After main trunk dies, offshoot of tree bears mystery fruit

Q: We planted what we thought was a lime tree around 10 years ago. After a poorly managed pruning, its main trunk died and an offshoot managed to grow into a main trunk. Now we have a 20-foot-tall, nicely shaped tree bearing an unknown fruit. Its fruit starts out resembling a lime but grows much larger. The clippings and leaves smell like a lime, but the juice is very much like a lemon. We’ve harvested them when they were slightly green, and the taste resembled a lemon. They never turn completely lemon yellow.

A: Your fruit is a rough lemon. The rough lemon was the rootstock, and your dead lime was the scion. The more cold hardy rough lemon survived the low temperatures of your winter (these temperatures usually occur just before daylight) while the more tender lime did not. The lime tree generally freezes at temperatures much below freezing (32 degrees). The surviving, more cold hardy rough lemon (reported to survive temperatures below 20 degrees) was the rootstock and grew into a tree. As such, the rough lemon became the fruit of your tree. Rough lemon is thought to be, by the way, a cross between a mandarin orange and a citron.

The rough lemon is thought to be mostly rind, making it less edible than other types of lemon. Because of its thick rind, the rough lemon is mainly used for citrus rootstock. There are several varieties of rough lemon that can serve as a citrus rootstock, including Florida, Schaub, and Vangassay. Which variety of rough lemon doesn’t make a difference as a rootstock.

Q: My Italian cypress branches began to fall over about six weeks ago. We have lived here two years and for the most part the branches have always been upright. Last year I watered them weekly by hand and this year I put them on drip during the summer and adjusted it to water every two days. I tried researching what the problem might be but have not had any success. New growth appears green. I suspect the change in watering might be the cause.

A: You are probably right about watering and the Italian cypress. Watering Italian cypress causes the tree to grow after watering each time, giving it extra water during the spring and summer months. These types of trees produce sturdier growth that would remain erect if watered less often during the heat.

Italian cypress are Mediterranean trees that come from parts of the world with wet winters and dry summers. Irrigating Italian cypress frequently during hotter months causes them to grow fast, which results in their “floppy” growth. Watering too frequently results in branches that cannot support their own weight. I would guess that might happen when they are getting watered because of watering needed by mesic plants on the same irrigation line. That really presents a problem for you if this is the case. Ideally, the Italian cypress would be better off irrigated deeply and not too often with other similar arid landscape trees such as mastic or Chinese pistache.

You can correct most of what you have by hand pruning these bent stems inside the canopy so that the cuts are hidden. To do that, take one of the long spindly stems and follow it back inside the canopy. Find a pruning location on that stem where there is a side branch or side stem. Remove the spindly growth by pruning it just above this side stem but inside the canopy. This will hide your pruning cut and make it less obvious. Cutting this bent stem at the edge of the canopy will make the cut more obvious and unattractive.

Q: My nectarine tree was planted about two years ago. It has yellow leaves. It gave me some nectarines this year, but they were small. I attributed that to the tree being new. It is about 5 feet tall. I gave all the trees a dose of iron last spring. Not sure what I’m dealing with now. My peach tree, which is next to the nectarine, appears to be yellowing but not as much. Any suggestions?

A: To see if we are dealing with a lack of available iron, spray the leaves. If the leaves turn green after spraying, then it is definitely an iron availability problem. Your spring application of iron worked. But the iron application might have run out of steam because you didn’t follow the label directions.

There are two ways to fix an iron problem permanently: either lower the alkalinity (lower the pH) or give it more iron. To lower the alkalinity (and add organics to the soil), give the wet area beneath the tree compost once a year or less. Rake back the surface layer first. To the wet area of the soil near the drip emitters, add compost. Till this compost in the upper couple of inches of soil, being careful not to damage the roots. Or lay the compost on top of the wet soil surface.

I opt for laying it on top of the soil surface and then letting it bleed into the soil during the winter since it does little to damage the existing roots.

If you lower the alkalinity first, then there is not much iron that needs to be added.

Bob Morris is a horticulture expert and professor emeritus of UNLV. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.