single Hydrangea is beautiful, but a line of multiple Hydrangeas in full bloom is absolutely gorgeous. Unfortunately, like most plants, placing Hydrangeas too close together can cause fungal disease due to lack of air circulation and fewer blooms due to plants competing for water and nutrients. So how far apart should you plant Hydrangeas to allow for optimal growing conditions?
To figure out how far apart to plant Hydrangeas, add one foot to the width that variety reaches when mature. This means that a variety expected to grow to 6 feet when mature should be planted 7 feet apart.
The exact distance differs for each different species and variety. As a general guide, here are the estimates for the most common types of Hydrangeas.
- Bigleaf Hydrangeas require 7-11 feet between plants.
- Mountain Hydrangeas require 3-5 feet between plants.
- Oakleaf Hydrangeas require 7-9 feet between plants.
- Smooth Hydrangeas require 4-6 feet between plants.
- Panicle Hydrangeas require 7-12 feet between plants.
- Climbing Hydrangeas require 6-7 feet between plants.
To keep Hydrangeas that are in close proximity at their healthiest, water your Hydrangeas more frequently and thoroughly soak the soil. Adding slow-release fertilizer to these Hydrangeas allows them to produce full blooms because they will not need to compete as much for nutrients.
Putting It All Together
Finding the correct soil conditions for Hydrangeas is not difficult. For the most part, they require the same conditions as most other popular garden plants–soil with good drainage that falls towards the middle of the pH scale.
Hydrangeas can tolerate a wide range of pH levels but thrive between 5.5 and 7.5. The reason that gardeners obsess so much over whether Hydrangeas need alkaline or acidic soil is that Bigleaf Hydrangeas can have different colored blooms depending on the soil.
It is possible to amend your soil to cause certain varieties of Hydrangeas to change their flowers’ colors. Just be aware that raising or lowering the pH of soil takes time. You will have to continuously add acidic or alkaline materials to keep the flowers the desired color.
Besides acidity, the other area of concern for soil is the composition. Hydrangeas grow best in loam or sandy-loam soil because this soil allows water to drain and retains enough moisture for the plant. You can grow Hydrangeas in clay soil or sandy loam soil if you are willing to amend the soil with compost, peat moss, or other organic materials to loosen the soil.
Remember that Hydrangeas really aren’t all that picky about their soil. If other plants do well in the soil, chances are that Hydrangeas will be fine too. It’s just when you try to alter conditions to change your Hydrangeas’ flowers that you have to fuss about the soil more.