Q: My buddy in Morro Bay has trouble growing tomatoes, but it’s easy for me at my house in Atascadero. He claims it’s because of the summer fog, but I think it’s how he takes care of them. Who’s right?
— Bill, Atascadero
A: Your friend happens to live in a microclimate that is not ideal for growing tomatoes. His climate is substantially cooler than yours in the summer and almost all standard tomatoes need nighttime temperatures above 55 degrees F to set fruit.
We all hear about how we live in a Mediterranean climate and we do, but there are smaller microclimates within San Luis Obispo County.
Finding your own microclimate zone will make it easier for you to plant a successful garden.
The USDA has developed 11 hardiness zones across the U.S. based on high and low temperatures. A more comprehensive mapping that takes into account multiple ecological factors has been provided by Sunset Western Garden Handbook. San Luis Obispo County can be divided into a few of these smaller microclimates.
Area 7 covers inland North County from Atascadero to Paso Robles and east. It has hot summers and mild but distinct winters. Plants that require marked seasons such as flower bulbs and deciduous fruit trees grow well here.
Area 14 includes Arroyo Grande and San Luis Obispo, and features a mild climate described as having chilly winters with year-round maritime air influences. Most nontropical plants do fine in this area.
Area 16 encompasses the coastal mountains. It gets more heat in the summer than area 17, but it still has maritime influences.
Area 17 covers the coastal towns of Cambria, Cayucos, Pismo Beach, Morro Bay, Los Osos, and west Nipomo. These areas have cool summers with fog and wind and mild winters. Heat-loving plants don’t do well in this zone.
Begin by determining your zone and follow the maxim: right plant for the right place; choose plants that are adapted to your zone. For more information on growing tomatoes, click this link to a free UC publication: Growing tomatoes in your home garden. And as always, the Master Gardener Helpline is ready to take your call and help with your gardening questions.