Tall Thistle (Cirsium altissimum)

Difficulty: ⭐⭐☆☆☆
(Relatively easy — but must be timed carefully to avoid wind dispersal and bird loss)

Seed Collection Times:

Late summer into early fall — typically August through October

Signs Seeds are Ready:

• Blooms fade and heads become dry and fluffy

• Silky white pappus (fluff) emerges from the seed head

• Seeds (achenes) are attached to the pappus and pull free easily when mature

• Goldfinches often visit plants just as seed is viable — a reliable signal that it's ready

Tip: Begin checking a few days after peak bloom — tall thistle ripens quickly.

Seed Collection Steps:

1. Clip dry seed heads just before or as fluff begins to emerge

2. Place into paper bags or mesh sacks to allow air-drying and prevent seed loss

3. Let dry for 3–5 days in a warm, ventilated area

4. Gently pull fluff and collect seeds by hand

5. Use a screen or light winnowing to separate seeds from chaff

Note: Seeds are heavier than fluff — use a tray or shallow bin to reduce loss.

Germination Tips:

• Seeds are generally non-dormant, but cold stratification for 30–60 days can improve success

• Sow in fall for best results or cold stratify in the fridge

• Germination in 1–3 weeks under moist, warm soil conditions

Note: As a biennial, plants usually flower in their second year and reseed naturally.