How to Grow and Care for Blackthorn

Close up of Blackthorn Blossoms

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In This Article

Its many good charms offset the dark tidings and omens of despair rumored through history to follow Prunus spinosa, commonly called blackthorn.

Once thought of a plant that would bring bad luck upon any house that takes the blossoms through its doors, the modern shrub is now considered less evil and more a culinary and horticultural delight. Its bad reputation originates from its wickedly sharp thorns that can grow to almost four inches long. Before the invention of antibiotics, the thorns would break under the skin of people who had bad encounters with the shrub and lead to often life-threatening infections. Thanks to modern medicine, that outcome happens less frequently. Instead, those who encounter the shrub are greeted with its pretty blossoms and delicious fruits.

Though the name blackthorn will not be familiar to most, what will be familiar is the fruit and its byproducts. The blackthorn's fruit is called a sloe and is used to make sloe berry gin, regular flavored gin, numerous other regional spirits, and various jams, jellies, and treats.  

Botanical Name Prunus spinosa
Common Name Blackthorn
Plant Type  Shrub
Mature Size 9-12 ft. tall
Sun Exposure Full sun
Soil Type Moist, well-drained soil, Sandy soil
Soil pH Neutral 
Bloom Time Spring
Flower Color White
Hardiness Zones Zones 4-8, USA
Native Area  Europe and Western Asia
Toxicity Non-toxic

Blackthorn Tree Care

This native to Europe and western Asia might be tricky to find in national garden stores. You may need to hunt around in specialty nurseries or order it online. The blackthorn is well worth the hunt with its beautiful white blooms, which some will mistake for cherry blossoms, and varied form that can be useful as a hedge, fruit tree, or ornamental shrub.

The blackthorn is easy to care for simply because it will require no further care once planted and established correctly. However, getting to that point requires you to decide how you will be using the plant. Will it be a tree, shrub, or hedge? Will it be purely ornamental, or will you use the fruits? These are the options you need to consider, and this will inform you how little or how much care you will need to give to your tree.

After these decisions are made, the care guide can be established, and you know how to proceed and how much or how little care your blackthorn will require.


Light

When planting your blackthorn tree, look to plant it in a location that gets full sun or dappled shade. Your tree will produce the most amount of blossoms and most abundant fruit production in the full sun. If using the tree as a hedge, dappled shade will do, but realize there will not be many blooms.    

Soil

A fantastic attribute of the blackthorn is its soil adaptability. While it thrives in neutral soil, it will tolerate acidic and alkaline soils as well. The blackthorn does best in moist, well-drained sandy soils and will also tolerate the high levels of soil salinity common in roadsides and marine environments. No matter the soil conditions you give your tree, it should do well as long as it is not in standing water.

Water

After planting your tree, you will need to regularly water the blackthorn using the standard rate of two to three gallons of water per inch of the trunk’s diameter during the first year after the tree’s planting. After the first year, no supplemental irrigation should be required unless the area experiences extreme drought conditions. To minimize evaporation, you will want to mulch your tree out to the dripline, no deeper than two to three inches, without touching the trunk.

Temperature and Humidity

In order for the blackthorns to thrive they should be located in a climate that offers cool, wet springs and warm sunny summers. Blackthorns will do best in USDA zones 4-8.

Fertilizer

Testing your soil is advised before considering using any fertilizer. If the soil around the blackthorn is deficient, fertilizing poor soil with a general all-purpose tree or shrub fertilizer will improve the tree’s vitality. Of course, this can be solved by amending your soil by mixing a good amount of compost into the hole and soil while planting your blackthorn.

Is the Blackthorn Tree Toxic?

Though the plant's thorns are notoriously dangerous and known to cause injuries that carry increased risk of infection, the tree itself isn't toxic.

Pruning

Before proceeding to prune blackthorn, it is absolutely vital that you wear thick puncture-proof leather gloves that rise to the elbow and safety glasses to protect your eyes. You should also never put yourself in a position where you will be bending under the branches.   

Another safety precaution you can take is carefully cutting off the thorns on the lower branches with pruning shears. Doing this extra step is time-consuming but makes weeding and pruning much easier and safer to accomplish going forward.

That said, the only reason a blackthorn really needs pruning is if it becomes rowdy, starts invading unwanted areas, or is being trained as a hedge. Otherwise, you can let it go.

If pruning must be done, wait until after fruiting and know that blackthorns can take severe pruning and still survive.

Warning

The blackthorn gets its name somewhere: The thorns can grow four inches long. Before pruning make sure to wear the proper safety equipment. Blackthorn thorns are dangerous and can cause serious puncture wounds.