Clay soil is perhaps the most common type of soil, and many gardeners sometimes have difficulty growing in it.
However, this does not apply to hydrangeas because they can tolerate heavy moisture-retaining soils. Yes, these will not be the best conditions for these plants, but they will grow there.
I had two hydrangea bushes growing in yellow clay, and over the years, there have been no problems with them. Moreover, in the clay, they get more moisture, which reduces the need for watering.
Here is one issue we need to discuss. If you have clay soil in the yard and you dig a hole and fill it with the loose substrate (compost, peat, etc.), then during the rains, there may be a problem called the “bathtub effect.”
If the hole has less dense soil than the rest of the garden, then during prolonged rains, there may accumulate water and possible root rot. Yellowing of the leaves is the main sign of root rot. The solution to this problem is here.
However, this is rarely confirmed by practical experience. The only exception may be when you plant a hydrangea at the foot of the slope. Water will flow down and will accumulate in a place where the soil is looser. Similar situations are also possible. For example, you plant a hydrangea too close to the pipe that drains water from the gutter.
In this case, you do not need to improve the soil with which you fill the hole before planting. You need to plant in clay soil without adding other materials.
It is also not superfluous to check whether the water stagnates in your yard. You need to dig a hole 20 inches wide and 10 inches deep and fill it with water.
If, after 6-7 hours, there is no water left, then everything is fine.
Otherwise, you have a problem with stagnant water that can be solved with drainage (we’ll talk about this below).
Amending clay soil for hydrangeas
Many gardeners recommend amending the native soil, and this is a good practice. However, there are a few pitfalls you should be aware of. Also, if you want to improve your soil, then you need to do it right.
The first thing that matters is the size of the hole; if you want to plant a hydrangea in a hole that has the same size (or slightly larger) as the root ball, then it makes no sense to amend the soil. Because in the first year, the roots will be difficult to penetrate into the native soil, and it will be wrapped in a ball.
The benefit of soil improvement will only be if you dig a planting hole twice or even three times larger than the root ball of the plant.
In this case, the roots will be easier to develop in the first year, and when the hydrangea is established, it can easily penetrate the clay soil.
The next factor that matters is the proportions of the components of the soil mix. The amount of material with which you improve the clay should not exceed 5-10%. This is due to the fact that the soil will be too loose then all the water around will gather near the plant roots (I have already written about this).
In addition, hydrangeas are quite strong plants, and they do not need too fluffy soil. It is enough to lighten it a little to make the plant easier in the first year. After rooting, hydrangeas will feel great even in clay soil.
And last but not least is how you will improve the native soil. There are many different materials on the market for this, but I recommend using good quality compost.
Various materials for improving soil structure have advantages and disadvantages that we will not talk about now. Compost is the best material for this because, in addition to loosening, it makes the soil more nutritious for hydrangeas, the richer the soil, the better.
When choosing compost, get the most information about its manufacturer. It will also be useful if you find out what compost is made of and what technology was used.
It is best that the compost was made from one-two-year branches of young, healthy trees. The decomposition process should take place with access to air to all layers of the bulk.
Planting and care
When planting hydrangeas in moist soil, which is clay, you can place the plant in a sunnier position because it will have enough moisture not to fade in large amounts of sunlight.
As I mentioned above, the planting hole should be at least twice as large as the root ball of the hydrangea.
Fill the hole with amended soil and put a plant there so that the place where the shoots and roots meet are not buried in the ground.
It is best to plant a little above the surface of the garden (half an inch). Over time, the ground will settle, and the plant will be at the same level as the surface. Otherwise, a small pit may form where excess water can collect, which can lead to crown rot.
Next, fill all the free space in the hole with the prepared substrate and compact it a bit. After that, water the hydrangea, and after the water is absorbed, add more soil if pits are formed.
Also, I always recommend shading the plant for one or two months after planting. This will ease the conditions for rooting and reduce the effects of transplant shock.
Watering hydrangeas in clay soil
In the first year after planting, you need to be careful and timely water the hydrangea. Clay soil holds moisture well enough, so you will be a little easier to maintain it.
Check the soil moisture regularly. The peculiarity of clay is that in the absence of rain, the top layer of soil dries out, and a crust is formed. However, the soil under it can be quite moist.
To determine exactly whether a plant needs watering, you need to insert the stick into the ground to a depth of more than one inch and then determine the humidity.
If the soil has dried more than an inch, then you need to water it immediately. The amount of water will vary depending on the size of the hydrangea (on average 1-3 gallons).
The next year after planting, watering can be reduced. In dry weather and clay soil, the hydrangea needs watering every ten days or more often if the heat is too strong.
Also, try not to water too much water as the clay can absorb a lot of water, and as a result, the roots will be waterlogged. This can result in unpleasant consequences.
Don’t forget about mulching.
As I mentioned, when the clay soil dries on the surface, a crust is formed, which will be difficult to soak during watering. To avoid this unpleasant effect, you need to mulch the hydrangeas.
Mulch will help keep the soil moist and reduce watering frequency. In addition, it will regulate the temperature of the ground. In the heat, there will be no overheating of the roots, and the summer heat will linger longer.
There are a large number of mulching materials on sale. Some are better, and some are worse. There are even some that should be banned from selling at all (for example, shredded car tires).
I recommend mulching with pine bark. Its advantage is that it lasts longer compared to other materials.
Scatter the mulch on an area equal to the size to which the hydrangea extends.
The thickness of the mulch layer should be 1 to 2 inches. A thicker layer will not allow air to the surface, and a thinner one will not protect from rapid drying.
Do not pour mulch on the stems as this can lead to stem rot. There should be a gap of at least one inch between the crown of the plant (the place where the stems come out of the ground) and the mulch.
What color will hydrangeas be in clay soil?
Exactly what color will be the flowers of hydrangea grown in clay soil is difficult to say because the color depends on the acidity of the soil.
Clay soil can be both acidic and alkaline, depending on what other components are contained in it.
However, such soil tends to be alkaline, so most likely, the color of hydrangea flowers will be pink.
If there are organic residues around the bush, then the soil may become neutral, and the color will change to purple.
As you know, the most desirable color of hydrangea is blue. This color can be achieved only in acidic soil. The fastest way to acidify the soil is to add aluminum sulfate, which can be purchased at a garden center or nursery.
However, you need to be patient and wait at least a year to get the desired result.
Acidification of the soil can also occur naturally due to the decay of plant residues and mulch. But it can take several years.