Monday, May 31, 2010

Winter Citrus Problems Showing Up in Spring

     One of the problems of answering gardening questions on the radio: a lack of time to fully explore all possibilities. For example there was this exchange on a recent show.

Cross Section of Rootstock Citrus

Bill asks:
"My young citrus trees (Santa Teresa lemon and Valencia orange) had their first crop this year and the fruit was near worthless. The rinds were very thick and the flesh contained very little juice. In addition the oranges were nearly tasteless. I fertilized them with organic fertilizer according to package directions. I live in Elverta (Sacramento County) and have a sandy clay soil. What might I have done wrong?"

Fred responds:
"It sounds like rootstock fruit. If the fruiting wood goes in decline and the suckers take over from beneath the graft, one of the byproducts is fruit that fits your description: thick rinds, little juice and fairly tasteless. One way to make lemonade out of these lemons, so to speak, is to use the thick rind as a zest.

In his excellent book, "Citrus", citrus grower Lance Walheim explains the importance of growing citrus varieties on different rootstocks. The advantages of citrus rootstocks include keeping the overall height of the tree smaller, offering disease resistance, imparting more cold hardiness as well as better soil adaptation. 

But if that rootstock takes over, possibly if the top part of the tree is killed in a freeze, watch out. Besides inedible fruit, citrus trees that grow from rootstocks such as Flying Dragon and Trifoliate orange have thicker leaves and many more thorns along the stems. 

When you see those sprouts beginning below the bud union, cut them out.

Bill responds:
"No, no this is not root stock. I carefully removed the sprouts of rootstock which was some sort of trifolate orange and I had the trees protected from frost."

Fred responds (while looking anxiously at the clock):

"If it is not rootstock growth, then you may want to take a sample branch or a sample of the next fruit harvest to a good nursery for a positive I.D. Or, take those samples (or pictures of the tree) to Harvest Day at the Fair Oaks Horticulture Center on Saturday, August 7. There will be representatives of  there who can help identify it."

 I would never claim to know all the answers. One big advantage of my job: access to people who do have the answers. I forwarded this question to Mary Helen Seeger, one of the principals of wholesale citrus tree growers, Four Winds Growers.

Mary Helen provides another possible culprit to Bill's dilemma:

"This year, a lot of citrus fruit was damaged during the freeze," she explains. "It is especially noticeable on young trees as there is not much canopy to provide some frost protection.  During a hard freeze, the vesicles burst and then, over time, they lose their juiciness, leaving the fiber of the vesicles. Lemons are more thin-skinned when they first turn yellow and are usable.  During the winter, the fruit grows larger and the rind gets thicker. Oranges do that as well, but not to the extend that lemons do (in my experience.)

Anyway, don't give up on the trees yet.  It has been a challenging year for plants with the wild temperature swings. Keep amending your soil with compost and organic matter to balance the clay.  Keep amendments  away from the trunk. Check out for more tips."

And Mary Helen adds:

"Fred, remember to tell people to make sure large citrus trees in the ground are deeply watered and fertilized this time of year, to prevent "June drop". That's when temperatures rise suddenly, often accompanied by winds."

Consider it done, Mary Helen.


  1. Thanks for the info! And I want to know where Bill got his Santa Teresa Lemon from- I've been trying to find one for a while! They're suppose to be one of the best for making limoncello :)

    I have a citrus question that I'm hoping you can answer. I have a young citrus tree (about 2 yrs old) that had one branch die. I can't see any visable wounds, and so far the rest of the tree is fine. I'm going to cut the branch out- but do you know what could have caused it? Is it old frost damage? I had Christmas lights on my trees every night from December-February, and covered them with sheets when we had frost.

  2. Carri, it is quite possible that the winter cold caused that branch dieback. The symptoms could take weeks to manifest itself. Here is a link from UC, with pictures, of all sorts of problems that attack citrus limbs, trunks and roots:

  3. Click, click, click. Cherry branches without leaves or any visible signs of growth bend at a near 90-degree angle from top to bottom. So unlike the avocado tree located 25 feet away -- which is essentially a DEAD TWIG. Thanks for your help. The Lapin is hanging on.