Remove all debris from the gap. Scrape the debris first with a putty knife and clear it out with a shop vac.
Push wood putty that's the same color as the pumpkin pine hardwood floors into small gaps. The wood putty can be formed into the gap and smoothed over with a putty knife.
Sand smooth the wood putty once it's dry, using sandpaper. This way, it will blend in with the pumpkin pine hardwood.
Tint rope using a matching wood stain so it blends nicely with the color of thw hardwood floor. This method can be used to fill long gaps between the tongue-and-groove floorboards. Wait for the rope to dry. The circumference of the rope must fit fully inside the gap.
Push the rope into the floor gap using a putty knife. Once the rope is flush with the floor, the gap will be filled and concealed.