When to Plant Tomatoes in Unheated Greenhouse

Time factor cannot be set aside in agriculture, in fact, time is agriculture itself, they work hand in hand to ensure maximum production. Knowing the accurate time of the year to plant tomatoes will help determine the appropriate time for you to transplant your seedlings to your unheated greenhouse Which in due time will help produce the best tomato crops.

You might be thinking when should you plant tomatoes in your greenhouse, will the perfect time to start tomatoes depends on the region where you want to grow tomatoes along with the sun light which that region gets. Most of the time after the fall of the frost in the mid February is the perfect time to grow tomatoes


The perfect time to sow your tomatoes seeds indoor is around 8 to 10 weeks before the last expected frost date in your geographical zone. The main reason why seeds are sown indoors is to make sure that they germinate to healthy seedlings. Tomato seeds need a warm weather condition to enable the proper growth of their seedlings. The seedlings should then be transplanted immediately into your unheated greenhouse. This particular planting operation will of course be followed by so many risks, but these risk can be minimized with an accurate precision of the right and appropriate time to plant tomatoes.

The prepared and hardened seedlings are to be transplanted 4-5 weeks before the last expected spring frost in your geographical area approximately late April-July.


The appropriate time plant tomatoes into the soil in an unheated greenhouse is a major factor that determines whether you will fail or succeed. So many environmental factors will work against your tomatoes if you take a wrong turn. However, the questions asked above causes controversy among tomato farmers. At the same time causes wrong decision making. They are also a major bone stuck in the throats of tomato farmers worldwide due to unpredictable weather conditions.

Planting seedlings too early(probably in the late month of January and early or late February when the intensity of light is low and not abundant enough for tomato growth) will result in leggy, poor plants. This effect will produce fewer tomatoes later in the season! The seedlings become stunted as they grow to maturity. This is not caused majorly by insufficient light alone but also little too much water. The pale color of their leaves also indicates that they are not getting enough light.

On the other end, late planting also exposes the tomatoes to high temperatures at nights, thus the leaves of the seedlings start to fall. If timing is gotten right from the beginning of planting, an additional source of heat will not be needed in an unheated greenhouse.



 Favourable weather conditions before transplanting

This particular period of the year(4-5 weeks before spring frost) is the most favourable for transplanting tomato seedling. Tomatoes need 3 to 4 months of warm conditions which will be fully available before the frost. This gives enough room for the fairly dry weather to produce the best and quality fruits. Tomatoes need consistent night temperatures between 55°F and 75°F to set fruit.  Planting your tomatoes too late will expose them to temperatures above the ones earlier started, thus stopping the production of a plant growth hormone (gibberellins). This causes delayed ripening of fruits when night temperatures rise above 85°F, and at the same time plants will quit growing when temperatures go above 95°F. Therefore planting late or early does not favour tomatoes production in an unheated greenhouse.

Presence or absence grow Lights

The introduction of grow light to tomatoes in unheated greenhouses when the seedlings are planted early has proven to be successful. Seedlings may be planted in late February if a grow light is used to provide more light for the seedlings to grow. The presence of the extra grow light takes care of issues of the seedlings becoming leggy,(too tall with thin stems) hence not be able to support the weight of their own leaves as they grow.

The benefit of using a grow light is that tomatoes can be planted early. Ripe tomatoes can be picked early before the cold nights comes around. Therefore the presence or absence of grow Lights determines exactly when to plant tomato seedling will take place. A situation where additional grow light is produced, a farmer may decide to begin his or her planting as early as possible in turn maximizing his or her opportunities. On the other hand, it’s absence means that planting will be delayed until the light intensity is sufficient enough to support the proper growth of tomato seedlings in an unheated greenhouse. So if you don’t have a grow light, never be in a hurry!!


The right time to carry out an operation on a farm is a very important aspect of agriculture as a whole and not only in tomato production. Knowing exactly when and how to carry out an operation is a major factor that determines the success of a farmer. The right time to plant tomatos seedling is an important operation and should not be taken with levity if a farmer wants to be successful. In order words, timing and high productivity are related directly.

Accurate planting time gives you high productivity, Unlike Heated greenhouses that are approximately not affected by any weather conditions. A farmer using an unheated greenhouse will likely be faced by so many environmental conditions that can damage his or her tomatoes. This makes accurate timing very important. Start too soon and your tomatoes seedlings will be subjected to environmental conditions that can cause severe damages due to the low temperatures at nights. Hence the low light intensity during the daytime is not adequate enough for proper growth will cause damages. Effective growth can only be possible with the introduction of grow Lights!

Tomatoes planted at the most appropriate time in a very good condition will most probably overcome another that was planted early in the season when environmental factors were not favourable. In due time the latter will be more productive than the former. This particular case is very common among tomato farmers with low planting time knowledge, a scenario called PLANTING PEER PRESSURE. This occurs when a particular tomato farmer decides to run down to his or her greenhouse and start planting just because other farmers are doing the same. But it should also be noted that  Sow seeds too late and the season will end before the tomatoes have had time to reach maturity– especially in areas with the extremely short season.



Plant tomatoes at the right time

The major secret, at the same time a tip to success, using an unheated greenhouse is to preferably sow seed indoors around the middle of March and then towards the end of April. The seedlings should be transplanted to your unheated greenhouse. If you intend to take freshly harvested tomatoes to the market for sale earlier than other farmers, a grow Lights should be readily available for proper growth.

 Avoid Frost

Frost can cause serious mechanical damage to your tomatoes seedlings. This gives ways for other diseases to attack the young seedlings which will then increase the cost of maintaining the effects of disease caused by the frost on the long run. On this note, you cannot leave seedlings or young plants outside overnight until all danger of frost is past.  Approximately, It might be early may for some region. please note: this differs and can only be determined based on the local weather conditions of your locality. Based on this fact, farmers should know that weather conditions differ completely in another region and assumptions of planting time should not be based on other locality but based on a locality or place where your greenhouse is located.

Later In the Season

If peradventure you have missed out in the “sow by date” operation. It is a bad idea to start tomato plants all over again from the seedbeds. The tomato seedlings will be affected by harsh weather that comes with off-season before it reaches maturity. Altogether, the missed planting operation can be caught back on track by the farmers. This happens only if he or she buys tomatoes seedlings in plug plants or pot from the garden centre with a sounding reputation of growing healthy seedlings. Such a practice consumes lesser period of time, but the choice of varieties is less than when starting from seed. where there is a huge number of tomato seedlings availability and also the choice to plant only the strongest and healthy plants is strict.
When to grow tomatoes in a greenhouse, Well this is a question which is asked allot of time, The perfect time to grow tomatoes in an unheated greenhouse depends on the region in which you are growing the tomatoes


It is always very easy to be tempted to start too early due to the financial reward pictured when the estimation of the rate of return is carried out. I get the same urge myself to run down to my greenhouse and start sowing as early as February rather than waiting for the best time which is most of the time March. But experience has it that, results will always be better when you wait patiently and sow in March which is the most appropriate time to sow. That should be around the last two weeks of March.

Though the window of opportunity is small, taking maximum use of this opportunity will end with good outcomes.  And also getting the timing right, that is knowing exactly when to run down to your greenhouse to plant tomatoes seeds is crucial for success. Likewise getting it wrong on the other hand can be an utter disappointment especially in short-season areas, where little or no amends can be made to turn back the hands of time.

On this note, other CRUCIALs for success in unheated greenhouse tomato farming cannot be ignored. And must be included, put into consideration and practice in an unheated greenhouse.

  •  Proper check on the Light intensity.
  • Geographical temperature and relative humidity control.
  • Water check.
  • fertiliser application at the appropriate time.
  • Temperature of the growing media.

How to grow tomatoes in an unheated greenhouse. Time is the most important factor when it comes to growing tomatoes in an unheated greenhouse. Most of the time the fall of the frost during the mid February is considered to be the perfect time for growing tomatoes.

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