May Tips & Events for Santa Clara County
"Queer things happen in the garden in May. Little faces forgotten appear, and plants thought to be dead suddenly wave a green hand to confound you." ~ W.E. Johns
Monthly Tips
Have you noticed that different plants attract aphids of different colors and shapes? Once you’re done admiring nature, you may want to take action to protect your plants. Aphids are classified as sucking insects, which means that they suck the juices right out of plants. They take the nutrients needed for plant growth, and the plant will start to get weak and possibly die. If you monitor your garden regularly and find aphids when their population is still small, you may be able to simply knock or hose them off the plant or prune out the infested part of the plant. When aphid populations are large, nature can help you control them — beneficial insects will be attracted to eat the aphids. You can encourage beneficial insects in your garden by including a variety of plants that flower at different times throughout the season. Avoid chemicals which kill good and bad indiscriminately. If ants are protecting the aphids in a plant, control the ants. Decide what population you will tolerate in your garden, and have patience because it can take time to establish a healthy ecosystem.
Photos, clockwise from upper left: Bean aphid, melon (cotton) aphid, potato aphid, and cabbage aphid, all by Jack Kelly Clark
Transplanting Vegetables
Vegetable seedlings - by Laura Monczynski
As vegetable seedlings start to outgrow their pots, you can transplant them into larger pots, raised beds, or the ground. Make sure the seedling is well-watered before moving it. To remove the plant, either turn the pot upside down — with your other hand positioned to catch it! — or pull the entire root ball out with a fork or other utensil. Be sure never to handle the seedling by the stem, with its vascular tissue that conducts water and food. If the roots are packed together or circling, gently pull them apart. Then gently move the plant to its new home, lightly packing the soil around it. Make sure the soil is at the same level on the stem as in its original pot, except for tomatoes and peppers which can be planted deep. Immediately water thoroughly. A little fertilizer can also be added when transplanting. Transplant shock can be minimized by not changing too many conditions at once, e.g., temperature, wind, or sun exposure.

Photo: Newly sprouted squash seedlings, by Laura Monczynski
Direct Seeding
Seed structure from MG handbook
Some of the larger summer vegetables can be planted from seed directly into the garden this month. These include watermelon, cantaloupe, corn, and summer and winter squash. They tend to have larger seeds, and a rule of thumb is to plant them at a depth of two to three times the diameter of the seed. If you have a seed packet, follow instructions for planting depth, spacing, and thinning. These larger plants tend to grow quickly and out of the reach of many pests that impact small, tender, young seedlings. Amend and thoroughly water the soil before planting so that the seeds are not washed away with watering. Drop the seeds in holes and cover them with soil, or push them down into the soil. Then water again. Keep a close eye on emerging seedlings and protect them from pests as needed.

Photo: Typical seed structures illustrated in a garden bean seed, from California Master Gardener Handbook
Bamboo has a reputation for spreading out of control, but not all varieties are classified as running bamboo. There are clumping bamboos which are easier to contain. Bamboo is a grass, albeit one that can grow over fifty feet tall. Tall bamboo is often used as a privacy screen. It does best in full sun or partial shade. It is fairly drought tolerant and is an easy plant to grow. Deep barriers may be able to keep it from spreading. If planting in a container, check regularly to make sure the roots are not escaping from the drainage holes and thus growing beyond the pots into your yard or your neighbor’s. Foothill College in Los Altos Hills has a bamboo garden with over 80 varieties of bamboo if you’d like to see how many different ways bamboo can grow.

Photo: Bamboo escaping under a wall, by Laura Monczynski
Bamboo escaping under a wall Photo by Laura Monczynski
Lawn Care
Lawn photo from Sacramento County Master Gardeners
Photo: fescue lawn, courtesy Sacramento UC Master Gardeners
As the weather changes, many of our management techniques have to change. Lawns need more water as the temperature increases and the humidity lowers. But please be sure not to overwater as we head into another drought. Adjust timers monthly throughout the year. In the warmer months, lawns may need water twice a week. It is not good to water daily. If watering is daily and brief, the roots will stay shallow and susceptible to drying and burning. If watering is daily for a long time, then too much water is being wasted by going below the root zone or running off. Make sure you are mowing to a height appropriate for your type of grass. Fertilizing in May is good, even if you are grasscycling, which only provides about 20% of a lawn's fertilizer needs. Grass is all leaf so the primary nutrient needed is nitrogen. Keep on top of weed removal.
Upcoming Events
Vegetables transplanted into a raised bed
Easy Raised Beds and Containers for Vegetables, Saturday, May 1, 10–11:30 am, Palo Alto Demonstration Garden, 851 Center Drive, Palo Alto

Plant Clinic, Saturday, May 8, 10 am–noon, Online

Growing Great Basil, Tuesday, May 18, 7–8 pm, Online

Springtime Household Pests, Thursday, May 20, 1–2 pm, Online

Plant Clinic, Saturday, June 12, 10 am–noon, Online

Integrated Pest Management for Rodents, Thursday, June 17, 1–2 pm, Online
Check our calendar for the latest schedule of events. Videos of many past presentations are also available.

Photo: Transplanted vegetable seedlings
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:

Have a gardening question? Contact our Help Desk (for Santa Clara County residents). Start by reviewing our plant problem diagnosis tips and then:
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