Page 18 - Our Plums - Les Pruniers de chez nous.pdf

Plum botany and classification

Plums are included in the genus Prunus of the Rosaceae family along with other fruits such as cherries, peaches and
apricots. The cultivated varieties of plums described in Our Plums were derived from a fairly large number of plum
species which are described below. The most important source of commercial cultivars is the European plum (P.
domestica) which is thought to have originated from a cross between P. cerasifera and P. spinosa. European plums tend
to be of high quality but many cultivars lack winter hardiness. The fruits range in color from green and golden yellow
to red and dark purple. Prunes are plum varieties with firm flesh and a high sugar content that can be dried whole
without spoiling. All of the prune type plums belong to P. domestica or P. insititia.
Japanese plums, P. salicina, were originally imported to North America from Japan in the late 1800s. They produce
attractive fruit which tend to be large, of good dessert quality, but not great for cooking. The trees are even less hardy
than European plums which means that they can only be grown in the mildest regions of Canada. Japanese plums have
been used extensively in crosses with species such as P. cerasifera, P. simonii, and especially P. americana to generate
hybrid type plums. Hybrid plums tend to be hardier than Japanese plums and the fruit can be used for processing and
cooking.
Native American plums (mainly P. americana and P. nigra) are also a source of many cultivars which are especially
valued for their winter hardiness. They tend to produce small, tough skinned, low quality fruit but they are useful in
cold areas where other varieties cannot be grown. Sandcherry-plum hybrids are the result of crosses between P. besseyi
and P. salicina. These crosses were done to generate hardy plum varieties that could be grown in the prairie provinces
and other areas with very cold winters.

Common name Latin name Origin Number of chromosomes

Apricot or Simon plum P. simonii Carr. China 16
Beach plum P. maritima Marsh. US 16
Canada plum P. nigra Ait. Canada, US 16
Chickasaw plum or mountain P. angustifolia Marsh. US 16

cherry P. americana Marsh. US 16
Common wild plum
P. insititia L. Europe, Asia 48
or American plum P. domestica L. Asia 48
Damson plum P. spinosa L. Europe, Asia 32
European plum
European sloe or P. hortulana Bailey US 16
P. salicina Lindl. China 16
blackthorn P. hortulana mineri Bailey US 16
Hortulana plum P. cerasifera Ehrh. Europe, Asia 16
Japanese plum P. subcordata Benth. US 16
Miner plum P. besseyi Bailey US 16
Myrobalan or cherry plum P. munsoniana Wight & Hedr. US 16
Pacific coast plum
Western sandcherry
Wild goose plum

Plum pollination
Most plum varieties require cross-pollination to set fruit properly and often will not set fruit when grown by
themselves. Some of the European plums are either partially self-fruitful (Bluefre, Shropshire Damson) or fully self-
fruitful (Bradshaw, Mont-Royal, Stanley, Yellow Egg). The self-sterile European plums require cross-pollination by
another variety of European origin.
Japanese plums are often partially or totally self-unfruitful. They can be pollinated by varieties of almost any other
group except those of European origin. Japanese plums cannot be used to pollinate European type plums.
Hybrid type plums are self-sterile and cannot be pollinated by other hybrid plums. They are pollinated by American
type plums with the cultivar Assiniboine being especially valued in this respect. Hybrids between P. americana and P.
simonii, such as 'Kaga' and 'Toka', and Japanese type plums are also useful in pollinating hybrid plums.

Harvest dates
The harvest dates given in this book were obtained from trees planted in the Montreal area (Canadian hardiness zone
5b), at the Central experimental farm in Ottawa (zone 5a), at the Frelighsburg (Quebec) sub-station (zone 4b), at the
research station in La Pocatiere (zone 4a), Quebec, and at the research station in Morden (zone 3b), Manitoba. We have
found that harvest dates in Montreal, Ottawa and Frelighsburg occur at approximately the same time and that they are
12 to 13 days before those in the La Pocatiere area. Morden harvest dates are about 8 to 10 days after those in
Montreal.

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