Washington Marijuana Seeds: Legal Stores, No Adult Home Grow

Washington was one of the first two states to legalize adult use, through Initiative 502 in 2012. Adults 21+ can possess an ounce of usable cannabis and set amounts of edibles and concentrates under RCW 69.50.4013. But the law never added a home grow right. As the Department of Health puts it, personal home grows are prohibited without a medical cannabis authorization.

Patients are the exception. Under RCW 69.51A.210, a patient entered in the medical cannabis registry may grow six plants and keep 8 ounces from them, or up to 15 plants and 16 ounces if the practitioner recommends more. Authorized patients who skip the registry are limited to four plants and 6 ounces. No housing unit may hold more than 15 plants.

Growing without an authorization can be prosecuted as manufacturing a controlled substance, which is a felony in Washington.

The Cascade crest divides Washington into two climates. The 2023 USDA map runs from zone 4a on high northeastern peaks to 9b in tiny coastal pockets. Near Seattle-Tacoma, the median last frost is March 2 and the first is November 23, about 266 frost-free days.

West of the mountains, summers are dry and mild, but fall rains usually return in late September. Dense flowers ripening in October face a real risk of botrytis, the gray mold behind bud rot, and coastal fog keeps leaves damp. The Olympic Peninsula’s wettest valleys rank among the rainiest places in the lower 48.

East of the Cascades, the rain shadow creates semi-arid farmland with hot summers and cold winters. Spokane gets about 168 frost-free days, from April 26 to October 12, and Yakima about 149, from May 8 to October 4. Mold is rare there, but frost brackets a much shorter season.

If you do not hold a medical authorization, you cannot legally germinate marijuana seeds at home, even though you can buy cannabis at a licensed store. Authorized patients should register with the Department of Health to get the higher plant limit.

Home grow bills appear almost every session. The 2026 version, SB 6204, would have allowed six plants per adult and 15 per household, but it stalled in the Senate Rules Committee.

Washington’s licensed producers show how much the Cascades matter. Many licensed outdoor farms sit east of the mountains, where sun and dry air ripen plants cleanly, while western growers rely on greenhouses to dodge October rain.

Many Washingtonians are waiting on a home grow law, while authorized patients need seeds now. Either way, read our explainer on how US seed laws work before you order, because the federal treatment of viable high-THC seeds changes on December 11, 2026.

West of the Cascades, damp air is the main storage risk. Keep seeds sealed with a silica packet in the fridge, out of the light, as described in our seed storage guide. Only patients with a valid authorization may germinate them.