Question: I want to plant another oak tree on our 2 acre area, but I have heard that the oak tree died suddenly. What kind of oak tree should I grow, and which plants will thrive around my oak tree? Also, how much water do I need to water oak seedlings and other mature oak trees?
Answer: Since its first appearance in the mid-1990s, the sudden death of oak trees has killed hundreds of thousands of native and tan oak trees in California. Trees in the red oak group are susceptible to the disease, but so far, oak trees in the white oak group have not been affected by the sudden death of oak trees.
The valley oak Quercus lobata is a good white oak, suitable for planting in valleys with fertile soil, below 1,000 feet above sea level, and away from salt water. The valley oak grows into a very large tree; make sure to give it enough room to grow. Quercus garryana, the Oregon white oak, is another good choice, growing in many habitats below 7,000 feet above sea level. It is smaller than the valley oak and is better tolerant of crowding. Finally, the blue oak tree Quercus douglasii grows in barren rocky soil and hot, dry foothills at an altitude of 500 to 2,000 feet.
All white oaks, especially blue oaks, are susceptible to powdery mildew. Therefore, it is best to plant them at least one mile from the ocean.
When planting young oak trees, be sure to give them enough water. Remove nearby weeds that compete for water and use mulch at least 1 or 2 feet away from trees to help maintain soil moisture. Make sure that the mulch does not touch the trunk. Water the seedlings near the base of the tree, but as the tree grows, water away from the base at the drip line.
Plant young trees in autumn or winter to take advantage of winter rain. For the first year, water the seedlings every day in hot and dry conditions until the oak trunk is at least one inch in diameter. As the tree builds, you can gradually reduce watering.
All oak trees native to North Bay like to fetch water in winter and spring when the soil temperature is cool. However, if the soil is dry in spring and the probability of rain is low, you can give the oak tree extra water.
A good way to do this is to place a soaking hose inside the tree's drip pipe, cover the hose with a mulch and let the water flow until the top 12 inches of soil becomes wet. This may take from 20 minutes to several hours, depending on the soil.
If your tree is on a steep slope, start the timer immediately after you start watering. Let the water flow until you start to see runoff, then turn off the water and record how long has passed. Wait at least an hour, then turn on the water again, let it run for one minute less than the first time. Turn off the water before seeing runoff.
Mature oak trees adapt to dry, hot summer conditions. They usually cannot tolerate regular summer irrigation, which promotes the growth of fungi, which attack the roots and canopy of oak trees. However, during periods of prolonged drought like now, even mature oak trees can benefit from infrequent watering, maybe once a month or so, depending on your soil. Deeply soak the outer two-thirds of the root zone under the tree, 6 feet from the trunk, to the edge of the tree's drip line.
When landscaping around mature oak trees, it is best to plant the landscape at least 10 feet from the canopy. Do not plant plants that require water at the drip line or inside the local oak tree. Try to grow native California plants suitable for living under oak trees, such as acacia, monkey flowers, light blue eyes, or California poppies. Many native plants are also colorful, attractive and resistant to pests. Native grasses such as California fescue and blue gamma grass are becoming more and more popular. They grow naturally under oak trees and require little water and maintenance.
For more information on growing oak trees and choosing compatible plants, see "Living in Oak Trees: A Management Guide for Woodland Owners and Managers" at bit.ly/3g6eIUj. Sudden oak death: bit.ly/35fh6Cg
It's time to grow garlic! Most local nurseries have various garlic bulbs grown specifically for home gardens.
To grow garlic, separate each clove from the bulb and place the pointy side up, 4 to 6 inches apart and 2 to 3 inches deep. When you are in the nursery, pick up some bulbs that bloom in late winter and early spring, such as daffodils and tulips.
It is not too late to grow more cool-weather vegetables, such as cabbage, peas, radish and vegetable salad. You may not know that mache, also known as "corn salad", is a mild-tasting green salad that you can spend the winter in your garden. It can also be cooked like spinach and used in soups.
Have you lost some plants due to drought? Consider replacing them with native California plants. This is a good time to plant native shrubs, trees and flowers. They are very adaptable to our climate and soil, use less water and promote wildlife biodiversity in your garden.
If you have deciduous trees, consider composting the leaves. You can run a lawnmower on them to break them down and promote decomposition.
Use municipal green trash cans to dispose of diseased plants or seeded weeds. High temperatures are needed to kill weed seeds and pathogens; commercial compost piles can be heated to 190 degrees. If you live in Sonoma County, do not put poison oak trees, yucca tree ornaments, bamboo, cactus, or palm leaves in the green trash can. Instead, throw them into the trash cans of ordinary landfills.
The contributors to this week’s column are April Lynch; Steven Swain, UCCE Environmental Horticulture Consultant, Sonoma County and Marin County; Laura Ekin; Karen Felker; Laura Southworth; and Debbie Westrick. Send your gardening questions to scmgpd@gmail.com. The University of California Sonoma County Master Gardener Program (sonomamg.ucanr.edu) provides home gardeners in Sonoma County with environmentally sustainable, science-based gardening information. The Master Gardener will only answer the questions selected for this column in the newspaper. For other questions, please contact their information desk: 707-565-2608 or mgsonoma@ucanr.edu.
Update: Please read and follow our comment policy: