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Mastering Your Garden

© SAN DIEGO FLORAL ASSOCIATION and Master Gardener Association of San Diego County

These stories may not be published in any form or copied onto another media without written permission from San Diego Floral Association.

Reprinted From: January/February 2023 Volume 114 No. 1

Mastering Your Garden

Plant of the Year: Coffee

By Jodi Bay -  UCCE Master Gardener, San Diego County

In San Diego County, agriculture is a $1.7 billion business according to the County of San Diego 2020 agriculture report.  Edible crops such as fruits, nuts, vines, and vegetables account for $343 billion or about 26% of overall revenue. The remainder comprises ornamental plants. There has been slow growth in edible agriculture in San Diego due to acreage loss, water costs, and lower production due to aging trees. To compensate, an upcoming growth crop for San Diego County is coffee (Coffea sp.). Coffee is not only an emerging crop but is a plant that home gardeners can grow in their garden or as a houseplant.

Legend states that a goat herder in Ethiopia saw his goats became more energetic after eating coffee berries.  He shared his finding with the local monastery whose monks felt energized after eating the berries. Initially, the berries were mashed into a fermented pulp for consumption, and in the 15th century coffee berries were roasted and ground. Word spread throughout the Middle East and Europe about coffee, and it became the beverage of choice for mornings and social events by the 17th century. Coffee supplanted tea as the beverage of choice in the United States in the 1700s when the taxes on tea were raised and the Boston Tea Party occurred. 

There are two popular types of coffee: Arabica (Coffea arabica) grown primarily in countries around the equator such as Brazil, Ethiopia and Columbia; and Robusta (Coffea canephora) grown mainly in Asia and Africa.  Robusta coffee plants have easier care and resistance to leaf rust and some nematodes.  It is a taller plant reaching heights of 19 feet, has a higher antioxidant level, and grows in altitudes from sea level to 3000 ft. Arabica produces coffee with better flavor with higher lipids and sugar amounts than Robusta and comprises 75% of the world’s coffee production. It grows best at higher altitudes between 1800 to 3600 feet.

Parts of coastal California from San Luis Obispo to San Diego have growing conditions for coffee similar to the Central America mountains. Coffee plants prefer climates that have high humidity, reliable rainy seasons, wind protection, low frost, and temperatures between 59 to 75°F. They grow best as an understory crop (i.e., grown under the canopy of another plant) in partial sun. Coffee plants prefer well-draining, slightly acidic soil that has been heavily amended with organic material. 

Growing coffee plants in a container outside or as a houseplant inside is an option if the garden soil is not conducive for optimum growth. Use a slightly acidic mix (pH below 6) amended with organic material. Add a complete, slow release NPK fertilizer when repotting or transferring into soil and fertilize lightly once every two to three months. Plant in a pot larger than the root ball and repot as that plant grows. Place in indirect sun, away from drafts and at a temperature above 65°F. Keep the plant moist, not wet, and ensure that drainage is good.

Diseases and pests of the coffee plant are minimal in the U.S. but can be significant in other countries.  Some to be aware of are Coffee Berry Borer, a small black/brown beetle that drills holes into the blossom end of coffee berries. This beetle is spread by transporting affected plant material. Coffee Leaf Rust is a fungal pathogen identified by yellow, circular spots on the top of the leaf and orange or white lesions on the underside. It causes plant defoliation and reduces berry yield. It is transferred from one infected plant to another via air, clothing, or other means. Coffee Berry Disease is also a fungal pathogen that causes small, dark, sunken brown spots on the green berry. It mummifies the berry and can be identified by a pale pink lesion on the berry.  It is transferred by water and insects. 

Small, white, fragrant flowers bloom two to three years after transplanting. C. arabica blooms are self-pollinating while C. robusta requires cross-pollination. Harvestable berries arrive 9 to 11 months later and are ready to hand pick when they are a bright red. Avoid harvesting overripe or green berries so as not to affect the coffee quality.

Processing the berries quickly is essential for quality coffee. The berries are processed to remove the outer hulls using either a ‘dry’ or ‘wet’ method, dried, stored and aged for improved flavor. Roasting is the last step and is the process of adding heat to bring out the taste and aroma of the coffee bean. The roasting process takes years to master to learn the best combination of heat and time to create the perfect cup of coffee.

For questions on home gardening, contact the UCCE Master Gardeners of San Diego County Hotline at (858) 822-6910 or by email at help@mastergardenerssandiego.org.

Jodi Bay has been a Master Gardener since 2012. She is chair of the Tool Care Committee and is an instructor in the Beginning Vegetable Gardening workshops which teaches new gardeners how to grow healthy and bountiful vegetables.

© SAN DIEGO FLORAL ASSOCIATION and Master Gardener Association of San Diego County

These stories may not be published in any form or copied onto another media without written permission from San Diego Floral Association.