A "Sprout Monster" is a new kind of Effect Monster, like Tuner Monsters needed to perform a Bloom Summon for a Bloom Monster. All Sprout Monsters have a condition that has to be fulfilled before they can be used for a Summon. Those conditions can range from easy ones (e.g. Can be used for a Bloom Summon if this card destroyed a Monster by battle during this turns Battle Phase.) to very situational (e.g. Can be used for a Bloom Summon if you control at least 3 face-up Continuous Spell Cards.).