Alkali-marsh Butterweed
Senecio hydrophilus
Care
part shade
Standing
3–7ft tall
Prized
Alkali marshes and wet meadows of the Central Valley and adjacent areas, below 1000 ft elevation.
Care Guide
Planting
Plant Alkali-marsh Butterweed in partial shade in soil that can handle standing water - this plant thrives in wet, swampy conditions including alkaline and salty soils where most plants would struggle. Space plants to accommodate their mature height of 3–7 feet, and plan on 1–2 meter spread since they produce multiple stems in a cluster. Fall or early spring planting will give this biennial or perennial the best start in the Bay Area.
After Planting
Water consistently to maintain the wet conditions this plant craves; unlike most garden plants, it actually prefers standing water and won't tolerate drought. Don't prune back the hollow, waxy stems - let them grow tall and full to support the large yellow flower clusters. The biggest mistake is planting it in typical well-draining garden soil; Alkali-marsh Butterweed will rot or decline if soil dries out, so save it for a rain garden, pond margin, or other naturally wet spot in your landscape.
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Wildlife Supported
Insects
caterpillars feed on foliage during spring-early summer development
fungal infection on aerial plant parts
larval host plant for spring-summer generations
larval development on plant tissues spring through early summer
caterpillar host plant during spring and early summer