January Freeze: what does it mean for my olive trees?

As you know, we had a hard freeze the first week of January. We’ve been touring orchards and answering questions. We want to take this opportunity to share with everyone our thoughts, observations and provide “grower to grower” feedback.

Joining in on this conversation is Dr. Robert A. Lane, Professor of Plant and Soil Sciences in the Department of Agricultural Sciences and Engineering Technology at Sam Houston State University. Lone Star Olive Ranch had the distinct pleasure of consulting with Professor Lane on installation of the Gibbs Ranch orchard from the ground up, beginning in 2014/2015. Actual planting at the SHSU Gibbs Ranch took place in late February of 2016, with half of the three-acre orchard planted to Arbequina and the other half with several other varietals.

Q&A with Professor Lane and Lone Star Olive Ranch

1.  It was really cold and my trees are not looking happy.  Should I be worried?

Professor Lane:

Our trees had only been in the ground nine months when the first hard freeze (34 hours below freezing and a low of 23°F) hit us. We had some really nice, mild weather in October and November and the trees grew a lot during that time period, which is not necessarily a good thing going into winter. I had hoped we could at least get through the first winter with little stress to the newly established trees, since younger trees are more susceptible to freeze damage. The first hard freeze followed a period of temps being in the 30s and 40s, at least allowing the trees to harden off a bit. Observing the orchard a couple days later, it appeared that the young trees suffered just a bit of tip die back and the plants had come through with minimal injury. Then the temperatures shot up to the 60s and 70s from 12-29-16 to 1-3-17. I’m afraid these conditions caused the trees to lose most of their “hardening” against the cold. Beginning early morning on January 6, temperatures again dropped below freezing and stayed there for 55 hours, reaching a low of 17°F. I am very concerned, especially after observing the trees this morning (1-15-17).

Lone Star Olive Ranch:

These are the cold temperatures that make everyone nervous because these temperatures do serious harm and can kill trees. These types of temperatures being 17°F and staying under 32°F for the length of time we endured. It came fast, it came hard and it stayed under freezing in our area for more than 24 hours. Should growers be worried? Yes, we do believe there are legitimate reasons for concern. Key factors affecting us: (1) below freezing for greater than 20 hours; (2) rapid changes in temperature extremes; (3) heavy winds following the weather event; and (4) preparedness. The latter meaning, the forecast was way off. As a result, we were caught off guard.   Have we lost our trees? No, but we will likely have losses and our greatest losses will be evidenced in diminished production for the 2017 harvest season.

2.  I'm not sure what I need to be looking for.  What does cold or freeze damage look like?

Professor Lane:

The initial damage to our trees included tip die back, lack of luster to the leaves, and cupping of the leaves as well as some necrotic or chlorotic lesions. Five days after the extremely low temperature, the trees showed more extensive damage, with many leaves turning completely brown, especially on Bouteillan, Manzanillo, Ouslati and Pendolino. Leaves on the Arbequina appear to have less damage at this point, but I think it is still too early to tell how serious the damage is. I was back in the orchard this morning, seven days after the deep freeze, and I noticed a great deal of leaf drop, even if the leaves were still completely green. Some trees have lost up to 50% of their leaves. As I ran the branches through my hands, more leaves turned loose, so I know the leaf shedding is not yet complete. I noticed many of the smaller branches have split bark and the cambium layer beneath is brown, so I know there has been extensive damage to the plants. So far, the cambium on the trunks of most trees is still green. I’ve included a few photos of what I observed this morning.

Lone Star Olive Ranch:

Day one there was minor evidence of leaf burn, tip die back and bark split on unharded trees. As the week progressed, symptoms started to express more significantly. Some varietals more pronounced than others. For example, Pendolino, Leccino, Kalamata, Amiffisa, Koroneiki and Arbosana – these trees were hit pretty hard. Aspects of damage to look for include tip burn; bark, wood and leaf discoloration; abscission (defoliation or flushing of leaves); limb die-back; and bark split.

3.  What do I need to be doing to minimize damage now?

Professor Lane:

I really don’t know of anything we can do now except to ensure the trees have adequate but not excessive moisture in the soil and hope for milder conditions than normal through the remainder of the winter, but obviously, we have no control over that. We plan to wait until spring to see where recovery/new shoots begin to develop on the trees before we start pruning away any dead tissue. In California, they may spray with copper based bactericides/fungicides to prevent olive knot infection, but I don’t have enough experience with olive to know if this will be an issue for us.

Lone Star Olive Ranch:

Retroactively, there is no curative. What’s done is done. It is truly a waiting game to see how the trees recover. I do recommend documenting events in your orchard and continual assessment of damage. Not all damage will be self-evident. Some can take weeks to present in the field. The action plan is truly in the preventative planning. With hindsight knowledge, we would have applied a foliar copper compound to all trees and deeply irrigated the orchards. Bottom line, damage is going to happen when we get down into those staying hard freeze numbers.

4.  What’s the time-frame for assessing damage?

Professor Lane:

While my personal experience with olive is limited, I have provided an explanation above of what I’ve seen to this point. However, I think it will be April or May before we will know the true extent of the damage. Perhaps, and I think likely, the damage may become even more obvious as production is measured next summer/fall. For those with producing trees, I have a hard time imagining that fruit yield will not be reduced as a result of this freeze.

Lone Star Olive Ranch:

Signs of damage are already starting to present. For example, bark split was evident immediately or within a 24 hour window post freeze. Tip die back and burn was again immediate. Desiccation continued throughout the week. We are also seeing abscission and evidence of some axillary bud damage. As we move into spring, we’ll be able to see if vegetative buds survived the freeze and we’ll be looking for misshapen, twisted, distorted or cupped leaves. Damaged branches will likely have fewer inflorescences and develop more slowly. Fruit for 2017 could express as smaller and yields significantly reduced due to damage to fruiting buds. During the growing season, we’ll be looking for die-back of large-sized limbs, which would generally be the result of weakened limbs affected by bark split.

5.  When do I make an action plan and what should I do?

Professor Lane:

As mentioned earlier, I plan to wait until spring, possibly late April, to more accurately assess the extent of damage, especially since we have more winter remaining. We will be restaking and retying some of our young trees to minimize root disturbance from the whipping winds. Once the hard freeze probabilities have diminished, we will apply three tablespoons of a balanced controlled release fertilizer along with one tablespoon of 16-6-12 to each live tree (our trees are only about four feet tall). I want to encourage rapid regrowth early in the spring and summer and hope my nitrogen supply is running out in late summer to reduce the amount of succulent growth going into next winter. I’m pretty sure we will be doing some replanting as well.

Lone Star Olive Ranch:

We’re all nervous and worried. There are inherent risks in farming. We always create our management plans well ahead of time (pre-spring, summer, harvest, fall/winter) and adjust it as needed throughout the year.  Our action plan is to move optimistically forward and tackle the challenges ahead.  Every field will likely not be the same.

Our first step is to give the trees an opportunity to recover. Every step after is contingent on the weather (rain and how long we stay cold). The present plan:

  1. initiate irrigation mid-February to stimulate root activity;
  2. boost orchards with fertilizer based on current soil reports and leaf analysis;
  3. prune conservatively mid-to late March to remove damaged or dead wood;
  4. boost orchards again with fertilizer (will be assessed based on need);
  5. remove the dead; and
  6. continue to assess and follow progress.

The needs are (1) good water and (2) fertilizer to restore foliage or regrow canopies.

The goals are (1) improving the health of the trees, (2) controlled, sustain growth; (3) fruit for harvest 2018.

For now, sit tight.  Take notes about what's going on in your orchard.  Take photos for reference.  Tequila helps too!  Things may look worse before they look better.  It's going to take time for recovery.  What is lost, can be replaced.


Photos From Gibbs Ranch January 15, 2016

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