Sulphur Cosmos, Mexican Aster
cosmos sulphureus
Also known as: ["Sulphur Cosmos","Mexican Aster"]
Overview
A vibrant annual flowering plant native to Mexico, known for its bright yellow to orange daisy-like flowers.
Benefits & Perks
["long-flowering","disease resistant","deer resistant","wildlife attractant (bees, butterflies, birds)","drought tolerant","low maintenance"]
Botanical Classification
| Phylum: | Magnoliophyta |
| Class: | Magnoliopsida |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Cosmos |
| Botanical Name: | Cosmos sulphureus |
Plant Characteristics
Basic Information
- Category: Flowers
- Suitable Location: outdoor garden bed in full sun exposure
- Suitable For:
- Is Weed: No
- Allergenicity: low
Environmental Needs
- Climate: {"temperatureRange":"10–35°C"}
- Hardiness: {"zones":"8–11"}
- Misting: rarely required, only if grown in very dry indoor conditions
- Drainage: Fast-draining to prevent waterlogging.
- Soil Type: Well-draining, loamy soil with added organic matter; can tolerate poor soils.
Maintenance Level
- Maintenance Level: low
- Toughness Level: high
- Pruning Frequency: Deadhead weekly during blooming season; light pruning as needed for shape.
- Pruning Intensity: Light to moderate; avoid heavy pruning unless necessary to control size.
Care Details
Ideal Sunlight Coverage:
Full sun (6–8 hours of direct sunlight daily); tolerates partial shade but blooms less.
Sunlight Tolerance Tips:
Acclimate plants gradually to intense sunlight; protect from harsh midday sun in hot climates; ensure good air circulation to prevent sunburn.
Care Requirements
Care Difficulty
easyeasy
Sunlight
full sun
Rotate plants for even light exposure; use shade cloth in extreme heat; avoid placing in drafty areas.
Watering
every 7–10 days, or when top inch of soil is dry
Water at the base to avoid foliage wetting; ensure soil dries slightly between waterings; avoid overwatering to prevent root rot.
Soil
well-draining, loamy soil with moderate organic content
pH: Slightly acidic to neutral (pH 6.0–7.0).
Avoid heavy clay soils; mulch to retain moisture; test soil pH annually.
Temperature
Warm temperatures (65–85°F or 18–29°C); thrives in heat; sensitive to frost.
Avoid sudden temperature changes; protect from frost; ensure good air circulation in hot weather.
Fertilizing
every 4–6 weeks during active growth
Fertilize less in winter; apply fertilizer to moist soil; use slow-release fertilizer for steady nutrients.
Propagation
Methods
Stem cuttings or seeds; seeds are the most common and reliable method.
Step-by-Step Propagation Guide
- Sow seeds 1/4 inch deep.
- Keep moist.
- Thin seedlings when they have 2–3 true leaves.
- Transplant when 3–4 inches tall.
Best Time: Spring or early summer when temperatures are warm and growth is active.
Environment
Warm (70–75°F or 21–24°C), humid environment with bright indirect light.
Medium
Well-draining seed starting mix or perlite and peat moss blend.
Hormone
Not necessary for seeds; rooting hormone can help for stem cuttings.
Timeline
Seeds germinate in 7–14 days; stem cuttings root in 2–4 weeks.
Tools Needed
Seed trays, potting mix, water spray bottle, labels.
Quick Tips
Use bottom heat for faster germination; thin seedlings to prevent overcrowding; harden off seedlings before transplanting.
Pruning & Repotting
Pruning Guide
Method
Snip spent flowers just above a leaf node; trim leggy stems to encourage branching.
Pruning Plan
Deadhead spent flowers to encourage continuous blooming; remove leggy stems to promote bushier growth.
Tools
Hand pruners, scissors, or sharp snips.
Checklist
Use clean tools; deadhead regularly; trim only as needed; dispose of pruned material.
Repotting Guide
Best Season
Spring, before the growing season begins.
Pot Size
One size larger pot (e.g., from 4-inch to 6-inch pot); ensure good drainage.
Method
Gently remove the plant; trim any circling roots; place in a slightly larger pot with fresh soil; water thoroughly.
Suggestions
Repot only if the plant becomes root-bound or outgrows its container; generally not necessary for annuals.
Checklist
Choose appropriate pot size; prepare new soil mix; handle roots carefully; water after repotting.
Advanced Care Tips
Watering Mastery
Watering Checklist
Check soil moisture before watering; water deeply; ensure drainage; avoid wetting foliage.
How to Apply Water Properly
Water thoroughly until it drains from the bottom, ensuring root zone saturation; water early in the morning to minimize evaporation and fungal issues; allow soil to dry between waterings.
Watering Schedule Tips
Water deeply once a week during active growth; reduce frequency in winter or during dormancy; adjust based on rainfall and soil moisture.
Soil Improvement
Add compost or well-rotted manure for fertility; mix in perlite or sand for drainage; ensure soil is loose and airy.
Temperature Stress Management
Signs of Temperature Issues
Wilting, yellowing leaves, stunted growth, or bud drop in extreme heat or cold.
Cold Stress
Growth slows or halts; leaves may turn purple or brown; plant may die in frost.
Solution: Provide frost protection; move potted plants indoors; avoid planting in late fall or early spring in cold regions.
Hot Stress
Wilting, leaf scorch, or reduced flowering in extreme heat; soil may dry out quickly.
Solution: Water deeply and mulch to retain moisture; provide afternoon shade if possible; avoid fertilizing during heat stress.
Fertilizing Guide
Fertilizing Checklist
Check fertilizer type; dilute correctly; apply to soil, not foliage; follow seasonal schedule.
Fertilizing Method
Use balanced liquid fertilizer diluted to half strength every 4–6 weeks during growing season; avoid over-fertilizing to prevent leggy growth.
Common Problems & Solutions
Toxicity Warning
Cats
Non-toxicCosmos sulphureus is not considered toxic to cats. The plant does not contain any known toxic substances that would harm felines if ingested or contacted.
⚡ Toxic If:
Generally non-toxic
Dogs
Non-toxicCosmos sulphureus is not considered toxic to dogs. There are no known toxic compounds in this plant that would pose a risk to canine health if ingested or touched.
⚡ Toxic If:
Generally non-toxic
Humans
Non-toxicCosmos sulphureus is not considered toxic to humans under normal circumstances. It does not produce any known toxic compounds that would cause adverse effects upon ingestion or contact.
⚡ Toxic If:
Generally non-toxic
Frequently Asked Questions
Q: How tall does Cosmos sulphureus grow?
A: It typically grows to 2–4 feet tall.
Q: Does Cosmos sulphureus require full sun?
A: Yes, it thrives in full sun with at least 6 hours of direct sunlight daily.
Q: Is Cosmos sulphureus deer-resistant?
A: Yes, it is generally resistant to deer browsing.
Quick Reference
| Family: | Asteraceae |
| Care: | easy |
| Light: | full sun |
| Water: | every 7–10 days, or when top |
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