Darcy-- no one has mentioned the evil squash vine borer. look up some photos of what 'frass' looks like, and also the moth itself (it's black & red & you will see it flying all over your plant laying its evil eggs). if it has gotten your plants, the eggs may have hatched and the little grubs eat away at the inside of the plant, working their way down to the base. and leaves wilting & turning yellow around the edge is the first sign... eventually you will go outside and your whole plant(s) will be dead overnight. you have to act fast if you want to save them. let us know if you see the signs (the moth &/or frass) & you need more help.

redtitan23, The yellowing may simply be natural aging of the old leaves. I would however take a close look at the plant and see if it has any scale insects. I can't tell from the pictures you've posted, but in image 850 I think I can see a large scale insect (the tan oval near the leaf stem) and a small one on the lower left leaf which is partially visible. If you have one scale insect, you probably have many. If you see sticky clear drips of what initially looks like water drops on leaves, this is another sign of scale insects. If you have scale insects, you can reduce their numbers simply by rubbing them out with your finger, but that is a less than entirely effective method of control since they are often under leaves and on young branches. Meyermike has many postings that tell people what to do about them. I use two applications two weeks apart of a horticultural oil spray in the fall before I move the plants inside, and this year have not seen any scale or other typical pests on my plants.

I've been trying to nurse a lemon tree back to health. I'm in northern Los Angeles (Zone 10). The previous owners of my house planted a young lemon tree under another tree (in complete shade). In October, I transplanted it to a sunny area of the yard. The leaves have always been pale and yellow. I have two other citrus trees (including key lime planted in the ground nearby) - both have rich green leaves and are flowering/fruiting. The lemon tree has had a little bit of new growth since the move, but no blooming. Since March, I've been deep watering once every couple weeks (if it's dry), and the sprinkler runs twice a week. I've fertilized a couple times with fish emulsion and a few handfuls of worm castings. Last month I fertilized with 10-6-4 citrus fertilizer (expecting the leaves to turn green if it was a nutrient deficiency), and it still looks about the same. It seems like no matter what I try, it looks about the same (where as the same treatment is working wonders for the two other trees - no need for citrus fertilizer) The pictures may be a bit deceptive since none of the leaves are really green. There are leaf miners on some of the leaves (but a gardener friend said to leave the leaves alone and the worm castings would eventually help) Any suggestions? Are the leaves of a lemon tree different color from other citrus? Should I dig down and try to look at the roots?

I will tell you a story about pH and iron... 15 months ago in Guatemala City we had a black sand "rain" from a volcanic eruption. Turns out that sand is 18 percent iron; and that my friends, is deadly toxic...killed about 300 small Meyers in my nursery before I figured out what to do, as iron toxicity in a nursery is absurd; after almost a whole day of researching I found a similar occurence in Africa; and the solution was to raise the pH so the plant absorbs less iron (note: afte a year it is still killing my roses, but Magnesium sulfate helps). The bottom line is if the soil or water pH is too low, that actually encourages iron absorption. I suspect that this little tree probably picked some heavy metal toxics in the nursery and it will take a little time to clear it out (Mn, Zn, and Cu toxicity manifests as Iron deficiency. Magnesium shortage (sometimes a problem here in volcanic soils) manifests itself in a very clear Christmas tree shape of green on the leaf with the surrounding parts yellow. As Mike said, and I said earlier, you seem to be doing the right things, the plant appears healthy and growing... so have faith and give the litte guy a chance.