May Tips & Events for Santa Clara County
My garden is my most beautiful masterpiece.” ~ Claude Monet
Monthly Tips
Guess what this is!
What’s Wrong Here?

Do you have an apple or pear tree that looks like this? Common early symptoms—usually seen in May and June— include leaves turning black and new branches bending over at the tip in a “shepherd’s crook” shape. Later, you may see young fruit turning black, and oozing from branches or the trunk. You might see it on quince and pyracantha as well.

Read to the end to learn what this is.

Photo: Purdue University
Fruit Thinning
Fruit trees often set more fruit than they can support, resulting in small fruit and sometimes limb breakage. Peaches, plums, apricots, apples, pears, kiwifruits, and persimmons almost always need to be thinned. Thinning too late reduces the chances that remaining fruit will achieve full size. Remove excess fruit when they are about ½–1" in diameter. Apricots and plums should be thinned to 2–4" apart; peaches and nectarines to 3–5"; for apples and pears, leave one to two fruit per cluster.

Photo: Young peaches before thinning, Allen Buchinski
oung peaches before  thinning - Allen Buchinski
Planting soil-mixes
Potting Mix vs Planting Mix

Is there a difference between potting mix, potting soil, and planting mix? The best advice is to read the label. The terms for bagged mixes aren’t regulated, so they can vary by manufacturer. What’s important to know is that not all bagged mixes can be used in pots. Some are meant to be used as garden fill, amendment, or mulch, so they won’t provide the right water retention, drainage, or nutrients for container gardening.
Irrigate in Circles and Spirals
When you add a new plant to your landscape, it’s important to keep the root ball well watered until the roots start extending into the surrounding soil. The root ball can dry out even when the surrounding soil is moist, so an irrigation emitter is often placed right at the base of the plant. However, the irrigation needs to change as the plant matures. As the plant grows, move the irrigation away from the base and instead start irrigating in circles or spirals around it. For trees and large shrubs, continue expanding the irrigation spiral as they grow.
Place dripline in a circle or spiral around plants and trees - California Urban Forests Council
Photo: Place dripline in a circle or spiral around plants and trees, California Urban Forests Council
Use a thick mulch to keep soil cool and conserve moisture
Drought Tips for Vegetable Gardening

Vegetables are not drought tolerant, but you can still make water-wise decisions when you grow them.
  • Plant only as much as you can use. Produce that isn’t harvested wastes water.
  • Plant in groups or triangular patterns rather than straight rows. This lets you water more efficiently, and the plants form a leafy canopy that shades the soil.
  • Mulch, mulch, mulch to decrease moisture loss and reduce competition from weeds.
See the link for more tips.

Photo: Use a thick mulch to keep soil cool and conserve moisture, Karen Schaffer
Tree Squirrels
Tree squirrels are a common nuisance across Santa Clara County. They dig in pots, gnaw bark from plants, eat fruit and flower blossoms, and dig holes in yards. They are active during the day and distinguished from ground squirrels by their long bushy tails, lack of markings, and quick escapes up the nearest tree. They can be difficult to manage due to their persistence. Refer to the linked pest note for options. A UC blog posting provides details about hunting and trapping regulations. For more information, register for a May 19 webinar on squirrel pest management.
Western gray squirrel Dr Lloyd  Glenn Ingles - California Academy of Sciences
Photo: Western gray squirrel, Dr. Lloyd Glenn Ingles, California Academy of Sciences
Pruning failed to eliminate fireblight - which continues to spread - Purdue University
Photo: Pruning failed to eliminate this fireblight, which continues to spread, Purdue University
What’s wrong here? — Answer

Fire blight is a bacterial disease affecting apples, pears, and related plants. Open flowers are the most common entry site. Infected flowers and flower stems wilt and turn black on pear trees and brown on apple trees. Some infections affect only the flowers, while others extend into the twigs and branches, causing small shoots to wilt and form a crook at the end. When it spreads into the tree, wood beneath the bark will have pink to orange-red streaks, and cankers can form, releasing a bacterial ooze. Prune out infections. The best way to avoid it is to select resistant varieties.
Upcoming Events
Our monthly Plant Clinic Online is an opportunity to chat with a Master Gardener via Zoom to diagnose a plant problem. You can also listen and learn while other people ask questions. It takes place on the second Saturday of the month (May 14), from 10–noon. Priority will be given to questions that are emailed in advance; instructions are in the Zoom registration confirmation. Registration required.

Container Gardener, Tuesday, May 3, 6:30–8:30 pm, Fremont Unified High School District Adult School, Room 106, 589 West Fremont Avenue, Sunnyvale

Open Garden Palo Alto Demonstration Garden, Saturday, May 7, 10 am–noon, Palo Alto Demonstration Garden, 851 Center Dr, Palo Alto

Jump Into the Summer Garden, Saturday, May 7, 10–11 am, Palo Alto Demonstration Garden, 851 Center Drive, Palo Alto

Talking About Tomatoes!, Saturday, May 14, 10–11:30 am, Martial Cottle Park, 5283 Snell Avenue, San Jose

Plant Clinic, Saturday, May 14, 10 am–noon, Online

Open Garden Palo Alto Demonstration Garden, Saturday, May 14, 10 am–noon, Palo Alto Demonstration Garden, 851 Center Dr, Palo Alto

Seed Swap !, Saturday, May 14, 10–11:30 am, Martial Cottle Park, 5283 Snell Avenue, San Jose

Squirrel Pest Management, Thursday, May 19, noon–1 pm, Online

Open Garden Palo Alto Demonstration Garden, Saturday, May 21, 10 am–noon, Palo Alto Demonstration Garden, 851 Center Dr, Palo Alto

Summer Vegetable Gardening, Wednesday, May 25, 7–8:30 pm, Online

Open Garden Palo Alto Demonstration Garden, Saturday, May 28, 10 am–noon, Palo Alto Demonstration Garden, 851 Center Dr, Palo Alto
Check our calendar for the latest schedule of events. Videos of many past presentations are also available.
About Us
University of California Master Gardener volunteers promote sustainable gardening practices and provide research-based horticultural information to home gardeners. Visit our website for more information including:


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