When you're preparing soil for blueberries, it’s important to understand the soil conditions that blueberries prefer.
Get your soil right, and your blueberries will be very productive and thrive for many years - potentially decades.
But blueberries are more finicky than many plants, and won’t be healthy or productive unless you get the soil just right.
So if you like blueberries, the extra effort you put into preparing your garden soil for blueberries will be very much worthwhile.
The best soil for blueberries is a sandy loam that is well drained and contains lots of organic matter. And soil for blueberries should also be acidic.
In fact, blueberries prefer a very acidic soil. The ideal soil pH for blueberries is in the 4.0 to 5.0 range.
If you happen to be fortunate enough to live where the soil pH naturally falls within that preferred pH range, the job of preparing your garden soil for blueberries will be quite easy.
The further your soil is outside of that range, the more work you’ll have to do to modify your soil for blueberries. But unless your soil is highly alkaline, you should be able to modify it enough to grow blueberries.
It’s unlikely that the soil in your garden is too acidic for blueberries, but if that happens to be the case, you can use lime to raise the pH of your soil.
Of course, you must know what type of soil you have before you can make plans for amending it to make it suitable for blueberries. So you’ll need to either have your soil tested, or test it yourself.
The number one reason for the failure of blueberries in home gardens is due to the pH of the soil being too high. So getting the pH of your soil correct before planting your blueberries is an important step.
If you need to lower the pH of your soil for blueberries, use your soil test results to determine how much the pH must be lowered, and then follow one of these courses of action:
Your pH is around 5.5 or less...
If your pH is in the 4.0 to 5.5 range, then just adding peat moss as an organic amendment when you plant will be sufficient (see below for specifics about adding organic matter).
Actually, if your soil is below 5.0, you don't need to do anything just for the purpose of lowering pH. But you'll still want to add some organic matter.
Your pH is 5.5 to 6.5...
Use sulfur to lower the pH of your soil, and also incorporate peat moss in the soil at the time of planting.
Be aware, though, that you’ll need to start the process of modifying your soil’s pH months before planting your blueberries. If it’s planting season right now, and you need to substantially modify the pH of your soil, you’d be better off getting started with the process of modifying your pH now, and putting off planting until next season.
Your pH is Above 6.5...
You’ll probably have a real challenge growing blueberries in your soil. You might want to consider growing blueberries in containers rather than directly in the soil.
Though you can try to lower the pH of your soil, it’s very difficult to achieve and maintain the amount of change you’ll need for your soil to be hospitable to blueberries.
But if you like to experiment, you might want to try a new method for planting blueberries. Instead of planting in the ground, you actually plant on top of the ground in a bed of pine bark.
To use this method, you’d just form a bed of pure pine bark (without soil mixed in). Make the bed at least 6 inches deep, and then plant your bushes directly in the pine bark. The blueberry roots will grow throughout the pine bark, which is a naturally acid material.
The pine bark will gradually break down, and you’ll occasionally need to add more pine bark on top of the bed, like mulch, to maintain the thickness of the bed. Using this method, you should end up with a bed that’s rich in organic matter (which blueberries love) that also remains at a pH level that’s just right for blueberries.
The pine bark bed will also provide good drainage – although you’ll still need to be certain that the site of the bed is well drained.
If you try this, be prepared to water quite frequently because the pine bark will not hold moisture very well at first. After the pine bark has begun to decompose a fair amount it should do better at holding moisture.
You might also need to fertilize a bit more than for a traditional in-ground planting.
I’ve never used this method myself (I happen to live in an area where the soil is perfect for blueberries). But I understand some commercial growers are using this method with success in areas with less-than-perfect blueberry soil.
Sounds like it would be fun to try!
Remember, though, that you must use pine bark with this method. Bark or shredded wood from any other source will not be acidic enough for blueberries.
Soil for blueberries should be rich in organic matter. But because blueberries are pH sensitive, you must be careful about the type of organic matter you add to your soil.
Sphagnum peat moss is an excellent source of organic material for blueberries. Pine bark and pine sawdust are also good. (If you’re going to use fresh pine sawdust, it’s best to incorporate it into the soil several months before planting.)
Preparing a Bed...
To prepare a bed for planting blueberries, apply organic material in a band about 2 feet wide and a good 3 to 4 inches deep (the amount of organic material to apply will vary according to the amount of organic matter already in your soil and the amount of pH modification needed.)
Till or spade the organic material into the soil to a depth of about 6 to 8 inches.
Preparing Individual Planting Sites
If your soil is already close to the proper pH (below 5.5), there’s no need to prepare an entire bed. Instead, you can just prepare the soil for blueberries at each location where you’ll be setting a plant.
To do this, dig a hole about 18 inches deep and about 18 inches wide. Pour about a ½ bushel of fluffed peat moss into the hole (a 5-gallon bucket is roughly ½ bushel). Now shovel enough soil back into the hole so that the hole is only about 4 inches deep.
Use a hoe to mix the peat and soil. Keep working the hoe in an up and down motion until the peat and soil are thoroughly mixed. While you’re mixing the soil and peat, make sure that you score the sides of the hole somewhat with the corner of the hoe (this will encourage the blueberry roots to grow beyond the confines of the hole). Fill the remaining few inches of the hole with soil.
If you need to, you can go ahead and plant your blueberry plant right away. But if you can, it’s ideal to prepare the hole a few weeks ahead of planting. Be sure to mark the center of your hole, of course, so that when you do plant, the plant will be centered in the modified soil, and not off to the side.
(My Dad and I once planted an entire acre of blueberries – 600 plants – using the above method, digging each hole with a shovel. There were some tired arms and aching backs by the time the job was done (and we were sneezing peat moss for a couple of days!). But 25 years later, those plants are still thriving, and producing several tons of blueberries every year.)
NOTE: Be sure to break up any clumps in the peat moss before pouring it into the hole. And if you’re going to plant immediately after preparing the hole (rather than waiting a few weeks), thoroughly wet down the peat/soil mix before planting.
Blueberries will not grow well in soil that does not provide good drainage. Planting your blueberries in soil that drains poorly will ensure that your plants will perform poorly, if they survive at all.
Forming a raised bed can be a solution for growing blueberries on poorly drained soils. In fact, research has shown that using raised beds for growing blueberries on poorly drained soil is as effective as installing a subsurface tile drainage system.
But how can you know whether the drainage of your soil is adequate?
Try this test: Pick an out of the way spot that’s in the same type of soil in which you’ll be growing your blueberries, and dig a hole about 8 inches deep. Next time there’s a heavy rain, monitor the water level in your hole.
If the water drains completely out of the hole within 24 hours after the heavy rainfall, then the drainage is probably fine for blueberries. But if there’s still water standing in the hole after 24 hours, you’ll either need to choose a different site for your blueberries, or plant them on a raised bed.
If your drainage test indicates that you’ll need a raised bed, make the bed about 4 feet wide and about 8 to 10 inches high. If you’re going to have multiple beds, make sure that they’re far enough apart to allow adequate drainage between the beds.
When you’re deciding where in your garden to plant your blueberry bushes, choose a spot that receives full sun if possible. Blueberries need full sun to produce fruit to the maximum of their capability.
If you plan to incorporate blueberry bushes into your landscape, and fruit production is not a primary concern, then the amount of sunlight the plants receive is less critical. Blueberries will do OK in a location that doesn’t receive full sun, but they may not produce much fruit.
And since your blueberry plants will need frequent waterings, especially in their first year, you might want to make convenience of watering a consideration when selecting the location for your blueberries.
While you might have to work hard to prepare your garden soil for blueberries, I think you’ll find all of that hard work to be worthwhile.
Because when grown in a suitable environment, blueberries are very long-lived plants. They’ll remain vigorous, healthy and productive for 30 to 40 years, or even longer.
So if you take pains now to make sure your garden soil gives your blueberries what they need, you can look forward to enjoying the beauty and bounty of your blueberry bushes for many, many years to come.