Jacob's ladder

About Jacob's ladder

Jacob's ladder is named for its leaves: pairs of small leaflets lined up like the rungs of a ladder. In spring it carries loose clusters of nodding, bell-shaped flowers in soft blue, sometimes white, that native bees and bumblebees visit (NC State, Wildflower Center). P. reptans is native to moist woods and stream banks from New York to Minnesota and south to Georgia and Arkansas; P. caeruleum, the taller European species, comes from Europe and Asia (Wildflower Center, Cornell). Both are easy, tidy plants for a shady, moist bed.

P. reptans is hardy in zones 3-8 (NC State, Mt. Cuba); Cornell rates P. caeruleum zones 3-9 and Michigan State to zone 2. It dislikes hot, humid summers and is often short-lived in warm areas (NC State, Cornell).

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Set out nursery plants in spring or divide clumps in early spring or late summer (Wildflower Center, Cornell). Sow seed as soon as it ripens or very early in spring (Wildflower Center). We found no sourced day count to first bloom.

Soil

Moist, humus-rich, well-drained soil; it has little drought tolerance and goes dormant if the soil dries out (Wildflower Center, NC State).

Mix compost or leaf mold into the bed for the moist, humus-rich soil it grows in naturally (Wildflower Center, NC State).

Feeding

• Early spring, just before new growth starts: complete slow-release fertilizer such as 12-6-6. Without a soil test, Clemson suggests 1-2 lb per 100 sq ft for perennials, watered in. Follow a soil test.

Dry soil and hot afternoon sun scorch it; water at the base rather than over the leaves to limit fungal problems (Ohio State, Mt. Cuba).

Harvest

P. reptans blooms in April and May, and P. caeruleum from late spring into midsummer (Wildflower Center, Cornell). Cut faded flower stalks back to the base to tidy the plant, cut down on seedlings and sometimes get a second, smaller bloom (Cornell, Ohio State).

Varieties (8)

Cornell, Mt. Cuba Center, Chicago Botanic Garden and Purdue Arboretum document these 8; 'Blue Pearl' is named without details.

Diseases and problems

Fungal leaf diseases

In the kitchen

Safety: NC State lists no toxicity for Jacob's ladder, and we found no poisoning reports. It isn't a food plant, so don't eat it; old root remedies (see history) are not advice.

Pets: Not listed by the ASPCA. Note that the ASPCA's 'Jacob's Ladder' entry is a different plant, carrion flower (Smilax herbacea), which it lists as non-toxic; Polemonium itself isn't on its lists, so discourage pets from chewing it.