Both the almond and the apricot belong to the prunus family, also known as the "stone fruits". Cherries, peaches and plums belong to this family too. All members of the prunus have a bitter cyanide compound in the seed that makes them poisonous. Occasionally, a seedling tree of the almond or the apricot will have sweet edible seeds, with no poisonous content. It is these trees that provide us with the edible nuts. By budding and grafting, we can clone these trees in great numbers.
The major almond producing regions of the world are California and Italy. Small pockets of production exist in the rest of Europe and Asia. In central Asia, where the almond is not hardy, sweet pit apricots coined "alpricots", are used as a nut. The alpricot trees have been so highly selected there, that there is a high frequency of seedlings that produce the sweet seeds. The flavour of the nut is similar to the almond, so a dual purpose tree results, producing both fruit and nut.
Almonds and alpricots have a short dormancy period and are among the earliest trees to bloom in the spring. It is this early blooming characteristic that makes their blooms susceptible to late frost injury. This results in the loss of the crop, since injured blooms will not set fruit. Land areas that are protected by a large body of water like the Great Lakes, particularly the fruit growing regions of Lake Ontario and Southwestern Ontario, are suitable areas to grow these crops. Even in these favoured climatic regions, commercial crops are chancy at best. They are best suited for the hobbyist and market gardener.
Almonds originating from Southern Europe and California are only borderline hardy in the fruit growing districts of Ontario, and they seldom ripen early enough for our season. A selection called Hall's Hardy almond is a hybrid that is hardy and early ripening, but the nut is bitter and unsatisfactory. Almonds from central Europe have been found to be the most suitable for Ontario. They have proven to be the most hardy and early enough ripening.
"Plum pox", also known as sharka, is the most devastating viral disease of stone fruit from the genus Prunus and is found mainly in Europe. The disease is caused by the plum pox virus (PPV), and the different strains may infect a variety of stone fruit species including peaches, apricots, and of course alpricots plums, nectarine, almonds, and sweet and tart cherries.
Plum pox was first discovered in North America in Pennsylvania in 1999. It was decided to check the commercial fruit growing region in Ontario and it was then discovered in a small area of the Niagara Peninsula. The Niagara area was immediately placed under quarantine and efforts were made to eradicate the disease.
After years of fighting the disease without success, it was decided to continue the quarantine and "manage" the disease on a smaller scale and remove the infected trees that were identified.
The plum pox virus can be carried in live nursery stock, in grafts and budwood of infected plants, and is transmitted from one plant to another by the feeding of several species of aphid. To control the spread of the disease, all trees sold in the Niagara quarantine zone must be brought in from non-infected areas.
Plum pox virus does not kill infected trees, but it causes yield losses to growers and reduces the marketability of fruit. The fruit is not poisonous but inedible.