Growing Tomatoes in the Arizona Deserts

It's so hard to find good, flavorful tomatoes in the store. Even the specialty fruit and vegetable stands have tough, flavorless fruits. This is because of new varieties that were developed to be strong enough to be harvested by machine. I understand the economic pressures, but that doesn't stop me from mourning the loss of sweet, juicy tomatoes.

The only way to get good tomatoes is to grow them. Here in Arizona, that can be tricky, but it doesn't have to be. The rules are largely the same here as anywhere else, except that the schedule is a bit "off" in comparison.

Each of the thumbnail images in this page is a clickable reference to a larger copy of the image.

In the southern deserts of Arizona, we have two growing seasons. Unlike other areas, neither of these are during the hot summer. The first one starts in February (if we're lucky, or March if not), and runs into early June. The second can start in August or September, and runs until the cold gets here.

If we have a cold winter (lots of short freezes) the spring season is the nicest of the two, because the freezes kill most of the whiteflies and similar insects that plague the gardener. It's not uncommon to watch your garden go all the way to harvest with only a very few pests. A warm winter is the opposite, with pests galore from the outset.

The fall season will have lots of pests, and isn't as nice for tomatoes, since the weather is cooling toward the end. Though the plants will get a great start, due to the warmth of the soil at the beginning.

These two growing seasons are short, compared to a growing season in the midwest, so you have to plan carefully to achieve success. Like places with colder springs, you need to start your plants indoors and transplant them as early as possible.

Because our seasons are short, we have the best luck with varieties that were developed for areas like the US/Canadian border. My favorite slicing tomato is the Early Girl. My favorite cherry is the Sweet 100. Another slicing variety that seems to work well is the Champion.

All of these varieties are indeterminate, meaning that they are plants that grow very tall, vine-like, and need to be supported. I've had poor luck growing the bush-like determinate varieties like Big Boy. Your mileage may vary, but I don't waste space on the bushes. I find the climbing varieties to produce far more fruit than the others, though the fruit is smaller than that of a Better Boy, etc.

So, left to my own resources, I plant lots of Early Girl and a few Sweet 100. If you're a compulsive cherry tomato nibbler, you may wish to plant more Sweet 100, but each plant is capable of producing hundreds of cherries.

Our soil isn't "soil" at all, but is granite that has been worn down to a fine consistency by thousands of years of water and weather. It has no nutritional value, and has a high enough pH that only native plants will flourish in it. So, to grow tomatoes (or anything else that doesn't occur naturally here), you have to replace the "soil" with something more like a midwesterner would recognize.

My recommended mix of ingredients is:

After mixing this together, you'll need to mix in Soil Sulphur to bring the pH down to between 7 and 7.2. Some of your plants will be picky about pH, and you can treat them individually as they grow. Needless to say, you'll either need a soil testing kit or make trips to a nursury that will test for you.

Bone meal and blood meal add nutrients that your plants will enjoy, and should be mixed in before planting. Be very careful not to inhale the bone meal! There are a number of diseases that may or may not be transfered by inhaled bone, so please don't take any chances. Wear a mask when scattering and mixing it. Once mixed in and watered, there should be no risks to you.

While this seems like a lot of preparation, it needs to be done only once. After you've finished the basic mix, your garden will be usable for many years, for any kind of vegetable. Of course, you'll need to add organic matter each year, since the plants consume it. I mix in enough steer manure to bring the volume back up to the level it was at the beginning of the past season. Tomatoes love steer manure. It is a key ingredient in the growing of very sweet fruit.

Before you do your planting each season, mix steer manure into the top 6 or 8 inches of your new soil, smooth the surface, and water the entire garden slowly and deeply. Once soaked thoroughly, turn off the water, and do not disturb the soil for a week. Whatever you do, don't plant until the soil dries out. Digging in wet soil can hurt the soil's texture.

The University of Arizona's Agricultural Extension Service has a very nice discussion of "intensive gardening" in raised (and lowered) boxes. You should read this, and explore all of their Master Gardener site.

One of the secrets to successful gardening is the consistent availability of moisture to the plants. If we can keep the soil from going through repeated wet/dry/wet/dry cycles, we'll have plants that are happy and that don't exhibit the problems associated with water stress. Vermiculite is what I use to make this happen.

Vermiculite starts out as a shiny rock that they heat to fantastic temperatures in an oven. It explodes in the oven, becoming a rock sponge of sorts. It weighs practically nothing, and can soak up an amazing amount of water. It looks "at home" in your soil mix, compared to perlite, which looks like styrofoam beads. It's relatively inexpensive, when purchased in big bags, and lasts forever.

So, imagine that you're a plant root living in a growing mix that has lots of vermiculite in it. The vermiculite will be your ready source of nutrient-rich moisture between waterings, since it soaks up the moisture during watering and releases it to the plant afterwards.

Vermiculite is especially important in raised garden beds, since the moisture would otherwise drain out the bottom very quickly, resulting in the undesirable wet/dry cycles.

As I mentioned before, consistency in watering is very important. For this reason, I automate the watering with a timer-controlled setup, using regular, off-the-shelf parts from a sprinkler supply store. You can tell the salesman that you'll be doing drip irrigation of your vegetable garden, and he'll know what you need for valving and pressure regulation. As far as the plumbing in the garden, I'll show you that here.

In my raised garden boxes, I bring the PVC water pipes up the outside of the box, and then in at a corner. The picture at right shows the pipe coming up from the ground to where it enters the box. Note the PVC ball valve in the pipe. This lets you regulate the flow into a box, and even turn a box off if it isn't being used.

Once inside the box, I terminate the half-inch PVC in an SS coupler, into which I've glued an adapter for half-inch drip line. This lets me use this large drip line to distribute the water to the smaller drip lines and emitters in the box. The half-inch drip line is replaced each season. The picture at right shows the large drip line inserted in the SS coupler and adapter.

Note! In Arizona, the sunshine will destroy exposed PVC pipe in no time. It is very important to paint all exposed PVC pipe with glossy, metallic gold paint. This is very important! Don't forget to do this!

The half-inch drip line is routed around the edge of the garden or box, and is held in place by nail-in pipe anchors. It is sealed at the far end, by folding it back onto itself and either taping or using the figure-eight plastic gadgets made for this purpose. Having it available around the edge lets you deliver a customized amount of water to about any plant in your garden.

Water is delivered to individual plants using loops of the laser-drilled quarter-inch drip tubing, that are connected to the half-inch tubing with barb couplings, and sealed at the other end with "goof plugs." This arrangement is very easy to build, and lets me customize the amount of water that is fed to each plant. A huge tomato plant needs more water than a marigold does, so it gets more loops. I can add loops as the season progresses, and as I watch for signs of water stress. I can also remove loops when an area is shut down for the rest of the season, plugging the now-unused hole in the half-inch line with a goof plug.

The nursuries can't be counted on to have plants for you when you need to plant, so you should start your own seedlings indoors. Relatively-large peat cups or 4-inch plastic pots filled with a good potting soil should be used, to give your seedlings lots of room to grow roots.

When you're planting the seeds, use your finger to punch a deep hole in the potting soil in the center of the cup, and fill that hole with vermiculite. You'll be inserting the seed into the vermiculite, which will keep a little moisture against the surface of the seed all the time. This dramatically increases your success in starting the seeds. Because your success rate will likely be very good (assuming good seed, of course), you should put no more than 2 seeds in any pot. They're probably both going to germinate, and if you pull out a plant to try to thin them, you'll likely damage the roots of the remaining plants. Again, since you're going to have excellent luck getting your seeds to germinate, there's no reason to hedge your bet by putting lots of seeds in each cup.

As soon as the seeds are planted, water them deeply with a fine mist. Do this daily, to keep them moist. Keep them in a warm place, and they'll sprout quickly and begin to grow. They will want lots of light while they're growing, and the "full spectrum" flourescents are very good. These are available at the Home Depot, and at many other places. You probably want to stay away from lamps that claim to be for growing plants, as some Federal agencies track buyers of those.

If you're starting your plants for the spring season, it's probably cold outside (well, cold for here). The plants will grow better roots when the soil is warm, and it's not outside. You can start the garden soil warming by covering it with clear plastic. This won't warm it very deeply, but any help we can get is appreciated. Once the soil reaches about 65 degrees, the plants will really take off.

You transplant your seedlings when you suspect that most of the freezes are over. I wouldn't wait past March 1st in any case. You can protect them from freezes with the plastic "Wall O'Water" devices. They form a water-filled cylinder around your seedlings outdoors, and prevent the cold weather from hurting them. Amazing gadgets.

Make little cylindrical collars from cut-up stiff paper, and put one around each plant, taping each collar to keep it closed if needed. Press each slightly into the ground. This will keep cutworms from snipping off our new plants.

After planting, we water the garden deeply with a watering wand, install the irrigation equipment, and cover the soil again with clear plastic. If we can, we should build a framework to support the plastic, greenhouse-like over our seedlings. If we can't, we cut slots in the plastic for the tops of the seedlings to grow through. In any event, the clear plastic will keep the breeze away from the soil, while letting the sun's rays warm the soil below. Put a Wall O'Water on each plant to protect them from the unexpected frost.

Once the temperatures are reliably warmer, you can remove, drain, roll and store the Wall o'Waters. When it's getting up into the 80's each day, you should slice the plastic with scissors and remove it. You're going to be adding steer manure to the top of the garden around the plants (called "top dressing"), and the plastic will be in the way. We'll add steer manure every few weeks. The plants LOVE it.

Of course, another reason to get the plastic off once the weather warms, is that the soil will get really hot if we don't, and hot soil dries out much faster than cooler soil. To keep the soil cool when the heat really hits here, we will put bark on as a mulch, to shade the soil from the intense summer sun. One problem with doing this, is that it makes it harder for us to add manure (we have to scrape back the bark, add the manure, and then redistribute the bark). Another problem is that it makes a place for earwigs and other destructive insects to hide.

You'll recall that these varieties are climbing plants. Without support, they will fall over and break. With support, they will grow to immense heights and produce tens of pounds of fruit each.

I built a supporting structure from EMT conduit and redwood 4 by 4 lumber. There are two upright supporting 1-inch conduits on each end, and three horizontal 3/4-inch connecting ones across the top. If I were doing it again, I would have 4 or even 5 horizontal conduits. Note the nylon support strings tied to the horizontal conduits. The hose tied to the center conduit is a "mist system" to cool the foliage in late June, when the temperatures can reach 115.

The upright conduits are secured to the inside of the garden boxes with appropriately-sized u-bolts (with big washers on the outside). I tie strings horizontally between the uprights at each end, and then more horizontal strings from those strings to the strings at the far end of the box. This gives me the lower anchors for the many vertical strings I will use to support the tomatoes. Each twisted or braided nylon string will support a single productive stem and all of that stem's fruit.

Each day, as the plants grow, I gently train each upright stem around a vertical string. It takes no more than 5 or 10 minutes each day to do all stems of the 20 plants I have growing. Some texts recommend that you pinch off the side shoots, but I don't do this. Since I am providing customized watering and feeding to each plant, there's no reason to restrict the plant's growth. I do pinch them off when they reach the top support. At that point, the plants are 8 feet tall!

No discussion of growing plants in the Arizona deserts would be complete without a volume on our frolicking furry friends, the squirrels, chipmunks and rabbits.