The Year of the Splitting Orange

Washington Navel and other varieties of citrus are beginning to ripen in our area, and many backyard gardeners are horrified at what they are seeing currently, wondering if Mother Nature is pulling some sort of Halloween prank.

 

 Jim asks: “I have a beautiful navel orange tree and for the past two years the fruit keeps splitting. The oranges start out fine and all of a sudden as they get bigger, they split right down the middle.”
Donna chimes in: “My reliable orange tree is going south. I watered it for 10 minutes every morning and evening during summer. Is this splitting issue a disease?”

Teresa, writes to the garden e-mail bag: "My mom has a wonderful orange tree, and the fruit is just starting to grow. However, most of them are splitting before they even get larger than a fist. What makes them do that?"  Steve echoes this chorus: “Why are my oranges splitting now?”

You may be facing the same conundrum with your own backyard citrus.

  
    The short answer: splitting oranges are usually due to stress to the tree, usually a combination of fluctuating temperatures, humidity, soil moisture and possibly fertilizer levels. Oh, and an on-going drought.

    The long answer, from Pam Geisel, a UC Cooperative Extension Farm Advisor, who has studied the problem of citrus split: When hot weather is combined with high winds, navel orange trees become drought stressed and begin to take water from the young fruit, causing the fruit to soften and the leaves to cup. If the tree is then irrigated heavily, the dehydrated fruit swell, causing them to crack. Young trees or dwarf varieties with relatively small or shallow root systems, as well as trees grown in very sandy or porous soils that do not retain moisture well may be more susceptible to fruit splitting.
    Backyard gardeners can help minimize fruit split in navel oranges by paying attention to the summertime weather forecasts. When hot winds are predicted, irrigate before the winds begin. After the hot winds subside, irrigate lightly for a few days and then resume a normal irrigation schedule. Adding four inches of an organic mulch to the surface beneath the tree can also moderate soil moisture loss, as well as feeding the soil and controlling weeds.
Geisel also advises: "Instead of a single large application of quick release fertilizer each year, smaller monthly applications throughout the growing season (Feb. through May) may help keep nutrient levels constant."

Citrus grower Lance Walheim, author of the book, "Citrus", says that a good watering pattern for oranges includes adjusting it to the weather. Allow the top three or four inches to dry before irrigating deeply. He explains that too much water retards the spread of roots and promotes soil-borne diseases. An orange tree that gets too little water will grow poorly and may die. Keep an eye out for the signs of moisture stress on the orange trees: wilting or off-colored foliage.

    Ask a dozen citrus growers how they fertilize, and you may get 12 different answers. The University of California has several recommendations: "Apply one application of nitrogen (ammonium nitrate, ammonium sulfate, or urea) in late December to February. Alternatively, fertilizers can be applied in several applications. Many commercial growers apply 1/3 of the total nitrogen needed in February, July, and September. Using a balanced citrus food may help to correct mineral deficiencies as well as provide a more complete nutrition. Manure should be applied in the fall so that the winter rains can leach the salts. Steer and chicken manure should be used sparingly because they are high in salt and may burn the trees. Mature citrus trees use 1-1.5 lb. of actual nitrogen (N) per tree per year."

I'm no fan of quick release, ammonia-based products; it's too easy to apply too much, and could damage your tree. Others have weighed in on why these salt-containing formulations are bad for your garden. But for those of you that can't resist those $3 bags of Sulfate of Ammonia piled up outside the drug store, remember that Sulfate of Ammonia (20-0-0) consists of 20% actual nitrogen. So, applying one pound of actual nitrogen over three feedings per year per mature citrus tree equals about a pound and a half of ammonium sulfate per application, spread evenly beneath the outer dripline of the tree, following the label directions.

     My citrus feeding regimen for my containerized (half-barrels) citrus trees is organic, applied every other week during the growing season (February through September): a combination of water soluble fish emulsion and sea kelp. Fertilizer leaches through containerized plants more quickly than in-ground plants. So, a light feeding, but more often (every other week instead of monthly), mitigates that loss.

There are plenty of complete and balanced organic fertilizers available for fruit trees, some that only need to be applied a few times a year.

Timed-release synthetic fertilizers offer the convenience of supplying  nutrients at an even rate, but are usually more expensive. 

Whichever fertilizer you choose, apply it according to the label directions. 

     Lance Walheim also advises against fertilizing oranges after the end of summer. Late applications of fertilizer to deficient trees, he says, can lower fruit quality, make  the rind tougher and exposes new growth to the ill effects of a winter freeze.
    There are no pests or diseases that cause splitting, nor is there a chemical control for it, explains Pam Geisel. It is a problem that stems from environmental or cultural conditions. Blame the weather this year. Next year, mulch, water and fertilize that navel orange tree correctly to help minimize the fruit split.

Droopy Leaves on a Hot Afternoon. Water...Or Not?

Do your plants have droopy leaves on a hot afternoon? 

   

There are two schools of thought.

One school says plants conserve moisture on a hot afternoon by allowing their leaves to sag.


The other school says: "Don't believe that first school."

Drooping leaves are usually indicative of a lack of water from the root zone. "Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water," writes Washington State University Horticulture Professor Linda Chalker-Scott. "Tomatoes, zucchini and black-eyed Susans...are not water conservers. Chronic wilting of these and others can eventually cause leaf tip and margin necrosis (or tissue death). It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed Susans will be decreased."
She advises applying a layer of mulch around those plants to help conserve water.

Also, check the moisture at the root level before watering.
To determine the amount of water at the root level:

• A day or two after watering, dig down 8 to 10 inches with a trowel or small shovel, near the drip line (outer canopy) of the plant. Doing this in two or three spots would be more helpful.

• At that depth, grab a handful of the soil. Squeeze that handful. If it is muddy and watery, reduce your watering for plants that require regular (but not frequent) irrigation. If it is so dry you cannot form a clod in your hand (it turns to dust instead), increase your watering (for those plants that require moderate amounts of water).

• If you can form a dirt clod in your hand, yet break it apart with a little effort, that is probably the correct soil moisture for your plant.

• Steve Zien, owner of the Citrus Heights-based organic landscaping consulting service, Living Resources, recommends the use of a soil sampling tube to determine the moisture at root level. "Just press the tube down six to eight inches into the soil after you are done watering," says Zien. "When you bring it back up, the open slot along the side of the tube will let you see if the soil at that depth is wet, moist or dry. Adjust your watering time so that the soil sample is moist, not too wet or dry."

• An easier, but more unreliable way to measure the water content of the soil: purchase an inexpensive (under $10) moisture meter, available at most nurseries. Test its accuracy by putting its probe into a glass of water. If the probe does not read "wet", choose another. Expect it to function for only a year or so.

• Battery operated moisture meter probes may set you back a few more dollars, but in my experience - with proper care (clean them after each use, don't leave them outdoors) - they will last many years.

• Extended, infrequent, slowly applied irrigation is the most efficient watering method. Soaker dripline or drip irrigation systems work best. Here in the Central Valley, foothills and Bay Area, run them for 3 to 6 hours at a time, twice a week, in the summer. This is only a guideline to get you started. Adjust that timing to your particular soil type and plants.

• And, don't forget: add more drip emitters and drip lines as the plant grows, especially for trees and shrubs. Make sure to get water to the outer canopy of the plant (and beyond) where the roots travel.

Improper watering is the number one cause of plant failure. Knowing how wet the soil is at the root level can help you keep your plants healthy.

Keep in mind: different plants have different watering needs. Learn those needs, then group plants together with similar watering requirements when designing your landscape. The Sunset Western Garden Book is a good source for that information.

Signs of not enough water at the root level of plants:
Wilted leaves in the morning. Wilted leaves in the afternoon.
Wilted leaves in the evening.
Red-brown margins of leaves.
Premature fall color of leaves.
Growth reduction.
Leaf drop.
Branch dieback.

Signs of too much water (also called aeration deficit) at the root level of plants:
The soil has a foul smell, like rotten eggs.
Soil is a blue-gray color.
Yellowing, wilting and/or dropping of leaves.
Limited new growth.
Small, corky outgrowths on the undersides of leaves.

Be warned, though: sometimes, symptoms of overwatering and underwatering can be the same (such as leaf wilting). And, symptoms of soil water problems may actually be another problem...that was caused by your watering regimen! Root rots, for example, thrive in saturated soils.

Frequent, light watering leads to shallow rooting, increasing the chances of plant problems.

How much water does your lawn need?

Some tips from the UC Integrated Pest Management Website:


• Avoid planting turf species that require frequent watering, such as bluegrass or ryegrass.
• Design your landscape to minimize water runoff onto hard surfaces and into storm drains.
• To reduce runoff, install non-irrigated buffer areas, which include water-efficient plants or permeable features, next to sidewalks or on slopes.
• Aerate heavy or compacted soils, so water can easily move down to reach grass roots.
• Install an irrigation system that you can adjust to properly water areas of your landscape that have different requirements.
• Water only when your lawn needs it.
• Water requirements vary according to turf species, location, and month of the year.
• Most lawns need water when the top 2 inches of soil have dried out.
• Shady and sunny areas and different soil types will have different water requirements.
• Deeper, less frequent watering is best for most lawns. Water only 2 to 3 times a week.
• Make sure your sprinkler system isn’t producing runoff, especially on slopes. If you see runoff, use shorter watering times and repeat the cycle to allow time for the water to move into the soil.
• Water early in the morning when evaporation and wind are minimal.
• Adjust your watering schedule seasonally, and shut off your irrigation system during rainy weather.