Hi Dave,
welcome to the forum.
A lawn mower requires quite some energy, most of them about 1 1/2 DIN-hp (approximately 1,100W), but many of them even more.
If you charge a fairly good battery with solar power your lawn mower will work. The question is the weight of the battery, which adds on to the total weight.
Also, to charge the battery you'll need a powerful solar panel.
Just lean back and imagine the difference concerning expenses for that project.
Boncuk