For optimal growth and fruit production, tomato plants require overnight temperatures consistently above 50°F (10°C).
Start covering your tomatoes as soon as nighttime temperatures drop below 50°F (10°C). While they can survive mid-40s, they stop growing, and blossoms may drop. Once temperatures hit 40°F (4.4°C) or below, you must cover them to prevent cold damage or frost.
50°F is not too cold for established tomato plants to survive, but it is the threshold where they stop thriving and growth slows down. Because tomatoes are warm-weather plants, nighttime temperatures consistently below 50°F can stunt development, weaken the plant, and reduce fruit production.
Regardless of what you might read or see in nursery promotions, planting tomatoes in October or November is not a fruitful experience, literally. The night temperatures are too low for the flowers to set fruit. Tomatoes planted in August or early September will grow quickly in the warm soil, warm nights and long days.
Another temperature to keep in mind: tomato plants will not survive in temperatures below 35 degrees Fahrenheit, and will not thrive at temperatures below 50 degrees. Gardeners can use a frost date calendar to note their region's average dates of last frost in spring and first frost in fall.
Tomato plants are highly sensitive to cold and can suffer varying degrees of damage depending on the severity and duration of the low temperatures. Symptoms range from stunted growth and lack of fruit in cool conditions to complete plant death when exposed to frost.
Coffee grounds provide tomato plants with slow-release nitrogen for leafy growth, trace minerals like potassium and magnesium, and beneficial organic matter. They also help improve soil drainage and can slightly deter pests like slugs and snails.
As the growing season draws to a close, tomato plants are often still loaded with fruit. To speed ripening late in the season, remove the growing tip of each main stem about four weeks before the first expected fall frost.
Baking soda (sodium bicarbonate) is used to control fungal diseases, deter pests, and slightly reduce soil acidity. However, it must be applied with caution; overuse can cause dangerous salt buildup and damage plant tissue.
Never plant fennel, brassicas (like cabbage, broccoli, and kale), potatoes, or corn near tomatoes. These plants can stunt tomato growth, compete aggressively for nutrients, or spread devastating diseases and pests.
Tomato plants fruit from June until the first frosts, thriving in the warm, light conditions of summer. However, the ripening process slows down as the days become shorter, so fruit that develops from September may not ripen before the first frosts arrive. Tomatoes ripen most quickly in a warm, light environment.
To keep tomatoes warm overnight, cover them before dusk with frost blankets or old bedsheets, never letting plastic directly touch the leaves. Trap radiating ground heat by placing upside-down 5-gallon buckets over the plants, or surround them with gallon jugs filled with hot water.
Whether 40°F is too cold depends entirely on the type of plant. It is perfectly fine for cold-hardy crops, but dangerously cold for warm-season plants.
Yes, tomatoes will survive 50-degree nights, but they won't thrive. The ideal night temperature is between 55°F and 85°F. Consistently dropping below 50°F can slow growth, restrict nutrient absorption, and stunt the plant's development.
If there is a frost predicted for your area, in addition to covering your tomatoes and peppers, you should harvest all of the tomatoes.
Water-filled tubes trap heat during the day and release it at night to protect tomatoes and other sensitive plants from frost. A tomato teepee (or water teepee) is a reusable, cone-shaped plastic sleeve with tubes that form the wall. You fill the tubes with water and place the teepee around your plant.
To grow bigger tomatoes, maximize the fruit's size by pruning excess branches, restricting the plant to just one or two main stems, and plucking off early blossoms. This diverts the plant's energy into sizing up the remaining tomatoes rather than spreading resources across too many fruits.
The best homemade tomato fertilizer is a nutrient-rich, liquid compost tea. It delivers a gentle, balanced boost of essential macronutrients (nitrogen, phosphorus, and potassium). To make it, steep a shovelful of aged manure or compost in a 5-gallon bucket of water for 24 hours, strain the liquid, and water your plants.
Hydrogen peroxide can be highly beneficial for tomato plants if used correctly. It is a cheap, effective, and readily available remedy used to control fungal diseases, manage pests, and aerate waterlogged soil. However, because it is a strong oxidizer, using too much can damage your plants.
Overwintering tomato plants allows you to keep the same genetics year-round, resulting in an earlier and larger harvest the following spring. The easiest and most successful method for indoor climates is rooting cuttings (suckers) in water over the fall and winter.
Encouraging the last few to ripen
The simplest is to bring them into a warm room and place them in a paper bag with a ripe banana or apple. Both release ethylene gas, which encourages ripening. Keep the bag loosely closed, check daily, and you'll often find the tomatoes take on full colour within a week.
To give your tomatoes the best start, place a mix of compost (or worm castings), a handful of bone meal (for phosphorus), and a tablespoon of Epsom salts (for magnesium) at the bottom of the hole. Always cover these amendments with an inch of dirt before placing the plant in so the roots aren't directly burned.
Plants that prefer alkaline or neutral soil, along with those that require dry or well-draining conditions, generally dislike coffee grounds. Applying coffee grounds can stunt their growth by making the soil too acidic, altering nutrient balances, or trapping excess moisture around the roots.
Tomato plants love the nutrients these provide, but these amendments must be broken down first. Eggshells supply much-needed calcium (which prevents blossom end rot), and coffee grounds offer nitrogen. However, direct, chunky applications take too long to decompose to help your plants immediately.