Growing organic tomatoes in the desert southwest are worth the effort!  They do take a lot of TLC, but it the end results are very gratifying.

The most important thing to keep in mind, aside from good soil, is the variety.  Many species sold in nurseries do not do well in the desert southwest.  I have had excellent success with Early Girl, Celebrity and Heatwave (for slicing tomatoes) and Viva and Roma (for paste tomatoes).  Cherry and grape tomatoes also do well here, as do yellow tomatoes.  Be sure the varieties are disease resistant (against verticillium wilt and fusarium wilt) which will be identified on the plant tag or seed packet.  These are viral soil diseases that affect mainly tomatoes. Organic seeds are not treated with fungicide, so beware of overwatering seeds which encourages damping off disease.

I prefer to start my plants from seeds since my plot is quite large.  A smaller plot with room for only a dozen or so plants would not be too expensive if you bought 6 packs or 4” pots.

You aren’t the only one that will enjoy tomatoes-birds think they are just great too, so unless you have a completely caged in enclosure, you will need to cover the plants securely with bird netting.  Birds are pretty tenacious, so make sure the bottom of the netting is secured with rocks, metal pins, or in my case, metal T-posts.  Birds will check the edges regularly, so you will need to as well. Unfortunately there is no other organic and animal friendly way to keep birds away from your plants, unless your entire garden area is enclosed in netting or chicken wire. Scare tactics don't work as the birds get used to them once they figure out they are not really threatened.

I make my own tomato cages from concrete reinforcing wire.  They really make the best cages, as the ones you can purchase are often pretty flimsy.  You can also make them nice and roomy; mine are at least 2' in diameter which gives plants lots of room to grow and remain upright. The openings are nice and big so you can get your hands in between to pick fruit.

Tomatoes also prefer afternoon shade.  If your garden plot is in full sun, then you will need to provide shade by building a structure to hold shade cloth (minimum 30%) over the plants.  I use my tomato cages to support the shade cloth (placed over bird netting, of course).  Be sure to stake the cages with rebar and wire so they don’t blow over. 

30% shade cloth over tomato plants works if you don't have afternoon shade

Soil diseases are a big problem for tomatoes, but fortunately there are few pests.  The one that will cause you the most trouble is the tomato hornworm.  Once you see one of these, you will do anything to never see another.  They can get quite large if you let them, growing to several inches long and over 1/2” wide.  They are green with ‘horns’ and blend in perfectly with the green leaves of the plants.  You will recognize their damage immediately.  Seemingly overnight there will be leaves missing on the tops of the plants, and tiny brown droppings on the lower leaves.  For organic control, you can hand pick them, but I prefer to use Bacillus thuringeniensis (Bt) which is discussed further in Article 8, Biological Insect Controls.

Make sure you don’t plant your seedlings too close together, or you will have fruit that won’t ripen.  One side will be forever green while the other side turns red.  Be prepared for some varieties to get 4’ tall and 3’ wide, especially Roma, Viva, Celebrity and Cherry tomatoes.  Allow at least 3’ or more between these varieties.

If your new plants are tall and leggy, plant them in a shallow trench lying down with the top 1/3 of the plant above the soil line. Don't worry, they will straighten up in a few hours. This encourages a more vigorous root system as the stem will grow roots too.

A common problem with tomatoes is blossom end rot. This is often caused by one of two things. The most common cause is uneven watering.  All it takes is one really hot day and not enough soil moisture, and the tomato will form a brown sunken end which often ends up ruining the whole thing. Mulching is a key here, and of course a regular watering schedule, but sometimes it just happens anyway. Another cause is thought to be a lack of calcium in the soil. Even though there is a lot of calcium in ground water in the southwest, it is not available to plants as it is bound too tightly to the water molecule. Adding water soluable calcium to the soil may help, but my experience has been it's the watering problem.

Cracks in tomatoes comes from uneven soil moisture (too wet or too dry) or when they get a sudden boost from rainfall and grow so quickly they split. Mulch your plants with straw or compost to reduce this problem.

Fusarium and verticillium wilts are soil diseases that look pretty much the same on a diseased plant.  Although fusarium is more common in the west than verticillium, both can be a problem. The symptoms are rapid wilting (not remedied by watering) and dying of the plant. There is no cure, so remove diseased plants right away to help prevent spread. Other than rotating crops, solarization may be your only other option. (See below).

Curly top and tobacco mosaic virus both cause tomato leaves to curl under. Both can be fatal. Curly top virus spreads by leafhoppers; tiny green grasshopper-like insects. They are hard to control using organic methods as floating row covers get too hot underneath in the summer and although Rotenone and Pyrethrums will kill leafhoppers, they are not necessarily safe products. (See article on Biological Insect Controls.) Tobacco mosaic virus can be transmitted into your garden if you smoke tobacco. If you do, make sure you always wash your hands before working around your garden, and never smoke in the garden.

If your tomato plot succumbs to a viral disease, you will need to do one of the following organic solutions:

1. Do not plant tomatoes or peppers in that plot for at least 3 years.

2. Use a soil innoculant at planting time, which helps, but does not guarantee resistance.

3. 'Solarize' your soil by spreading heavy 6 mil CLEAR plastic over the infected area, weighing down or burying the edges, and leave it to bake in the sun for at least 3 months.  Clear plastic is better than black, as it allows the sun's rays to penetrate and intensify the heat underneath, which will sterilize the soil.  Use this as a last resort, as this method will not only kill pathogens, but also earthworms and beneficial microbes.

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