9 Common Tomato Growing Mistakes to Avoid

Tomato plants have a reputation for being a little fussy to grow, and it may seem like lots of things can go wrong when growing tomatoes. But often the cause of a bad harvest or disease-riddled plants is the result of a simple mistake that's easy to avoid. Here's a look at the 9 most common tomato growing mistakes, along with tips for avoiding each blunder this season. Even if you're a beginning tomato grower, you're now well on your way to a successful growing season that will give you a plentiful harvest of homegrown tomatoes.

Mistake 1: Planting tomatoes too early or too late.

Gardeners in cold regions routinely set out tender young plants before the last frost of the season. Freezing temperatures zap seedlings in short order. Even if the seedling isn’t killed by a late frost, it will likely be stunted and spend several weeks regaining strength and vigor. In Zones 7 and below, aim to transplant tomato seedlings outside after any chance of frost has passed and when nighttime temperatures are regularly in the upper 50s.

Tomato growers in warm regions experience a different timing challenge. Tomatoes in Zones 8, 9, and 10 must be planted very early in the growing season so they fruit before intense heat sets in. Tomatoes grow best when daytime temperatures are between 70 and 80°F and night temperatures are between 60 to 70°F.

Mistake 2: Starting with poor seedlings.

In the garden center, it's tempting to reach for the tallest transplants even if they're lanky or are blooming and on the cusp of producing fruit. Resist the urge. Bigger is not better in the case of tomato seedlings. When shopping for tomato seedlings, or growing your own, aim for a plant that is stocky with a straight stem and bright green leaves. Tall spindly seedlings and blooming plants often take weeks longer to establish in the garden than stocky seedlings.

Mistake 3: Shallow planting.

Tomatoes, unlike most plants, can produce roots along their main stem. Because of this special ability, tomatoes seedlings can be planted several inches deeper than they were growing in their nursery pot. Plant seedlings so that the top of the root ball is two to three inches below the soil level. Deep planting will spur a larger, more expansive root system than if the transplant was situated at ground level.

Mistake 4: Inconsistent watering.

Tomato plants thrive when they receive about 1 inch of water per week. When rainfall doesn’t provide the necessary moisture, supplement by hand watering or delivering water with a soaker hose or drip irrigation.

Tomato plants that weather big swings in moisture availability are more likely to have cracked fruit or succumb to blossom end rot. For example, too much moisture after a period of dry conditions leads to the plant taking up lots of water and expanding fleshy fruit before the surrounding skin can expand, resulting in split tomatoes. Blossom end rot takes hold when soil moisture isn’t available to help the plant access calcium necessary for good fruit development. Bottom line: Be sure tomato plants receive about 1 inch of water per week.

Mistake 5: Overhead watering.

When watering tomato plants, avoid splashing the leaves. Instead, deliver the water to the base of the plant with a watering wand, long neck watering can, or soaker hose. This direct-to-the-roots watering method helps discourage foliage diseases, especially those that get splashed up from the soil. Plus, it also maximizes the amount of water delivered to the plant roots and reduces moisture lost to evaporation so you avoid wasting water in your garden.

Mistake 6: Not staking tomatoes.

Tomatoes trained to grow in a cage or grow up a sturdy stake produce more useable fruit than those that are allowed to sprawl across the ground. Pests and diseases plague ground dwelling tomato plants. Sink a stake or tomato cage into the ground near the plant at planting time. As the plant grows, thread stems through the openings in the cage or tie stems to the stake.

Mistake 7: Planting seedlings too close together.

Tomatoes plants, except for bush or patio types, grow best when planted at least 3 feet apart. Ample space between plants allows for easy air flow, which is essential for drying foliage quickly after rain or morning dew. Foliage that dries quickly is less likely to succumb to disease.

Mistake 8: Planting in the same spot year after year.

Don’t grow tomatoes in the same location every year. Many pests and diseases can survive in the soil from one year to the next, plaguing the new crop. Experts recommend establishing a 3-year crop rotation for tomatoes and their close relatives—peppers, potatoes, and eggplants.

Another great way to limit soil-borne diseases is to remove all tomato plant debris at the end of the season, especially if your tomatoes were infected with diseases. You’ll reduce the chance of the disease popping up again next season by doing a thorough clean-up once your plants die.

Mistake 9: Neglecting to harvest.

Hot weather can ripen and then rot fruit quickly. Rotten fruit harbors pathogens that can spread to nearby plants and cause trouble the following growing season. When tomatoes begin to ripen, plan to harvest daily. Take two harvest pails to the garden—one for ripe fruit and one for rotten fruit. Leave no ripe or rotten fruit behind.