My thoughts actually turned to gardening. If you just leave the plant, it might grow, but it might not. Some take more tending than others, but even the ones that will grow untended are likely to have at least some issues with bugs or weeds, and so mightn't grow to their full potential. A good gardener, though, regularly checks on his plants, removing weeds at the first sign, ensuring the soil is optimal for the plant, protecting the plants from insects and adverse weather. In short, a good gardener doesn't leave things to chance, and his beautiful garden is the result of his hard work.
Similarly, love requires tending and not just leaving things to chance. It seems to me that leaving it to chance is a good way for things to fail. A plant might weather a bad storm or freeze without work, but its death is also quite likely. A couple might weather a crisis without working on their relationship, but many couples split when such crises arise. But if both parties commit to working on their relationship, success is much more likely. I would argue that love will definitely grow if both are committed to work on it, so one needn't answer that question "I don't know".