The best time to plant a plum tree, Kali, is mid- to late March, April, or June—depending on your location. (You do not want to do it when there is snow on the ground!) You want to give it time to establish roots before the heat of summer sets in. Extension services provide lots of information (and occasionally offer programs); the Penn State service has this detailed advice on growing from seed: http://extension.psu.edu/plants/gardening/fact-sheets/home-orchard-production/growing-new-fruit-tree-plants-from-seed
The best time to plant a plum tree, Kali, is mid- to late March, April, or June—depending on your location. (You do not want to do it when there is snow on the ground!) You want to give it time to establish roots before the heat of summer sets in. Extension services provide lots of information (and occasionally offer programs); the Penn State service has this detailed advice on growing from seed: http://extension.psu.edu/plants/gardening/fact-sheets/home-orchard-production/growing-new-fruit-tree-plants-from-seed
We hope this helps!