So I transplanted my super healthy looking cucumber seedling outside thinking they had grown enough to survive outdoors. What I didn’t take into consideration was that plants could also get a sunburn. NM State describes this really well but basically this is what’s going on: When you start your plant (in my case cucumbers) indoors from a seed they grow what you may call “shade leaves” which are developed under low light. These leaves don’t have full protection from direct sun light.
In the photo above on the left you can see my cucumber plant was developing white spots around the edges, took a light green color, and was almost crispy to touch only two days after it was transplanted outdoors. To avoid getting your seedlings sun burnt you need to gradually expose them to outdoor conditions. Maybe start with only two hours of direct sunlight a day and over a period of week or two increase this period until they’re fully ready for those strong UV rays from the sun. This is called hardening off.
After you’ve made the mistake I’ve made and transplanted your seedlings outdoors without hardening them off there’s no going back. Your seedling will lose those sun burnt leaves. Now you hope that you’re seedling is still healthy enough to produce brand new sun leaves. During this difficult transition period your plant will need less water since you killed all those poor indoor leaves. But do increase watering as the new leaves start coming out.
On the right hand side above you can see my plant managed to recover from its sun burn and got its healthy dark color back with plenty of new leaves.