Best fertilizer for plum trees

While there is not a whole lot of blooming going on in other parts of your garden, January and February are the months to tend to your citrus trees. A tiny bit of pruning, a whole lot of feeding, and the requisite check for fast drainage are key to healthy and abundant trees and crops.

Like children, citrus is an investment in the future. You tend to your young trees, and harvest the early but not necessarily favorable crops, and in five to 10 years have a tree loaded with fruit that tastes the way nature intended it to.

It’s called “raising” fruit as opposed to “growing” fruit. It takes time.

Let citrus trees develop in a natural form. First, they grow up for a year or so, then bend over in broad, weeping forms. Your job as the keeper of your tree is to make sure the weeping branches stay at least a foot off the ground. Branches that touch bottom are bridges for snails, fungus and other problems.

Because a weeping form shades the inside of the tree, get inside there and prune away branches that have died out. Any dead wood or branches that cross and create friction scars should be pruned away. Be careful not to expose the trunk of your tree to too much sunlight. Citrus trunks are susceptible to sunburn. Newly exposed parts of the tree should be painted with trunk protectors (available at nursery centers.)

Next, check for drainage. A tree that is watered by a sprinkler system that also waters your lawn is being watered too much. Over-watering causes leaves to turn yellow, leads to root fungus, and will eventually kill your tree. On the other hand, a tree that gets water only during the rainy season suffers from drought in the form of lousy fruit.

You did it in the beginning, so do it again. Create a watering basin around your tree. Use a rake to hill up the soil and fashion a doughnut-like watering basin below the drip line (the leafy perimeter.) Then use a slow hose or drip system to water at least once a month.

Yellow leaves with green veins also indicate an iron deficiency. This is most noticeable in the winter months when the soil is cold. Iron chlorosis severely stunts plant growth, and if left to go on too long, is irreversible.

Apply a dry, chelated iron product like Ironite, according to package directions. Sometimes a second and third application is needed before the tree recovers.

The feeding roots of a citrus tree sit in the top 2 feet of soil, 3 to 4 feet out from the trunk all the way to the drip line.

Apply citrus fertilizers in this area, according to package instructions.

People with lots of citrus trees on their property might want to become acquainted with Orange County Farm Supply in Orange. It’s a fun place to prowl around for bulk Farmer John-size fertilizers and other ranch-related products. Call (714) 978-6500.

Citrus life cycle

The life cycle of a citrus tree is unlike any other kind of plant. In Southern California, these trees truly use each and every month to develop. In other words, there is no down time in the orange grove.

Winter is spent stocking up on nutrients. All parts of the tree, not just the leaves, but also the trunk and branches, get in the act and store food.

February and March are the months when citrus store the most, preparing for their bloom in early spring. (What would spring smell like in Southern California without the familiar scent of citrus?)

The sex life of a citrus is complex. Some are self-pollinating, and others, such as some grapefruits and mandarins, require a pollinating tree.

I won’t explain birds and bees here, and I have no way of knowing what type of tree you have — just know that sometime after each bloom period, new fruit will begin to develop.

Blooms typically appear on new (this year’s) growth, not on the older parts of the tree. In our region, where the trees grow year-round, there may be new growth spurts in winter, summer and again in fall.

In May, June and July expect “June drop” — a process during which the tree naturally sheds fruit it does not have the stored energy to ripen.

When the remaining fruit finally changes from green to orange, opinions are then formulated about the quality. Don’t be too hasty.

Fully formed oranges that look ripe enough to pick do not actually turn sweet until they are chilled. That means that they may have to hang on the tree for a while.

Very often, the longer you leave citrus on the tree the sweeter it will be. Let your taste buds be the guide, not the calendar.

Related article: A to Z plant guide: How to grow everything in Southern California

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Plum Tree Fertilizer: How And When To Feed Plum Trees

Plum trees are divided into three categories: European, Japanese and the indigenous American species. All three can benefit from plum tree fertilizer, but it’s important to know when to feed plum trees as well as how to fertilize a plum tree. So what are the fertilizer requirements for plums? Read on to learn more.

Fertilizing Plum Trees

Before you apply plum tree fertilizer, it’s a good idea to do a soil test. This will help you to determine if you even need to fertilize. Fertilizing plum trees without knowing whether or not it is necessary not only wastes your money, but it can result in excessive plant growth and low fruit yields.

Fruit trees, including plums, will absorb nutrients from the soil, especially if they are surrounded by a lawn that is regularly fertilized.

When to Feed Plum Trees

The tree’s age is a barometer on when to fertilize. Fertilize newly planted plums in the early spring before it leafs out. During the trees second year, fertilize the tree twice a year, first in early March and then again about the first of August.

The amount of annual growth is another indicator for if or when to fertilize plum trees; trees with less than 10-12 inches of lateral growth from the previous year probably needs to be fertilized. Conversely, if a tree has more than 18 inches of growth, it probably doesn’t need to be fertilized. If fertilization is indicated, do so before the tree blooms or sprouts.

How to Fertilize a Plum Tree

A soil test, the amount of the previous year’s growth and the age of the tree will give a good idea of the fertilizer requirements for plums. If all signs point to fertilization, how do you correctly feed the tree?

For newly planted plums, fertilize in the early spring by broadcasting one cup of 10-10-10 fertilizer over an area that is roughly three feet across. In mid-May and mid-July, apply a ½ cup of calcium nitrate or ammonium nitrate evenly over an area about two feet in diameter. This feeding will supply additional nitrogen to the tree.

In the second year and thereafter, the tree will be fertilized two times a year in early March and then again the first of August. For the March application, apply 1 cup of 10-10-10 for each year of the tree up to 12 years. If the tree is 12 years or older, apply only 12 cups of fertilizer to the mature tree.

In August, apply 1 cup of calcium nitrate or ammonium nitrate per tree year up to 6 cups for mature trees. Broadcast any fertilizer in a broad circle at least as large as the circle created by the limbs of the tree. Be careful to keep the fertilizer away from the trunk of the tree.

Plum Tree Identification

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When fruit is visible on the tree it is simple to identify a plum tree. In the absence of fruit it is not so simple. At a glance, other fruiting trees can look very similar and the only way to tell them apart is through subtle differences. Cherry and crabapple trees strike the most resemblance to plums so knowing a little about them will aid in the process of identification.


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There are two distinct kinds of plum trees. Fruiting plums bear the edible fruit you find at the grocery store. The non-fruiting or ornamental plum trees are referred to as flowering plums. The flowering type may develop small edible hard fruit but it is only of interest to the birds. Flowering plums have been bred for their colorful foliage and attractive flowers. Most of the fruiting plums have a common rounded crown and are a medium sized tree. The flowering plum varieties may come in weeping, horizontally branched and dwarf forms.


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Plum leaves are oblong in shape with a pointed tip. The leaves are surrounded by serration similar to what is found on a knife. Species plums have green leaves but many of the hybrid varieties will have red to purple leaves. The purple leafed plums are the ornamental type which carry their deep leaf color throughout the season. The colorful leaves are the strongest reason to plant a flowering plum. Some of the most popular dark leaved plums are variations of Prunus cerasifera. Common varieties are Thundercloud, Pissardi and Newport.


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There are two types of edible plums. The European variety is the most common in temperate weather regions. Like many fruit trees, this plum is very hardy and needs a winter chill period to fruit well. This group includes the Italian Prune Plum and the Damson Plum. The other fruiting type is the Japanese plum. Examples of Japanese plums are the Santa Rosa and Satsuma varieties. Plums may be yellow, red or purple and the fruit comes in different sizes from 1 inch to around 5 inches. European plums ripen late in the season and Japanese plums are earlier.


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Plum bark tends to be dark, smooth and unimpressive. Older plum trees will have slightly rougher bark but nothing ornamental enough to mention. This is one way to tell a plum from a cherry or crabapple. Cherry bark has obvious horizontal lenticels or lines on the bark that go around the trunk. Crabapples develop plated bark that looks like rough squares up and down the trunk.


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Fruiting plums are in the rosaceae family, which have simple five petaled flowers. The ornamental plums are bred to have single or double white or pink flowers. Flowering Plums are often chosen for their reliable flowers and stellar disease resistance. The Double Flowering Plum, Prunus triloba is a good example of this. This plum is a multistemmed shrub no taller than 12 feet at maturity. When in bloom, Prunus triloba will be completely covered with double pink flowers.


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When choosing trees for their fruit, the reasons are obvious–people seek them for taste, reliability and hardiness. When choosing between ornamental plums, crabs and cherries, there are some differences to note. Flowering cherries are very popular with the most varieties available but they are the most disease prone. Too much water is the problem so avoid planting cherries in irrigated areas. Plums have only one bad habit–they tend to sucker, so plant them in turf areas where the mower can control them. Crabapples have no cultural issues but produce more fruit, which can be attractive but may create more clean up. Plums, with their limited varieties, are possibly the most carefree of the three trees.

How To Fertilize A Plum Tree

How and if you fertilize and water a plum tree will depend on several factors including: soil type, soil fertility, weather conditions and location. These trees grow satisfactorily in moderately fertile soils without fertilizer. However, fertilizer is needed in soils of low fertility or where competition from other plants is heavy.

Best Growing Conditions

Sun – The best and most fruits will be produced when trees are growing in full sun. However, trees that receive a little shade during the hottest part of summer days will still produce good crops of fruit.

Soil Type Preferred – Plum trees grow and produce the best fruit in well-drained but moist fertile soil that is rich in organic matter, but tolerate a wide range of soils as long as water and nutrients are not limiting and soil pH is adequate. Plum tree roots will not tolerate soils where water remains on or near the surface for more than one hour after a heavy rain. They are tolerant of heavy clay soils if drainage is good. In soil with low fertility or compact clay it’ll be worth your time to mix in some organic compost to the native soil. They like the soil to hold a good supply of water, especially when the fruits are developing in summer, but not so much water that the soil stays constantly soggy or wet.

Soil pH Preferred – Plum trees do best in a slightly acidic to neutral soil, somewhere between 6.0 and 6.5 on the pH scale. Whenever growing plants that prefer a specific pH it’s a good idea to test the soil. Testing kits are available at most local nursery and garden centers or you can buy soil test kits online here. Your local Extension Service might provide soil testing services as well. Depending on the results of the soil test, you can add lime to raise the pH or soil sulfur to lower the pH (make more acid).

Type Of Fertilizer

Plum trees planted in very fertile soil may not require fertilization until they’ve used up many of the nutrients. The best way to decide on wether or not to fertilize is to observe the tree itself. If growth is stunted and you don’t see at least 1 foot of growth per year, or what otherwise should be dark green leaves have become light green, this indicates a need for fertilization. If the leaves are light green the tree cannot photosynthesize effectively for the best fruit production. Fertilizer will darken the foliage over time and help to stimulate good fruit production.

Trees can be fed with organic plant foods or inorganic fertilizers, such as 10-10-10. Avoid the use of fertilizers that have a high nitrogen content (the first number in fertilizer). When feeding plants that will put produce on the kitchen table, I always go with organic. Organic plant foods and composts are usually non-burning and will not have chemicals or other inorganic substances in them. The type of fertilizer you choose to use is up to you.

Nitrogen Consideration – Although nitrogen is a necessary element for basic plant growth, plum trees, and most other fruit trees, react dramatically if there is too much nitrogen (the first number in fertilizer). The nitrogen redirects energy from fruit production to foliage and shoots. If there’s too much nitrogen in the soil fruits might prematurely fall to the ground before they are fully developed.

When To Fertilize A Plum Tree

Feed plum trees just after new leaves have emerged in late winter or early spring. The surge of nutrients at the soil level will spur the tree to grow with vigor and produce good fruit.

Fertilizing Newly Plum Trees…

When planting a plum tree during the dormant season, when trees have no leaves, do not apply fertilizer. Wait to fertilize until new growth begins to emerge in spring. Container-grown trees can be fertilized at planting time when planted during the spring and summer, however avoid fertilization two months prior to the typical first frost date in your area. Late fertilization can stimulate new tender growth that can be damaged, and damage the entire tree, from an early freeze.

Fertilizing Established Plum Trees…

If you choose to go with an inorganic fertilizer, a basic 10-10-10 or 8-8-8 fertilizer works well. The size of the tree will determine the amount of fertilizer you’ll apply. For each 1-inch of diameter of a tree apply 1 pound of fertilizer. Use a ruler to measure the diameter of the trunk at 1 foot above the ground. Depending on the size of the canopy, you can hand sprinkle or use a hand spreader to broadcast the fertilizer around the perimeter of the canopy, which is where most of your mature tree’s feeder roots will be.

Alternatively you can use a non-burning organic type fertilizer, or you can use a layer of organic compost as mulch (composted cow manure, etc), so that less chemicals are added to the soil that could end up in your fruit, and eventually in your body.

Watering Plum Trees

The frequency and the amount of water a plum tree will need depends to a large extent on the soil and the age of the tree. As a rule of thumb, 1 inch of water per week from rain or irrigation is adequate. Just keep in mind that soil should be moist but not constantly soggy. Plum trees, like most other fruit trees, do not like constantly wet feet! If water stands more than an hour on the surafce of the soil steps need to be taken to improve drainage.

Irrigation of young trees is especially important during the first season or two, but be careful not to overwater.

Mature plum trees are quite drought tolerant but will need sufficient water during the fruiting period to produce a good yield of healthy fruit.

Other Tips

  • Always keep a sufficient layer of much around your trees to control competition from weeds and help retain moisture.
  • Excessive nitrogen can cause too much foliage growth.
  • Yellowing and dropping of leaves may indicate drought and the need for supplemental irrigation or fertilization.

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