American alumroot | The Morton Arboretum

Family (English) Saxifrage
Family (botanic) Saxifragaceae
Tree or plant type Perennial
Native locale Chicago area, Illinois, North America
Size range Medium plant (12-24 inches)
Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily)
Hardiness zones Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
Soil preference Moist, well-drained soil
Tolerances Occasional drought
Season of interest early winter, midwinter, late winter, late spring, early summer
Flower color and fragrance White, Other
Shape or form Broad, Mounded, Round
Growth rate Moderate
Wildlife Butterflies, Hummingbirds, Insect pollinators

Size and method of spreading:

American alumroot is often around 1 to one-and-a-half feet wide and 1 foot tall, but the tall stems of flowers can reach 2 to 3 feet. The plant may be propagated through division or seed.

Native geographic location and habitat: (include C-value if appropriate)

American alumroot is native to the Eastern United States. C-value: 10.

Attracts birds or pollinators:

Hummingbirds, butterflies, and small bees are attracted to American alumroot flowers, including the specialist pollinator plasterer bee species Colletes aestivalis. The foliage may attract some flea beetles and aphids.

Leaf description:

The leaves of American alumroot are medium green colored, but cultivars are available with variegation. Leaves grow around the base of the plant (basal leaves) and are attached by long, slender stalks (petioles) that are the length of the leaves or longer. The upper surfaces of the leaves and the petioles are often covered in short hairs, but the petioles can be hairless (glabrous). In warmer climates, the foliage of American alumroot is evergreen, but the amount of evergreen foliage is temperature dependent in colder climates. The shape of the leaves is round with a slightly heart-shaped base (cordate), with seven to nine shallow lobes that have slight serration to the edges (dentate margins).

Flower description:

American alumroot flowers are bell-shaped and grow in groups of branching stalks, with four to five flowers per group (panicle). These branching stalks originate on a long leafless center stem (scape) that rises above the foliage. The scape, branching stalks, and pedicels are covered in short hairs. Each flower has five petals that are often green or creamy white in color, are surrounded by five green appendages (sepals), and have long stringlike protrusions (stamens and style). The stamens will be tipped with orange (anthers). The petals, sepals, and stamens are fused together at their base, forming a cup (hypanthium) around the female reproductive organs (pistils).

Fruit description:

The fruit of American alumroot are small and dry with a seam where they split to release seeds (capsules). The tips of these capsules have two long, narrow beaks that protrude from them.

Plant care:

American alumroot prefers medium moisture, which is important in preventing general foliage decline and potential leaf scorch that can occur in too dry conditions. Clumps should be divided every three to four years. Deadheading spent American alumroot blooms can help to encourage additional blooming. For the best foliage coloration, it is recommended to grow American alumroot in sunny areas with partial shade in the afternoons. They also benefit from a wintertime mulch that can protect them from being pushed out of the ground by cycles of freezing and thawing.

List of pests, diseases, and tolerances:

American alumroot is not susceptible to major pest or disease issues. The unpalatable foliage makes these plants resistant to mammalian herbivores.