I'd be inclined to look first to an insect infestation, particularly mites.

Al

First, diagnosing a plant problem when able to look at the plants is difficult, doing it over the internet is darn near impossible in many cases. There are many things that can result in the description you gave and this is what makes proper diagnosis so difficult.

Generally the method I use to attempt a diagnosis is to look at the plant trying to spot any known bad bugs. It is helpful to familiarize oneself with the indicators of mites, aphids, scale, beetles and whatever else is common in your area.

If the check for bugs fails then I move on to disease with fungus being the most common. Often you can see the fungus on the plant itself, but not always. Sometimes fungal issues are on the roots.

Most of the time, but not always, serious damage from anything is a cultural problem. Plants in the wrong soil (ph way off, bad drainage etc) or plants getting water or sunlight in the wrong amounts are all suspects. The wrong cultural conditions weaken the plant making it a target for pests and disease. So, do your reading on what your plants require for optimal health and honestly examine what they are getting. If they aren't getting close to optimal often a change of scenery is the solution although it does sound like your plants are pretty far gone.

To prevent insect damage (before it starts occuring) I like bioneem or neem oil products which make the plants less tasty and so discourages predation. Fungal issues are also most effectively treated with fungicides (synthethic or organic) before the problem occurs. There is some evidence that neem oil products help prevent fungal issues by creating a barrier between the fungus and the plant, but I really don't know that for sure.

Overall though my philosophy is I give a plant one chance in my yard. If I know I am meeting the cultural condtions as best as I can and the plant fails I find something else to grow. I might give a plant a second chance if I think I can do better the next time by either relocating it or protecting it.

Good luck.

Oh, by the way, I have no experience at all with it, but hear much of florida has a serious nematode problem so you might check in with the florida gardeners forum and ask your question there to get more location specific information.

Thank you all.

I checked and did not see any evidence of bugs, so I will treat for fungus.

Mine do this every year at the end of the summer after they get to a certain height. Could it have somrthing to do with the heat stress or growth? Every spring they return and are healthy.

When is a good time to move a Mexican Heather plant if I want to move it. I planted it thinking it was an annual, but have learned that it will come back and is actually a periennial, so I need to move my plants.

Where do you live? Adding your zone and city/state to your user page would be helpful for those wishing to respond to your question(s). I overwinter them indoors here in 6a Michigan.

Al

I this plant a perriennial???

Yes. I grow Cuphea hyssopifolia as bonsai. It's hardy to 9 (if no frost) and in 8 it might survive, but will likely be killed back to ground level in freezes.

Al

So is Mexican Heather a annual or periennial?

Deb, I think it depends on where you live. I know here in zone 7 it is an annual but I think it is a perennial in zones 9 and above.

I lived in zone 7b for most of my life before moving to 7a, and although it was marketed as an annual, Mexican Heather came back every year in 7b.

I have 4 year old zonal geraniums which I want removed and replaced with Mexican heather. I have tried John and Bob's soil optimizer and Bayer All in One Flower Care, but the plants seem to be too old to bloom. Please let me know what soil amendments or type of soil to use before we plant the Mexican heather, so that it thrives.

Mine has come back every year in 7b as well. Hopefully it will do the same this year.
I have one that is about 2 feet wide and 1 foot tall.

I am growing a Mexican Heather as a Bonsai Tree. It's only a couple of years old so it is still tiny and with wire on it. This is my first time growing a Cuphea hyssopifolia ( Dwarf Mexican Heather ) Bonsai tree, so I am not 100% sure if I am caring for it right. Apparently this plant likes "Part Sun to Full Sun" light conditions (preferably shade in the morning, full sun in the afternoon) and "Normal to Moist" Water conditions. That is what I read online anyway =/ Just how hardy is this plant? Currently here in England we're having a small heat spell [Amazing ¬.¬] so it is really warm outside with a lot of sun, and there hasn't been rain for while now. Some of the leaves are turning slightly yellow at the tips, so I am a little worried, and not sure on what to do.

Just to be gloomy, neppyneptune, this one is short-lived and is suitable for zones 10-12.

I don't know what its root system is like. I'm assuming similar to an Erica or an azalea: fibrous and resentful of root pruning. If your current soil mix is not giving the results you're looking for then you could look there first. Consider using Walter Pall's 'aggressive feeding' regime. I did this last growing system and I'm very pleased with the outcomes.

PS When you want to ask a question (rather than answer one) do start your own thread. If you're a newbie to the forums look just under the green tool bar on the page with the list of postings, on the left side, to see the 'new message' link.

Given what you're growing - and your location, you might choose to post on the House Plants forum for getting tips on over-wintering and feeding.

Good luck!