Passalong plants. The term can evoke the sights and scents of a lush garden with its roots literally reaching back through generations of families and friends. Entwined among a plant’s blooms are often the memories of a favorite person, a special place or a happy time. Rick Durham, University of Kentucky associate Extension professor, believes that sharing plants is a good way to get to know your neighbors and build community relationships. “I think it’s something that, a lot of times, is lost in our communities these days. We tend not to rally around each other unless there’s some kind of a crisis. It’s kind of a fun thing to do as a community.”Apart from the emotional reasons for sharing a cutting of a favorite plant, there’s the purely practical side – it’s an inexpensive way to fill a garden. Passalong plants are typically defined as those that are easily propagated. That often means that they spread freely. For a new gardener or for someone who is trying to fill expanses of empty space, this can be an easy and inexpensive way to get started.Caution should be taken, however, to avoid invasive species. Plants such as purple loosestrife (Lythrum salicaria) or chameleon plant (Houttuynia), for example, can rapidly take over a bed and easily spread beyond its borders. Knowing a plant’s growing habits first can save a lot of work when trying to tame it later. Durham said examples of good passalong plants include cannas, hostas, daylilies, iris and sedum.The decision on the time of year to divide plants should be based on when they bloom. Propagate plants in the season opposite their bloom season. If they’re spring or early summer blooming plants he recommends propagating them in the fall. If they are late summer or fall blooming plants propagate them in the spring. Durham cautioned that even well-behaved plants may take over a space after a few years. One option, he suggested, would be to compost the excess plant material. Another would be to carry on the tradition and pass them along to friends, with the gentle hint , of course, that perhaps they might like to share a few of their own.It’s not necessary to have gardening friends to reap the benefits of passalong plants. Many community groups, such as arboretums, botanical gardens, garden clubs or other civic groups hold public plant exchanges. Contact your local county Extension office for information about plant exchanges in your area. In the central Kentucky area, The Arboretum in Lexington will hold its spring plant exchange on May 13, beginning at 9 a.m. Admission is free to Friends of The Arboretum and $1 for everyone else.