Fruit Tree Nutrients

Question from Tom:
I have planted many varieties of citrus and stone fruits in my yard within the last year. They are all low chill selections and should do well in the Rancho Bernardo area of San Diego where I live.

I am comfortable with pruning and watering the trees. What nutrients my trees need is a mystery to me. I am not sure how much fertilizer to use and I am confused by all of the micro nutrients such as iron. Currently I have been using a Kellogg organic fruit tree fertilizer in late spring on the stone fruit. I use Vigoro citrus fertilizer every 2-3 months on the citrus. I sprinkle a few small handfuls under the drip line and water during application.

My citrus leaves have a tendency to eventually become yellow and or pale. Some of my stone fruit leaves have purplish red spots and leaf edges (not curl). My bareroot cherry trees have some yellowing leaves that have been randomly dropping like they would in the fall when going dormant.

My soil is about 70% sand and 30% clay with varying amounts of organic material depending on the area of my yard. By itself my soil has a tendency to dry out in the summer and become as hard as cement. I have placed about 2-3 inches of mulch to keep the soil moist. The soil pH ranges from 6.5 to 7.0. I am concerned that my soil may be part of the problem.

Does it sound like I am fertilizing enough? I am considering hiring a consultant to analyze my situation. Do you have any recommendations?

Answer from Pat:
Fertilizing citrus trees is a big topic handled in depth on pages 63, 64, and 65 of my new organic book and in all my previous month-by-month books. There are several ways to go and choices to be made according to the needs and likes and dislikes of the gardener. Basically, citrus are big feeders and need up to 1 pound of pure nitrogen per year for a mature tree and proportionally less for smaller trees. They also need phosphorus, potassium, and trace elements in lesser amounts. Since I have covered this topic in such detail and length in my new organic book, and because without copying those three pages here I cannot provide all the details I must suggest you refer to this book, either your own copy or go to the library and read it there. Suffice it to say that most home gardeners starve their citrus trees, but also that there is no way or need for an organic gardener to exactly translate one pound of actual nitrogen and other requirements into products you buy on a shelf, though technically that would be one way to go. The real task for the organic gardener is to build up the organic content of the soil which in turn creates the microbial action to create and release natural nitrogen. Many suggestions for what to use are given on page 63 and 64 including the fact that many organic gardeners simply mulch their trees with a layer of horse manure under the canopy and drip line and beyond with horse manure and let the rains wash it in. (Don’t pile manure or mulch against the trunk.) Beginning this late, you have lost the chance to fertilize prior to February bloom. Organic fertilizers take time to work. Nonetheless, mulch the trees and fertilize now with the organic products you have, using more than suggested (of organic fertilizers, only, not of synthetic fertilizers), water in deeply, and continue to feed through the warm seasons of the year.

Regarding deciduous fruits, the jury is still out on feeding these and this is why so little information is out there for gardeners to access. For many years I have been investigating the results of agricultural experiments and trying to translate the best practices of commercial growers into language and methods for the home gardener and arranging it month-by-month as you need it. Fertilizing and mulching deciduous fruit trees is covered in my book on pages 86 and 87. Basically they are much less hungry eaters than citrus trees. Deciduous fruit trees should be fed lightly and never given too much nitrogen or you will get all leaves and little or no fruit, but they appreciate a deep organic soil as explained above. The time to give nutrients is when the buds are swelling in early spring, but with organics, except for fast-acting ones, you can apply a little earlier since they take time to work. See pages 86 and 87 for suggestions of what to use. Be very careful not to over-fertilize. Unless in extremely poor soil they will be fine, so I think what you did by fertilizing with organics in early spring was fine. I wouldn’t overdo it. Water deeply and infrequently rather than shallowly and often, as apparently you are already doing. Next year feed them in early February so the fertilizer will be working by the time buds are swelling and flowers opening.

Pale or yellow leaves dropping leaves on citrus or stone fruits means that you haven’t given them enough nitrogen. Apply a stronger, faster-acting nitrogen fertilizer such as blood meal or guano and water it in thoroughly. Chicken manure would help too since it contains phosphorus and potassium. Purple spots on leaves could mean lack of potassium or lack of trace elements. Nutrients are sometimes locked up in saline soils. Make sure your trees have all the nutrients they need. Apply John and Bob’s, humic acid, kelp and also to increase drainage in heavy soils products containing Yucca schidigera to increase drainage. Please see the chart on Generic Organic Fertilizers and Soil Amendments under Fertilizers on this website for what to use. Additionally, in this rainy year we have had some diseases proleferated. Curling leaves on peach and nectarines might mean peach leaf curl. See the Q & A on that subject on this website, also see the section on peach leaf curl 384 and 385 in my book and other pages given in index. Use dormant sprays in winter. If disease is a problem now, try controlling with Serenade (trademarked organic product.)

Problem soils can gradually be fixed by adding organics at regular intervals. You don’t need to hire an expert to tell you this, besides an expert might be a guy who learned all about synthetic fertilizers in ag. school and might not be on the organic path. Instead, use your time and money to gradually build up the organic structure of your soil with annual applications of horse manure in fall and your problems will be gone. I know because I’ve seen it work. But make sure your tetanus shot is up to date. Sand and clay together, unless naturally occurring, can lead to something akin to concrete, but even in that case organics can cure the problem. It just takes time. Fertilizer alone won’t do it. The worst soil in the world can be fixed up with organics and the very process of plant roots going down into the ground helps break up soil. For a full lineup of organic materials to use and how to use them see the chart on page 28 of my organic book. Also apply gypsum every two years. See the opening chapter in my book for full explanation on pages 21 and 22. This will help increase drainage. Good luck. It may take you a few years to correct soil problems but persevere. With diligent applications of organic materials, especially manure, and the help of slow natural rot and earthworms who will appear like magic, you will win out in the end. Try to get horse manure from a good horse owner who picks up daily. This will avoid the salts from salt licks. Read the opening chapter of my book beginning page 16, you will learn a lot. There are so many good things like humic acid, seaweed, and alfalfa that you can use. Some of these things can work real miracles. Also encourage beneficials to clean up the bad bugs.