When you ask a Master Gardener a question about almost anything, quite often the answer will be, “It depends.” It's not that we don't know the answer, but rather that we need more information to answer correctly. This is especially true when it comes to a question about fertilizing vegetables, such as, “It's mid-season. Should I fertilize my tomato, sweet corn and bean plants?”
To answer this question, we need to know what you did before planting. If you incorporated a three- or four-inch layer of compost, then likely you don't need to fertilize now. A healthy addition of compost pre-planting will provide most of the nutrients the plants will need.
If you fertilized the soil before planting, we'll want to know what you applied and how much. Organic fertilizers are slow release and will last longer than chemical fertilizers. The latter release their nutrients quickly and may require replenishing.
We also will want to know the nutrient values of the fertilizer you used. Vegetable plants require 16 essential nutrients, the most important being nitrogen (N), phosphorus (P) and potassium (K). On a fertilizer package, the NPK content is expressed in that order, with each value representing a percentage by weight. For example, a 10-10-10 fertilizer (a “balanced” fertilizer) is 10% nitrogen, 10% phosphorus and 10% potassium by weight.
Master Gardeners welcome this kind of question because it means the person seeking advice is not just going to the garden store and purchasing fertilizer at random. At this time of year, some gardeners are prone to applying fertilizer “just in case,” an approach that can produce negative results.
Vegetable plants have differing nutrient requirements so applying the same fertilizer to all is not a good idea. What's good for your tomatoes is not necessarily good for your corn. Tomatoes seldom need additional nitrogen during the growing season. Feeding with nitrogen will just encourage them to produce excess foliage.
The only nutrient I might feed my tomato plants during the growing season is calcium, which helps prevent blossom-end rot. However, I don't add calcium unless I see that tomatoes are actually developing the problem. I sacrifice a few tomatoes by waiting, but that's preferable to adding unneeded calcium to the soil.
Sweet corn, on the other hand, requires copious amounts of nitrogen during the growing season to ensure that the ears develop fully. I never feed bean plants with nitrogen as they create, or “fix,” nitrogen in the soil rather than consume it.
Before adding fertilizer, always ask yourself a simple question: Why I am doing this? If you can't answer the question, then don't add the fertilizer.
Free Guided Tree Walk: On this fun, informational walk through Fuller Park in downtown Napa, you will learn about the park's history and get acquainted with 41 different trees. Wear comfortable shoes. Water and restrooms are available. All are handicap accessible. The book "Trees to Know in Napa Valley" will be offered for $15 each, cash or check only. . Walks begin promptly. Fuller Park is at 560 Jefferson Street in Napa. ONLINE REGISTRATION or call 707-253-4221. Walk-ins are welcome, but you can be assured of receiving a complimentary map if you register at least 48 hours in advance.
Do you want to become a UC Master Gardener of Napa County?To apply, you must attend an information meeting. The first meeting is on Saturday, July 29, from noon to 1:30 pm, at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For other meeting dates, location and times, or to learn more about the program and volunteer commitment, visit the UC Master Gardener of Napa County website .
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County (http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
- Author: Pat Hitchcock and Jim Murphy, UC Master Gardeners of Napa
In a restricted area, such as an apartment complex or a small, confined yard, containers may be the ideal way to raise vegetables. Pot selection, container soil, container positioning, sunlight and heat deflection from walls or fences all contribute to a successful growing experience.
You can use many different kinds of containers, such as wooden planters, clay pots, plastic buckets or even plastic bags filled with planting mix. They must have drainage holes. If you are placing containers on a wooden surface, such as a deck, reduce the possibility of rot by raising the containers on small blocks to allow for air circulation.
Be sure your containers are deep enough for the crop you want to grow. Six to ten inches is sufficient for shallow-rooted plants like arugula, basil, chives, lettuce, green onions, radishes and mizuna. With a deeper pot, 10 to 15 inches, you can try carrots, celery, Chinese cabbage, garlic, leeks, Swiss chard and patio tomatoes.
Go for 18- to 24-inch-deep containers if you want to try beans, broccoli, kale, peas, peppers and short-vine (determinate) tomatoes. A container 20 inches in diameter and 18 inches deep will give you plenty of room for several small lettuces or for one pepper or tomato plant.
The planting medium needs to be both porous and moisture retentive. Because you may need to move your pots occasionally, it also needs to be lightweight. Garden soil is too dense and heavy. A good-quality potting soil will contain compost and nutrients for plants, plus vermiculite or perlite for drainage and peat or coir for holding moisture.
Finding the perfect place for your containers may be the most challenging part. Leafy vegetables such as lettuce need four to six hours of sunlight daily, but fruiting vegetables like peppers, beans and tomatoes need eight hours. An area near a wall that reflects sunlight can be too warm for some plants.
Container soil can get a lot warmer than the ground. Try shading the containers themselves if they are in a warm spot, while allowing the growing plants to get all the sunlight they need.
Container plants require more frequent watering than plants in the ground, and they also need more frequent fertilizing. Most commercial potting soils include fertilizer to get plants off to a good start. After six weeks or so, start fertilizing every other week with a half-strength liquid fertilizer formulated for vegetables or container plants. Nurseries sell organic and inorganic types. Check label directions for the suggested dilution, then double the recommended amount of water to get a half-strength solution.
For container gardens that are always on view, consider the many vegetables that are ornamental. Look for colorful versions of lettuce or Swiss chard, for example. A combination of leafy lettuces, blooming chives and a viola could produce an instant salad mix in a cool location. For the warm season, try a patio-type tomato with sweet basil at the base. Nurseries often have pots with such pre-planted combinations, but it's fun to create your own.
In April, the options for edibles are almost limitless. You can still start some cool-season vegetables, but it is also planting time for warm-season crops. The Napa Count Master Gardener website has several planting calendars in its “Healthy Garden Tips” section. Find that section under the “Gardening Resources” button on the left side of the home page.
Edible container gardens aren't limited to vegetables. Many perennial herbs do quite well in pots. Try thyme, oregano, marjoram and parsley. Edible flowers such as nasturtiums and violas also thrive in containers. Don't let lack of a garden plot keep you from the pleasure of harvesting your own edibles.
Tomato Plant Sale: U. C. Master Gardeners of Napa County will hold their fourth annual Tomato Sale and Education Day on Saturday, April 23, from 9 a.m. until sold out, in a new location at 1710 Soscol Avenue, Napa. Choose from 28 varieties, including heirlooms and new varieties in a range of colors. These healthy, Master Gardener-grown seedlings include types for fresh eating and for sauce.
Workshops: U. C. Master Gardeners of Napa County will hold a workshop on “Growing Tomatoes” on Sunday, April 10, from 2 p.m. to 4 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville. The workshop will focus on techniques for a successful harvest, including soil temperature requirements; tomato types; care and fertilizing; support choices; and integrated pest management. Register with the Parks and Recreation Department at
707-944-8712 or on its web site.
The “Growing Tomatoes” workshop will repeat on Saturday, April 16, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. On-line registration (credit card only); Mail-in/Walk-in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Spring and Summer Vegetables From Your Very Own Garden
By Pat Hitchcock, U.C. Master Gardener of Napa County
When should home gardeners start planting their spring or summer vegetable patches? A recent warm spell with near record-breaking daytime temperatures might have inspired you to consider getting some seeds and plants into the ground.
Your dreams of fresh produce might have been encouraged if you saw all the vegetable seedlings at local nurseries. However, nature is probably not finished with winter yet. Many of those nursery seedlings will not thrive if we have chilly days and nights ahead.
A look at the data can be enlightening. Here are the average monthly high and low temperatures for Napa: February, 62°F and 42°F; March, 67°F and 44°F degrees; and April, 71°F and 45°. But these temperatures are averages, which means that many days have lower lows or higher highs. The record shows that our area has a 90 percent chance of experiencing frost in January, dropping to a 10 percent chance in April. So there is still some chance of frost in the next eight weeks.
What does this mean for vegetables? Annual vegetables belong to several different plant families, but they may be loosely divided into two kinds: cool season and warm season. Cool-season vegetables grow best and produce the highest quality crop when average temperatures are 55°F to 75°F, and they usually tolerate slight frost when mature. In contrast, warm-season vegetables require long, hot days and warm soil to mature. They grow best when average temperatures are 65°F to 95°F, and they are damaged by frost.
March and April are much better for cool-season vegetables than for warm ones. Not only are the temperatures better suited to cool-season produce like broccoli, but they are anathema to warm-season vegetables. If we get frost, these tender plants would need to be protected from exposure that would otherwise kill them. The soil right now is pretty cold as well, and the heat-loving vegetables would not grow much until both soil and air temperatures warm up.
Fortunately, there are a lot of cool-season vegetables and many of them mature in 45 to 70 days. The list includes radishes, beets, carrots, lettuce, kale, spinach, Asian greens, broccoli and cauliflower. So you can plant these cool-season vegetables now and be finished with harvesting in May, in time to plan warm-season veggies. If you have limited garden space, this is one way to maximize production.
In Napa Valley, May is the first month when the average night temperatures hit 50°F, while daytime highs are 76°F on average. Over the summer and into early fall, daytime temperatures climb to the 80s and low 90s and nighttime averages stay in the 50s. These temperatures provide a four- to five- month growing season for the vegetables that need warm soil and warm air to thrive.
The long growing season is helpful because many warm-season plants need a lot of time to mature. In many cases, the part we eat is a fruit, botanically speaking. Melons, tomatoes, winter squashes and pumpkins are all fruits that we eat when ripe. Sweet corn, green beans and summer squash are immature fruits.
May is also the month when soils have warmed enough to plant warm-season produce. Although nurseries sell seedlings of many vegetables for you to transplant, several warm-season crops do better when started from seed planted directly in the ground. These include beans, squashes, cucumbers, melons and pumpkins. The minimum soil temperature needed for these seeds to sprout is 60°F. If you plant the seeds in cold soil, they will not sprout and may rot. In warm soil, the seed will come up readily, rapidly establish a good root system and grow well.
Is it time to plant vegetables? Yes, as long as you choose cool-season plants. Hold off on summer's heat-loving crops until the weather is warmer.
Workshops: U. C. Master Gardeners of Napa County will lead a workshop on “Growing Spring and Summer Vegetables” on Saturday, March 12, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. Learn the requirements for success with summer vegetables from seed to starts. Topics include soil types and temperature; when to plant seedlings; how to water, fertilize, harvest and manage pests and diseases. On-line registration (credit card only); Mail-in/Walk-in registration (cash or check only).
The workshop will be repeated on Sunday, March 13, from 2 p.m. to 4 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville. Register for the Yountville workshop at the Parks and Recreation Department at 707-944-8712 or on its web site.
Compost Workshops: on March 5 starting at 9 am and again at 11 am and Worm Composting on March 19 at 9 am. Preregistration is required. Find more information and registration links at our website http://ucanr.edu/ucmgnapa
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.