Perennial ragweed
Ambrosia psilostachya · Asteraceae
The gardener's calendar
Ideal time to plant perennial ragweed: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.
ID card
- Family
- Asteraceae
- Type
- Perennial herb
- Foliage
- Deciduous
- Blooming
- July to September
- Adult size
- 60 to 120 cm in height
- Hardiness
- Down to -15°C
- Origin
- North America
- Growth
- Fast
Care
Light exposure
Perennial ragweed thrives in full sun, ideally 6 to 8 hours per day. Bright exposure promotes abundant flowering and a more compact plant. Avoid partial shade which slows growth and reduces flowering.
Watering
Water regularly when first establishing, then moderately once established. The plant tolerates dry soils well in summer. Reduce watering in autumn to prepare for winter dormancy.
Soil
Choose well-drained soil that isn't too demanding in terms of fertility. Perennial ragweed adapts well to poor to average soils, even rocky ones. Avoid overly wet or marshy areas that promote rot.
Pruning and cutting
Prune lightly in spring after the last frosts to encourage dense branching. In late autumn, cut the clump back to ground level. Pinching young stems can create a bushier, more compact form.
Fertilizer
A moderate application of balanced fertilizer in spring is more than sufficient. This plant is undemanding and thrives without intensive feeding. Avoid excess nitrogen which would prolong foliage at the expense of flowering.
Pests and diseases
Perennial ragweed is generally robust and rarely troubled by problems. In overly humid conditions, watch for root rot. Regularly aerate the foliage and clean up debris on the ground to prevent fungal issues.
Did you know?
Perennial ragweed is a native plant of the North American Great Plains, where it plays an important role in grassland ecosystems. Its pollen is known to be highly allergenic, making it a plant to consider carefully depending on your region and individual sensitivities.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
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- SneezewortAchillea ptarmica
- Canadian goldenrodSolidago canadensis
- WormwoodArtemisia absinthium
Tips generated and checked by Viridia — adapt them to your local climate.