Washington state has legalized marijuana for personal use which means you do not need to obtain a card/recommendation to purchase marijuana from a dispensary or delivery service for recreational purposes.
That said, there is a medical marijuana program in Washington. To become a marijuana patient in WA you must get a medical marijuana authorization from a healthcare practitioner permitted to authorize marijuana for medical purposes; this allows you to grow four plants. Medical cannabis patients with a valid WA medical marijuana authorization can choose to join the state’s medical marijuana medical marijuana authorization database and get a medical marijuana card from a medically-endorsed marijuana retail store. This allows you to grow up to 15 plants and purchase products sales tax-free.