Grafting Citrus Trees by Chip Budding in a California Nursery

This article shows a highly efficient bud grafting technique used for grafting citrus trees in citrus nurseries.

Grafting Citrus Trees by Chip Budding in a California Nursery.
Grafting Citrus Trees by Chip Budding in a California Nursery.

I saw chip budding of citrus performed at TreeSource Citrus Nursery in California’s central valley. Chip budding is a bud grafting technique used for grafting orange trees, grafting lemon trees, and for grafting citrus trees of all varieties. Chip budding to young citrus rootstocks makes it possible to propagate a large number of citrus trees in a small space.

Grafting Citrus Trees by Chip Budding in a California Nursery – YouTube Video

In addition to this article, I have made a YouTube video showing citrus propagation by chip budding.

 

Asian Citrus Psyllids Spread Huanglongbing, a Deadly Citrus Disease

In California our citrus trees are under severe threat from a deadly disease called huanglongbing. This disease is spread by Asian citrus psyllids and by people who graft with infected citrus budwood.

Asian citrus psyllid.
Asian citrus psyllid. Photo by Jeffrey Weston Lotz, Florida Department of Agriculture.

Shielding Citrus Trees from Asian Citrus Psyllids

California wholesale nurseries, which sell to retailers, produce citrus trees inside of insect proof structures in order to shield their trees from Asian citrus psyllids.

Inside of an insect proof structure where citrus trees are propagated.
Inside of an insect proof structure where citrus trees are propagated.

 

Starting Citrus Trees with Disease-Free Budwood

California wholesale nurseries always bud their trees using certified disease-free budwood. Nurseries start this process by getting disease-free budwood from the Citrus Clonal Protection Program or CCPP.

 

The CCPP budwood is used to propagate the nursery’s budwood mother trees.

Budwood from these mother trees is used to propagate increase trees.
Budwood from these mother trees is used to propagate increase trees.

 

These mother trees are registered with the California Department of Food and Agriculture and are periodically tested to ensure that they are free of disease.

Mother trees are registered with the California Department of Food and Agriculture (CDFA) and are periodically tested for disease.
Mother trees are registered with the California Department of Food and Agriculture (CDFA) and are periodically tested for disease.

 

The budwood from the nursery’s mother trees is used to propagate many increase trees.

Budwood from these Increase trees is used to bud citrus trees for sale.
Budwood from these increase trees is used to bud citrus trees for sale.

 

The budwood from increase trees is used to propagate citrus trees for retail sale.

In summary, one citrus bud generates a nursery’s mother tree, which generates hundreds of increase trees, which generate thousands of trees for retail sale. If a nursery were to begin with diseased budwood, it would result in thousands of diseased trees being propagated and sold. For this reason it is critical that citrus propagation start correctly with disease free budwood from the CCPP.

 

Protecting Citrus Budwood Sources Inside of Insect-Proof Structures

All citrus budwood sources including mother trees and increase trees must be protected from Asian citrus psyllids inside of insect-proof structures.

Citrus budwood increase trees protected by insect-proof structures.
Citrus budwood increase trees protected by insect-proof structures.

 

In order to enter or leave an insect-proof structure, employees go through a double-doored vestibule where only one door may be open at the same time.

Exterior door of the entry vestibule.
Exterior door of the entry vestibule.

 

A fan is triggered to blow insects out of the structure whenever the outside door is opened.

Interior door of the entry vestibule and fans that are triggered by opening of the exterior door.
Interior door of the entry vestibule and fans that are triggered by opening of the exterior door.

 

Budding Citrus Trees in the Nursery

Because of the small size of the rootstock, the chip budding technique shown here is more challenging than most other grafting techniques. The advantage of budding on a small sized rootstock is that it allows the propagation of a large number of citrus plants in a limited space, thus improving production efficiency.

The first step in the chip budding procedure is to cut the tops off of the rootstocks that have been grown from seeds.

Trimming the citrus rootstocks.
Trimming the citrus rootstocks.

 

At TreeSource Citrus Nursery, teams of three people perform the chip budding procedure. Two people are budding and a third person wraps the bud grafts from both budders.

One wrapper wraps the citrus grafts from two budders.
One wrapper wraps the citrus grafts from two budders.

 

Tools are sterilized whenever the budders switch to a new variety.

Sterilizing the grafting knife in between varieties.
Sterilizing the grafting knife in between varieties.

 

The budder first removes leaves and thorns from a row of rootstocks to make way for buds of the grafted variety.

Removing leaves and thorns.
Removing leaves and thorns.

 

For each tree in the row, the budder then cuts out part of the rootstock to prepare a space for the chip bud to be inserted.

Preparing space for chip buds.
Preparing space for chip buds.

 

Then for each rootstock, the budder cuts a bud from a budstick of the grafted variety and inserts it into the rootstock.

Cutting and inserting citrus buds into the rootstocks.
Cutting and inserting citrus buds into the rootstocks.

 

The wrapper carefully wraps each bud graft with a special grafting tape called buddy tape.

Wrapping the chip bud grafts.
Wrapping the chip bud grafts.

 

The bud will emerge right through the tape, which does not need to be removed.

budded citrus plants
Citrus buds growing through the grafting tape.

 

After the bud is wrapped, the roostocks are cut off above the buds and a tree seal is applied.

Cutting the rootstocks off above the bud grafts.
Cutting the rootstocks off above the bud grafts.

 

Applying tree seal.
Applying tree seal.

Bud Grafted Citrus Trees Ready for Sale

The finished product is called a citrus liner and is ready eight to twelve weeks after budding depending upon rootstock variety and the time of year.

Budded citrus liner.
Budded citrus liner.

 

Some citrus liners are shipped to other citrus nurseries that will allow the trees to grow to a larger size before reselling them.

Budded citrus liners.
Budded citrus liners.

 

Other citrus liners are planted in larger pots and then sold to citrus farmers after reaching a larger size.

Budded citrus trees grown to a larger size.
Budded citrus trees grown to a larger size.

 

Buying Citrus Trees from Reputable Nurseries is Critical

Huanglongbing is the deadliest known citrus disease. It spreads much more readily than other citrus diseases via Asian citrus psyllids and by movement of citrus budwood and citrus trees. When buying a citrus tree, it is very important to buy from a reputable nursery in order to avoid the inadvertent spread of disease.

Acknowledgement

I thank TreeSource Citrus Nursery for allowing me to view their grafting technique and share it with you.

Resources for Californians

Please visit CaliforniaCitrusThreat.org for more information on how to stop the spread of deadly citrus disease.

California Law Regarding Citrus Propagation

In California, the collection of any citrus propagative materials, including budwood and seeds, from non-registered sources is illegal. Any citrus trees grown or grafted in California must come from source trees registered with either:

Funding

This article was funded by a grant from California’s Citrus Research Board.

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