Great blue lobelia is a native perennial for the damp spots most flowers refuse: spikes of true-blue flowers, 2 to 3 feet tall, from late summer into fall, just as the shade-edge garden runs low on color. Hummingbirds, bees, and butterflies all work the blooms.

Plant it in sun to part sun in soil that stays moist — low spots, streamside banks, rain gardens, or beds you can water regularly. It tolerates wet feet and deer browse. Let some stalks set seed and it will colonize politely.