With spring making every effort to show up this month, it’s time to think about planting. Mt. Lebanon Nature Conservancy is offering 21 species of native perennials at its third annual sale, Saturday, May 18.

Online pre-orders start April 1 at lebonature.org, with order pickup and an in-person sale from 10 a.m. to 1 p.m., at the Unitarian Universalist Church of the South Hills, 1240 Washington Road. Nearly all the species will be sold in container strips of four or five plants.

The species on offer are grown as “landscape plugs,” which look different from plants you might see at a garden center. Landscape plugs are young plants with highly developed root systems, propagated in 4- or 5-inch-deep cells.

The plugs establish quickly and have a high transplantation success rate. They generally reach flowering size in the first season.

Mark where each plant will go in your garden. Dig holes as deep as the plug and only slightly wider, using an auger, trowel or weeding knife.

Water the plants before taking them out of the containers.

Pop the plugs out of the plastic cells by pushing up through the bottom gently with a chopstick. Do not pull the plants out by the foliage, or tease apart the roots.

Place the plugs into the prepared holes and fill in around them, tamping the soil firmly as you go to maximize root contact with the soil. Keep the plant base at soil height, not deeper or shallower. Water immediately.

Make sure each plant is well marked to ensure it is not disturbed and that it gets watered as needed. Some plants go dormant early and become hard to spot in the summer. Water around the base of each plant when necessary but as seldom as possible. During droughts, water when plants begin to show signs of stress. This approach encourages the deep roots of native plants to do their job of reaching down, down, down for moisture.