Watermelon Runtz is an indica-dominant feminized seed from Silent Seeds, the Rotterdam seed bank that calls itself the heir to Dinafem Seeds. It crosses Watermelon Zkittlez with Runtz and sits in the Silent Seeds exotic feminized line.
What stands out is its size outdoors. Silent Seeds rates the plant at 2.5–3 meters tall with 1,200–1,400g per plant, while indoor gardens can expect 450–550g/m² in 58–65 days of flowering.
Watermelon Zkittlez and Runtz
Both parents trace back to the Z. Leafly lists Watermelon Zkittlez, also called Watermelon Z, as an indica-dominant cross of The Original Z and Watermelon, testing around 24% THC. Leafly names limonene, caryophyllene and myrcene as its dominant terpenes and pegs it as an end-of-day strain.
Runtz is the better-known half. Leafly credits the Cookies Fam with the Zkittlez × Gelato cross and the Runtz crew, led by Yung LB out of Long Beach, with making it famous. Runtz was named Leafly Strain of the Year in 2020 and has since spawned more than 20 variations worldwide, from Pink Runtz to Blue Nerds. Leafly also notes its purple to lime-green coloring.
Putting the two together doubles up on Zkittlez ancestry, with Gelato entering one generation back through Runtz.
How Watermelon Runtz grows
Silent Seeds describes a relatively slender plant that throws numerous side branches. Those branches finish with dense, spherical flowers coated in resin, and the plant can stretch well past head height in an outdoor garden.
Indoors, Silent Seeds sets the flowering window at 58–65 days. The breeder puts indoor yield at 450–550g/m², and outdoor plants at 1,200–1,400g each, which is where the 2.5–3 meter height comes into play.
Silent Seeds lists THC at 18–22% and CBD under 2%. Those figures come from the breeder and cover the seed line, not any single harvest. It describes the flavor as fresh-cut watermelon with tropical fruit and a cream cake finish, landing in fruity Kush territory overall.
Silent Seeds and the Dinafem legacy
Silent Seeds operates from Rotterdam in the Netherlands under Synex Group. The team includes former Dinafem staff, and the company claims more than 20 years in seed production. It still sells select Dinafem-era genetics such as Moby Dick and Critical+ 2.0.
The catalog runs across feminized, autoflowering, CBD-rich and fast-flowering seeds. Silent Seeds also works with outside names, listing partnerships with Julian Marley, Sherbinskis, Lemon Tree and Cookies, Berner's global brand, the same camp Leafly credits with the original Runtz cross.
Watermelon Runtz sits in the premium exotic feminized collection. It sells in packs of 3, 5 and 10 seeds, with the 3-pack listed at €28.
A Watermelon Zkittlez family tree
Watermelon Runtz is not the only cross built on this parent. Watermelon Mimosa takes the same Watermelon Zkittlez side and pairs it with Jesus OG #10 instead of Runtz, trading candy-family genetics for an OG parent.
Watermelon Runtz goes the other direction. Instead of adding an OG, it stacks a second Zkittlez descendant on top, keeping the cross firmly inside the candy-fruit family. The indica-dominant label from Silent Seeds reflects that heavier Watermelon Z base.