I am trying to make my sim get his LTW ( 8 perfect plants ) and I picked the perfect quality death plant from the grave yard and it got me thinking. which houses arround sunset valley have plants and/or PERFECT plants in the backyard? Are there any?

I haven't checked out every plant, but the ones I've seen are always normal quality.

Have your sim plant the normal quality. Then when you get nice quality produce plant that and so on. That's how you get perfect quality.

Also look at this thread if you need more help. I think it should be stickied....
Gardening FAQ

You do have to grow the perfect plants yourself to fulfill this LTW (it was the first one I did). And No, there are no perfect plants on other lots. I did it by planting 8 different plants and at each harvest I would replant 1 of the harvested items. I would also delete the old one even if it was still producing jut to keep the size of my garden manageable. Do take the time to read through the Gardening FAQ. It will help you a great deal.

The Boyd Wainwright house has flamefruit. Otherwise the way to find out is put your sim doing something, or put game on pause, pan the camera away from your lot and zoom in on and examine the other lots individually to see who's got what on their lot.

I'm pretty sure I've seen neighborhood maps somewhere that list where certain plants are found. Just exploring the neighborhood works, too!

I haven't paid attention, but as Sisaly said, I'm pretty sure most of them are normal quality (although I did also notice that the death flower bush was perfect).

They are normal quality, but some fruit from normal plants are nice and a few are very nice, so you plant the very nice one and some nice if you don’t have enough. At higher gardening skills you plant will be one to two levels higher than the seed again. You harvest some great fruit and plant excellent plants, after that you get outstanding seeds who become perfect plants.

For uncommon, rare and special seeds it’s best to search for seeds on the ground, around the science dome and graveyard are good places to search, the seeds can be of any quality even perfect so you can usually manage perfect plants in two generations for most plants. I was able to get the lifetime reward in week two, best of all, as soon as you have 8 different perfect plants on the lot any sim with the gardening lifetime reward cash it in.

Remember to fertilise growing plants to have them grow up faster.

I've had sims that plant great plants (got from a harvest) and after they are planted in the ground, they show up as perfect plants, but this is only for certain plants, not all of the great ones become perfect, usually it's the tomato, apple and lettuce that becomes perfect this way or it will be 2 of those and the grape that become perfect. That is with sims with level 10 gardening and the super green thumb reward. They didn't have to have the green thumb trait to accomplish it.

I made a park with virtually all perfect plants including a few Omni plants a long time ago. You can harvest from the park and then plant on your home lot...

http://forum.thesims3.com/jforum/posts/list/69715.page