It was funny because when I went to answer your question an advertisement for Green Giant corn popped up! How apropos is that?
A significant impact lightning (cloud to air or cloud to ground) is its ionization effect. In soil the lightning can allow the soil to leach with salt and hold more moisture. Otherwise it would be very dry, even after a rainfall - like sand on a beach. As ionic bonds breakdown the water is then slowly released whereby plants can absorb the water by using less ENERGY. A point of clarification is needed. Between periods of rainfall or irrigation, ionized soil from lightning can retain water that can be slowly released to a plants roots. Too much saltiness (salinity) combined with ionization and not enough free water (rainfall or irrigation) can stress plants and their budding/flowering systems. But in general, without ionization of the soil by lightning or some other natural process, soil would become too dry for many plants to be able to thrive between periods of rainfall.
Ionization of air particles allows the air to retain greater amounts of moisture and thereby weather systems can form and move allowing moisture to fall back to earth. Lightning ionization can also act as a massive air filter by suspending fine particles of dust by the charges associated with lightning and ionization.
I hope that the two processes I briefly highlighted above give you a greater appreciation of the importance of lightning on the environment as it impacts living organisms, especially plants.