How We Grow Peaches Organically at Woodleaf Farm

Woodleaf Farm is a small organic peach farm at 1300’ elevation in the foothills of the Sierra Nevada Mountains north-east of Sacramento. The farm contains 1200 peach trees, including 40 white and yellow flesh varieties and 400 misc. fruit trees. The first trees were planted in 1985. The farm has been certified by California Certified Organic Farmers since 1982.

Soil testing and Fertilizer Applications

Peaches need a soil high in nutrient and mineral content. In order to have a clear understanding of which fertilizers are necessary we take regular soil samples. The amount of biological activity, ie. soil micro-organisms which are responsible for the release of nutrients in soil and hence (affect fertility ratings), varies depending on the time of year. In order to obtain a consistent reading it is important to take soil tests at the same time each year so we have a concrete basis for comparison. It is important to be able to read and understand the results of the soil tests. If you are doing your own soil testing and are unsure how to read the results, consult someone who does so that you can reap the greatest benefits from the test. May and June are the months that show the highest nutrient reading.
Optimal levels of calcium in the soil should be 65-70%, magnesium should be 10-15%, potassium at 3-7%, hydrogen at 5-10%, and sodium at less than 3%. The pH should be between 6.3 and 6.8. This is ideal because at these percentages the minerals are at their optimum availability for use by the plants.
The calcium-magnesium balance is particularly important. When there is too much magnesium present the soil particles bind together tightly so that less air gets into the soil. Other minerals also have difficulty binding to the soil colloid, and there is less biological activity. For most California soils yearly applications of gypsum, a sulfur source at a minimum of 250 lbs. per acre will help lower the magnesium which will in turn allow calcium levels to increase and will add enough sulfur for the year.
Nitrogen plays a different role in an organic system as compared to a conventional farming system. For example, instead of simply adding a concentrated dose of soluble nitrogen to maintain appropriate nitrogen levels, as conventional farmers do, organic farmers focus on the soil ecosystem as a whole. With an organic matter percentage of 4% – 5% in the soil and a leguminous cover crop (ie. clover) a peach orchard soil could additionally use about 100 lbs. of actual nitrogen per acre. 2-6 tons of good compost per acre/per year should provide plenty of nitrogen. With a compost which is 1.5% nitrogen, 6 tons of compost provides 180 lbs. of actual nitrogen, a little over 1/2 of which is available in the first year. Therefore, 6 tons will provide the desired 100 lbs. per acre. Too much nitrogen will prompt excessive growth.
Based upon the results of our soil tests, the average amount of fertilizer we use per acre per year is about six tons of compost, 250 lbs. of gypsum, 200 lbs. of sulfate of potash, 10 lbs. of Solubor(boron source), three bloom sprays, one to two pre-harvest foliar nutrient sprays and one dormant spray. The cost of the fertilizer per acre is about $250 for the compost, $20 for the gypsum, $50 for the potash, $12 for the Solubor and an average of about $20 per sprays for each acre. The total for the year is about $440 per acre .
We apply all our composts and rock minerals on top of the soil without working them into the soil. We let the nutrients penetrate the soil through irrigation The irrigation, the micro-organisms, and the earthworms work the nutrients into the root zone. When you disk in the orchard you risk damaging the tree’s root system and creating compacted soil through which air, nutrients, and water cannot penetrate. Also, when a disk is used the soil becomes exposed to the sun which destroys organic matter and inhibits the growth of beneficial micro-organisms. Phosphorus doesn’t move through the soil very well and so it is important to add as much as a ton per acre of soft rock phosphate into the soil when the orchard is first being prepared for planting.
When a peach tree is kept growing vigorously by maintaining soil fertility, it is able to produce large crops and stay healthy with a small amount of disease pressure.

How to Start a New Orchard

Start preparation for planting a new orchard in the summer or early fall. Rip the soil if necessary. Take a soil sample and add any needed minerals. Add 10 to 50 tons per acre compost and disk it in. Install irrigation and seed a low growing perennial clover or perennial orchard grass. Seed by mid-October. Irrigate as needed to germinate seed. With irrigation it is fine to place the seed on top of the ground without harrowing it in.

First, buy trees that are healthy and have good root systems. We use Lovell rootstock because it can tolerate wet soil better than Nemaguard. In clay soils, plant the trees on high ground. We use a hump and hollow drainage system where the entire tree row is raised about 8 inches higher than the drive row. It is best to have the trees in rows that run north to south. This catches the morning and afternoon sunlight without shading much of the tree.
Plant in January or as early in the spring as is possible. The soil should not be too wet. Dig a hole just wider than and as deep as the roots on the tree. Cut off any broken roots and rub off any sprouts below the bud union. Spray a solution of Galltrol to protect the roots against crown gall. Galltrol is an organic bacteria that will go into any cut and take up the sites that crown gall would otherwise take, (it is necessary to order Galltrol in advance from a chemical supply house). Plant the tree at the same soil line as it was grown in the nursery, spread the roots as you add all of the soil, pack the soil around the tree to get rid of air bubbles. The cut where the tree was budded onto the rootstock should point north to prevent sunburn. Water the trees if you packed dry soil around them. Prune the newly planted tree to a good bud on the trunk at 24” to 32”. Paint the newly planted trees with a white latex paint on the east, south and west side to protect against sunburn.
When the tree growth begins, add 1/2 to 3/4 lb. of a slow release nitrogen source such as feathermeal around the drip line of the new tree. Next add 5 gallons of compost over the feathermeal making sure to keep compost a inch or so away from the tree trunk. In May or June, add 1 lb. of a quick release nitrogen source like corn gluten meal followed by 5 gallons of compost. The following year in April, add 1 lb. of corn gluten meal and 5 gallons of compost. At 400 trees per acre, each time 5 gallons of compost is applied it takes approximately 6 tons per acre of compost. This may seem like too much compost (or too much work!), but it can give the tree a strong start which is important for early production and disease resistance. Young trees are delicate, so we hand weed around trees the first year and put the mulch around the tree to help slow the grass or clover growth.

Foliar Nutrient Sprays

Over the years we have discovered the value of a foliar spray program. When the trees became stressed during the wet spring of 1995, we applied foliar sprays every three to seven days. The trees responded with healthy new growth. Foliar applications provide a direct nutrient “hit” which the leaves take in almost immediately through the stomata. Foliar feeding has been said to feed the plant 10 to 20 times more efficiently than the same amount of nutrients applied to the soil. Foliar fertilization can also correct a soil nutrient deficiency quickly or add helpful nutrients in a stressful season.
Normally we apply 1-2 dormant sprays, 3-4 bloom sprays, 2-3 spring foliar nutrient sprays and 1 pre-harvest foliar nutrient spray. We apply the foliar sprays in the evening or very early morning because at these times the moisture stays on the leaves the longest and the leaves stomatas are able to absorb the nutrients most efficiently.
We use a 300 gallon, air-blast sprayer and apply about 250 gallons per acre. When the ground is too wet we have a 240 foot drag line on the sprayer that we drag into the orchard and spray by hand so as not to compact the soil.
We use a number of different spray materials including:
Hydrolyzed fish meal – for nitrogen and trace minerals, applied at 1-5#/acre. in the spring.
Maxi-crop – for enzymes and trace minerals, applied at 1/2-1#/acre.
Azomite – for soluble nutrients and trace minerals, applied at 5-6#/acre.
Compost tea – for organisms and micronutrients, applied at 30-70 gallons/acre.
Vinegar – for lowering pH from 7.1 to 6.7, applied at 1 gallon/acre.
Corn Calcium – for carbon, complex sugar and trace minerals, applied at 1 quart/acre.
Micronized sulfur – applied at 3#/acre, or up to 15#/acre when needed for disease suppression.
Sulfate of potash – (soluble fines) – for potassium, applied at 1-20#/acre.
Solubor – for boron; applied at 1/2-1#/acre (use only 10#s total per year).
Thermax 70 – for sticker-spreader, applied at 2 oz./acre.
Ascorbic acid – for disease resistance, applied at 2 oz./acre.
Multi-ke-min – for micronutrients, applied at 1/2-2#/acre.
Humax – for humic acid, applied at 1 quart/acre.

How to Make a Sweet Peach

To make a sweeter peach you can put on 2-3 weekly foliar sprays before harvest. The best foliars for a sweeter peach seem to be kelp and rock dust (Azomite). In some of our research, we have found that applying three sprays gave us a peach that was 15% sweeter than those without the sprays.

Peach Leaf Curl

Peach Leaf Curl can be controlled with a late fall and pre-pink bud copper spray. The copper that we use is Kocide 101. For the home orchard there is a powder of Tri Basic Copper that works the best. One good brand is Micro-cop.
It is not necessary to always use copper in the fall and spring. I have gone several years in one test block using only kelp and rock dust sprays with no leaf curl until the fourth year. Unless you have a history of leaf curl problems, you will usually only get a small leaf curl problem the first year, then if that problem is left unchecked it can grow into a horrible leaf curl problem the following year.
Copper can become toxic to plants if overused. In some orchards it is common practice to apply 2 or more copper sprays each year. In some soils 2 yearly copper sprays can quickly build up in the soil and become excessive. Excess copper can tie up zinc, iron and phosphorus and make it inaccessible to plants as a nutrient source. Use copper only when necessary.

Brown Rot Blossom Blight

Brown rot blossom blight is the main problem that we face as organic peach growers. Brown rot can cause twig damage that will continue to create problems at harvest and into the next growing season. Warm moist weather at bloom will create the worst brown rot problem.
Our choices of fungicides are very limited. By being very diligent in our cultural practices we are able to limit our reliance on the fungicides. The nutrient and mineral content of the soil, tree, and the ripening peach need to be kept at high levels through soil amendments and foliar sprays. This creates a healthy tree and nutrient rich peaches which are less susceptible to brown rot and also have the best taste. At harvest time brown rot can become a major problem when humidity is high or when there is rain. At these times we use foliar sprays of rock dust, micronized sulfur, and kelp as a defense. It is important to apply the foliar spray before there is any rain. This spray will decrease the brown rot population before it has a chance to explode.
The copper, micronized sulfur and rock dust sprays in the fall and the spring are helpful at lowering the incidence of brown rot.
Varietal difference can be great in peach trees. We have a number of varieties that have fewer brown rot problems year after year. These varieties are: Springcrest, Flavorcrest, Suncrest, and Cassie. The varieties that are the most problematic are: Red Top, Red Haven, 49ER, and O’Henry.
It is important for every farmer to keep track of how different farming practices affect their operation. We have learned how to set up a system of research that is now a part of our farming year. Every year gives us good insights into what practices to continue and what needs to be modified. Our research has been giving us direction, but we are a long way from having a total organic solution to the problem of brown rot.

Insect Control

Peach twig borer can be controlled by adding 1 lb. of Dipel (Bacillus thuringiensis or Bt) per acre to each of our 3 bloom sprays. Bt is a bacterium which, when ingested by the borer, feeds on it’s intestinal tract and kills the borer. We apply 3 blossom sprays with 10 to 15 lbs. of micronized sulfur, 4 lbs. of Azomite rock dust, 4 lbs. of sulfate of potash 1 lb. of Dipel for peach twig borer control. Apply the first spray at pink bud, the second at full bloom and the third at petal fall. Since we have been applying that spray, we have had very few peach twig borer strikes. Applying Dipel every 10 days during harvest and pre-harvest didn’t seem to work at all. In a problem year we use pheromone twist ties to confuse the males who then cannot find a female with whom to mate.
Oriental fruit moth has never been much of a problem in our orchard. The year after there were a few strikes we put out pheromone twist ties and have not seen more than a few strikes since.
Yellow jackets have created a problem in the past. With the small, yellow Sterling trap with the Sterling attractant lure inside, it is possible to trap all of yellow jackets around the farm.
Birds have become less of a problem over the years, even though there are more birds each year that make their nests here. If we give the birds water and bird seed during the harvest season we get less damage. Also, inflatable eyes, snakes, and owls successfully scare away birds when positioned within the tree a few days before harvest.
Bees have been a problem in the early varieties because there is so little wild nectar around at that time of year. Bees prefer flowers to peaches therefore, by not mowing the clover in the orchard it will go to flower and the bees will feed on the nectar.

Pruning

Peach trees produce fruit on one year old wood. Pruning is done to encourage the tree to continue to produce healthy new wood that is 12” to 18” long and 1/4” to 3/8” in diameter. We cut out branches that are too close to each other and any dead or sick, branches or twigs. The best fruiting wood will be horizontal wood.
We do two major pruning each year, the winter pruning and the summer pruning. The orchard spacing is 6’ X 15’. The shape of the tree is called a central leader. It has a lower area of fruiting wood that is 7 feet diameter and 7 feet tall and an upper fruiting area that is 4 feet diameter and goes up to 13 feet. We prune out any wood that is from the ground up to about 2 feet. Above 13’ we leave 2’ of vertical wood that we strip of all fruit. This will take the excess vigor from spring and summer growth. Every year we replace that 2’ of wood.
The winter pruning is done either at the end of the growing season (October), or toward the end of winter(January or February). In October it is easier to see the dead wood. Dead wood harbors more fungus sites than healthy wood and therefore it is important to prune it out. The whole tree needs to be pruned enough so that the branches have space around them. It is better to prune a little heavier than lighter. Leave branches that will shade the trunk of the tree with leaves, which will decrease the chance of sunburn. Leave uncut as many 12” to 18” long whips as possible, this is where the majority of fruit will be next year.
Two prunings a year is not a common practice for most peach growers, but by doing a summer pruning you are helping the fruiting wood that will be supporting next years crop. The summer pruning also rids the tree of wood that is too vigorous and branches that are too close together. It is also necessary to reduce the height of the tree to the same height that you pruned during the winter pruning.
To train a newly planted tree the first year, rub off any shoots below 18”. Start pruning when there is about 12” of growth in the spring. Do a small amount of pruning 4 or 5 times during the first summer to get the shape you desire. For central leader shaped trees, select the tallest, straightest shoot to be the central post. Cut a few inches of growth off of all the other branches that are just below the central post. This will give the central post an extra bit of dominance. Start shaping the lower scaffolding by cutting back a branch with a heading cut, making sure that the new branch you are choosing will maintain an angle of 30 to 45 degrees. Too flat an angle combined with a heavy crop could break the branch. In a heavy crop year, it is necessary to tie some of the lower scaffolding branches to the central post.

Thinning

By spending the time to do a good job of thinning we help insure a good crop of large fruit. We thin in early April. Our thinning practices are a little different for each variety. After thinning, we go through the entire orchard again in 3 or 4 weeks and take off all the fruit that is too small. In general, we keep the peaches about 8” apart but this varies by variety.
If we thin too soon after bloom we run the risk of having split pit in some varieties so we start thinning when the peaches are cherry size.
It requires a lot of energy for the tree to harden the pit in the peaches, so it is best to have all the thinning done before pit hardening time, about 6 weeks after fruit set.

Water

The sprinklers we use are Dan mini-sprinklers. At 20 psi each sprinkler uses 35 gph with a 22’ diameter. We use pressure compensated sprinklers spaced 12 feet apart in the row and the rows are 16 feet apart. With sprinklers at a height of 14”, we can go months before needing to weed around the sprinklers. Every week during the hottest summer months we put on 12 hours of irrigation or about 3” to 4” of water. Rainbird type sprinklers throw larger droplets of water and beat the ground more than mini-sprinklers do. This can glaze the surface of the soil and not let as much oxygen into the soil.

Harvest

It takes more labor to harvest the peaches the way we do it, but our markets demand ripe, sweet peaches and we get a premium for delivering them that way. During harvest, we will pick through each variety 3-4 times. We only pick the peaches that have good size and color. If left on the trees for a couple more days these peaches would be overripe. We pack the peaches in a single layer box and store them in a cold storage at 32-35 degrees. Within 3-4 days we sell all the peaches at the farmers market. We pick about 3 to 5 days later than we would if we were picking for wholesale.
Any mummies left in the trees will become brown rot fungus sites in the spring. At harvest throw all mummies on the ground. With good biologically active soil the mummies should rot into the soil by fall. In the fall, after the leaves have fallen, any mummies left on the tree need to be picked off and burned or disposed of away from the orchard. If in the fall the mummies are thrown on the ground they will sporulate in the spring and can cause a terrible brown rot outbreak.

Summary

Talk to other growers and learn what works for them. What varieties, what markets, who pays on time. Go to as many field days and workshops as you can, and when you still don’t have an answer, hire a consultant to help with soils or farm design. It is worth spending the money to learn some more.

Woodleaf Farm is as unique as your farm. The soil here is shallow, the rain is heavier here than in the valley and the frost can damage bloom late into the spring. With the coming of every season there are new challenges that need to be met with thoughtful action. To be successful requires a combination of growing and marketing skills.

Farming can bring great joy if it is done for your soul and to nourish the world and not just to make big money (which it isn’t so good at anyway!!).

Good luck, Carl Rosato

Carl Rosato
Organic Farming Consultant; soil testing and balancing
woodleaffarm@gmail.com