Hello David,

The best time to root poinsettia cuttings indoors in Michigan is late spring through early summer, when the plant is in active vegetative growth and days are long. University sources emphasize that poinsettias root most reliably when cuttings are taken during their vigorous growth phase, typically late spring or early summer. Commercial guidance also notes that poinsettia propagation becomes more difficult under high summer heat, so the earlier part of that window (May–June) is ideal for home conditions. More information at this link:

Propagatingpoinsettias.pdf

Best timing for Michigan indoor propagation

Even though you’re rooting indoors, the plant’s physiology still follows seasonal patterns. You’ll get the highest success rate when:

The mother plant is producing fresh, non-woody shoots (late spring–early summer).

Indoor light levels are naturally higher, reducing the risk of stretch and rot.

Temperatures are warm enough for rooting (70–75°F), which aligns with typical indoor conditions in late spring.

Rooting cuttings in winter or early spring is possible, but success rates drop because stems are less vigorous and indoor light is weaker. 

Preparing the cuttings

University recommendations for poinsettia cuttings consistently emphasize:

Cut length: 2–3 inches with 2–3 mature leaves.

Leaf trimming: Remove the bottom leaves entirely. You may cut the remaining leaves in half to reduce transpiration—this is optional but helpful in a dry home environment.

Latex bleeding: After cutting, allow the milky sap to stop flowing before sticking the cut. This reduces rot.

A rooting hormone (IBA) improves uniformity and speed, though it’s optional for hobby propagation.

Humidity management without causing mold

Poinsettia cuttings need high humidity, but stagnant, wet air encourages Botrytis and stem rot. You can strike a balance indoors:

What to do

Use a clear plastic bag or humidity dome, but keep it propped open slightly for airflow.

Mist the cuttings lightly once or twice a day—don’t soak the medium.

Place the pot in bright, indirect light (your east window is perfect; a south-facing window is fine if filtered).

Keep the medium moist but airy. Your bark/grit mix is good; poinsettias dislike saturated soil.

What to avoid

Fully sealing the bag (this traps condensation and encourages mold).

Allow leaves to touch the plastic.

Overwatering—poinsettias root best in porous, fast-draining media. More information at this link:

Propagatingpoinsettias.pdf

If mold appears, increase ventilation and reduce misting frequency.

Temperature and light

University propagation guidelines call for warm temperatures (72–82°F) for rooting, but you don’t need greenhouse precision. Indoors, aim for:

Day: 70–75°F

Night: 65–70°F

Light: Bright but not direct midday sun; morning sun is ideal.

Avoid drafts and cold windowsills at night.

Sanitation to prevent rot

This is one of the biggest success factors:

Use clean, sharp tools (10% bleach or alcohol wipe between cuts).

Use fresh potting mix—never reuse soil.

Remove any fallen leaves immediately.

Don’t overcrowd cuttings; leaves should not touch.

Additional tips for higher success

Stick cuttings 1 inch deep into the medium (consistent depth improves rooting). More information at this link:

Propagatingpoinsettias.pdf

Keep cuttings shaded from harsh sun for the first week.

Expect rooting in 3–4 weeks under good conditions.

Once rooted, gradually acclimate them to lower humidity over 5–7 days.

I hope this helps!