Tips for a Top Tomato Harvest

By Sally McCabe, Community Educator for the Pennsylvania Horticultural Society

No surprise--Tomatoes top the charts of most-planted crop in vegetable gardens in the US. With so many choices, from the charming cherry tomato to large heartier varieties, this popular fruit offers countless opportunities to brighten your menu throughout the summer.

At the Pennsylvania Horticultural Society (PHS), we are in our second year of our Harvest program, a collective action focused on increasing food production and food security. This is an opportunity for gardeners to plant food crops to share with their families, neighbors, and the community through organizations such as food pantries.

Last year, Harvest gardeners donated more than 44,000 pounds of food. Tomatoes were a much-appreciated part of this contribution, so we’d like to take this opportunity to share our tips for you to grow more and better tomatoes than ever before.

Beating the Heat

As the climate continues to change, we’re consistently facing more summers with daily high temperatures above 90 degrees. Most tomatoes will not set fruit if the day-time temperature is constantly above this level of heat, and the same is true if the night-time temperature is above 72 degrees.

A tomato plants may look green and vigorous, but the blossoms dry up and fail to produce fruit.

The reason this happens is that the heat causes the female part of the plant, the pistil, to grow considerably longer than usual. The result is that the pollen from the shorter male parts, stamens, can no longer pollinate the stigma at the end of the much longer pistil.

Most regular tomatoes can still produce before the heat wave comes and then in early autumn after the heat wave. But during the middle of summer? That’s a challenge. The solution? Plant varieties designated as "hot-set" tomatoes, since they will fruit despite higher temperatures. In the meantime, be patient; be consistent with watering to keep them healthy during times of heat stress.

Trellising and Trimming

Most of the pros highly recommend caging or trellising and pruning tomato plants for the best results. Thinning out and getting plants elevated gets more sunlight and air to the leaves, resulting in healthier plants with less pest and disease problems. Getting fruit up off the ground also helps keep ground-dwelling pests from chomping on your prize tomatoes.

Even if you are not trellising them vertically, chose 2 to 3 main stems and get rid of the rest. Additionally, once the plant reaches three feet tall, consider pruning off the lowermost leaves and continuing to remove suckers.

Water and Mulch

Unless Mother Nature delivers a good soaking rain every week, give plants 1-2 gallons of water every few days. This is especially crucial when fruit is setting. Plant basil nearby as an “indicator” plant; basil will wilt whenever the ground dries out, giving you a visible warning that it’s time to get out the watering can.

Spread an inch or two of mulch around (but not on top of) your tomato plants after a good rain. This will keep a steady supply of moisture in the soil, helping to prevent the wet/dry/wet/dry cycling that causes blossom end rot, cracking, and other stress-related issues.

Share the Harvest as a Team

This year, as part the Harvest program, anyone has the option to sign up as a Growing Team with family, friends, or neighbors to pool crops, track their collective impact, and compete for prizes. Participants will receive virtual resources on food growing and harvesting, including guides, checklists, and ongoing webinars. Gardeners will be able to share tips, ask questions, or just brag about their gardens through PHS’s social media channels and remote networking opportunities. Additionally, you can access PHS’s list of local retailers and nurseries to know where to purchase supplies and tools.

Whether you’re growing alone or with others, you can help combat food insecurity. Learn more about gardening and how to share that bounty by registering at phsonline.org/harvest.