How should I integrate my exterior lights to an existing Lutron system?

Where this came from: this question was asked on r/homeautomation — not here. We answered it there, in public, and this is that answer.

Before anyone can give you a real answer, two things matter: which Lutron system you actually have (Caseta, RA2, RadioRA 3, HomeWorks QS or QSX — the processor model or what the app calls itself), and what the "Luminaire box" actually is. If it's an FX Luminaire Luxor controller, that's the one landscapers pick most often, and your integration problem isn't a defect. Luxor does its own zoning and colour over the low-voltage side with its own protocol and its own schedule. Lutron has no idea any of that exists. Your landscaper didn't do anything wrong; he installed good gear that simply isn't a Lutron product.

So the honest answer is that in most of these houses you don't need to replace anything, and you don't need to hire anyone. What people actually want from "integration" is: exterior comes on at sunset, goes off at 11, and one keypad button kills everything outside. You get all of that by letting Lutron control power to the transformer and leaving the zone and colour work in the landscape controller. Lutron processors have an astronomic timeclock built in, so sunset/sunrise offsets and the "all exterior off" button live on the Lutron side where the rest of your house already is.

Two things I'd be firm about if you go that route. Do not put a landscape transformer on a dimmer. Switch or relay only, and mind the inrush on a magnetic transformer — I'd want a proper contactor or relay module doing the actual switching rather than leaning on the rating of a small in-wall switch, and I'd have the electrician confirm the load before anything gets ordered. Second, pick one master for the schedule. The failure I see over and over is Lutron turning the transformer on at sunset while the landscape controller still holds its own timer, and now two systems are fighting over the same lights and the homeowner thinks the Lutron is broken. If Lutron owns power, the landscape controller's internal schedule should be set to always-on or its equivalent, so it just runs whatever scene it was left in when it gets voltage.

Where it gets more expensive is if you want individual zones or colour changes on a Lutron keypad. Lutron can't reach those, because the zoning happens downstream of the transformer. That takes a bridge — a Control4 or similar controller talking to both sides — and honestly I'd only do that if you already have or want a Control4 system for other reasons. Buying a controller purely to put four landscape zones on a Lutron keypad is not a trade I'd make. There may be a cleaner path depending on your exact controller and Lutron generation, but I'd have to check the current driver and integration options before I told you it exists, and I'm not going to guess at that in a forum post.

If you post a photo of the label on the landscape controller and the transformer, plus the model off your Lutron processor, I'll tell you which of the above you're actually looking at and whether it's a fifteen-minute programming change or a real project. Disclosure: I'm a Lutron dealer since 1999 and I do remote Control4 and Lutron work for a living, so I have a dog in this fight, but the switch-the-transformer answer above is the one I give people for free because it's usually the right one.