I will be the first to tell you that I am not an expert on palms...at all. But I have quickly familiarized myself with the most popular ones around town: Queen Palms, Pygmy Dates, and Sago Palms (which is really a Cycad, but let's not get too technical.) For Palms, the do-or-die moment comes down to the center crown of the plant where new growth shoots out.
Sago Palm center "cone"
If that center "cone" is mushy, more than likely the palm is a goner. You can spray that center part with a copper based fungicide to keep any rotten material from infecting live material, but there really is no guarantee that the plant will re-leaf out this Spring. I DO NOT recommend tearing out any palm until mid April to be sure the new growth isn't going to surprise you later in the season. These are expensive plants to replace, so wait and be sure before you remove them.
Pygmy Date Palm: I did not see any sign of green on this palm, but the new growth area was still firm.
If the center "cone" is hard and intact, more than likely the palm will make it. I've gotten the chance to visit a few of my clients homes that are in North Houston which got much colder than the Cypress area. Their Queen Palms didn't look happy, but they weren't dead. There was a little bit of green left on some of the fronds, which is a good sign that they should survive.
A little green left on some of the inner fronds is a good sign!
In either case, DO NOT remove any dead palm leaves until the palm has had a chance to put on a new set of leaves. The only material that is okay to remove is anything that has already fallen away from the center growth area.
Trim fallen leaves, but leave on any upright growth until new growth appears.
So, if the leaves are still attached and upright, leave them on until you see new growth appear. Leaving the old fronds on helps distribute the plants energy evenly, which will prevent your new growth from appearing gnarled and twisted when it finally pushes out. Once the new growth has appeared and grown out a bit, you can then trim away any dead material from the freeze damage.
Hibiscus and Oleander
Unfortunately, I have yet to find a Hibiscus that I believe made it through the freeze. Every one I've touched and done the scratch test on has been a mushy mess of dead material. You can do this also, not only with Hibiscus, but with all your plants. Scratch the stem: If you find green, you're in business. If you find brown, dead material, it's a goner.
A scratch test will tell you if the plant is still alive.
This one is black inside, and the bark easily pulls away.
Every Hibiscus I've scratched has been dead down to the ground. We may get a surprise later in the Spring with new growth from the roots, but I'm not holding my breath on that one! Personally, I would rip them out and start over. I've had so many people say, "But I've had that one for X amount of years." or "But, my "so and so" gave that to me!" I simply say in return, "It's a plant, not a marriage!"
Oleanders are hit or miss. Some are still green, but a bit frost damaged. Others are crispy critters all the way down to the roots. I've taken the same philosophy on these as I have on the Hibiscus.
Oleander with minor frost damage
Oleander with severe frost damage.
Scratch the stems and if you get green you can wait for them to re-leaf out. If you get brown, either trim them all the way back and wait for new growth from the roots, or start over with new ones. Either way, it will take awhile for the Oleanders to bounce back. They aren't as fast growing as Hibiscus are, so it will probably be a couple of years before they look good again. Patience is a virtue, my friend!
Microlife and Superthrive
I've mentioned these two products before on several other blog posts, but have to mention them again because I believe in their miracles whole heartedly. I've had plants that were sticks come back for me with this combination. Microlife is an organic, slow release fertilizer. Superthrive is vitamins and hormones that are beneficial to stressed, diseased, or newly transplanted plants. I recommend fertilizing everything in your yard with Microlife and then go around and water in the Superthrive on top of that. This combination will help jump-start the life in your soil to get the plants back in shape for spring and summer. While these two can't bring dead back to life, they can help a really stressed plant recover more quickly. The quicker a plant recovers this spring, the better it will be able to survive the heat that will be here before we know it.
I hope I answered some of the concerns many Houstonians have had, but if you'd like to leave a comment below, I'd be more than happy to answer any more you might have!