5 Common Tomato-Growing Mistakes

Homegrown tomatoes simply taste better—rich, juicy, and full of flavor that store-bought varieties can’t match. Beyond taste, growing your own tomatoes is a step toward food independence and sustainability. Tomatoes are easy to grow as long as you pay attention to a few details.

Tomatoes are also one of the most productive garden crops—just a few plants can yield pounds of fresh fruit throughout the season.

I'm going to help you grow fabulous tomatoes this year and avoid the 5 top mistakes most people make when growing tomatoes.

Mistake #1

Growing healthy tomatoes organically begins with understanding the soil and the specific nutrients they need. Mistake #1 is having poor soil nutrients. Namely calcium.

Calcium

Tomatoes have a high need for calcium. The fruits grow fast and calcium is vital for strengthening and stabilizing cell walls. So its important to have a continuous supply of calcium to prevent the dreaded blossom end rot.

Blossom rot does not spread from plant to plant but you should remove infected fruits. Leave the plant because future tomatoes can be just fine. Fungicides and insecticides are not very effective since its a nutrient and water issue.

You can add bone meal to your garden in late fall or early spring. Bone meal provides calcium and phosphorus through a slow, steady release and lasts about 6–12 months in the soil so it is something you need to apply annually. I like the Down to Earth Brand.

However, bone meal doesn't deliver nutrients immediately so that why we apply it at least six weeks before planting. The soil microbes must first mineralize it, breaking it down so its available for plants.

A popular and effective vegan alternative to bone meal is rock phosphate. It provides phosphorus and calcium to plants, similar to bone meal, but is derived from rock deposits rather than animal bones. It does take a bit longer to break down so plan a head.

Gypsum can be added in the fall and will make the soil lighter as well as add calcium. Its a great additive for heavy clay soils.

There are also calcium chloride sprays on the market that you apply on the foliage. Use caution with these. It's important to understand that it's not a cure for existing blossom end rot, and it's best used as a preventative measure or in conjunction with other soil amendments. Also these sprays can cause plant injury if not used correctly.

Soil Parameters for Tomatoes

• Soil pH: Tomatoes prefer a slightly acidic pH between 6.0 and 6.8. This range allows for optimal nutrient uptake. If your soil is too acidic (<6.0), consider adding lime. If it's too alkaline (>7.0), elemental sulfur or organic compost can help lower the pH naturally.

• Soil Texture: Loamy, well-drained soil with good water retention is ideal. Tomatoes do not like soggy roots, so soil should be rich in organic matter but not compacted.

• Organic Matter: Aim for 5–8% organic matter. Compost, worm castings, and well-aged manure improve structure, water retention, and microbial life.

Mistake #2

Mistake #2 is also nutrition related. Fertilizer. Never add fresh manure - not even more mild manure such as rabbit - because you will get lots of leaves and little fruit. Add lots of well aged compost to the bed.

I do spray tomatoes with fish emulsion during transplanting and bud formation. I'm a big fan of fish emulsion which is a good organic fertilizer and has low levels of nitrogen.

Mistake #3

Consistent water is very important as well. Mistake number three is related to the absorption of nutrients. The calcium needs ample moisture to move around the plant. When drought occurs the fruit continues to develop but will be affected by a calcium deficiency.

Unfortunately, waterlogged soils can interfere with the root’s ability to take up nutrients as well. We cant control the rainfall but we can make sure we have good draining soil. Tomatoes need at least 1 inch of water per week.

Tomatoes benefit from a thick mulch such as straw. Not only does the mulch retain water but it keeps soil organisms from splashing up on the leaves.

Mistake #4

Tomatoes like it hot. It’s important to aim for good transplant timing. Tomatoes can be picky about transplanting and don’t like change. To help with making a good transition set your seedling trays outside on nice days.

I often take my trays from the grow room to the greenhouse and then from the greenhouse to outdoors. Gradually expose them to outdoor conditions over 7–10 days to toughen them up. This is called hardening off and helps them get used to the temps outside.

Tomatoes can be planted when the soil temperature reaches a minimum of 60°F (15°C). In Zones 6 that's late April/early May. Zone 5 friends may need to wait till Mother’s Day. Once they are ready to plant in the ground, dig a deep hole with your trowel and plant them right up to the first leaves. I often remove the lowest leaves before planting in the ground. Do it a couple days before setting in the soil.

By planting the seedlings deeply you give the tomato an advantage. They will send roots out of the stem to better anchor and feed the young plant.

Plant tomatoes 18 - 24 inches apart if you are using rows.

If you are using raised beds with deep soil you can have them on the closer end. Here we are trellising tomatoes which leads me to the next mistake.

Mistake #5

Mistake #5 is not having good support in place for your tomatoes. Indeterminate tomatoes grow tall and like to have a stable structure to climb on. One of my favorite types of trellis is cattle panels. They are sold at farm stores as livestock fencing. They are pricey but last for years. A tomato laden with fruit gets pretty heavy.

The traditional metal cages work but often need support. I typically pound in a metal fence post and then tie the cage to the fence post to give it extra support. PVC pipe can also be glued together to make a strong and interesting looking support.

I typically sink 6 foot metal fence posts every four feet and run hemp string in between them. As the tomatoes grow I make sure they have good contact. I never prune my tomatoes.

Another reason trellising is important is because it increases air flow among your plants. Air circulation is important especially in humid conditions to prevent mildews. I have a video on mildews that tells you how to recognize and prevent them.

I have a few bonus tips to help with your tomato growing. Be careful not to injure the roots if cultivation is needed near the plants. Best to cultivate shallowly with a hoe as the tomatoes dont like to be disturbed.

Tomatoes and marigolds are besties. Plant them together. Marigolds are a great companion plant for tomatoes and they look pretty. Studies have shown that marigolds help repel whiteflies and nematodes.

Tomatoes do well in containers, and even in hanging bags like the ones on the right side of the picture. This is a great way to use some vertical space.

Tomatoes and peppers obviously do great in grow bags. The bag on the left is 10 gallons and the right one is 7. Grow bags are super cool. They allow air circulation which means healthy roots.

Great for patios or along a walkway. Get the ones with handles so you can move them if needed. Keep in mind that plants in grow bags will need more frequent watering then those in garden soil.

Author, Ame Vanorio, is a Master Gardener and had a USDA certified organic farm for many years. She is also an author and you can check out her page on Amazon.