Tall Thistle
cirsium altissimum
Also known as: ["Tall Thistle","Field Thistle"]
Overview
A tall, herbaceous plant in the Asteraceae family, known for its spiny leaves and purple flower heads.
Benefits & Perks
["wildlife attractant (bees, butterflies, birds)"]
Botanical Classification
| Phylum: | Magnoliophyta |
| Class: | Magnoliopsida |
| Order: | Asterales |
| Family: | Asteraceae |
| Genus: | Cirsium |
| Botanical Name: | Cirsium altissimum |
Plant Characteristics
Basic Information
- Category: Herbs & Weeds
- Suitable Location: garden bed or container in a location with good air circulation
- Suitable For:
- Is Weed: No
- Allergenicity: moderate
Environmental Needs
- Climate: {"temperatureRange":"5–30°C"}
- Hardiness: {"zones":"4–8"}
- Misting: rarely required, only if ambient humidity is very low
- Drainage: Fast-draining to prevent waterlogging.
- Soil Type: Well-draining, loamy soil with added organic matter; avoid heavy clay.
Maintenance Level
- Maintenance Level: moderate
- Toughness Level: moderate
- Pruning Frequency: As needed, typically after flowering or in early spring to remove old growth.
- Pruning Intensity: Moderate; remove up to one-third of the plant if overgrown, but avoid heavy pruning during flowering
Care Details
Ideal Sunlight Coverage:
Full sun (6–8 hours/day) in cooler climates; partial shade in hot regions to prevent scorching.
Sunlight Tolerance Tips:
Acclimate plants gradually to intense sunlight; provide shade during peak afternoon hours in hot climates; adjust placement based on seasonal light intensity.
Care Requirements
Care Difficulty
moderatemoderate
Sunlight
full sun to partial shade
Rotate plant for even light exposure; use shade cloth in extreme heat; avoid direct midday sun in summer.
Watering
every 7–10 days during active growth, reduce in winter
Water thoroughly but infrequently; ensure soil dries between waterings; avoid overwatering.
Soil
well-drained, loamy soil with moderate organic matter
pH: Slightly acidic to neutral (pH 6.0–7.0).
Use a mix of potting soil and perlite; avoid compacted soil; ensure pots have drainage holes.
Temperature
Prefers cool to moderate temperatures (60–75°F or 15–24°C); tolerates cooler nights.
Protect from frost; provide shade in summer; maintain moderate temperatures for optimal growth.
Fertilizing
every 4–6 weeks during growing season, none in winter
Apply fertilizer after watering to prevent root burn; stop feeding in fall to prepare for dormancy; use a low-nitrogen formula for flowering plants.
Propagation
Methods
Stem cuttings or seed propagation; stem cuttings are more reliable for home growers.
Step-by-Step Propagation Guide
- Take a 4–6 inch cutting.
- Remove lower leaves.
- Dip in rooting hormone.
- Plant in propagation medium.
- Maintain humidity and warmth.
Best Time: Spring or early summer when the plant is actively growing.
Environment
Warm (70–75°F or 21–24°C), humid environment with indirect light.
Medium
Well-draining mix of perlite and peat moss or cactus potting mix.
Hormone
Rooting hormone is recommended to improve success rates.
Timeline
Roots typically form in 3–6 weeks; new growth may take an additional 2–3 months.
Tools Needed
Pruning shears, rooting hormone, small pots, propagation tray, plastic wrap or dome.
Quick Tips
Use healthy, non-flowering stems; maintain consistent moisture; provide bottom heat if possible.
Pruning & Repotting
Pruning Guide
Method
Pinch back tips for bushier growth; cut stems just above a leaf node or bud.
Pruning Plan
Prune to maintain shape, encourage bushier growth, and remove dead or diseased parts.
Tools
Pruning shears, sharp knife, disinfectant (e.g., rubbing alcohol).
Checklist
Disinfect tools; prune dead/diseased parts; shape the plant; remove spent flowers.
Repotting Guide
Best Season
Early spring before new growth begins.
Pot Size
Choose a pot one size larger (1–2 inches wider) than the current one.
Method
Remove plant gently; trim roots if necessary; place in a new pot with fresh soil; water lightly after repotting.
Suggestions
Repot every 2–3 years or when roots fill the pot; necessary to refresh soil and provide space for growth.
Checklist
Select appropriate pot; prepare new soil mix; handle roots carefully; water after repotting.
Advanced Care Tips
Watering Mastery
Watering Checklist
Check soil moisture; water deeply; ensure drainage; avoid wetting leaves.
How to Apply Water Properly
Water at the base of the plant, ensuring moisture reaches the root zone; allow excess water to drain away; water early in the day to minimize evaporation.
Watering Schedule Tips
Water deeply once the top inch of soil feels dry; reduce frequency in winter to prevent root rot.
Soil Improvement
Add perlite or coarse sand for drainage; incorporate compost for fertility; ensure soil is loose and airy.
Temperature Stress Management
Signs of Temperature Issues
Wilting, leaf discoloration, stunted growth, or bud drop in extreme heat or cold.
Cold Stress
Slows growth, may cause leaf damage or dieback in prolonged freezing temperatures.
Solution: Provide frost protection in winter; avoid placing in drafty areas; mulch around the base to insulate roots.
Hot Stress
Leaves may wilt, scorch, or drop; growth may slow in excessive heat.
Solution: Provide shade during peak heat; increase humidity; water more frequently but avoid waterlogging.
Fertilizing Guide
Fertilizing Checklist
Check fertilizer type; dilute properly; apply during growing season; avoid winter feeding.
Fertilizing Method
Use a balanced, water-soluble fertilizer diluted to half strength every 4–6 weeks during the growing season; avoid fertilizing in winter.
Common Problems & Solutions
Toxicity Warning
Cats
Slightly ToxicCats that ingest Cirsium altissimum may experience mild gastrointestinal discomfort. The plant's spines pose a risk of physical injury if ingested or if the cat comes into contact with them.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Dogs
Slightly ToxicIngestion of Cirsium altissimum by dogs may lead to mild gastrointestinal upset. The plant's spines can also cause physical injury if chewed or swallowed.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Humans
Slightly ToxicCirsium altissimum, commonly known as tall thistle, contains compounds that can cause mild gastrointestinal distress when ingested. The plant's spiny nature may also cause physical irritation upon contact with skin or ingestion.
⚠️ Symptoms:
🌿 Toxic Parts:
⚡ Toxic If:
if eaten
Frequently Asked Questions
Q: Is Cirsium altissimum toxic to pets?
A: There is insufficient data to confirm toxicity to pets.
Q: How tall does Cirsium altissimum grow?
A: It can grow up to 6 feet tall.
Q: Does Cirsium altissimum attract wildlife?
A: Yes, it attracts bees, butterflies, and birds.
Quick Reference
| Family: | Asteraceae |
| Care: | moderate |
| Light: | full sun to partial shade |
| Water: | every 7–10 days during activ |
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