As in sports, a strong defense is required for gardening success. This is certainly the case with tomatoes, which can suffer from diseases and nutritional disorders that are best prevented at planting time. Here is a checklist of tomato planting skills known to every veteran tomato gardener, which can go a long way toward preventing tomato problems before they start.
1. Choose Dependable Varieties
It’s always best to grow two or three tomato varieties of different types, but the same tomatoes that look great in catalogs may not the best choices for your garden. If you don’t know where to start, check in with an online gardening group in your area for local recommendations. Where I live, last year’s virtual taste test winner in our little Facebook group was ‘German Pink’ (shown above), followed closely by ‘Mr. Stripey’. Local farmer’s markets also are excellent places to look for (and sample) varieties likely to grow well in your area.
2. Don’t Start Too Early
Tomatoes are sensitive to frost and chilly winds, and they tend to sulk when set out in cold soil. Ideally, soil temperatures 4 inches (10cm) below the surface should be above 60°F (15°C) at tomato planting time. Wait until six weeks before your last frost date to start seeds indoors. That way, the weather will be warm and settled by the time the seedlings are ready to transplant. Should spring run late but your plants are ready, surround them with roomy enclosures to block blustery winds. The “walls” can be plastic, cloth, or row cover (garden fleece).
3. Add Compost to Planting Holes
In summer when tomatoes are struggling to grow, bloom, and nurture green fruits all at the same time, they can develop nutritional disorders related to shortages of calcium and magnesium. Both nutrients can be provided by rich compost, particularly food waste compost that is well endowed with eggshells, a good source of slow-release calcium. Over the years, I have developed the habit of harvesting my food waste compost each spring and setting it aside for my tomatoes. Each tomato planting hole gets a generous helping. It must be working, because I have not seen blossom end rot (darkening of the bottom end of tomato fruits) in years.
Heavy rain can cause tomatoes to develop magnesium deficiency, which is best treated with Epsom salt sprays on as as-needed basis. Unless you have sandy, acidic soil that tests very low in magnesium, the University of Minnesota advises against adding Epsom salts to tomato planting holes because it can interfere with the plants’ uptake of other nutrients. Note that if you periodically add dolomitic limestone to your soil to raise an acidic pH, it contains plenty of calcium and magnesium in slow-release form.
4. Maintain Moisture With Drip Irrigation and Mulch
Fluctuating soil moisture also plays a role in blossom end rot, and dry-to-wet soil cycles can lead to issues with fruit cracking, or tomatoes with thick skins. Frequent surface watering that wets the lowest leaves can backfire by creating good conditions for early blight and other leafspot diseases. A drip irrigation hose covered with mulch simplifies keeping the soil lightly moist, and it becomes a huge time-saver in summer when gardening time is in short supply. In addition, a good mulch limits the splashing of muddy raindrops, helping to further suppress diseases.
5. Keep Foliage High and Dry
A high leaf-to-fruit ratio favors the production of big, tasty tomatoes, so plan to support the heavy bushes with sturdy cages, fencing, or both. Leafy, upright plants also limit how many fruits are damaged by sunscald. Opinions vary on tomato pruning, but I think trimming out only the lowest branches (to increase air circulation) is sufficient.
6. Patrol for Pests
Only a few pests can penetrate the nicotine defenses of tomato plants, but tomato hornworms can be serious pests in much of North America in summer. In spring, slugs can damage young tomatoes, so make a habit of checking for mysteriously missing leaves, and gather offending slugs by hand. Where slugs are a chronic problem, delay mulching of tomatoes until the weather warms in early summer.