Growing tomatoes

 All you wanted to know about growing Tomatoes but didn't know who to ask

Nothing like tree-ripened tomatoes from your garden (Photo:Gardner's Path)

Acknowledgement: This post is dedicated to the late Marcia Proctor Fein, my mentor and Master Gardener par excellence who introduced me to scientific growing methods including IPM (Integrated Pest Management) by University of California, Davis and Agriculture and Natural Resources (UCANR)  Thank you Marcie!!

Enjoying your sun-ripened garden-grown organic tomato (Solanum lycopersicum L.) is one of life's most gratifying experiences ... oodles of flavours to tease and tantalize your taste buds. 

If you don't know what I'm talking about, it's time you read this post ...

The tomato plant is a temperate herbaceous and grows mostly annually, though a few biennial and perennial forms (for example tamarillo or Solanum betaceum) exist. 

The tomato is a globular or ovoid fruit (yes it is botanically a fruit though most often we think of it as a vegetable - thanks to a US Supreme Court ruling in Nix v Heddon, circa 1887, which ruled tomato to be classified as a vegetable for taxation and import duty purposes). Botanically, the fruit exhibits all of the common characteristics of berries; a simple fleshy fruit that encloses its seed in the pulp. 

The outer skin is mostly thin (except paste tomatoes which are selectively bred) and fleshy tissue that comprises the remainder of the fruit wall as well as the placenta. 

Tomatoes are a rich source of Vitamin A, Vitamin C, folic acid, and antioxidants. Also rich in carotenes, such as lycopene and beta-carotene . It also contains tomatine, an alkaloid with fungicidal properties. 

The French call the tomato, "pomme d'amour" or 'Love Apple," because they believed it was an aphrodisiac.

Origins

The cultivated tomato is related to wild tomatoes originating from Peru, Ecuador and other parts of South America. Mexico is presumed to be the most probable region of domestication, going as far back as 700 BC, with Peru as the centre of diversity for wild relatives. 

Tomato cultivation was first incorporated within the Mesoamerican farming system of milpa, a polyculture association of the three sisters: maize (Zea mays), beans (Phaseolus spp.) and squash (Cucurbita spp.). This trilogy was the only source of carbohydrates, proteins and fats. Over time, chilli pepper and tomatoes were introduced to add essential vitamins and minerals, ensuring milpa satisfied nearly all nutritional necessities while enchasing taste.

Soil

Tomatoes are heavy-feeders and grow well in most mineral soils, but they prefer deep, well-drained sandy loams rich in compost; and at least 7 hours of direct sunlight. 

Deep tillage enables adequate root penetration in heavy clay-type soils, yielding a bountiful harvest of tomatoes. 

Tomato plants grow best when fertilized at two specific times during the growing season: right after planting and just before the fruit develops. If your soil is lacking in nitrogen then a balanced liquid plant food like N-P-K 5-5-5. If the soil has compost amendments then you can use N-P-K 5-10-5 or even 5-10-10

Tomato is moderately tolerant to a wide range of pH, though higher yields are seen with a pH between 6.5 and 6.9. 

As with most plants, the presence of Mycorrhizal fungi, especially vesicular-arbuscular mycorrhizal (VAM), the ubiquitous soil microbes that form a symbiotic relationship with the plant, is a sign of healthy soil. 

Climate

Tomatoes require a warm climate for growth and do not tolerate frost.  

Optimum temperature is around 26°C/78°F (day), 12°C/54°F (night) and the night temperatures of the soil are above 18°C/64°F. 

Temperatures above 31°C/87°F reduce the rates of flower fertilisation, plant development and fruit ripening.

Transplanting

In North America, you can gain a head start on the growing season by buying transplants or starting seeds indoors six to eight weeks before your area's average last frost date. Wait for the soil to warm, and then transfer the tomato plants outside. 

When transplanting make sure the cavity is two times the size of the root ball. Put phosphorus-rich bone meal, liquid seaweed or fish emulsion at the bottom of the pit to ensure a good yield, water heavily then bury the seedling including one or more whorls of the bottom true leaves - these will regenerate as adventitious roots (roots that form from any non-root tissue) providing additional robustness. 

Lay long, leggy transplants on their sides in trenches 3 to 4 inches deep, keeping just the plant tip above the soil.

Earthing-up consists of massing up earth at the plant base to ensure the growth of adventitious roots (roots that form from any non-root tissue)  providing better anchorage. The first earthing-up occurs between the first and second week after transplantation and is repeated between the fourth and fifth week. On occasion, this practice is also performed during weeding.

Growing

The two broad categories of tomatoes are determinate (mostly especially hybrids that ripen at the same time) to indeterminate (usually heirlooms that breed through the season and may reach up to 1.5 to 3 meters in height requiring additional support). 

Hybrid varieties are cultivated to be disease-resistant, for their shape, size, and texture, and also to mature at the same time for easy mechanized harvesting. Industrial production often involves growing tomatoes in open fields requiring simultaneous fruit ripening and machinery harvesting. In addition, traits such as high sugar and total soluble solids content are required for the processed food market. In the case of fresh market tomatoes, traits such as large fruit size, uniform fruit shape, uniform colour, long shelf life and fruit firmness are important. All these factors have resulted in selective breeding of hybrids that have unfortunately greatly reduced diversity

Tomato trellis for indeterminate varieties (Credit: House beautiful)

Indeterminate varieties must be supported by a trellis, e.g. Drive 8-foot stakes at least 12 inches into the ground and 4 inches away from the plant stem; then attach tomato stems to the stake with garden twine, self-adhesive tape, or strips of cloth. Alternatively use 5 foot wide galvanized metal mesh shaped as a cylindrical cage to support the plant and facilitate access for crop management and pest control.

Heirloom tomatoes (Credit: Love and Lemons)

So what exactly are heirloom tomatoes? According to Farmer's Almanac, heirloom plants come from saved seeds that have been handed down for generations over at least 50 years, hence the name "heirloom." Heirloom tomatoes can be green, pale yellow, bright orange, deep red, purple, and even chocolate brown. They can vary in size and shape — some are small and smooth, while others are large, lumpy, and lopsided - but while not heavy producers they all have a very unique flavour and appearance. 

Pollination

In heirloom varieties, the flowers have a style shorter than the tip of the anther cone resulting in self-pollination that ensures self-compatibility through inbreeding, resulting in the next generation of seeds being true-to-type variety of the parent. 

Pollination is by wind but you can stimulate it by providing vibrations in a greenhouse environment. 

For varieties where the style is longer than the anther cone resulting in cross-pollination by wind, bumble bees and other pollinators, so growing from a seed packet is more reliable than growing from a fruit.

Companion plants

Borage (Credit: Honey Bee Co)

Borage is an excellent companion plant because it helps reduce the dreaded hornworm by attracting beneficial insects. It also attracts pollinators, including bees and butterflies, to the garden. Both the leaves and flowers of borage are edible and used as garnishes or herbs.

Basil, a familiar culinary herb with fragrant foliage, which some gardeners believe repels thrips and hornworms. Likewise, some gardeners also say Marigolds make great companion plants since they repel a variety of pests, including whiteflies, nematodes, slugs, and snails. While helpful these are effective only in cases of low infestation.

Pruning and guidance of the plants

Pinch off tomato sucker branches (Credit: Spruce)

It is important to pinch off the weak shoots that appear in leaf axils - this will create a plant architecture which facilitates better sunlight exposure, air 
circulation, and stronger plant physiology that stimulates plant development, provides more efficient phytosanitary control and achieves higher quantitative and qualitative yield.

As a plant grows, trim the lower leaves from the bottom 12 inches of the stem to prevent soil contamination during watering. 

Some gardeners prefer to remove any leaves below which there are no tomatoes. This concentrates the plant's energy towards fruit production.

Irrigation

Drip irrigation for tomatoes has gained popularity as it controls the amount of water delivered without wastage or splashing. 

In the early stages of growth, tomato seedlings requires frequent irrigation to delay maturity and prolong plant productivity. 

However once the plant starts to produce flowers, then drastically cut back the watering. While this may seem counter-intuitive it forces the plant into survival mode where it puts out more fruit that is also more flavorful. Frequent harvesting of tomatoes will ensure a steady crop.

Apply 2 to 4 inches of organic mulch, such as straw, hay, or bark chips, about 5 weeks after transplanting to help retain moisture, keep soil from splashing the lower leaves, and control weeds.

The most common mistakes made when planting tomatoes

1. Planting too early or too late in the season. Remedy: Plant after the last frost when night temperatures of the soil are above 18°C/64°F.
2. Starting with poor-quality seedlings. Remedy: choose seedlings that are stocky with a straight stem and have bright green leaves
3. Shallow planting. Remedy: Plant seedlings so that the top of the root ball is two to three inches below the soil level.
4. Inconsistent watering. Remedy: Plants need 1 inch of water per week or when the soil is dry 1" below the surface. Use drip irrigation to deliver the precise amount of water at regular intervals.
5. Overhead watering. Remedy: To prevent splashing soil on the leaves due to overhead watering, remove the lowest whorl of leaves and deliver water directly to the root system.
6. Not supporting indeterminate plants. Remedy: Stake and support tomato plants to prevent soil-borne diseases
7. Planting seedlings too close together. Remedy: Cull the weaker seedlings leaving 3 feet distance between two tomato plants
8. Planting in the same spot year after year. Remedy: Establish a 3-year crop rotation for tomatoes and their close relatives—peppers, potatoes, and eggplants. After every growing season, grow a non-solanaceous plant for the next two seasons.
9. Neglecting to harvest. Remedy: Harvest frequently. Overripe, rotten fruit can spread diseases and also reduce the productivity of the plant since it has prepared enough seeds to survive another generation.

Common diseases

• Septoria leaf spot is a common disease, which causes numerous, small spots on leaves

• Catfacing refers to misshapen tomatoes caused by exposing flowering tomato plants to temperatures below 50°F damages the flowers. Damaged flowers then developed into misshapen, irregular fruit. The cause of damaged flowers isn’t limited to cold temperatures though, excessive nitrogen fertilizer, exposure to broadleaf herbicides, along with overexuberant pruning are other potential causes of catfacing. Fruit that is scarred, misshapen and deeply creviced is safe to eat if the flesh is firm, appropriately coloured, and fresh, simply cut away the damaged parts and use the rest of the fruit.
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Tomato blossom-end-rot 

• Blossom-End Rot causes the bottom side of the tomato to develop dark, sunken spots due to a calcium imbalance when soil moisture isn’t available to help the plant access calcium necessary for good fruit development Some gardeners add diluted milk (50% milk, 50% water) for a quick jolt of Calcium. Adding crushed eggshells does not make the calcium immediately available to the root system.

Early blight in tomatoes 

• Early Blight is a fungal disease caused by Alternaria Solani resulting in leaves dropping. In July, the risks of blight increase, due to the combination of high humidity and warm days and nights. It starts with dark, concentric spots (brown to black), about 1/2-inch in diameter, on the lower leaves and stems. If you catch it early and destroy infected leaves, your plant may survive. The best defence for outdoor tomatoes is good ventilation and stripping off the lower leaves as the fruits develop. This also helps the ripening process, as tomatoes have maximum exposure to sun. 

• Late Blight is a fungal disease that causes grey, moldy spots on leaves and fruit, which later turn brown. The disease is spread and supported by persistent damp weather. Unfortunately, once your tomato has late blight, there’s really no solution. 

Tomato Spotted Wilt Virus (Credit: Potato News0

• Spotted Wilt Virus creates blotchy fruit and distorted leaves and causes young growth to be narrow and twisted, and the leaves become mottled with yellow. Unfortunately, infected plants should be destroyed (but don’t put them in your compost pile).

• Fusarium Wilt starts with yellowing and wilting on one side of the plant and moves up the plant as the fungus spreads. Unfortunately, once this disease strikes, the plant needs to be destroyed. If this is a recurring problem select hybrid tomato cultivars that are 

• Powdery Mildew is a fungal disease that leaves white spots or a dusting of white on the leaves. As fall sets in, many older plants suffer from this and it's time to remove the plant before the mildew spreads to healthy ones.

• Cracking: When fruit growth is too rapid, the skin will crack. This usually occurs due to uneven watering or uneven moisture from weather conditions, such as (very rainy periods mixed with dry periods). Keep moisture levels constant with consistent watering and mulching.

Tomato leaf curl

• Leaf roll is a non-damaging plant disorder, which causes tomato leaves to roll in on themselves. It is a viral infection either spread by aphids or carried through infected seedlings

• Sunscald occurs when tomato fruits get too much sun probably due to overzealous pruning, causing white spots and then moldy areas in exposed areas. Once damaged is not reversible. 

• Yellow shoulders occur when the topside of tomato fruit never ripens and remains hard and yellow

Preventing disease

The cultivated tomato is a member of the genus Solanum within the family Solanaceae. The Solanaceae, commonly known as the nightshade family, also includes other notable cultivated plants such as tobacco, chilli pepper, potato and eggplant - all contain varying amounts of toxic glycoalkaloids.

What is even important to know is that you have to rotate crops between Solanaceae (1 season) and non-Solanaceae (next two seasons) to avoid the build-up of soil-based pathogens like Fusarium oxysporum f. sp. radices-lycopersici, Pythium ultimum, Rhizoctonia solani and Pyrenochaeta lycopersici. 

Also, it is important to keep the area weed-free year-round even during the non-growing season since these serve as hosts for insect vectors like the Western flower thrip (Frankliniella occidentalis) – and Tospovirus (tomato spotted wilt virus)

Another great way to limit soil-borne diseases is to remove all tomato plant debris, including the root system at the end of the season, especially if your tomatoes were infected with diseases. 

Common pests

Tomato Hornworms

Aphids under a tomato leaf

Tomato cutworms

Tomatoes are susceptible to many pests including stink bugs, cutworms, tomato hornworms, tobacco hornworms, aphids, cabbage looper, whiteflies, tomato fruit worms, flea beetles, red spider mites, slugs, agromyzid leafminer and Colorado potato beetle. 

Let's take a closer look at some of them

• Tomato hornworms are large caterpillars that feed on leaves and fruit.
• Aphids can colonize tomato plants in large numbers. You may notice leaf curling, discoloration, and sticky leaves.
• Cutworms can cut young tomato plants off at the base.
• Flea beetles are small, quick-moving insects whose feeding leads to many small holes in leaves. 
• If tomato fruits are already damaged, you may see sap beetles feeding inside the fruit.

Controlling pests

• To dislodge many pests like Aphids, spray plants with a good jet of water.

• Handpick bigger insects like Tomato Hornworms with gloves on, dropping them into a bucket of soapy water.

• Apply insecticidal soap directly to the insect on the plant. This works for smaller pests, such as aphids and spider mites.

• Apply horticultural oils like neem oil or sprays diluted in water, to suffocate insects by creating an impermeable layer

• you can artificially boost the immunity system by applying a diluted solution of salicylic acid. 

• Intervention may be needed for infestations. Only as a very last resort use insecticides, keep in mind that you may be killing beneficial insects as well.

• In the worst case if you have to cull the plant, do not compost it - instead incinerate it or seal it in a plastic bag and dispose with the trash.

How to Harvest and Store Tomatoes

Tomatoes are prime for plucking when they're fully coloured and firm. Early-season tomatoes mature in 40 to 70 days, mid-season in 60 to 70 days, and late-season tomatoes in 80 to 100 days from planting.

Weather plays a role in the timeline; tomatoes ripen best at temperatures close to 24°C/75°F. When the temperature plunge with the first frost, the tomatoes will stop maturing on the vine, likewise when temperatures rise to about 32°C/90°F, the fruits start to soften and develop poor colour. 

If you pick green tomatoes at mature size, they will ripen indoors.

Never refrigerate fresh garden tomatoes. Doing so spoils the flavour and texture that gives garden-fresh tomatoes their awesome taste.

To freeze, core fresh and unblemished tomatoes and place them whole in freezer bags or containers. Seal, label, and freeze. The skins will slip off when they thaw.

References

1. Organisation for Economic Co-operation and Development. (2017). Tomato (Solanum lycopersicum). In Harmonisation of regulatory oversight in biotechnology: Vol. VOLUME 7 © OECD 2017 (Chapter 2, pp. 69–104). https://doi.org/10.1787/9789264279728-6-en
2. Boeckmann, C. (2024, January 17). Growing Tomatoes from Planting to Harvest. Almanac.com. Retrieved January 21, 2024, from https://www.almanac.com/plant/tomatoes
3. Hughes, M. (2023, March 23). 9 Common tomato growing mistakes to avoid. Better Homes & Gardens. Retrieved January 21, 2024, from https://www.bhg.com/tomato-growing-mistakes-7369574