You may wonder why I messed with a good thing. Why repot a perfectly happy and apparently healthy tree? My original reason for changing the mix was fungus gnats. I was fighting a losing battle with them and realized the soil medium had to change if I was going to get rid of them.Thus began the latest saga with the lemon tree.
When the leaves on my tree started to yellow there were a few possibilities: transplant stress, overwatering, fertilizer issues (too much, not enough?) and pests.
Let me try to go through each of those:
Transplant stress: The leaves didn’t start to yellow until about 3 weeks after, and it was such a strange presentation. I expected to lose some leaves, but not that many. I worried I didn’t get enough of the mix between the roots and there was too much space in there. I debated taking it out to look but I believed the job was done well using the sticks and tamping the pot and tree down a bit. I’m glad I didn’t take it out of the pot again to check because I think it was transplanted well.
Overwatering: The mix was much looser than the previous soil and it was designed to drain well. I just couldn’t believe that this was the problem since I was watering with the same frequency before and after changing the mix.
Maybe I was underwatering?? But there seemed to be more leaves dropping after watering and the tree never looked like it NEEDED water. I remembered my initial debacles with establishing watering frequency so I knew it wasn’t dry.
Fertilizer: The granular was the same fertilizer I had been using very successfully The only change was adding Foliage-Pro but it was very diluted. The other possibility was that the tree was due for another granular feeding and I had waited until after it got used to the new mix before feeding it, maybe it was hungry?
The final option: pests. This is how the problem was discovered (I can only hope this is it).
To avoid overwatering the tree, I started using a wooden chopstick. I pushed it in close to the middle of the roots and let it sit for about a minute. If it came out very lightly damp, I would water the tree in 2 days. The tree was last watered Friday the 17th, I checked the tree in Tuesday the 21st. Since I was used to watering the tree once a week in the old mix, I figured it would need at least a weekly watering in the NEW mix since the new mix is looser and allows more air, thus dries out faster. With the chopstick check, I realized that it would need watering about every 6 days. Okay.
Wondering if the pH of either the mix or the water was off, I ran a pH test on our house water. Apparently, if you use rain water, it is generally neutral. Our house water was alkaline. Now, reading about citrus trees, I know that they (like a majority of plants) like slightly acidic soil conditions.
To counteract the alkalinity of house water, you can add a little white vinegar. But from what I’ve gathered you don’t normally have to do this after repotting because the fresh mix is fairly acidic. After about 6 months, the soil is a bit more alkaline so you start adding white vinegar to make the soil solution more acidic.
Thinking I had added too much lime when I made the mix I added a bit of vinegar to the water with Foliage-Pro. Watered the tree on Thursday and there were leaves down again but not as many as before. I knew the faucet water was alkaline, but I needed to know the pH of the soil to see if I NEEDED to add vinegar. To figure out the soil medium solution pH, I took some of the 5-1-1 mix I had left over and covered it with water. After it sat for a little more than a day, I strained it through cheesecloth and tested it with a basic kit I got from HD:
So, pretty acidic. I guess I don’t need to add vinegar now. I’ll retest in a few months. Good to know the recommendation is correct: you don’t need vinegar at first. I’ll be curious to see what it looks like 6 months down the line.
After watering and waiting, I noticed that more of the leaves had started to yellow and then I looked even more closely…and saw this very, very fine webbing between the leaves and branches. I looked closer and saw these tiny little bodies walking inside!!! Holy CRAP! I turned over the leaves that were starting to look bad…MORE webbing and tiny little creatures. UGH.
My first thought was spider mites because I had seen some postings about them. Quick search on gardenweb and found a recommendation for 50/50 mixture of 70% rubbing alcohol and water. I sprayed e-v-e-r-y blessed leaf top and bottom. I put a fan on it to facilitate drying. I wiped EVERY leaf, a lot fell off. 😦
To wipe the leaves, I used paper towels I soaked in an alcohol/water solution. I tipped the tree on it’s side and twirled it around to look underneath the leaves and make sure I got all of them. I’m pretty sure they were dead since nothing was moving anymore but I wanted them OFF the tree. I then sprayed the tree one last time, especially the growing tips that still had new, folded leaves that prevented me from going too far in.
My camera is not designed for great close-ups but here is what I wanted to show you (all pictures can be clicked to enlarge) :
What’s interesting is that if you just glanced at the tree, you wouldn’t see most of these webbings. The tree had so many leaves and the grow lights were so bright the webbing was pretty much invisible. I had to move branches and change the lighting to see it.
So here’s my thinking: the tree already had these mites and the stress of repotting allowed them to expand their foothold. I had seen some little dark spots under the leaves but ASSUMED it was dirt from the repotting.
Clearly those little dark spots under the leaves were not specks of dirt. Once the tree was stressed, those little buggers expanded until I finally saw the webbing. Interesting to note that the dropped leaves don’t have mites on them, they must move off the dying leaf which only makes sense. How dumb do I feel right now? Learn from my mistakes…LOOK at your ailing plant.
I’ll be ready to spray again. I need to look more closely at my tree from now on. I bet some of those leaves were stress leaves, but certainly not all of them. I hope I have this licked.
One thing to say about Al’s 5-1-1 mix, it makes the pot soooooo much lighter and easier to handle.