I have been growing outdoors but using extra light to keep them on a 24/0 schedule and will be flowering soon. I live in a warm climate, so I started them in wintertime. Right now spring is starting and days are getting longer.
The plants are an unknown Kush strain and are about 2 1/2 months old. I was hoping to flower them using just the sunlight, but I already have a 13 on / 11 off schedule, and by the end of their flowering it will be about 14.5 on and 9.5 off.
I know this would slow down the flowering, but will it even work? Should I run them on a 12/12 by covering them for a few weeks first or should I keep them going at 12/12 the whole time?
To keep your marijuana plants in flowering, you will need to provide a consistent 12/12 light schedule until harvest.
Any schedule where you have to remember to manually put something to cover your plants at the exact same time every day will be difficult to maintain.
If the light schedule isn't kept consistently, it's likely you'll have issues (hermies) during the flowering stage.
It's important to understand that marijuana plants need to receive 12 hours of uninterrupted darkness every night to stay in flowering.
If they start getting shorter nights, they'll revert back to vegetative.
Marijuana plants need at least 12 hours of darkness every day in order to produce buds and remain in the flowering stage. This 12/12 light schedule must be maintained until harvest.
So if you do decide to cover or move your plants every day, make sure especially that they never get a short night. A short day is okay, but a short night (or one with light leaks) is the main cause of hermies and re-vegging.
I've heard stories of people who have successfully moved or covered their plants every day, but never known someone who tried it themselves. Usually I've heard this technique used to induce flowering earlier, not to be used every day throughout the entire flowering stage.
Theoretically it should work, but I imagine it'd be hard to keep this up every single day for 2-3 months.
Have you considered getting a cheap grow light and just finishing them indoors?
You mentioned that summertime is just starting for you. Therefore another option is to let some or all of your plants to keep growing throughout summer until your natural autumn causes them to start flowering.
You could use twisty ties and LST (low stress training) to keep them short, and they'll have time to grow wide. Even one plant grown this way could gift you with a big harvest to last you through the next winter.