Hello Lisa and everyone,
Your Lantana certainly looks unhappy and I can add some commentary which may help sort it out though for reasons you will read about, I have mixed feelings about this particular plant.
In South Africa it has been declared a Category 1 invader plant which means that it must be removed from the garden immediately and destroyed. I think it is such a pretty and useful plant but it is a water guzzler and can if given a chance just take over in the garden; though is a container some measure of control is possible from its wide spreading roots.
Now when I discussed this last with my nurseryman Mike, he said there are some cultivars which are still sold in nurseries here (but these are non-seeding and sterile cultivars) and he recommended just leaving it off a shopping list to be safe. I thought this was such a pity because it is very pretty, colourful, invites bees butterflies and hummingbirds into the garden and is a practical bushy plant good with cascading down steep slopes and helping stabilising ground and with soil erosion. All of that having been said though, the berries can be poisonous, the leaves definitely are and there has been stock loss reported here in SA (not sure about USA).
I was a sad gardener who removed a lot of it from my back garden and must say I really miss the fab show it gave. I have replaced it with Bougainvillea which will hopefully give as good a show one day. I still see a lot of Lantana around here in Johannesburg, so not all have removed it from their gardens. Perhaps I will sneak some back?
Lantana needs full sun, acid-ish soil, warm soil, can put up with salty soils so near the seaside it does well. I used to go to a seaside hotel called the Oyster Box for annual hols where they had masses and masses of yellow Lantana cascading in bursts of colour and beauty. I haven�t been there for many years now, I wonder if they have heeded the injunction to remove it from their gardens?
Like most plants it needs good drainage but in general will die in cold wind or even a smidgeon of frost, hates the cold. When they are baby plants keep them moist and give them a thorough good soaking weekly. They are drought/dry condition tolerant but will not grow if they dry out completely. They are another plant that hates wet feet but the roots must get water.
Now to your picture. You say the soil is very dry (yet see the leaves while wilted are still green). This says that maybe the watering was too surface and while it looked like you had watered or they were wet from rain say, the roots never got access to the water. I would put the pot in a bucket of water, let all the bubbles happen, leave it there for 15 minutes or so then hang it up again. I would also prune it back so the fronds are level with the pot bottom and keep pinching back to strengthen the stems for about a month then just let it grow willy nilly; your container will contain it well enough. I would also give it a liquid fertiliser once a month. But that is what I would do. I am not sure you will read that anywhere! I would also put it in a larger hanging pot (maybe a basket type lined with coir or moss as an alternative) or, actually I would just plant it out in the garden, let it run under control � if that makes sense and it suit your conditions.
Must have sun. If no or too few blooms, stop feeding. Do not over water. Play Beethoven�s 5th symphony in full at close quarters and see what happens! Seriously!
Cheers