A. If your plants are Albizia julibrissin, they will grow outdoors in Western Pennsylvania. If they are one of several species of mimosa, they will not be winter hardy here. Both plants are in the pea family and commonly known as mimosa. Although Latin names can make people trip over their tongues, these names are the only way to know for certain that we are talking about the same plant. Albizia julibrissin is also known as Powderpuff Tree or Silktree.
Native of Asia
Silktrees are native to eastern and southern Asia. They have become naturalized in the United States from Maryland south to Florida, and west into eastern Texas. They do grow well in our climate but may be killed back to the ground in severe winters. Even if a severe winter kills them to the ground, they generally re-sprout from the roots. Their seeds frequently germinate in the soil under the tree or in adjacent flowerbeds, so you usually have seedlings coming up just in case the mature tree dies.
Silktrees prefer full sun and well-drained soil but are very tolerant of poor, infertile soil because they are in the pea family. Such plants are known as legumes, and they have the unique ability to fix nitrogen directly from the atmosphere. Silktrees can be troubled by vascular wilt and mimosa webworm and are often thought of as short-lived trees.
Invasive Alien Species
They are classified as an invasive alien species in areas where they have naturalized in the United States. They spread by sprouting from their roots as well as setting prolific seed crops. Since they are able to grow in very poor, dry soil, silktrees quickly colonize areas and squeeze out native plants that provide food and shelter for wildlife. They do seed themselves in our climate as well, but I personally have not seen them grow so prolifically that they threaten local ecosystems. Please be aware of their potential weedy character and grow them with care.