Swamp Doghobble

Size, growth and what to expect

A shrub of the coastal plain from Massachusetts to Florida and west to Louisiana, swamp doghobble grows wild in swamps and along the shores of rivers, ponds and streams. Expect a medium pace, roughly a foot and a half of new height a year on an average site, the rate our growth estimator assumes for it. It stands 4 to 10 feet tall in a clump 2 to 6 feet wide, and it sends out suckers to form a colony. Fragrant white bells about a third of an inch long hang in sprays up to 4 inches long from April into June, and bees and butterflies work them.

The flowers give way to five-parted light brown capsules that ripen in September and October. In fall the leaves turn red, orange and yellow. It is poisonous to dogs, cats and horses, and deer leave it alone. Swamp sweetbells, its other name, describes the fragrant bell-shaped flowers. It does not stand drought or wind.

How to grow Swamp Doghobble

Swamp doghobble takes wet, acid ground where most shrubs rot: a seep, a pond edge, low woods that stand in water after rain. It grows best in sun or part shade, and in full sun only where the soil never dries. The stems arch and the plant spreads by runners, so space it 4 feet apart with room to make a colony.

Saplings ship potted. Plant while the shrub is dormant. Heath shrubs have fine, shallow roots, so keep the root ball intact; set it in a hole three times as wide and no deeper, ball level with the ground, native soil back in. Sweet or limey soil is a reason to choose another plant, not to amend. Mulch with pine straw, thin near the stems. Seed is as fine as dust. Sow it on the surface of a moist, acid peat mix, uncovered, and keep it damp under a clear lid in good light. Seedlings are tiny and slow their first season, so leave them in the pot until they are big enough to handle.

Never let it dry out the first summer; water twice a week in heat unless the site is naturally wet. Deer and rabbits mostly skip the toxic foliage, so a guard is rarely needed. If a clump gets leggy, cut the oldest stems to the ground after bloom, since flowers come on last year's wood.

Each flower carries both male and female parts, so there are no male and female plants to pair. If the leaves go pale between green veins, the soil needs to be more acid. The whole plant is poisonous, like its rhododendron cousins, so keep it from grazing animals.