I want to grow tomatoes this year. Should I add Vitamin B1, crushed eggshells, or Epsom salt to the planting hole? I remember my grandmother using all three when I was a child, and she had the best homegrown tomato crop ever.

The short answer is no. Do not amend the soil in which tomatoes are planted with any of these substances. They will not improve the crop and could even be detrimental.

It is interesting, however, to understand why these practices got started. For a long time, vitamin B1 (also known as thiamine) was thought to stimulate plant root growth. The myth started when a commercial product that contained both auxin (a plant growth hormone) and vitamin B1 was marketed to enhance the establishment of transplants. Research has since revealed that the auxin stimulated root production and the vitamin B1 did little to help in plant establishment or growth.

Calcium is essential to prevent blossom-end rot, a common ailment in tomato plants. Crushed eggshells are a rich source of calcium; however, most soils contain sufficient calcium for good plant growth and fruit production. The problem is that inconsistent watering, planting too early in cold soil, or root damage can prevent the plant from absorbing the calcium that is already there. Adding more calcium to the soil will not help. Good planting and watering practices will.

Magnesium is an essential nutrient that plays a critical role in the growth and development of plants. Epsom salt is a rich source of magnesium. Like calcium, however, soil is rarely deficient in magnesium. Furthermore, excess magnesium can inhibit the uptake of calcium, which can lead to blossom-end rot; it can also damage soil structure. Therefore, the use of Epsom salt is discouraged.

What are best practices for planting tomatoes?

Tomatoes like well-drained soil, high in organic matter with a pH of 6 to 6.5 (slightly acidic). It is important for the pH to be in this range to allow tomato plants to absorb the nutrients they need for good growth and development.

Because the soil around many homes has been replaced with non-native soil with unpredictable characteristics, test your soil before planting. Amend the soil as suggested by the soil test and take steps to bring the pH into the recommended range.

Remove all weeds at the planting site. Weeds compete with your tomato plants for nutrients, water and space. They also harbor pests and diseases that will infect your tomato plants.

Because tomatoes develop an extensive root system, cultivate the planting site deeply before planting to encourage good root growth once the plant is in the ground.

After preparing the soil, dig a hole. The hole should be deep enough to bury the roots and lower portion of a tomato plant’s stem from which the leaves have been removed. The depth will depend on the height of the plant at planting.

Alternatively, you can dig a trench in which to plant your tomato. In trench planting you lay the tomato plant on its side in the trench, burying the roots and lower portion of the stem from which the leaves have been removed. Planting in a trench keeps the roots closer to the surface of the soil and warmer than planting in a deep hole. The trench should be about five inches deep and long enough to accommodate the roots of the plant and bare lower stem.

Fill the hole or trench with water; let the water soak in. Add a handful of slow-release fertilizer with low nitrogen content to the hole or trench. A formulation such as 5-10-10 (i.e., 5% nitrogen by weight, 10% phosphorus by weight, and 10% potassium by weight) is a good selection. Cover the fertilizer with 1-2 inches of compost or native soil.

As noted, remove the lower leaves and branches of the tomato plant, leaving only three or four branches at the top. Roots will develop along the main stem where the leaves are removed if buried in the soil. Place the plant in the hole or trench with the upper stems and leaves exposed, and the bare stem and roots buried. Fill in the hole or trench with native soil, taking care not to pack it too much.

Create a well, i.e., depression in the soil, around the base of the plant. Water, and wait for the water to be absorbed. Water again.

Mulch around the base of the plant to help retain moisture and deter weeds. You can use grass clippings, dried leaves, sawdust, or composted mulch. Alternatively, you can use black plastic or landscape cloth to cover the soil around your plants.

For more information on growing tomatoes, please see Washington State University’s “Growing Tomatoes in Home Gardens (FS145E)” available at https://pubs.extension.wsu.edu/growing-tomatoes-in-home-gardens-home-garden-series or University of Idaho’s “Growing Tomatoes in Cool, Short-season Locations. (Bulletin 864)” available at https://www.uidaho.edu/-/media/UIdaho-Responsive/Files/Extension/publications/bul/bul0864.pdf.

Join us on May 17

To learn more about growing tomatoes, join Clallam County Master Gardeners on Saturday, May 17, from 10:30 am to 12 p.m. at the Master Gardener Demonstration Garden at 2711 Woodcock Road in Sequim. A team of Master Gardeners will share tips on how to select, plant, maintain, and harvest tomatoes as well as how to avoid common problems. For more information go to https://extension.wsu.edu/clallam/master-gardener-calendar/

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Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener and tomato lover.