perennial flower
Swamp milkweed
The milkweed to choose for rain gardens and heavy soil.
Growing Profile
- Hardiness
- Zones 3a-9b
- Sun
- FullPartial
- Soil
- ClayLoam
- Water
- High
- Deer pressure
- Seldom damaged Use as a deer browsing cue, not a guarantee; heavy deer pressure can override resistance ratings.
- Black walnut
- Mixed or uncertain Use as a black walnut / juglone planning cue; tolerance varies by cultivar, soil, and distance from the tree.
- Planting depth
- Set the crown at the same level it grew in the nursery pot.
- Container min
- 2+ gal (good)
- Goals
- Pollinators & wildlifeCurb appeal & colorNative plants
Harvest & Use
- Window
- pink summer bloom
- Output
- 3-8 weeks of bloom/year
- First output
- 1-2 yrs
- Best for
- Pollinators & wildlifeCurb appeal & colorNative plants
Timing: pink summer bloom. This profile tracks 3-8 weeks of bloom/year with a harvest or display window of 3-8 weeks where defensible.
Plant photos
What it looks like in the garden
Use these photos to compare the plant's leaves, stems, flowers, fruit, and overall habit before you buy or plant.
Photos show a representative plant in the garden. Fruit color, size, and growth habit can vary by cultivar, season, nursery stock, and site.
Photo sources: Photo by David J. Stang / Wikimedia Commons (CC BY-SA 4.0)
Quantitative Profile
- Full output
- 2-3 yrs
- Mature size
- 1-5 ft H x 1-3 ft W
- Spacing
- 1-3 ft apart
- Planting depth
- Set the crown at the same level it grew in the nursery pot.
- Container min
- 2+ gal (good)
- Productive life
- 3-10 yrs
- Difficulty
- 1/5
- Reliability
- 4/5
- Data quality
- Medium profile, No pound-yield source
Pound return is the stock-style yield metric. These are planning ranges for comparing plants, not guarantees. Cultivar, rootstock, climate, soil, pruning, pest pressure, and wildlife can move actual results.
Planting Checklist
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Right-size container with drainage
Containers / Before plantingUse a container large enough for mature roots, with open drainage holes to prevent root rot.
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Expanding container potting mix
Containers / Before plantingUse a lighter container medium instead of dense garden soil in pots and grow bags.
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Hose timer
Watering / Install at plantingKeep new plantings and containers from drying out during establishment.
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Drip irrigation kit
Watering / Install at plantingDeliver steady root-zone moisture with less leaf wetness and less water loss.
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Organic mulch
Soil / After plantingHold soil moisture, suppress weeds, moderate soil temperature, and protect shallow roots.
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Hand trowel
Tools / Planting dayPlant starts, herbs, flowers, bulbs, and smaller container plants at the right depth.
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Shade cloth
Protection / Heat wavesReduce heat stress for cool-season greens, tender transplants, and containers in hot sun.
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Finished compost
Soil / Bed prepImprove bed structure and organic matter before planting annuals, perennials, shrubs, and trees.
Planting Strategy
- Planting depth: Set the crown at the same level it grew in the nursery pot.
- Container minimum: 2+ gal (good). Use 2+ gal per plant, or wider mixed containers with similar water needs.
- Start with one plant when testing fit in a new bed or container.
- Use the pairing map below to choose nearby companions or compatible varieties.
Risk Factors
- Match the site first: full, partial light, clay, loam soil, and high water.
- Use 1-3 ft apart as the first spacing model; adjust for hedges, trellises, containers, or local guidance.
- Plan around mature size: 1-5 ft H x 1-3 ft W.
- Native-plant matches are starting points; confirm regional nativity, straight-species versus cultivar status, and local invasive guidance.
- Local drainage, pests, chill hours, wildlife pressure, and microclimates can change the result.
Related Planning Guides
Comparable Plants
Companion Plants & Pairings
Compatible Cultivars
Repeated pollinator-friendly blooms work better as a patch than as isolated one-off plants.
Use it: Plant several of the same species together, then repeat the pattern nearby so pollinators can forage efficiently.
Plant Nearby
Native grasses and flowering forbs are more resilient and legible when planted as a matrix instead of isolated single specimens.
Use it: Use grasses as structure, repeat 3 to 5 forb species in drifts, and include spring, summer, and fall bloom windows.
Wet-site plants can anchor rain gardens and low spots together where average garden perennials would struggle.
Use it: Group by moisture tolerance: shrubs in the wetter anchor zone, sedges at edges, and flowering perennials where water drains within a day or two.
Sources & Methodology
This guide combines hardiness range, light, soil, water, harvest timing, traits, supplier links, plant relationships, and quantitative planning metrics. Pairings are screened for practical garden fit.
Quantitative values use extension and botanical-reference ranges where available. For less-studied cultivars, similar crops fill gaps conservatively. Ranges are intentionally broad so the profile stays useful without pretending to be exact.
Planning sources: NC State Extension Gardener Plant ToolboxMissouri Botanical Garden Plant FinderK-State Extension Master Gardener Handbook - Herbaceous PlantsUniversity of Maryland Extension - Types of Containers for Growing VegetablesIllinois Extension - Growing Vegetables in Containers
Supplier search: Amazon. Search links are not paid placements unless explicitly marked; affiliate listings may earn a commission. Last reviewed: 2026-05-31.