How to encourage an aquarium plant to carpet on it's own?

I have a small 10 gallon planted aquarium with Staurogyne repens as the main plant. My long-term goal is to have the S. repens cover most of the substrate. The substrate in my aquarium is organic soil covered with Eco-Complete substrate. I’ve had the S. repens in the aquarium for more than 6 months and it seems to be growing just fine, but it won’t spread across the substrate on it’s own. I have been trimming and manually propagating cuttings to spread it around. Is there any way I can encourage the S. repens to carpet across the substrate on its own?

(CO₂ is not an option)