Growing Healthy Tomatoes

Title, Growing Healthy Tomatoes, image with drawings of tomatoes in black and white and red and green.


t’s heartbreaking,” Amy Schulman said about her struggle with growing tomatoes. She sows them indoors from seed, planting them in a raised bed at her Lebanon Hills Drive home. They thrive until mid-summer, when the fruit turns black on the bottom. “I am like the world’s worst tomato gardener,” she says laughing. “I think I’ve harvested like six tomatoes.”

She’s relatively new to growing tomatoes, beginning four years ago, but has produced lush green transplants from her basement operation each season.

What she is describing is called blossom end rot. It’s not a disease, but a common cultural issue tied to watering. Upon further investigation, her tomato planter is just too small and it’s almost impossible to water enough to keep the plants happy.

Amy Schulman holding a box with six small tomato plants
Amy Schulman with some tomato seedlings which were used as centerpieces for her daughter’s bat mitzvah and then planted in the Temple Emanuel of South Hills’ community garden for SHIM.

“It just dries out and the sun’s so hot, even if I water them twice a day,” adds Schulman.

Blossom end rot is particularly disappointing for gardeners like Schulman, as a brown or blackish sunken spot appears on the bottom of the fruit, often times close to harvest. “It’s a lot of time and effort and money put into this process and at the end of the day, my harvest is very minimal to none,” a disappointed Schulman related.

Technically, blossom end rot is a calcium deficiency, but in most cases the calcium is in the soil and the plant can’t absorb the nutrient without moisture. Some varieties are prone to the problem and it’s often seen on plants growing in containers, especially when they are five gallons or less and allowed to dry out. In this case, the raised bed is several feet long and about 18 inches wide, not big enough to stay moist.

Self-watering containers like an Earth Box are one of the best ways to avoid blossom end rot when growing in pots. The box has a reservoir filled with water, under a shelf which is filled with soil. As long as that reservoir contains water, the soil will always have the moisture it needs.

Bigger is always better when it comes to tomato containers. If you’re growing tomatoes in conventional pots, choose one that holds at least 15 gallons of soil. Fabric pots like a Root Pouch work well, as they can be pushed together and share water through a principle called wicking. Three of those containers pushed together give the gardener 45 gallons of mass, which will stay moist longer than smaller pots.

Tomatoes are the No. 1 crop for home gardeners. Besides blossom end rot, the plants can be hampered by a host of fungal problems, many times due to what type of season Mother Nature offers up.

Growing healthy tomatoes always begins with improving the soil, a mantra I repeat in this column over and over. Compost is the key, as it’s a natural fungicide, drains well, also holds moisture and provides the nutrients needed for the plant to thrive.

Many times, adding compost and other organic matter will allow the plants to outgrow pests and diseases. Apply it in the planting hole, or cover the entire planting bed with a few inches every season, to replace what the plants took in the year before.

Two of the most common and maddening problems gardeners experience when growing tomatoes is early blight and Septoria leaf spot. Both are early season fungal issues which don’t usually kill the plant, but will defoliate it and diminish production of fruit.

A tomato with a septoria leaf spot, one of two fungal issues gardeners deal with when growing tomatoes.
Septoria leaf spot is one of two fungal issues gardeners deal with when growing tomatoes, especially when there’s a cool, wet spring.

Soil-borne spores splash up on the bottom leaves early on, and when the foliage stays wet for 24 hours or longer, the spores can infect the plant. Later in the season, as humidity and temperatures rise, the disease manifests itself by turning the foliage yellow with brown spots. The leaves eventually fall off the plant.

These diseases are more prevalent during cold, wet springs and when plants are put in the ground in early May. Waiting to plant until late May will help, as will removing bottom leaves on planting day, which creates more distance between the spores and the plants. Mulching at planting time covers the spores, making it harder for them to reach the plant.

Correct watering techniques will also keep the plants from having fungal issues. Watering deeply, early in the day, at the base of the plant lets the foliage dry out during the day. Many gardeners think watering at the end of the day is a great idea, figuring there’s less evaporation, but it’s not a good idea to let that water sit on the leaves overnight. Certainly, it rains at night, but watering later in the day will just compound the problem with fungal issues.

Growing lots of different varieties of tomatoes will also help. Each cultivar reacts differently to diseases. Some disease resistant varieties are Defiant, Legend, Matt’s Wild Cherry, Cherokee Purple and Early Girl.

A bunch of tomatoes on a plant with rotten leaves attached.
When early blight or Septoria leaf spot hit a tomato plant, it usually doesn’t kill it, but defoliates and slows fruit production.

Good air flow between tomatoes is important. Give the plants plenty of room—at least three feet, five if possible. They’ll benefit from growing in cages or being staked to keep them off the ground.

A small green tomato with water droplets hanging off of it.
Watering deeply in the morning and trying to keep moisture off foliage will help the plants fight off fungal diseases.

An organic fungicide like Revitalize from Bonide is a biological control, meaning it’s safe for family, pets and those living downstream. When May is cool and wet, applying a biofungicide will help fight off both early diseases.

The most effective way to beat the diseases in my garden has been something called succession planting.

We’ve all been taught that our transplants must go in the garden by the third week of May to get tomatoes before the season ends. That’s true for cultivars that take 90 days or longer to reach fruition, but early and mid-season tomatoes can be planted later.

Sungold cherry tomatoes only take 47 days after planting for harvest. Other quick growing varieties like Early Girl, Fourth of July, Red Racer and a host of others can be planted as late as July fourth and still produce tomatoes before frost.

Every gardener longs for the first tomato of the season, so the first planting in late May is critical, but leaving room and planting others every two weeks will go a long way toward growing lush, green plants. Putting all the plants in on the same day is basically putting all your eggs in one basket, assuming weather, pests and diseases will be on your side. That rarely happens in the world of gardening.

Tomatoes love warm soil and air temperatures; they want an Italian summer, not a Pittsburgh spring. One trick is to warm the soil before planting by laying down black landscape fabric a month before planting.

A bunch of picked sungold tomatoes with cracks.
Sungold tomatoes are prone to cracking, but are one of the first to be picked. It can also be planted later in the season for disease free plants which put on tomatoes at the end of summer.

Commercial products like Wall O Water, which are filled with water and placed on the area to be planted weeks in advance, heat up the soil as the sun warms the water. The Wall O Water surrounds each transplant to give it protection during the first few weeks of planting.

You can get the same effect by wrapping a tomato cage with translucent 3-mil-thick plastic, which can be found at local hardware stores as a paint drop cloth.

Even though Schulman has struggled with larger tomato varieties getting blossom end rot, her cherry tomatoes do well and she has not had to deal with fungal issues. Like most gardeners, Schulman enjoys sharing what she grows. “I start them in March and it’s this lousy weather outside and then gifting those plants to other people. Seeing those plants flourish and grow in their garden, that gives me joy.”