Scientific NameSolanum lycopersicum
General InformationPhoto: Dani California/Unsplash
When to Plant
Plant after the danger of frost has passed, April to June.
Plant in well prepared beds protected from high winds. Tomatoes prefer full sun all day. At a minimum, tomatoes require six hours of full sun. Given more sun, the plant will be more productive.
Bury the stem up to the point at which the topmost cluster of leaves begins, or approximately half way up the stem, removing any small leaves below that point. Do not damage the little hairs on the stem as they are potential roots. Depending upon variety, leave three to four feet between plants.
If you have grown your plants from seed or have purchased them directly from a greenhouse that has not introduced cold air to the growing process, be sure to harden them off before planting. Take up to a week to gradually introduce them to greater amounts of outdoor temperatures (six hours outdoors during the day and protected at night on the first day, moving to outdoors all day and all night on the last day of the hardening off period).
Indeterminate tomatoes require a tall (five to six foot) trellis, cage, or stake. Tie each sagging stem to the supports at multiple places to prevent sharp bends that can restrict the flow of water and nutrients.
Use minimum ten-gallon containers for indeterminate tomato varieties. Remove all of the old soil. Clean the container with soap and water, a bleach solution (one tablespoon bleach in a gallon of water), or isopropyl alcohol (70% or stronger). Replace the soil with a reputable, medium-textured, well-draining potting (not planting!) mix.
In Raised Beds
Add compost or other nitrogen-bearing amendments to create a nutritious soil. Loosen and work the compost and amendments at least three to six inches into the soil prior to planting. If you add soil, use a reputable, well-draining mix designed for raised beds (not potting or planting mix). Raised bed mixes are new but widely available. They are designed to avoid soil compaction deep in the bed that can hinder aeration and retain too much moisture.
Rotate tomato beds to avoid soil-borne diseases. Avoid growing tomatoes or other members of the nightshade family (Solanaceae) in the same location more than two years in a row.
In the Ground
Follow the same advice as for plants in raised beds. Consider adding cardboard and paper bags as mulch around the plants. Lay it down and cover it with compost. It smothers weeds, holds moisture and eventually improves the soil.
Do not allow soil to become too wet (soggy) or too dry (cracking). This is why it is important to use a specific soil mix. The right mix helps to pass excess moisture below the plant roots and holds needed moisture for a least a few days at a time.
Reduce water over the life of the plant.
Water regularly and deeply (no less than once per week) until fruit set (the point at which you begin to see tiny tomatoes emerging just below the withering flowers). Watering more frequently during this stage allows the stems and leaves to grow vigorously.
After fruit set, use a three-inch rule. Do not let the soil dry out deeper than three inches. Poke your finger two to three inches into the soil to check. Water only if the soil is dry below two inches. This minimizes further vegetative plant growth, but allows sufficient water to reach the flowers and fruit. Do not overwater at this stage or your fruit may crack or have less concentrated flavor.
Near the end of the harvest, if you stop watering altogether, the flavor in the remaining tomatoes will concentrate as the fruit ripens.
Never water the leaves. Use drip irrigation if possible.
Use a reputable organic tomato or vegetable fertilizer and follow the directions on the label, but do not start fertilization until flowering and fruit set are well under way. Earlier feeding can delay both flowering and fruit set. Homemade nitrogen sources can work well, but not too strong and not too often (every four to six weeks after flowering and fruit set have started).
Tomatoes are self-pollinating, which means they contain both male and female parts. The flowers must be vibrated at a specific frequency by wind or bees in order to release the pollen for fertilization. Buzz pollinators can vibrate their bodies to shake pollen from the enclosed anthers of tomatoes and other solanaceous crops. Honeybees are unable to provide the correct vibration to the tomato flowers, but bumble bees (Bombus spp.), carpenter bees Xylocopa spp.),and other native species can. Bee pollinated tomatoes have been found to have higher levels of vitamin C and to weigh more.
Tomatoes are ripe when you feel a slight give when you give them a light squeeze. Tomatoes that feel soft are overripe and should be used for sauces rather than slicing. A ripe tomato will also pull easily from the vine.
Tomatoes picked at the mature, green stage will eventually turn red, but allowing fruit to ripen on the vine produces the best flavor.
It is best to store tomatoes in a cool place as close to 60 degrees as possible. Do not store ripe tomatoes in the refrigerator, since temperatures below 55 degrees Fahrenheit will reduce their flavor.
Good Varieties for Marin
The single most important step toward growing great tomatoes is to purchase varieties suited to your climate – e.g. coastal cool or inland warm. The simplest way to make the right choice is to focus on the number of days to maturity listed on the plant label. Unfortunately, commercial growers do not provide a fixed definition of this term, except to say that it represents the required number of “warm and sunny days” from the date you plant to the date that you pick the first fruit.
However, there is a solution. Tomato plants thrive in daytime temperatures between 80 and 90 degrees and do poorly if night time temperatures drop below 50 to 55 degrees. Consider days that meet these conditions (80 to 90 during the day and not too cold at night) to be warm and sunny days that count towards days to maturity.
Your task is to estimate how many calendar days must elapse in your climate to reach the number of days to maturity shown on the label. For example, if you live in a cool climate (parts of Mill Valley or West Marin), it may take 90 or more calendar days for 70-75 “warm and sunny days” to occur – by which time it may be September. As a result, you would want to choose varieties with 75 or fewer days to maturity, as opposed to other varieties that require 85-90 days to maturity.
If you have had disease problems for tomatoes in previous years, choose varieties bred for disease resistance for best results. Fusarium (F) and Verticillium (V) wilt are common diseases that can destroy a whole tomato crop. Many varieties are resistant to these two diseases. Look for VF after the cultivar name, indicating resistance to the wilts. VFN means the plants are resistant to verticillium, fusarium and nematodes; VFNT adds tobacco mosaic virus to the resistance list.
To prevent disease problems, rotate the location of your Solanum family crops so they are not always planted in the same area.
Unpruned plants will bear fruit, but pruning will significantly improve your yield and fruit size. The goal is a plant with two or more main stems, but not so many as to block sunlight to the interior. Also, allowing more sunlight and air into the interior helps to prevent certain plant disorders.
The number of main stems you choose will depend upon how tightly your support structure crowds the plant. Narrow cages may limit you to two main stems per plant. Wider cages may permit three to four main stems per plant. Once you have chosen the stems you want to keep, pinch out the others as well as any suckers that may emerge from the root area.
As your main stems grow, pinch and remove any new branches that form at leaf nodes that may crowd the center of the plant or grow in undesirable directions. How many of these new branches you remove is a balancing act. If you allow the plant to become too dense, less sunlight will flow to the flowers and fruit in the interior. By contrast, if you thin the plant too severely, you will have fewer fruit-bearing branches and fewer leaves to feed the fruit that forms.
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