You don't say how big your plants are, but I think you need more plants for 'mass quantities' of pesto, at least double or triple the number of plants you have. Basil likes full sun, so the ones on the east might grow a bit slower than the one getting afternoon sun. I grow mine on the west side of the building and they get several hours of full sun. I started mine from seed and they are still only a few inches tall. It's been rainier than normal here lately so they aren't growing very fast, but I know when it gets warmer they will take off. It's hard to wait, but my pesto making is still a month or two away.

In the past, I have made massive quantities of pesto from 6 plants planted among the tomatoes. I keep the flowers nipped and pinch them so they'll bush out.
This year with all of our strange weather in CA, my basil is small, and wanting to flower even when it's only 6"tall!
We're having a heat wave (after NO spring until June, then a week of spring!) Oh my! So many different extremes!!!!!
I have some babies ready to go if the others flake out. I'll probably end up with a million plants in a month or so! LOL

It's been 110! I put them on the east because quite a few AZ growers said they will roast in full AZ heat.
I started them from seed and they aren't much bigger than when I transplanted them two months ago, although do take a few leaves off each week.
I just bought some more seed and some more plants so I'll stick some in full sun tomorrow. I need to get some kind of fence though ad bunnies ate all the basil in my full sun garden which is in my front yard, unguarded by the dobergirl.

Oh, thanks for the succession idea. I've never heard of that with basil! People here often grow it late into the winter with just a bit of protection.
As far as rain, we haven't had any in about three months or so, although they have been accidentally flooded a couple times by irrigation.
How much should they get fertilized? Do they maybe need some sulpher due to our high pH?

I bought a 4 inch pot from HD with 7 plants in it. I assume splitting it up would be best?
I'm going to start some seeds to plant out in August. Or, should I just direct sow?
Why do I have so much trouble with my favorite herb?
Oh, I also have some culantro and lemon grass. For my zone when should I plant these seeds and where? I'm in the Phoenix area. I figured the culantro would have a longer season than cilantro, which I grow in large quantities in the winter. Use it mostly for mint chutney and Asian/Mexican dishes. I've never tried the culantro.
I've really got to get a bunny fence so that I can plant some of my tastier herbs in the sunniest spot. Those darn bunnies even ate my green onions! Didn't touch Rosemary and lavender at least. They love their hot, dry sunny spot. The fennel is doing surprisingly well too, flowering and growing happily.

Good news! I guess the basil decided it was time to wake up since it's only 110 out! It's growing, not much but it's growing.
Something nibbled on the sweet basil but didn't touch the cinnamon basil. The okra and limas ALS have some holes but not yard long or sweet potato.

my basil is not growing after a year and the stem is woody now and weak

Ali: Have you been pruning the flower buds off? It might die off after a single season if you've let it go to seed. Otherwise, give it a lot of sun, mix some compost into the soil, and it should come back. In case it doesn't, you could just take a cutting and root it in some water, and you'll have a whole new plant.