Double Jam by Underground Seeds
Growers reach for Double Jam as a sativa-leaning option, a cross of Jamaican Purple × Jamaica Blue Mountain out of Underground Seeds. Indoors it typically finishes flowering in around 105 days after the flip to 12/12. The environment targets below are the same stage-by-stage bands the Cultivar journal grades real Double Jam grows against.
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Similar strains
| Breeder | Underground Seeds |
|---|---|
| Type | sativa |
| Flowering time | ±105 days |
| Environment | Outdoors |
| Lineage | Jamaican Purple × Jamaica Blue Mountain |
| Descendants | Chocolate Jamaican, Montaña Sur, Montaña Roja |
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🧬 Explore the family: Jamaican Purple · Jamaica Blue Mountain · Chocolate Jamaican · Montaña Sur · Montaña Roja
Ancestry Pedigree
Unknown or Legendary
Original Strains
Cannabiogen
Original Strains
Growing Double Jam: what to expect
As a sativa-leaning plant, plan for a big stretch after the flip (often 100–200%) — flip earlier than feels natural and keep training options ready. Sativa-leaning plants also generally prefer a lighter feed than heavy indicas. Growers familiar with Jamaican Purple or Jamaica Blue Mountain will recognize much of its behavior. Whatever the listing says, the cut in YOUR tent is the ground truth: log feedings, readings, and photos, and let the trends — not the label — drive decisions.
Double Jam FAQ
How long does Double Jam take to flower?
Double Jam typically flowers in around 105 days after switching to a 12/12 light schedule. Individual phenotypes vary, so judge harvest readiness by trichome color, not the calendar.
Is Double Jam an indica or a sativa?
Double Jam is listed as sativa.
What are the parents of Double Jam?
Double Jam was bred from Jamaican Purple × Jamaica Blue Mountain by Underground Seeds.
What environment does Double Jam like?
Standard cannabis bands work well: VPD 0.8–1.1 kPa in veg and 1.0–1.4 kPa in flower, with humidity stepping down from 65–75% as a seedling to 40–50% in late flower. See the stage-by-stage table on this page.
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