When To Start Greenhouse Tomato Plants?

Starting tomato plants in a greenhouse involves creating a supportive environment for them to thrive. The gradual increase in daylight hours is one of the first signs when to start planting tomato seeds in a greenhouse. Growing tomatoes in a greenhouse or high tunnel can extend the harvest season by several months up into late fall, but it’s not just about cultivating fruits; it’s about mastering an art.

When starting your greenhouse tomato growing adventure, it’s essential to pick the right tomato varieties and create a nurturing environment from the get-go. The extended growing season is the greatest benefit of having a greenhouse. When to plant tomatoes in a greenhouse, you can sow tomato seeds late February through the middle of March, or start indoors in mid-March and move them out in April after the last frost. Maintaining a stable temperature is crucial as fluctuations can lead to problems such as fruit tip rot and other issues.

Tomatoes do best at 28°C for germination, with a minimum temperature of 13°C for ten days to three weeks to give them the cold treatment. Sow from late February to mid-March if you’ll be growing your crop in a greenhouse, or from late March to early April if they’ll be outside. Tomato seeds require an optimum soil temperature of 21-27°C (70-80°F) for germination.

To grow the best greenhouse tomato, start seed mid to late March on a heat pad and move the plants 6 inches below grow lights after they sprout. If you have a greenhouse, start them two weeks before the last frost day, so start them two weeks earlier (early March). Start sowing in early February until early April, sowing the seeds in a tray or small pot of moist peat-free compost, top with a thin layer of compost.

When to put tomatoes in an unheated greenhouse?

To ensure a successful tomato growing season, sow seeds indoors in mid-March and transplant them into an unheated greenhouse by the end of April. The timing of sowing depends on the location and temperature. Tomato plants require a temperature of 10 degrees Celsius or higher for proper growth, and lower temperatures can damage them, especially if they are immature. To ensure proper growth, wait until the last expected frost dates in your area before sowing tomatoes inside an unheated greenhouse. It is essential to consider the location and temperature when planting tomatoes to ensure the best growing season.

Can a greenhouse be too hot for seedlings?

To ensure optimal greenhouse ventilation, use a maximum-minimum thermometer to monitor the temperature and be alert for signs of plant damage. Open doors and vents on sunny days, and temporarily remove panes to help during heat waves. Fit automatic vent openers to ensure roof vents open even when you’re not around, but remember that it takes time for the wax to expand. Provide alternative ventilation such as doors and side vents to prevent damaging temperatures. In changeable weather, vents and doors may need to be partially open to limit sudden temperature increases. Larger greenhouses may require automated ventilation and shading.

Shading is usually required from mid-spring until early autumn to release some heat but limits the light plants receive. Use only the minimum amount of shading to keep temperatures below 25-27ºC (77-81ºF), allowing as much light in as possible, especially for edible plants like tomatoes. Sun-loving plants like succulents may not need shading, but providing shade can make the greenhouse more pleasant.

When to put seedlings in an unheated greenhouse?

The optimal temperature for seedlings in an unheated garden greenhouse is between 10 degrees Celsius or 50 fahrenheit and 21 degrees Celsius or 70 fahrenheit. If the temperature drops below 10 degrees Celsius or rises above 21 degrees Celsius or 70 fahrenheit, protective measures are necessary. If the weather is too cold with low soil temperature, seedlings may need to be brought inside or provided with shade. Seedlings can tolerate colder temperatures than outside, but monitoring the temperature is crucial.

Most seedlings can tolerate temperatures as low as roughly 4 degrees Celsius or 40 fahrenheit, but it’s essential to check the specific variety. To provide warmth, consider using horticultural fleece, but remove it during the day to ensure ventilation. Overall, seedlings can tolerate colder temperatures in an unheated garden greenhouse, but proper monitoring and care are essential to ensure their well-being.

When can I put plants in a plastic greenhouse?

In spring, mini greenhouses can be filled with young plants ready for transplanting into the garden. These plants, particularly salad crops, can be grown directly from seed. In summer, they can be used for protected crops like tomatoes, peppers, cucumbers, and aubergines, while the remaining space can be used for homegrown Mediterranean crops. In autumn, cuttings from fuchsias and geraniums can be taken to provide plant material for next year. Salad crops like lettuce can be planted in the mini greenhouse to ensure a steady supply during winter months, and vegetables like Spring cabbage can be grown on ready for planting.

How early can you start plants in a greenhouse?

To transplant seedlings into the garden, sow seeds in a greenhouse six to eight weeks before the last frost date in your area. Harden off plants two weeks before transitioning to the garden, moving them outside for several hours each day. Gradually increase the hours spent outside over two weeks. Transplant the plants into their permanent locations when hardening off is complete. Some plants, like melon, cucumber, and dill, may not transplant well, so consider sowing them directly in the garden or in a large container in the greenhouse.

How big should tomato seedlings be before transplanting outside?

Transplanting tomato seedlings is a crucial process that requires them to reach a height of three to four inches and have three or more sets of leaves. It is recommended to do this at least four weeks before planting outdoors to allow the root system to develop. The container should be at least four to five inches deep and can be recycled flower pots or soda and coffee cups with a drain hole. To use a planting medium, use a commercial potting mix or create your own using peat moss, vermiculite, and perlite. Avoid using garden soil to prevent damping off the seedlings. Moisten the potting mix and let it set for a few hours or overnight.

Do tomatoes grow faster in a greenhouse?

Tomatoes thrive in a warm environment, so growing them in a heated greenhouse or before transplanting outside can yield the earliest crops. However, most people don’t have this luxury. To start tomato harvests quickly, RHS Chief Horticulturist for Communications, Guy Barter, suggests covering plants with fabric or using a light-weight material to prevent cold nights from affecting the plants.

Do I need to harden off seedlings before putting in greenhouse?

Hardening off is a crucial process for mature plants grown inside a greenhouse, as it involves slowly acclimating them to a new environment to prevent shock, damage, or even death. When plants are raised indoors in early spring and moved outside for planting, they must adapt to direct sun, cooler temperatures, lower humidity, increased air movement, winds, and pest and disease pressures, which are unpredictable and out of control.

Proper hardening off results in thicker cell walls and leaf structures, increased energy for root development, and reduced excess water, making the plant stronger, more rigid, and less susceptible to freeze damage. As plants grow slower, they create a firmer, less floppy plant that can handle the stresses of the outdoors. If not hardened off, wind, sun, or cold can lead to significant wilting, browning leaf edges, or even death.

Hardening off is a time-intensive process, ideally done over two weeks, but it is generally more sensitive than bringing home well-rooted, mature plants from a greenhouse and acclimating them to their new environment. It is essential to follow guidelines for hardening plants off when preparing for outdoor planting and to simplify the process when moving crops outside for sale or at home.

Do tomatoes grow better in a greenhouse?

Tomatoes thrive in greenhouses, producing larger, earlier crops. A detailed guide can guide you through each step in growing tomatoes. While they require attention like frost protection and regular watering, the benefits of home-grown tomatoes are worth it. There’s a wide variety of fruits, colors, textures, and flavors to choose from, making it a great choice for all tastes. Growing tomatoes also offers plants of different sizes, locations, and spaces, from tall to vigorous. Enjoy your home-grown tomatoes all summer long, fresh and juicier than in the supermarket.

Should I shade my greenhouse with tomatoes?

Plant growth relies on light, so only the minimum amount of shading is needed to maintain temperatures below 25-27ºC (77-81ºF). However, allow as much light in as possible, especially for edible plants like tomatoes. Sun-loving plants like succulents don’t need shading, but providing shade can make the greenhouse more pleasant. There are various ways to shade greenhouses and conservatories, including external blinds, which provide shade and a cooling effect by preventing sun rays from passing through the glass, and internal blinds, which allow sunlight to pass through the glass and generate heat but are more easily automated. There are various materials available with varying degrees of shading and permeability to allow air exchange.

Why are my tomatoes dying in my greenhouse?

Tomato plants can wilt and die when they are not properly watered, which can be caused by various factors. Lack of water, fungal wilt diseases, tomato spotted wilt virus, walnut toxicity, and stalk borers are some of the potential causes. Tomato plants require approximately 1 inch of water per week, which can be re-established when soils are dry. A thorough watering once a week during hot, dry weather is sufficient. If using an overhead sprinkler, water the plants in the morning to reduce foliar disease problems.

Verticillium and Fusarium wilt are two common diseases that affect tomatoes and other tomato plants. These diseases overwinter as fungal spores in garden soil or on infected plant debris. The fungus enters the tomato plant through the roots, grows up into the main plant, and blocks water and nutrient movement, causing the leaves to turn yellow and wilt.