By Gwen Kilchherr, Master Gardener
Tomatoes need no introduction! Have you ever tried a vine-ripened tomato with the heat of the sun still upon it? If you have, then you will know why the tomato is the most commonly grown vegetable in the United States. May is the month for setting out tomatoes in the garden in Sonoma County. While it is always tempting to start them sooner, it is not until May that the soil and air temperatures warm up enough to get them started properly.
There seem to be almost as many tomato varieties as there are ways to eat them. When selecting a variety, keep in mind how you are going to use the tomatoes (eat them fresh, cook into sauces, etc), the length of your season, past experiences, the growing conditions of your area, and what you like in a tomato. Try different varieties. If gardeners in your area have had a problem with harmful diseases such as verticillium or fusarium wilts, you will need to shop for disease-resistant varieties, which are readily available. With our County's climatic diversity, gardeners in Bodega or Sebastopol will find that they have success with different varieties than gardeners in Sonoma or Healdsburg.
Where you plant your tomatoes in the garden is important. Tomatoes need at least 6 to 8 hours of sun a day to produce well. So, a sunny, well-drained part of the garden is the best spot for them.
Soil is important for tomatoes: like most vegetables, they like their soil pH around 6.0 to 6.5. By taking a sample of your soil, and using a soil test kit, you will be able to determine your soil pH. Soil test kits can be purchased at your local nursery, and Master Gardeners can recommend how much lime or sulfur (which will raise or lower the pH) to add based on your results. Soil texture is also important: in troublesome, sandy soils which drain too quickly or in heavy, clay soils which take forever to drain and warm up in the spring, you can either amend each individual planting hole, or you can amend the entire bed. Either way, it boils down to working plenty of fully composted organic matter into the soil. Organic matter will feed the millions of microscopic soil organisms who live and work in your soil. This active soil life breaks down organic matter into nutrient-rich humus - in effect, making fertilizer for your vegetable crops. You could add an all-purpose fertilizer into the planting holes at the time of planting so that the transplants get off to a good start. Follow the package directions. Add a bit of agricultural lime for calcium, to help prevent blossom-end rot. Once you've been adding organic matter for a few years, it might not be necessary to add additional fertilizer.
If you talk to 10 different gardeners, you'll get 10 different ways to plant a tomato! But despite all the variations, which give tomato growers much to talk about, there are just a couple basic ways to transplant- trenching or straight up and down. In trench planting (which works particularly well if your transplants are leggy), you simply pinch off all the lower leaves and lay the whole plant in a shallow trench horizontally. Cover the stem with 2 or 3 inches of soil and bring just the top cluster of leaves above the surface. Mark the location of the rootball so that you don't disturb it later on when cultivating. This method may slow the plants down at the start but will provide more roots and make the plants a bit more drought-tolerant. If planting with the straight up and down method, pinch off the lower set of leaves and then plant them deeply, almost up to the next set of leaves. Roots will form along any part of the stem that is buried, and the extra roots will give you a stronger plant.
It is often said that tomatoes will grow like weeds—they'll keep sending out new stems and branching out all over the place. Every time you turn around, the plants are bigger and bushier. Well, to keep them from taking over the garden, and to insure cleaner, healthier tomatoes, many gardeners support their plants, train them to grow a certain way and regularly pinch off unwanted growth. Stakes and cages are the most popular supports. Letting your tomato plants sprawl saves work - no tying, no training, and no pruning. However, the disadvantages of letting the plants sprawl is that you'll need to put down a light mulch to keep the tomatoes from sitting on the ground where they'll be prone to rot. And, this mulch will need to be kept dry. It is also difficult to find the ripe fruits underneath all of the foliage before the insects and the animals devour them.
Left unpruned, a tomato plant will produce a surprising number of stems. Tomato pruning means pinching off the shoots or suckers that grow out from the stem right above a leaf branch. If you let the sucker grow, it simply becomes another big stem with its own blossoms and fruits. If you have the room to allow the plants to get big, then don't worry about pruning. If you want to keep them contained, then prune.
Finally, mulch your tomatoes! Mulch is simply a covering over the soil that keeps moisture in, blocks weeds and protects low growing tomatoes from resting on the ground and developing rot. There's something extra in using organic materials such as grass clippings, leaves, hay, and aged manures, because unlike plastic and other synthetic mulches, they decompose and provide food for all those micro-organisms, and in time, will improve the structure of your soil.
Tomatoes like an even supply of water through the growing season. They'll need at least 1 inch of irrigation water per week for steady growth. In hotter, drier areas, they could benefit from at least 2 inches of water per week during the summer months. Uneven watering can result in blossom-end rot on the fruits. Over-watering can result in cracked skins.
Tomatoes can also be started from seed indoors in February, and then planted out in the garden in May. The advantage to using seed is that there are many more varieties available in seed than in transplants. Contact Master Gardeners for additional information about tomatoes or for specific recommendations about growing tomatoes in your area of the County.
For a pdf file of the Master Gardener Document "Growing Tomatoes in the Home Garden" Click Here