By Susanne von Rosenberg, UC Master Gardener of Napa County

It's the middle of October, we haven't had any rain yet, and I'm working on and thinking about my spring vegetable garden. How can that be?

First of all, the middle of October is more or less the latest time that you can get some cool- season vegetable seedlings into the ground. Most of them, such as the brassicas (broccoli, cauliflower, Brussels sprouts and kale), will not mature before the cold weather sets in. However, they will get a head start in becoming established, develop a strong root system and reward you with rapid growth as soon as the days lengthen and warm up in the spring.

You can still get in one more round of some leafy crops such as fast-growing lettuce or Asian greens. Even if they don't get as big as they would if we had more sunlight and warmth, they will still form a harvestable crop by mid- to late November. Make sure that you protect your little darlings from birds and other critters. At this time of year, anything green and juicy is appealing to wildlife.

Another part of planning for my spring vegetable garden is deciding where to put those October vegetable starts. That means deciding which of my summer crops are ready to come out. This is a good time of year to harvest the last of your tomatoes and cut the plants to the ground or remove them. Tomatoes that ripen later are generally not very tasty and also more likely to succumb to diseases.

Similarly, my pole beans are largely exhausted and ready to be removed. I can't take out all of my squash plants yet because a few are still ripening fruit. However, those that have yielded enough or have only very immature fruits are also coming out. By the way, you can treat those very young winter squash like summer squash; they are edible and tasty.

Because I'm a great fan of cucumbers, I usually coax my cucumber plants as far into the fall as I can. You may also have vegetables that you just really don't want to let go of. That's part of the planning process as well. If you're saving seeds for next year, remember to do that before you remove the plants.

Not all of my summer vegetable plants have to come out at the same time because I don't need all that space for planting. The areas that I'll be planting next spring are great candidates for growing cover crops right now. I like to use fava beans, which are easy to plant. You can eat the young leaves (steamed like spinach) and the flowers (fun in salads), and you can leave some of the flowers to develop into fava beans. I usually like to let the plants mature in those areas where I'll put warm-season crops in late April or May.

Another thing I like to do in the fall is to refresh my vegetable beds, if needed. I have hardware cloth (often referred to as gopher wire) underneath all of my vegetable beds. This year, the gophers broke through in one bed and took out my acorn squash and mini pumpkins.

The other aspect of my spring-garden planning is determining what to plant where and when. I figure out when I need to plant various seeds or seedlings so I can harvest a crop around a certain time. Then I plot where I want to put those plants. I always rotate crops. It's important not to grow plants from the same family in the same spot every year. Crop rotation helps control pests and diseases and also helps balance the nutrient demand in the garden.

Once I know where those plants are going and when, I can decide where to put cover crops and which ones I'll leave in place to harvest. Then I check my seed supply. I make sure that I have the ones I want and that they are fresh enough to use. Some seeds, like lettuce seeds, don't last long, so it's best to purchase new seed ever year. I don't know anyone who plants a full packet of lettuce seeds every year, unless they are growing them as baby lettuce. If you know you won't need all those seeds, consider sharing with friends.

Most brassica seeds, as well as summer vegetable seeds such as tomatoes, squash, melons and beans, are viable for two years. When seeds get too old, they don't sprout as well, and even if they sprout the plants they produce won't be as vigorous. By knowing which vegetable seeds I need, I can order early to make sure I get the seeds I want and they arrive on time.

As you can see, even though the warm weather is winding down, there is still a lot going on in the garden.

Food Growing Forum: Last Sunday of the month through October. Register to get Zoom link at: http://ucanr.edu/foodgrowingforum2020
Sunday, October 25, 3 pm to 4 pm, “Planting Onions, Leeks and Other Alliums and What Else to Do Now”

Napa Library Talks: First Thursday of each month. Register to get Zoom link.  http://ucanr.edu/wildlifehabitat2020

Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.

For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.

By: Susanne von Rosenberg, UC Master Gardener of Napa County

Most of us know quite a bit about honeybees, and even other native bees. This summer I noticed quite a few bumblebees in my yard, and I was curious to learn more about them.

Worldwide, there are only 250 species of bumblebees; 26 are native to California. For comparison, California has 1,600 native species of bees (the world total is 3,600).

Like many other bee species, some bumblebees are also under threat. They can be threatened by human activities including habitat fragmentation, pesticide use, disease transmission and loss of native flowers.In June 2019 the California Department of Fish and Wildlife proposed four native bumblebee species for protection under the Endangered Species Act. They are Crotch's bumblebee, Franklin's bumblebee, Suckley cuckoo bumblebee and Western bumblebee. (Cuckoo bumblebees are more or less what you would expect: They invade the nests of other bumblebees, kill the queen and use the workers to rear their young.)

Like honeybees, bumblebees form colonies headed by a queen, but the colonies are much smaller, typically in the range of 50 to 400 individuals. Honeybee hives hold about 50,000 bees. The colony is formed by a queen, who burrows into the ground in the fall to overwinter and emerges in the spring to find a suitable nest site.

Nest sites are also usually underground and often are old mouse or other rodent burrows. She then builds cells, supplies the nest with pollen, lays eggs (which will have been fertilized the previous fall) and incubates the eggs on the pollen. She'll continue to gather nectar and pollen until the first female workers are ready to go out and get more. Once the new workers are able to supply the colony, the queen no longer has any need to leave the nest.

Like honeybees, bumblebees are corbiculate, which means they have pollen baskets on their hind legs. The queen will continue to lay eggs, and there will be several generations of workers during one season. By the fall, most of the colony will have died.

Young queens emerge from the nest in early fall to mate, often more than once. Male bees spend their whole lives looking for a queen to mate with. They are often forcibly driven out of the nest and rarely return once they emerge. Instead, they sleep under leaves or whorls of flowers at night.

Bumblebees vary in appearance but are generally plump and densely furry (covered in bristles). They are larger, broader and rounder-bodied than honeybees. Many species have broad bands of color that can be used to help distinguish different species.

Bumblebees are active under conditions in which honeybees stay at home and can readily absorb heat from even weak sunshine. The thick pile created by their bristles acts as insulation to keep bumblebees warm in cold weather; species from cold climates have longer bristles (and thus thicker insulation) than those from warmer climates.

Bumblebees can fly in much colder weather than honeybees because they can raise their muscle temperature by shivering. The temperature of the flight muscles needs to be at least 86°F before the bumblebee can fly. At an air temperature of 55°F, it takes about five minutes of shivering for a bumblebee to be able to fly.

Bumblebees are important pollinators of wildflowers as well as fruit and vegetable crops. Bumblebees can be separated into three different classes by tongue length: short, medium and long. Collectively, they can pollinate a wide variety of flowers. A few of the short-tongued species “cheat” to feed on long-tube flowers. They bite a hole in the flowers near where the nectar is produced and harvest the nectar through the hole.

Bumblebees also have a unique behavior called sonication. They vibrate their wing muscles to shake pollen grains out of the anthers of flowers. They'll visit flowers that don't produce nectar, such as tomato plants, to collect the pollen. Possibly bumblebees got their name from the buzzing sound they make when sonicating. They used to be called “humble bees” because they hum; that term eventually gave way to bumblebee because of their somewhat bumbling flight path.

You can help preserve bumblebees and continue to enjoy their antics by providing suitable habitat and food. Like other ground-nesting bees, bumblebees need areas of bare soil. If you till your soil, you will destroy the nests of any ground-nesting bees that may be present.

Bumblebees, like other bees, also benefit from a wide variety of nectar and pollen sources, particularly native flowers. If there aren't any native plants in your neighborhood, plant a small patch to help attract bumblebees. Better to create large groups of similar plants than to scatter them; larger groups are easier for bees to find.

If you are interested in learning more about bumblebees, download the U.S. Forest Service publication Bumble Bees of the Western United States, which covers all 40 species of Western bumblebees.

Bumblebee nesting (7 min)

Bumblebees and Citizen Science (30 min)

Food Growing Forum: Last Sunday of the month through October. Register to get Zoom link at: http://ucanr.edu/foodgrowingforum2020
Sunday, October 25, 3 pm to 4 pm, “Planting Onions, Leeks and Other Alliums and What Else to Do Now”

Napa Library Talks: First Thursday of each month. Register to get Zoom link.  http://ucanr.edu/wildlifehabitat2020

Pollinator Gardening, Sundays, 1 pm to 2 pm. Register to get Zoom link.

Got Garden Questions? Contact the Master Gardener Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.

For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.

By Cynthia Kerson, UC Master Gardener of Napa County

Recently, my husband asked me what to feed his container plants as they were starting to flower. I took his question as an opportunity to brush up on how to understand a fertilizer label.

Fertilizer labels have three hyphenated numbers, usually displayed as X-X-X. These numbers represent the percentages of nitrogen, phosphorous and potassium—in that order—in the package. A fertilizer labeled as 10-5-5 contains 10 percent nitrogen (N), 5 percent phosphorous (P) and 5 percent potassium (K). So a 10-pound bag would contain 1 pound of nitrogen, a half-pound of phosphorous and a half-pound of potassium. The remainder is filler that helps with dispersing the three macronutrients.

Organic fertilizers typically have macronutrient numbers in the single digits. Synthetic fertilizers, in contrast, use mineral salts, so it's much easier to make a concentrated product. However, the numbers tell only part of the story.

Synthetic fertilizers are more or less a one-pass event. Water dissolves the mineral salts and carries them past the plant roots, where they are taken up (or not). Excess synthetic fertilizer drains into the subsoil or, if we're unlucky, into groundwater.

Synthetic fertilizer, because it's water soluble, can also be carried off in irrigation or rainwater run-off. In addition, synthetic fertilizers reduce the number of soil bacteria.

In contrast, organic fertilizers require bacterial action before their nutrients are available to plants, so they feed plants more gradually and help sustain soil bacteria at the same time. This slow release of nutrients helps improve the health of your soil. Organic fertilizers, which are made from natural materials, contain nutrients in addition to those shown on the package.  

The filler in a box of fertilizer keeps the nutrients from clumping or drying out and makes the fertilizer easy to spread. Companies making high-quality fertilizer will consider the filler almost as important as the nutrients themselves.

For the most part, Napa Valley soils have adequate potassium and phosphorous but may lack nitrogen. All three are essential to plant growth. Phosphorous supports root development. It helps the plant build starches, sugars and oils necessary for plant health. Dull leaves, purplish stems and overall unhealthy appearance may signal a phosphorous deficit. Breaking up hard soil can help with phosphorous absorption. Bone meal and manure are good organic sources of potassium.

Nitrogen supports leaf development. Nitrogen is part of all living things and, in plants, is necessary for chlorophyll production and photosynthesis. Yellowing leaves and poor overall plant growth are symptoms of low nitrogen. Composted animal manure, fish emulsion and coffee grounds are also great sources of nitrogen. Another option is to plant legumes (such as peas or beans), which fix nitrogen in the soil, or other cover crops. Cutting cover crops when they are still green and working them into the soil to decompose will add nitrogen to your soil.

Finally, potassium, which is found in potash, encourages flowering, both for ornamental and edible plants. Potassium keeps plants healthy by supporting photosynthesis and flower development. Leaf scorching, curling leaves, poor fruit production, as well as an overall sickly plant, may indicate a potassium deficiency. Kelp is an organic source of potassium, as are wood ashes from your fireplace.

When soil pH is between 6.5 and 7.5, most nutrients are available to plants. While Napa Valley soils are unlikely to have a pH problem, it makes sense to check the pH when your plant shows nutrient deficiencies.

If you've applied a balanced fertilizer but your plants are still not thriving, adjusting the soil pH with amendments may solve the problem. Resist the temptation to keep fertilizing because excess fertilizer can cause problems. For most plants, acidic soil (low pH) is more problematic than basic soil (higher pH). However, some plants, including citrus, blueberries, azaleas and rhododendrons, prefer acidic soil. Garden centers carry special fertilizers for citrus as well acid-loving plants such as azaleas and blueberries.

Generally, in Napa County, a high-nitrogen fertilizer will do the trick. However, if you're using store-bought gardening or potting soil, you may encounter other deficiencies and need a different fertilizer formulation.

When you fertilize, keep in mind that the plant's roots likely extend past its canopy. You're feeding the soil, not just the plant. Spread the fertilizer beyond the plant's immediate root zone.

Food Growing Forum: Last Sunday of the month through October. Register to get Zoom link at: http://ucanr.edu/foodgrowingforum2020
Sunday, October 25, 3 pm to 4 pm, “Planting Onions, Leeks and Other Alliums and What Else to Do Now”

Napa Library Talks: First Thursday of each month. Register to get Zoom link. 
http://ucanr.edu/wildlifehabitat2020

Pollinator Gardening, Sundays, 1 pm to 2 pm. Register to get Zoom link.

Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.

For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.

By Susanne von Rosenberg, UC Master Gardener of Napa County

If you're observant and you own citrus trees, you may have noticed that they usually have three flushes of growth each year–in spring, summer and fall. Young citrus trees and lemons tend to flush periodically year-round.

During the flushes we need to be extra vigilant. Why? Those new leaves are especially attractive to the Asian citrus psyllid (ACP), which is a carrier for a devastating citrus disease called huanglongbing (HLB). HLB eventually kills the trees it infects, and there is currently no cure. Before it kills the trees, it affects the quality of the fruit. The fruit becomes misshapen and the juice bitter.

HLB has been found in Southern California since 2012, and the state is working hard to contain and control it. The goal is to buy time for scientists to find a cure. At this point, University of California researchers have identified one promising predator of ACP, Tamarixia radiata. Tamarixia strongly prefers ACP nymphs and can significantly reduce psyllid populations. Tamarixia and other natural enemies have reduced ACP populations in Southern California, but they have not eradicated it and have not halted the spread of HLB.

The most effective way to buy more time is to control the spread of the psyllid. Without its carrier, HLB cannot spread. An ACP nymph (immature insect) takes the bacteria causing HLB into its body when it feeds on infected plants. When it flies away as an adult, the bacteria-carrying psyllid can feed on a healthy tree and inoculate it with the bacterium. It only takes a few psyllids to spread the disease.

You might ask why we look for ACP when we could just remove the infected trees. Detecting infected trees is difficult because it can take several years for symptoms to show. Meanwhile, psyllids can pick up HLB bacteria and spread them only a few weeks after the tree is infected.

We've been lucky in Napa County. There have been no confirmed cases of HLB in Napa County nor any confirmed detections of ACP. There were a few detections of ACP in our vicinity, but none recently.

In Florida, where HLB spread widely, citrus production has been cut by more than half. California is doing its best to avoid that fate for its citrus industry and the many California homeowners who have citrus trees.

All of us need to do our part to help prevent the spread of HLB. The most important things you can do are to monitor your citrus trees for the psyllid and comply with citrus quarantine rules.

When your trees put out new growth, check for evidence of the psyllid. ACP feeds on all varieties of citrus and several closely related ornamental plants, including calamondin, box orange and Indian curry leaf. Inspect the tiny, newly developing leaves on your citrus trees. Walk around each tree and check for signs of psyllid feeding and damage, including notched leaves, nymphs, honeydew, sooty mold or adult ACP.

If you think psyllids are present, use a magnifying glass to look for the sesame seed-sized yellow nymphs with their waxy tubules. Nymphs feed only on tender new leaves and don't fly, so looking for nymphs on citrus flush is most effective.

Each nymph produces a waxy tubule from its back end to help expel the sugary waste from feeding on sap. The tubule's shape—a curly tube with a bulb at the end—is unique to ACP and can be used to identify it. Adult ACP are tiny, mottled brown and about the size of an aphid or a grain of rice. Adults perch with their hind quarters angled up. (No other insect feeds like this.)

Other psyllids such as Eucalyptus psyllids, tomato psyllids and Eugenia psyllid can be found in home gardens. You can find images of the Asian citrus psyllid and its life stages on the UC ANR website at http://ucanr.edu/acp. If you find signs of the insect, call the California Food and Agriculture Exotic Pest Hotline at (800) 491-1899.

To comply with quarantine rules, do not transport citrus plants, budwood or plant material such as leaves out of your area. It's okay to move clean, washed fruit free of any leaves or stems. Also, please purchase the trees only from reputable nurseries. Do not accept tree cuttings or budwood from friends or relatives.

Drying out or double-bagging citrus waste after pruning or cutting down a citrus tree ensures that live psyllids won't ride into another region on the foliage. Controlling ants in and near citrus trees with bait will also help. Ants protect ACP from its natural enemies, as they do for aphids.

Here is a 4 minute video to be informed about ACP.

Map showing location of ACP and Huanglongbing in California.

Food Growing Forum: Last Sunday of the month through October. Register to get Zoom link at: http://ucanr.edu/foodgrowingforum2020
Sunday, September 27, 3 pm to 4 pm, ”Harvesting Your Bounty and What Else to Do Now”
Sunday, October 25, 3 pm to 4 pm, “Planting Onions, Leeks and Other Alliums and What Else to Do Now”

Napa Library Talks: First Thursday of each month. Register to get Zoom link. 
Thursday, October 1, 7 pm to 8 pm, “Creating Wildlife Habitat” http://ucanr.edu/wildlifehabitat2020

Pollinator Gardening, Sundays, 1 pm to 2 pm. Register to get Zoom link.

September 20– Introduction to Gardening for Pollinators

September 27 – Pollinators and the Plants They Love

Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to  msgarden@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email.

INTERESTED IN BECOMING A UC MASTER GARDENER OF NAPA COUNTY VOLUNTEER? Send us your information through our website request.

For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.