Underwood Plum Tree
- Zone 3
Characteristics of the tree
The Underwood plum is a medium to large plum, weighing about 34g, with an oblong or conic form. The skin is red and moderately thick, with a somewhat tart flavour. The aromatic flesh is golden yellow; tender, sweet and very juicy. It is partly freestone, but still clings somewhat to the pit. The pit is long and small. These plums are ready for harvest for us around mid-August. They have a relatively long ripening period over a couple of weeks, and also store better than other plums; although they still have a limited fresh storage life. They are excellent for dessert and for jam.
Underwood plum tree is large and vigorous with a spreading growth pattern. Given good pollination, it is one of the most reliable bearers, producing large annual yields. The tree has a beautiful yellow fall colour, and is hardy to zone 3.
Underwood plum originated from the University of Minnesota breeding program where it was originally tested as Minn 9. It was introduced in 1921, making it one of the oldest commercially available cultivars from the program. It is a cross between Shiro (P. angustifolia x P. cerasifera x P. salicina x P. simonii) and Wyant (P. americana).
Plums are fast-growing trees, but stay relatively small. A plum tree at maturity will not usually exceed 5 metres or 16 feet in height. Its life expectancy is also quite short: one can generally expect it to live between 30 and 50 years. This illustration shows a 20-year-old plum tree that has attained its maximum height.
You should note that this illustration is meant only to give a general indication of what you can expect, and the growth of your tree might look somewhat different. The development of a tree depends on the soil type, irrigation, fertilisation and climatic conditions. What we show here is based on our observation of the growth of plum trees in zone 4, in rather poor soil. In zone 2, growth will probably be slower, while in a rich soil it could be faster.
All our plum trees are sold bare-root, without pots. They have been cultivated directly in our soil. Bare-root trees must be taken out of the ground and shipped during their period of dormancy, which is why we only ship trees in the spring. A big advantage with these kinds of trees, is that they take up very little space, and can therefore be easily shipped by mail all over Canada!
This photograph shows a 2-3-foot plum tree, just like one that you might receive. Depending on the height you choose at the time of purchase, the tree might be a little smaller (1-2 feet) or somewhat taller (3-5 feet.)
Our plum varieties are hybrids of Canadian, American and Japanese plums. If you are thinking of planting a plum tree, it is important to understand how their pollination works. Hybrid plum trees are self-sterile, and cannot produce fruit alone. Moreover, they are not good pollinators for one another. Even if you plant two different varieties next to each other, you are unlikely to harvest any fruit.
Instead, hybrid plum trees need a wild plum tree to pollinate them: either the Canada plum (Prunus nigra) which is considered the best pollinator, or the American plum (Prunus americana) which also works well. So if you intend to plant plum trees, you must also plant at least one of these nearby, unless of course you already happen to have one. One wild plum tree is enough to pollinate up to around five grafted plum trees.
One drawback of plum trees is that they tend to flower early, making them sensitive to freezing in late frosts. Some microclimates help to mitigate this, such as the proximity of a lake or ocean. We also have a trick to help prevent them from flowering too early: applying a layer of mulch or compost underneath the base of the tree while there is still a good amount of snow on the ground. This insulates the snow underneath, so that it melts more slowly, and by maintaining a colder environment around the base of the tree, delays the start of its flowering period.
