40th anniversary logo for 2020
September Tips & Events for Santa Clara County
A late summer garden has a tranquility found no other time of the year.
~William Longgood
Fire Effects
We and our gardens have all been affected to varying degrees by the wildfires. If you have fruits and vegetables in your garden, you may be wondering if they are safe to eat. The simple answer is that there will likely be some chemicals in the plants, soil, and possibly the water, yet the benefits of eating the produce are thought to outweigh any potential risks. University of California Cooperative Extension Sonoma was involved in a study after the 2017 fires and a detailed report is available for those interested in learning more. Chemicals present in smoke vary depending on what burns: toxins from building fires differ from those of trees and grasses. When working in a garden that has been exposed to smoke and fire, consider wearing a mask and gloves. Wash produce well before eating it. To help the garden recover, amend the soil with compost or fresh soil. Keep in mind the nutritional benefits of consuming fresh produce!

For the oenophiles out there, UC has published a report on the effects of fire on wine grapes. “Smoke taint” can produce undesirable flavors in the wine ranging from “wet ashtray” to “sweaty socks.”

More Information: Produce Safety After a Fire
Powdery Mildew
Have you ever seen a squash or melon without white powder on the leaves in the fall? This fungal disease is called powdery mildew. It affects several vegetable, fruit, and ornamental plants; yet it seems almost inevitable on members of the Cucurbitaceae family which includes cucumbers, gourds, melons, squashes, and pumpkins. It primarily affects the leaves, leaving the vegetables edible. It thrives in fall conditions with warm days and cooler nights. The best defense is to plant varieties that are resistant to powdery mildew. Also helpful is planting in full sun with good air circulation through the plants. Washing off the leaves, preferably in the morning, can buy some time. Powdery mildew generally affects the older leaves first, and you can remove these when they are too covered to be able to photosynthesize. Fungicides can help but you want to be careful about using them around something you are going to eat. At some point the plant may decline so much that it needs to be removed.

More Information: Powdery Mildew on Vegetables

Photo: Powdery mildew on melon leaves, by Jack Kelly Clark
Strong-smelling marigolds can benefit nearby plants by repelling pests Photo by Jack Kelly Clark
Companion Planting
Plants can do more than just look pretty or taste good. There are a variety of chemical reactions going on that we cannot see. These can be used to your advantage to increase the success of your garden. Some plants, like mint, can repel pests which might otherwise attack nearby plants. Others, like sage, can attract bees that can in turn pollinate plants elsewhere in the garden. A plant such as black walnut can put out chemicals that keep other plants from growing nearby. Basil is rumored to make tomatoes taste sweeter, but it may just be that it is convenient to grow them together because they are often used together in the kitchen. There is not a lot of solid scientific evidence for many beneficial planting relationships, yet there are some proven effects of various plants in relation to their neighbors. The California Center for Urban Horticulture at UC Davis has put together a Companion Planting Chart that you can use to do your own garden experiments.

More Information: Companion Planting

Photo: Strong-smelling marigolds can benefit nearby plants by repelling pests, by Jack Kelly Clark
Kohlrabi comes in white or purple Photo by Jack Kelly Clark
Vegetables to Plant Now
You can start most cool season vegetables now. That includes root vegetables such as carrots and beets. Many greens can be planted now and do better in the winter than in the summer. Lettuce, spinach, and bok choy are a few of the choices. Dark leafy greens like kale and collard greens can go in too. And don’t forget broccoli, cabbage, and cauliflower. Lots of choices to keep you eating well all year long! You can start them from seed directly in the ground while the soil is still warm enough to aid germination. Many can also be started from seed in pots, allowing them to get bigger and stronger before putting them into the ground where they could encounter pests. Or you can use transplants from the nursery. If this is the first time you're planting a cool season vegetable garden, you may be pleasantly surprised at some of the advantages. There are fewer pests and weeds, and harvesting does not have to be done as regularly or promptly.

More Information: Vegetable Planting Chart

Photo: Kohlrabi produces a juicy, crisp, bulb-shaped stem, by Jack Kelly Clark
By Dr. Raabe
Spring Bloom
It’s already time to start preparing for spring flowers. Now and over the next couple months, spring-flowering bulbs can be put into the ground. Some will benefit from about six weeks of storage in the refrigerator first. Hyacinths and tulips do well with some chill time, whether they are purchased new or dug up from last season. Start with firm bulbs that are free from blemishes. Plant in well-drained soil; bulbs can rot if they stay wet. For most flowers, dig a hole that is twice as deep as the size of the bulb. Plant the bulb with the pointy side up. Add a little fertilizer in the planting hole, and lightly pack the soil back into the hole. Then just wait for spring. If you forget where you planted them, you will have some beautiful surprises.

More Information: Bulb Planting Schedule

Photo: Tulip, by Dr. Robert Raabe
Upcoming Events
We're still mostly offering online events, but we've scheduled two open-garden-days in Palo Alto this month. We hope to see some of you there! Keep an eye on our events page for the latest schedule.

Wed, Sep 09, 7:00 p.m.–8:30 p.m., ONLINE Cool Season Vegetable Gardening

Sat, Sep 12, 10:00 a.m.–12:00 p.m., Palo Alto Demonstration Garden Open!, Eleanor Pardee Park, 851, Center Drive, Palo Alto 

Sat, Sep 12, 2:00 p.m.–3:00 p.m., ONLINE Vertebrate Pest Management for Your Garden (in Chinese) 

Sat, Sep 19, 7:00 p.m.–8:30 p.m., ONLINE Growing California Native Allstars

Thu, Sep 24, 6:00 p.m.–7:00 p.m., ONLINE Landscaping for Wildfire Protection

Sat, Sep 26, 10:00 a.m.–12:00 p.m., Palo Alto Demonstration Garden Open!, Eleanor Pardee Park, 851, Center Drive, Palo Alto

Sat, Sep 26, 2:00 p.m.–3:30 p.m., ONLINE Top Ten Habits of Happy and Successful Gardeners

Visit the UC Master Gardener Program website for additional information including an up-to-date list of events and classes.

Have a gardening question? Contact our Help Desk (for Santa Clara County residents). Start by reviewing our plant problem diagnosis tips.
  • Mon-Fri 9:30 a.m.–12:30 p.m., 408-282-3105
  • Fri ONLY 1:00 p.m.–4:00 p.m., 650-329-1356 (Closed Dec. & Jan.)
  • Or send us your question online

The University of California Cooperative Extension (UCCE) Santa Clara County Master Gardener Program volunteers are trained under the auspices of the UCCE. Our mission is to promote sustainable gardening practices by providing up-to-date, research-based horticultural information to home gardeners.

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