Avocado Tree Stumping: How Severe Pruning Saved Our Grove Through the 2008 Water Cuts

Avocado tree stumping means cutting a tree down to a short trunk so it can regrow a whole new canopy, and it saved part of our grove during the water cuts of 2008. It costs about two years of fruit, but a tree with no leaves needs very little water, so stumping can carry a grove through a shortage that would otherwise kill it.

Walk through our grove in North San Diego County today and you will notice trees with an unusual shape: thick old trunks with two or three big limbs rising from an old cut line, topped by full, productive canopies. Those shapes tell the story of how the grove got through one of the hardest stretches in California avocado farming.

Water restrictions in 2007 and 2008

In 2007, after several years of drought, San Diego County growers faced deep cuts to their irrigation water. Avocados have shallow roots and use a lot of water, so keeping every tree fully watered was no longer possible.

In 2008, my mother-in-law and our grove manager had to make hard decisions fast. There was not enough water for a grove full of mature, fully leafed canopies. Rather than lose the trees to drought stress and salt burn, they chose a proven survival method: cutting the trees down to the lower trunk, which growers call stumping.

Avocado Production in California: A Cultural Handbook for Growers, Book One records a 30 percent water cutback in 2007 for growers on the interruptible agricultural water plan, and says many growers used the time to stump back trees that had grown too tall. It also notes that even after the drought was declared over in 2010, water rates stayed high and set off a downward spiral of groves going out of business in the county.

Read nextAvocado Tree Sunburn and Pruning Water Sprouts: How to Protect Grove Yields

Why stumping an avocado tree works

An established avocado tree has a big root system and stored reserves in its trunk and roots. Remove the canopy and a few things happen:

• Water demand drops: With no leaves to lose water through, the tree needs very little, and the roots stay alive on minimal irrigation.
• Reserves go into new growth: The tree pushes new shoots from buds under the bark instead of feeding old wood.
• The tree comes back down to size: Tall, leggy trees return to a height that can be picked, with more light reaching the canopy.

How do you stump an avocado tree?

Avocado Production in California: A Cultural Handbook for Growers, Book Two lays out the method. Cut the trunk at 4 to 5 feet, either leaving 2-foot stubs of the main limbs or no stubs at all, and slope the cut so rain runs off. Paint the stump right away with whitewash or white water-based paint, because bare avocado bark sunburns badly. The handbook says not to use a pruning sealant.

Timing matters too. The handbook advises stumping as early in the year as possible, once the threat of rain has passed, and stumping a whole irrigation block at once. Irrigation can stop until new leaves grow, then the soil should be kept moist but not wet, guided by a tensiometer.

How long until a stumped tree bears fruit again?

About two years. The handbook puts it plainly: stumping takes a grove out of production for two years. In a trial that stumped a grove in May 1998, none of the three treatments produced a real crop in 1999 or 2000. In 2001 the trees came back with roughly 4,600 to 8,900 pounds an acre, depending on how they were pruned afterward.

That trial also shows why follow-up pruning needs care. Trees left alone after stumping gave the most fruit, peaking in the fourth year at 23,937 pounds an acre, but then crowded each other and yields fell. A central-leader system, topped at 14 feet, kept every fruit within reach of a picking pole from the ground. A vase system pruned in October lost most of its fruiting wood, because the handbook’s rule is to prune in spring and never after the summer flush.

The handbook also records a shortcut that failed: stumping every other row so the grove keeps some production. The stumped rows sat in the shade of their neighbors, grew upward without flowering, and only fruited once they reached two-thirds of their old size.

Managing regrowth since 2008

Stumping is not a one-time job. When a tree is cut back, buds under the bark break and send up dozens of fast, upright shoots. Left alone, they compete with each other and form weak branch joints.

In our grove, selective thinning over the following seasons let two or three strong shoots harden off and become the new main limbs. In the years since 2008, those limbs have grown into full, productive canopies.

What our stumped trees look like today

Our second video walks the oldest section of the grove. These trees were planted roughly 25 feet apart and now reach something like 40 feet into the air, and at the base of most of them you can still see the old stump cuts with the regrown trunks rising from them. The plan had been to stump about every third tree to meet a one-third cut in water; looking at them now, most of them seem to have been stumped in the end.

The trees came back healthy and huge, but the yields never fully returned to what they were. That is part of the cost of getting through a drought this way. The height is its own problem at harvest, which is why we prefer to keep trees lower, as we explain in how tall do avocado trees grow.

We are not alone in leaning on this. In the 2011–12 season, 7,800 of California’s 59,629 avocado acres had been topped or stumped, according to Book One.

Lessons in tree resilience

Farming in California means adapting to drought, water prices and the trees’ own cycles. Seeing these once-stumped trees thriving today is a daily reminder that a hard cut, made at the right time and followed by patient care, can give an old tree decades more life.

For the year-round care that brings a reset tree back into production, see our guide to growing avocado trees, and for the water side of a drought decision, how much water an avocado tree needs.