The irrigation system is the expensive part
Plants can be replaced for a few hundred dollars. A cracked backflow preventer, a split manifold, or a burst lateral line is a different conversation, and it is the single most common freeze call we get.
Water expands as it freezes. Anything holding water above the frost line, above ground, or in an uninsulated enclosure is at risk. That means the backflow assembly first, then any exposed piping, then heads that sit in low spots where water collects.
Shut the system off at the controller so it cannot run a cycle during the freeze. Then shut the water off at the isolation valve and drain what you can. Insulate the backflow assembly with a purpose-made cover or wrap and a bucket, not a bath towel, which soaks up water and holds it against the brass.
What actually kills plants in a freeze
It is rarely the air temperature by itself. It is the combination of how cold, how long, how much wind, and whether the plant went into it dry.
Dry soil is the biggest amplifier and the easiest to fix. Water holds heat, so soil with moisture in it releases warmth overnight and buffers the root zone. A deep watering a day or two before the freeze does more for plant survival than almost anything else you can do, provided the system is drained afterward.
Mulch matters for the same reason. Two to three inches over the root zone insulates the soil and slows how fast it gives up heat. It will not save tender foliage, but it protects the part of the plant that actually determines whether it comes back.
What to cover and what to leave alone
Cover tender ornamentals, anything newly planted that has not established roots, and container plants that cannot be moved. Use fabric, a sheet, or frost cloth, and get it to the ground so it traps ground heat rather than just draping the top.
Do not use plastic against foliage. It conducts cold straight through wherever it touches and often does more damage than no cover at all.
Established live oaks, mature crepe myrtles, and hardy natives generally do not need covering. Trying to wrap a mature tree is wasted effort, and the damage on those is usually limited to foliage that recovers.
The mistake almost everyone makes afterward
Do not prune the damage right away. Brown, mushy foliage looks terrible, and the instinct is to cut it all back the first warm afternoon. That damaged material is still insulating the living tissue underneath, and another freeze may be coming.
Wait until the danger has passed and you can see where new growth is actually emerging. Then cut back to living tissue. Plenty of plants that look completely dead in January push new growth in March.
The exception is anything that has become a hazard, like a split limb over a walkway or a driveway. That gets dealt with immediately.
What to check once it thaws
Run the irrigation system zone by zone and watch it, before you rely on it again. Freeze damage often does not show until the system is pressurised, and a split line can run for weeks underground before it surfaces on the water bill.
Check the backflow assembly for cracks and weeping. Check heads in low spots. Look for soggy areas that appear once the system runs but were dry before the freeze, because that is where a lateral line usually split.
If you would rather not do that yourself, a system check is exactly the kind of thing our WaterWise annual service covers, and we would rather find a cracked backflow in February than have you find it in June.