Fertilizing Fruit & Nut Trees

Fertilizing trees too much can be even more harmful than not fertilizing at all.  How do you know when enough is enough?

Research & experience shows that excess fertilization of fruit & nut trees can result in too much vegetative growth, reduced bloom & fruit set, reduced quality of fruit, & diseases such as fire blight, brown rot & powdery mildew.  Excess nitrogen creates a nutrient imbalance in the plant, which results in weakened cell structure in the leaves and branches which will have high levels of nitrates and the fruit will have lower levels of sugars.  That means the foliage is susceptible to disease and the fruit lacks flavor and does not store well.  On the other hand, Nitrogen deficiency results in weak growth and yellow foliage.

Balance is the Key

The key to proper fertilization is a balance of nutrients.  Nitrogen & Potassium are necessary for plant growth, and especially important in a tree’s formative years when you want to establish a strong scaffold of branches to bear the many years of abundant harvests.  Phosphorous is essential for disease resistance and flower & fruit development.  A common error of many backyard gardeners is to go too heavy on nitrogen (in the form of chemical fertilizers or raw manures) and neglect Phosphorous & Potassium as well as other essential nutrients.

Soil & Plant Analysis – The Instructions Are on the Tree

Soil nutrient analysis a useful tool.  We use A&L Western Labs in Modesto CA (209-529-4080, $30 for a complete analysis, with recommendations).  However, the roots of semi-dwarf and standard trees forage wide & deep and often tap soil that is not easily sampled for analysis.  Sometimes a nutrient is present in the soil but is not available to the tree because of soil pH or the deficiency of another nutrient.  Foliar analysis is often the only way to be certain what nutrients are present or lacking in a tree’s diet.  Foliar analysis is also available through A&L Western Labs, but is not the most practical solution for a home gardener. 

One of the best indicators of a soil fertility & tree health is reading the annual growth of the tree itself.  Look closely at the branches on your fruit tree.  If you follow the branch back from the tip you’ll see a clearly defined ring marking last year’s growth (or you’ll see the present season’s pruning cut).   By continuing backwards down the tree you can read how much a tree grew the previous season and how it responded to the previous year’s pruning cuts.  As a rule of thumb you want to see 6 to 18 inches of growth per year on mature trees in the home orchard (younger trees grow more vigorously and should put on more growth).  Refer to the chart below.  If your mature trees are meeting the growth parameters then your have adequate fertility in your soil, and adding more nitrogen may be detrimental.  If you are not meeting the recommended annual growth then read to the right for a guide of how much fertilizer to apply.  We prefer using composted manures as they are a balanced fertilizer, including all of the essential plant nutrients, not just Nitrogen.  For newly planted trees, use about one third of the fertilizer listed in the table below.

Nitrogen Requirements & Annual Growth of Fruit & Nut Trees

* - Fertilizer figures are for semi-dwarf trees.  For standard trees multiply by two, for full dwarf trees divide by two.  For newly planted trees divide by three.

Cover Crops - Why Haul All That Manure Around?
Planting a perennial cover crop of mixed grasses, legumes and herbs is an excellent way to provide long-term fertility for your fruit & nut trees.  Once established a perennial cover crop will provide nitrogen, attract beneficial insects and cycle nutrients, all to the benefit of your orchard-garden ecosystem.  We recommend planting a mix of legumes and grasses, with some tap root plants, such as parsley, dandelion, daikon radish, beets, carrots chicory.  For More information on cover crops, ATTRA (Appropriate Technology Transfer for Rural Areas) has a great online pamphlet on cover crops at http://www.attra.org/attra-pub/covercrop.html - principle

Peach Leaf Curl

If you grow peaches and/or nectarines, chances are you’ve encountered peach leaf curl – the curled, deformed leaves that sometimes appear on peaches and nectarines in the early spring.  Peach leaf curl is caused by a fungus, Taphrinia deformans, and can be either a nuisance or lethal to the tree, depending on its severity.  The fungus is found just about anywhere peaches are grown, and is particularly damaging following warm, wet winters.  Many exasperated gardeners have contacted us saying that even after spraying their trees they still have problems with the curl.  The first step in controlling any pest is understanding its life cycle, so we’ll explain the life cycle of Taphrinia deformans below.  Most disease problems can be successfully managed with cultural controls, but we’ve found that peach leaf curl is one of the few diseases that requires annual spraying.  A brief look at the life cycle of peach leaf curl will reveal that timing of this spraying is essential:  it must be applied before the dormant buds open, or it will not have any effect on controlling the disease.  The best material to use, lime sulfur, is also the least toxic.    

By the time a gardener sees peach leaf curl in the spring, the fungus has already penetrated the cellular tissue of the foliage and is doing its damage.  At this point the fungus is immune to treatment.  Though foliar feeding with concentrated kelp solution, such as Maxicrop or Algit, will help to fortify the tree and bring it through the infection, no amount of fungicide will help the situation.  Leaves affected by the curl eventually shrivel completely and fall off and the tree pushes new leaves to replace the damaged ones.  The peach leaf curl will continue to attack the new foliage until temperatures rise and humidity decreases.  It takes a good stretch of warm, dry weather before the disease symptoms will slow down and eventually disappear.   Though the symptoms are gone, the fungus remains, lying dormant until next season.  The fungus forms tough spores that are resistant to heat and desiccation in order to survive the summer.  These spores germinate with the first fall rains and remain active during the winter as long as temperatures are over 45 degrees F.  

As long as the dormant peach buds are tight and closed the fungus is not able to penetrate and infect the tree.   The infection happens when the buds open.  The key to controlling peach leaf curl is to spray after the spores have germinated, then before and during the period when the buds open on dormant peach & nectarine trees.  In the east this can mean applying one, well-timed application either in the fall when 90 percent of the leaves have dropped or in the spring well before bud swell.  In he warm, moist winters of the Pacific Northwest one to three applications may be necessary for control.  

The buds on peaches and nectarines actually open much earlier than most gardeners realize.  If you look closely at a bud that is fully dormant in December you’ll see a tightly closed bud protected by a waxy scale.  Several weeks before bloom the buds will swell and the scale will crack.  Once this happens the fungus is able enter the bud and infects the unformed foliage.  This bud swell happens in early to mid January in our area (Northern California) and in late January to early February in Washington. In colder areas it will be much later.  For the Pacific Northwest, Gary Moulton of Washington State University recommends applying the first spray in late December, and then at three-week intervals until bloom.  We apply our first spray in mid to late December, and then another in mid to late January.  In some years we have been not been able to apply the second spray because of weather conditions and have achieved good control anyway, but the second spray is highly advised.  If the Researchers at Washington State University found that lime sulfur (calcium polysulfide), a low-toxic spray that is approved for organic production, is the best material for controlling peach leaf curl.  Copper sulfate is also used, but copper is a metal that can build up in the soil and is toxic to earthworms and beneficial soil fungus, whereas the lime sulfur breaks down rapidly.

When you buy peaches and/or nectarines from Sandy Bar Nursery they will have been sprayed with lime sulfur.  You may notice the yellow sulfur residue on the branches.   This material is approved for organic production and breaks down rapidly into compounds that are benign or beneficial for the soil (calcium and sulfur are both nutrients essential to plant growth).   In order to control peach leaf control you will need to apply the lime sulfur the following winter.  If you live in an area with long, warm rainy winters, where the temperature remains above 45 degrees for long periods, it is advised to apply a second application to your new tree before or during bud swell. It is readily available in most gardening stores.  The recommended rates will be listed on the label, but be sure to follow the advice for timing that are explained in this article. 

Resistant Varieties – We offer a few varieties that are very resistant to peach leaf curl, including Frost, Oregon Curl Free and Q-1-8.  Red Haven resists peach leaf curl better and bounces back quicker than most other  varieties.

Cultural Control – A healthy soil and a healthy tree is the first step in disease control.  Fertilize your trees each year with compost and or aged manures.  It is good to add a source of calcium and phosphorous every 3-5 years, we use oyster shell flour for calcium and soft rock phosphate for phosphorous.  Foliar feeding with concentrated kelp solution, such as Maxicrop or Algit, will help to fortify the tree and bring it through the infection.  Turning in the fallen leaves in autumn or raking them up and adding them to your compost pile will reduce the amount of fungal inoculant.

Food Forests

If you’re attracted to fruit & nut trees, chances are you appreciate trees in the wild as well.  Perhaps it’s occurred to you during a hike in the woods that the forest flourishes without any human intervention at all – no weeding, watering, pruning, fertilizing or composting.  Wouldn’t it be ideal to design our gardens & orchards so that they function as a forest?   

More and more people are catching on to the idea of planting a food forest, that is, an orchard/ garden that mimics the diversity, resiliency and self-sufficiency of a natural forest.  Here are a few tips on how you can apply this approach of natural design to your own backyard.  

Plant in Layers

Any natural forest has several canopy layers in it, and you’ll want to replicate this in a food forest.  In hot areas the shade cast by larger trees can be a real asset to a garden, providing a niche for plants that are shade loving or less tolerant of heat.  In colder climates where heat and light are more precious you’ll want to plant fewer layers and space your plants out more to permit better sunlight penetration.   The upper story can consist of nut trees such as chestnut, hickory, stone pine and standard size fruit trees such as apples, pears, cherries and plums.  The next layer can consist of dwarf and semi-dwarf fruit and nut trees – apples, pears, peaches, apricots, plums, filberts, almonds,  Next you can plant a shrub layer of  bush and cane berries such as raspberry, blackberry, blueberry elderberry, gooseberry & currant.  Even the ground layer planting has more than one dimension to it – you can plant vines that grow up into the trees, cover crops that protect the soil and fix nitrogen, vegetables for your kitchen, and root crops that penetrate into the soil and bring up nutrients from the subsoil.   

Mulch!!

Dig around in any healthy forest and you’ll find a thick mulch layer teeming with life.  This layer of leaf litter and woody debris is the essential foundation for any in any temperate forest.   Mulch conserves moisture, improves soil fertility and structure and steadily provides nutrients through the slow decomposition of organic matter.  A forest produces its own mulch, but you can kick start your food forest by using any source of organic matter that is handy, including newspaper, cardboard, leaves (avoid walnut & eucalyptus), weeds, straw, hay or woodchips.  You can also grow your own mulch by planting species specifically for the organic matter that they produce, such as bamboo or broad leafed tree species .  Here at Sandy Bar we plant comfrey around our trees and cut it back every month to provide mulch for the trees.  Any green manure crop can be cut and laid down for mulch.   Keep your eye out for cheap or free sources of organic material, such as spoiled hay, leaves, or wood chips from tree service companies.  

Use Plants that Attract Beneficial Insects

You can build your pest management into your landscape by planting flowers that attract beneficial insects.  Beneficial insects are hunters and require a lot of energy in order to stalk their prey.  Flowers provide insects that energy through pollen and nectar, high-quality forms of protein and sugar.   The best flowers are those in the composite (sunflower) family (such as tansy, yarrow, daisy, cosmos) and the carrot family (celery, parsley, cilantro, dill, carrot), though there are many more.  Try it for yourself – allow any of these plants to go to seed in your garden and sit and watch them in the middle of a summer morning, you’ll see them swarming with ladybugs, lacewings, hover flies, tachinid flies and a host of tiny parasitic wasps that feed on insect pests and their eggs.  Spread these insectary plants throughout your garden or food forest and you have built-in pest control.  

Recycle Nutrients

A forest feeds itself by producing its own nutrients and recycling them.  Nutrients are readily leached out of a garden soil by rainfall whereas a forest holds onto its nutrients in a complex web of many layers of foliage, deep roots and a thick leaf litter.  You can cycle nutrients in a food forest by mulching, planting nitrogen fixing green manures and integrating animals into your system.  For more information on cover crops, ATTRA (Appropriate Technology Transfer for Rural Areas) has a great online pamphlet on cover crops at http://www.attra.org/attra-pub/covercrop.html - principle      

Plant Re-seeders

Some plants readily spread on their own, eliminating the need to prepare a bed, sow, weed & water.  Try planting arrugula, chard, daikon radish, red mustard and calendula in your understory and letting a few plants go to seed.   You’ll be rewarded with some self-sowing volunteers in your food forest.

Integrate Animals in the Food Forest

Animals are a great way to cycle nutrients in a food forest.  Chickens are a great addition to any orchard.  They forage on insects and fruit culls, graze down weeds and scratch up the soil, while depositing manure.  You can even harness chickens to prepare garden beds for you by using a “chicken tractor”.  A chicken tractor is bottomless pen on wheels that fits over a garden bed.  It can be left over a bed long enough for chickens to eat down crop residues and scratch up the soil, and then moved to another bed.  Ducks and rabbits can be used in a similar way.  (Check out the book Chicken Tractor by Foreman & Lee, Chelsea Green Publishing,  for an excellent how-to resource).  And don’t forget bees.  A single beehive will increase your fruit set while providing a source of honey, pollen and propolis.  

Mushrooms

Temperate forests support a staggering diversity of fungus species that play a critical role in nutrient cycling, soil building and overall forest health.  You can mimic a forest by inoculating your food forest with edible mushrooms such as oyster, shiitake, portabello king stropharia and many other species.  Mushroom spawn can be introduced into straw mulch, woodchips or sawdust.  We recommend starting with oyster mushroom spawn, as it is the most easily propagated mushroom.  Try inoculating a pile of clean straw and you’ll be amazed with the results.  Our favorite source for mushroom spawn and information is Fungi Perfecti, on the web at www.fungi.com.  Fungi Perfecti owner Paul Stamets is an absolute wealth of information on mushrooms.  Check out his book, Growing Gourmet and Medicinal Mushrooms.   It has a chapter devoted to “mycological landscaping” that explains how to inoculate landscapes with edible and useful strains of mushrooms.  

 

Plan for Succession 

If you’ve ever observed a meadow being taken over by brush and then trees, you’ve witnessed succession.  The first plants to grow in a bare patch of ground are pioneer species; tough plants that thrive on disturbed ground and reproduce quickly (grasses, brambles, annual weeds).  Next come the shrubs, which will start to make some shade and edge out the pioneer species.  Eventually tree seeds will find there way into the system, either blown in on the wind or deposited by birds.  You’ll want to replicate this when planning a food forest, substituting more useful food species.   If you’re starting with a garden then you already have an early succession plant community, and growing a food forest can be as easy as adding the middle layer of berries and dwarf fruit trees along with the upper canopy of nuts and large trees.  If you’re planting a food forest onto bare ground you’ll find there’s a lot of space in between your trees.  Rather than leave this open to colonization by weeds you’ll want to plant berries & shrubs along with cover crops and annuals.  As your planting matures, don’t be afraid to take things out.  Remember that in succession some plants are lost to competition.   You may need to thin tree canopies to allow more light penetration, remove lower branches or remove whole plants as they crowd each other.  

Food Forests – A Few Good Books

Tree Crops – A Permanent Agriculture, J Russell Smith - In 1929 Smith noted that the downfall of agriculture is its reliance upon repeated tilling of the soil to grow annual crops, resulting in massive amount of soil erosion and habitat destruction.  His book opens with a world tour of regions where annual agriculture has devastated landscapes, leaving land that no longer supports a healthy plant or human community.  He then presents his solution, which is to develop an agriculture based on trees rather than annual crops, and gives examples of forest agriculture from around the world. 

Introduction to Permaculture, Bill Mollison - The Australian Bill Mollison was heavily influenced by JR Smith’s idea and formulated them into his concept of Permaculture – A design process for sustainable human habitats that emphasizes the use of trees and perennials.  Mollison has written several books on Permaculture, and we find this to be the most practical, with lots of useful charts and diagrams.  The only drawback for us in the northern hemisphere is the extensive references to Australian species.

Container Stock VS Bare Root Stock

Each fall we get inquiries about buying trees in containers.  Over the years we have sold our trees in both containers and as bare root stock.   We have come to prefer bare root stock for a variety of reasons:

Value – When you buy bare root, all of your dollar is going towards the plant, whereas with container stock a substantial percentage of the cost is for the growing media and the container itself.  For example, one of our $22 bare root trees will typically cost $30 to $40 once it is potted.  

Vigor – Bare root stock that is planted at the correct time and according to our instructions will establish readily and grow vigorously.  One of the biggest problems with container stock is that it is prone to root crowding.  A fruit tree left in a container will become root bound and perform poorly when planted out. 

Training – When you plant a bare root tree you get to do the training of the primary scaffold branches to assure ideal placement of branches and proper crotch angle of branch attachment for maximum fruit load bearing.  Container plants usually come with their primary scaffold branches established, so you take your chances concerning branch placement and crotch angle.

Bulk & Weight– Bare root trees are the best value for a shipped tree.  Since they are fully dormant when shipped, the trees require only a lightweight medium around the roots to retain moisture.  The bulk and weight of container stock increases shipping costs dramatically.  The $22 price tag of one of our bare root trees would buy a much smaller container tree, which would cost more to ship.