Prunus spinosa, called blackthorn or sloe, is a species of flowering plant in the rose family Rosaceae. It is native to Europe, western Asia, and locally in northwest Africa. It is also locally naturalized in New Zealand, Tasmania, and eastern North America.
From Pottermore
Blackthorn, which is a very unusual wand wood, has the reputation, in my view well-merited, of being best suited to a warrior. This does not necessarily mean that its owner practices the Dark Arts (although it is undeniable that those who do so will enjoy the blackthorn wand's prodigious power); one finds blackthorn wands among the Aurors as well as among the denizens of Azkaban. It is a curious feature of the blackthorn bush, which sports wicked thorns, that it produces its sweetest berries after the hardest frosts, and the wands made from this wood appear to need to pass through danger or hardship with their owners to become truly bonded. Given this condition, the blackthorn wand will become as loyal and faithful a servant as one could wish.
Wandlore
In Ireland, Blackthorn is a wand of heroes and does indeed tend to pick an owner with a warrior spirit. It is difficult for these witches and wizards to accept that they can't win at everything– that they have limits. They may focus on the negative too much, and either be hard realists or pessimists.
These wands are prized in England, Spain, Portugal, Ireland, France, Wales, Scotland, Australia, New Zealand, Morocco, Algeria, Tunisia, and the United States, especially among Irish-American wizards. Some Irish wizards incorporate their wands into a shillelagh, a club originating from Ireland. It takes a while for them to reach their full potential, as well as many heartaches and sacrifices. Both luckily and sadly, these people are all too willing to sacrifice themselves or parts of themselves for their goals– no matter how misguided or lost. Their wand is similar and will do everything it can for its owner, even if its owner has neglected it or turned down a path of dubious morality. Until the wand and its owner have suffered together, this wand will be limited in power and scope. However, when their bond is fully developed, they make a deadly pair.
Friends are difficult for blackthorn owners to keep, as it takes them a while to reveal their 'sweetness.' They may try to 'test' potential friends in various ways, which doesn't help them bond with other people either. When they do decide or conclude that an individual is their friend, their loyalty knows no bounds. Though it is a fierce and aggressive wand, its specialties lie in magic to do with protection and barriers. There can also be talent with divination, especially in meteorology. Excellent for defense against the dark arts, flying, transfiguration, charms, divination, and astronomy. Care of magical creatures is often a difficult class for those with blackthorn wands.
Blue and red sparks are common in advanced spellwork. Their magic smells of ripe plums, clean air, and a hint of almond. About halfway through February, soak the wand in sheep's milk for its health. The position of Mars can affect this wand's consistency and feel. One example is that it is stronger and more combative when mars are in retrograde. Owners of blackthorn wands often feel a connection to owners of birch or hawthorn wands. Blackthorn is one of the most common woods that bonds with mistletoe.