The black leaves is your cue you are over-watering.
The black leaves can also suggest the roots are drowning and for that reason you should unpot it, inspect the roots for any sign of rotting, and you will most likely smell it as well. If this is the case, then wash all soil off the roots, remove any damaged roots and any stems that appear damaged.

Into a clean pot, with fresh potting soil that is expressly used for azaleas and other acid loving plants---make sure there is something between the soil and the drainage holes so as to keep soil from clogging up the holes.
Give it as much sun as you can. At this time of season, the sun's intensity is very low...the shortest day of the year is approaching with the winter solstace. So don't be afraid to put it close...but not touching, the window glass.
Later as sun values return in February/March, pull it back from so much light...but still give it good light.
The use of the artificial light is not, I think, doing the plant any good. Forcing the plant to grow when it is in poor health is doing it no favour. Its also prolonging the heat the plant doesn't like.

They like it warm during daylight...so the room temperature of 70 - 75 is welcomed. Nighttime temps are a different matter--55 - 60....usually lower than most homes keep it..but that is appreciated by the plant.
Most times, the plant wont flower if it receives too high nighttime temperatures.

STOP all fertilizing...until the plnat resumes growing.
Never feed a sick plant. Always get it back to health before feeding it.
The soil should be kept moist....not soggy, and water to drainage every watering, dump the excess after 5 - 10 minutes of drainage. Then allow the soil to resume back to its damp stage before watering again.

As is the case most of the time when plants first come from a nursery or garden center, the plant is in its best of health....perhaps even flowering. Then it goes into a home whose temperature does not repeat what it was getting before. There usually is an effect from such change...the plant is put in stress and sometimes loses leaves. This shouldn't be taken as serious unless the leaf loss is major.
Its treatment is not the same, its watering habit might be quite different with different water.

Allow water to gain room temperature overnight--try not use tap water or water that is too cold.

The use of the water tray--with pebbles, is recommended...yes, don't let the water touch the bottom of the pot; this is to provide moisture only.

When the plant resumes its good health and begins growing, you can begin feeding it...between April and November, with a acid-type fertilizer.

Hi, Jessie - How much fertilizer did you apply & how long had it been since the last application? Are you flushing the soil at every wastering to make sure salts from fertilizer and irrigation water are not building up?

Though the plant does appear to have been over-watered, black leaves are NOT an indication of over-watering. Black leaves indicate that the plant incurred damage while the leaves were turgid (full of water). Over-watering causes impaired root function and reduced root metabolism, both of which cause a drought response in foliage. The drought response is the same as if you didn't water the plant, because roots are not moving sufficient water to the canopy, causing leaves to first turn yellow, then abscise (shed) and or turn brown. I suspect that if you have black leaves that it was caused by chill injury.

While an emergency repot into fresh soil may be required if you discover the roots are decaying, there is no need to try to find a 'special soil'. Any free-draining and durable soil is entirely adequate. There is certainly no reason you cannot continue to supplement light by using the cfl. I'm not sure what the previous poster meant by "Forcing the plant to grow when it is in poor health is doing it no favour." This is very confusing because you can't 'force' a plant to grow. It grows when conditions are favorable - it doesn't when they are not. Making conditions more favorable simply ALLOWS the plant to grow, which is nearly always a good thing. Any plant that is not growing is dying.

"STOP all fertilizing...until the plnat [sic] resumes growing. Never feed a sick plant. Always get it back to health before feeding it."

This makes no sense to me and is poor advice. Plants can appear sick for a wide variety of reasons when they are deficient in nutrients. They will not mend themselves unless the missing nutrients are supplied. To tell you to 'never' feed a sick plant is a death sentence to any plant that exhibits either a nutritional deficiency or a condition caused by or related to a deficiency. Plants should have all nutrients present in the soil at all times, whether you 'think' the plant is growing or not, or you are guaranteeing stress. If nutrients are deficient, supplying them is appropriate, regardless of the time of year or whether or not the plant appears 'sick'.

I would:

* Unpot the plant & look/smell for root rot. If you detect none, put the plant back in the pot & be careful about how you water. If you do detect it, remove the soil and prune roots back to sound, viable tissue, then repot into a good soil that drains well & is durable. Ask if you'd like more info about soils.

* If you find no root issues but think the soil is retaining too much water for too long after watering, add an absorbent wick pushed up through the drain hole. Water thoroughly when you do water & then allow the plant to dry down enough that the wick feels dry where it exits the pot. The wick "fools" the water in the saturated layer at the bottom of the pot into "thinking" the pot is deeper than it is. As the water moves down the wick in search of the pot's 'bottom', it drips off the end of the wick, draining excess water from the pot.

Good luck.

Al

Thanks for the advice, jeannie, I will try to find some azalea type potting mix...at this time of year, I hope I can find it, and try a repotting into a clean pot.

The plant is growing, however. At least, even tho it looks like crap, it's still putting out new baby leaves and even one bud. Believe me, after seeing all those other buds fall off, flowering is the last thing I'm hoping for....just want the thing to not die.

We usually keep our house at about 69 or 70 during the day and then down to 65 at nite.

Do you have any idea why some of the leaves are yellowing that way? second photo, bottom center shows the yellowing best. Also, should I get distilled water for it? I have only watered it once so far, but used tap.

oops, tapla, just saw your post after i had posted last. i will read it now. thanks for replying!

tapla, I have only watered once since I got it about a week ago, as I thought my future DIL had been overwatering and it was still kind of moist when I got it. I watered it with miracle grow for azaleas, according to directions and let the water drain thru the drain holes. That was a few days ago.

Do you think I need to use distilled water?

Is there a potting mix sold somewhere like Lowes or Agway that I could use for repotting? I appreciate all your advice.

The black leaves, and even some of the yellowing ones, look like it could still be damage from the spider mites that's just now showing. What does anyone else think?

Also what effect might light have on this? I was under the impression that gardenias required more light than you can easily give them by just setting them near a window (Especially in Zone 5 winters where you're getting fairly short days). If that's the case, wouldn't a lot of leaf drop during the winter months be somewhat expected and inevitable without using a grow light or something similar?

On the contrary, leaves that once were green, then going through the stages of yellowing, browning, eventually turning black is definitely a cue that you are overwatering.
Leaves turn black because they are not able to further take up moisture. The roots are sitting in too much water...forcing the plant to draw water up, until such time, the plant is unable to proceed any further.
Root rot sets in....the leaves are the first sign of any problem that is caused from such watering practices.

At the stage of blackness, it has gone on far too long.
Yellow leaves might be the first sign of overwatering---along with other possible causes...but overwatering, being the one biggest reason for trouble, should be thought of first.
As the water is no longer able to do anything for the plant....even tho, water is sitting only a few inches away...the leaves are unable to draw any more, they are saturated...and so will turn black.

I think one of the easiest ways to have such result is by not having something between the soil and the drainage holes and letting the drainage water sit too long under the plant causing it to draw water it once got rid of, to be drawn back up and if the plant cant use it, it sits there, drowning the roots.

Distilled water is a viable choice if you believe the water from your tap has something in it that might cause problems.
But there are other sources of water without going the distilled route. Bottled water---very common these days...water that has sat for days in a watering can or water from snow you have brought in and allowed to gain room temperature can be used.

Plants react to changes that are abrupt. Cold drafts from floor vents or open doorways can cause yellowing leaves.
Too high nighttime temperatures can cause browning tips and edges.

amccour, I have been wondering about the effect that poor light quality and time may be having on the plant. I don't want to buy an expensive grow light for this one plant....others in my house do fine. Wish I could just stick a special bulb in one of my lamps. Would anything like that help?

jeannie and others, i was pretty sure that the plant had been overwatered before I got it, but when I checked the roots, they seemed fine. The only thing I could smell was the soil. There was no sign of rotting, no debris at the bottom. So now it's looking like maybe it wasn't overwatered after all.

The plant, when on the dry side, was easily lifted out of the pot. But after watering again this morning, not so. I can see roots on sides of the soil but not super crowded or anything, and below, hardly a thread at the bottom of the soil (and NOT because they rotted off, i do know what that looks like). They don't seem root bound, but maybe they are?

I have never had so much trouble with a plant and I would really like to bring this back to better health.

There really seems to be more than one thing going on here. The leaves are NOT going thru a stage of yellow then brown then black.

Many of the nice green leaves are going straight to large black splotches, which eventually take the leaf over completely if the leaf doesn't fall off first. You can see several of those in the first pic. They were green then boom. green and black.

others start green and are yellowing, still with green veins. This seems less pervasive in the plant and less life-threatening.... and I think it's the black that is the worst symptom.

thank you all for trying to help me!!

Hi, Jessie. Whether or not distilled water would be helpful depends on your watering habits and on the alkalinity/ pH of your water. It certainly wouldn't hurt anything to use it, but it may be an unnecessary expense.

While it's important to have nutrients in the soil of plants, even while they appear to be resting, you certainly don't need the full strength dosage described on the package - especially in winter. If there was residual fertilizer in the soil when you recently fertilized according to package directions, the combination might have made salt levels in the soil solution so high the plant was unable to absorb water or nutrients. Salt in the soil solution can pull moisture from leaves by exactly the same mechanism that salt pulls moisture from ham or bacon.

Plants absorb water best when there are NO dissolved solids in it (distilled). The higher the level of dissolved solids, the more difficult it is for the plant to absorb water and the nutrients dissolved in it. The key is to make sure the level of fertilizer is adequate at all times to prevent nutritional deficiencies, but still low enough that it doesn't impede water uptake. Do you see why watering in small sips insures that salts will build up in the soil - even if you aren't fertilizing - only using tap water?

Nothing is going to set the plant right over night. Did you check the roots for rot? Do that first and then you can decide your course. If the roots are not rotted, you should probably flush the soil thoroughly - just in case you are dealing with fertilizer burn. I can guide you through that procedure if you still have interest.

Al

Yes, I don't water in small sips. My second watering was this morning, with no fertilizer, and I flushed the soil...unfortunately with lukewarm tap water but I will use standing or bottled water after this...and allowed it to drain on my sink grate before putting it back in it's outer container. The roots are not sitting in water and there is some airflow around the plant's actual pot.

To me, the leaves look like they are diseased, but I'm no expert.

With my roughly ten year old gardenia the first sign of over fertilizing is dropping of buds. That was among the first symptoms you described. The mites are a big factor, but I would still look at the roots as well. Mine is in a west window, in a cool room all winter in zone 5 after spending summers in a screen porch and does fine with that light/temp regimen. If in a warmer room in winter, it may, indeed, need more light, but I would think a south window would do. If the mites are taken care of, I'd suspect the roots next (repot, change all soil) and go very easy on the fert (if used at all).

tj

The roots look fine, as I mentioned a few posts up. I do know that for a month before my fertilizing (only done once and with good drainage), after the plant was delivered to my future DIL, it was not fertilized. Whether or not it was overly fertilized by the grower/seller, I can't say, but it doesn't seem to have any slow release pellets in the soil, so I'm doubting that it has been over-fertilized. But thanks for the input.