Grafting Fruit Trees
The Mission Hills Garden Club’s August meeting had a substitute speaker. April Bright and Erik Collins were able to pinch hit and answered many questions about grafting fruit trees.
Collins and Bright have a property in La Mesa with an 11,000 square foot urban orchard of fruit trees and bushes. They have deciduous trees including pomegranates, figs, persimmons, grapes, apples, and Asian pears; and they have subtropical fruit trees with avocados and citrus and more. They also grow blueberries, blackberries, raspberries, and boysenberries. In raised beds they grow vegetables, and they are experimenting with hops.
Since the original topic was grafting, they explained a few basics that must be followed to have success. First, the graft must be the same cultivar as the rootstock. This means that a stone fruit such as peach or nectarine can only be grafted to the rootstock of a peach, nectarine, plum, apricot or any other related cultivar. Various types of avocado trees can be grafted to a healthy avocado rootstock. In other words, if the trees were mammals, only humans can have an organ from another human; the race is immaterial as long as the species is the same. Gorilla parts are compatible with other gorilla bodies, but a lemur’s heart cannot be changed for a gorilla’s; a lemon cannot be grafted to a plum tree!
The second essential is that they must have similar chill hours. Chill hours are counted when the temperature drops to between 45 and 32 degrees over the period ranging from November 1 until March 1. If your area has only 200 hours of chill, then you will only have success with plants that require fewer than 200 hours. You can find the number of chill hours for your area by going to http://www.sdedible.org/climate-zones/chill-hours-for-san-diego-2/. Metropolitan San Diego has received averages from 28 to 145 chill hours from November 1 through February in the years from 2006 until 2011. La Jolla’s hours range from 3 to 64; Escondido’s go from a low of 493 to a high of 824 hours.
Another consideration is the structure of the rootstock and that of the grafted limbs. With all grafts, the limb that receives the graft must be strong enough to bear the weight of a fruit-laden branch, and the grafts should be evenly distributed around the rootstock.
One of the greatest advantages of “mixing and matching” fruits on one tree is that you can graft fruits that ripen at different times of the year enabling you to prolong the fruit’s season. For example, Golden Delicious apples ripen in September; Granny Smiths ripen from late September to October, while Fuji apples ripen from October to December. All three of these apple cultivars have similar requirements for hours of chill.
You can also do this with avocados. Haas are great “Superbowl” party avocados, according to Collins. Reeds are ready to harvest from August through October. Avocados, says Bright, will not ripen while on the tree. They will however, rot, so they must be picked at some point. They ripen within 10 to 14 days after being picked, but they store on the tree for quite a long time, some for as long as three months. These three cultivars are good candidates to graft on a single root stock.
You can graft different types of citrus together. One rootstock may have a grapefruit section, an orange section, and a lemon section. To protect citrus from pests, spray them regularly to get dust off their leaves. This discourages leaf miners among other hungry creatures from destroying your citrus trees.
Bright likes to grow blueberries in pots. For some reason she finds they prefer to be somewhat rootbound, and they prosper more easily in pots than in the ground. Blueberries also like an acidic soil. One of the best ways to provide this is by adding two tablespoons of lemon juice per gallon of water. Fish emulsion is an acidic fertilizer as well. What you want is a PH factor of 4.5 to 5.5.
Potted plants typically need repotting about every three to five years. When the plant shows “diminished vigor,” it is time to dig out the plant and either re-plant it in a larger pot with fresh soil or “shave” the outer third of the root ball with a sharp shovel, replace the old soil with new, and put the plant with its shorn roots back in the soil. This is somewhat akin to having your split ends trimmed to maintain a healthy head of hair,
On October 6, 2012 Bright and Collins will present “Growing Blueberries and Blackberries in San Diego” at the San Diego Master Gardeners ‘Harvest to Home’ Fall Seminar. The seminar takes place from 8:45 to 3:00 p.m. at St. Madeleine Sophie’s Center, 2119 East Madison Avenue, El Cajon, California 92019. They will also be selling premium raw honey from their La Mesa hives and from hives located on 12 acres in Santee. For more information and to register, go to www.mastergardenerssandiego.org.
The next Garden Club meeting will be October 24 at 4070 Jackdaw from 6 to 8 p.m. Bring your children as this will be a family pumpkin carving event and contest. The winner gets bragging rights.
Category: Life Style
