-Step up your transplants in to 1 gallon nursery pots. Half gallon milk cartons, with drain holes added, work well. Hold these in a greenhouse or carry indoors until weather conditions are appropriate for planting.
-Tomato plants will only flower when grown in full sun. The more sun the plant can get, the more fruit you can get. A local Ag Extension Agent says "If there is a tree on the horizon, it's to close."
-Work LOTS of compost in to the planting area. I use about half a wheelbarrow full per plant, half mixed in, the other half as mulch.
-Add a cup of soft rock phosphate to the bottom of each hole. Set the bottom of the root ball directly into this material. This is the single most important amendment you can offer your new plants.
-Add mycorrihzal inoculants. These beneficial fungi will greatly enhance a plants ability to absorb water and nutrients.
-Look in to 'rock powders'; greensand, lava sand, basalt and granite, added to your garden soil, these provide long term stores of trace minerals making for stronger and healthier plants.
-Set your plants at LEAST 3 feet apart. Tomatoes are susceptible to mildew problems if they don't receive good air flow; think roses.
-Set your plants 'green side up'.
-Set your new plants deep. Pick off lower leaves and set so that only two sets of leaves and about an inch or two of stem are showing.
-DON'T over-water. This is the single most frequent mistake made. An established tomato plant will perform at its best when watered DEEPLY every ten days or so. You cannot give a plant too much water, but you can do it too often.
- A very inexpensive and effective prevention (and treatment) for fungus diseases... sprinkle a couple handfuls of corn meal around the base of the plants.
-Use ground cedar mulch on top of your compost to help deter root rot nematodes. I also like alfalfa hay as mulch. I like the golden color it turns, the earthy smell, and all the nitrogen it adds!
-Foliar feed regularly, about every two weeks. There are many recipes for foliar sprays and all have merit. Seaweed extract and molasses are probably the two most import ingredients to look for. This practice will eliminate 99% of spider mites and do a great deal to bolster overall plant health.
-Use a 'tea' of corn meal; soak half a cup in a gallon of tap water overnight; strain. Spray after long rainy periods to ward off or control powdery mildew and many other diseases. Works like magic!
-A Bacillus thuringiencus product if necessary to control hornworms. Spray only the plant with an apparent problem. Hornworms usually twitch violently when sprayed with water. If you notice a damaged plant, spray it down (in early morning) and watch for the 'dancing worm'. These are easily picked and discarded by hand.
-Cage up, trellis, or string guide indeterminate tomato varieties. This will give much needed support, and aid in fruit production. I would be disappointed if my plants didn't grow to at least 15" length each year.
-Seriously consider the use of grow web fabric, if you don't already. There are way too many benefits to list here.
-Grow several tomato varieties; you can never tell which will excel from one year to the next with our typically inconsistent weather.
-I like to plant a few bush beans at the foot, on the western facing side, of my tomatoes. All legumes add nitrogen to the soil. I will also grow snow peas and bluebonnets in my tomato beds as winter crops.
-Keep an accurate garden journal. You will be amazed how often you will refer back to this useful little tool. Include planting dates, plant variety names and sources, soil amendments, etc…