What Happens if Grow Room is too Hot?

Whether it’s from frost or hot summer temperatures, plants deserve your protection. While plants can tolerate extreme temperatures on both ends of the spectrum, they can’t do that for long. Whether the leaves are frost- or heat-beaten, the plant is salvageable when you respond quickly. 

However, prevention is better than cure. You can add a layer of protection from frost-bite or excessive heat. Importantly, plants differ in their tolerances (hardiness) to extreme temperatures. 

Arming yourself with the knowledge of the types of plants in your garden and their hardiness can be a lifesaver. Warmth-loving plants can wilt or blacken when temperatures fall below 32 degrees. 

On the other hand, cool-loving plants or houseplants can suffer from heat stress when temperatures go above 40 degrees Fahrenheit.  The leaves, stems or barks are more vulnerable to temperature variations than roots because air temperatures change more quickly than soil temperatures.

What Temperature Will Kill Plants?

When nighttime temperatures fall below 25 degrees Fahrenheit, most plants face imminent damage, especially when the period of lows is protracted and the air is still. Air conditioners help keep the air moving, freeing the plants from the ravages of freezing, stagnant air. 

Seeds have more resistance to cooler temperatures than seedlings or plants. Cool-loving plants, including greens such as broccoli and cabbage, are hardier to cooler temperatures than 40 degrees, but do poorly in summer temperatures. However, plants such as pinks, tomatoes, marigolds, zinnia or impatiens are more tolerant to nighttime temperatures above 55 degrees Fahrenheit. 

Cooler nighttime temperatures than 55 degrees can set fruit development back, although the plants can do better in higher temperatures. Sheet or cloche insulation can shield these warmth-loving plants when nighttime temperatures drop below 35 degrees. Else, they will die. 

While death doesn’t occur immediately, the frost-beaten plants can survive if you keep them warm during the day to facilitate thawing. Don’t cultivate them the day following a frost night. Be sure to remove and dispose damaged leaves or barks, if any.

How Hot Should My Grow Room Be?

Acclimating (hardening off) seedlings or seeds simulates the temperatures of the early spring or late winter. When plants are used to indoor temperatures, they can do well when temperatures hit above 40 degrees. 

When summer arrives, you can move the houseplants outdoors to break the monotony of indoor climate. However, don’t move them suddenly. Plants need time to acclimate to new conditions of humidity, temperature, or light. 

Else, if you take things fast, you subject them to wilting, yellowing, dying back or even dying.

Then, the question is: how do you prepare them for outdoors?

First and foremost, keep the windows clean to permit sufficient light. If you keep potted plants, then you will need to repot them with new soil from pot not garden. And because plants follow light, make sure you add support structures like shelves or ceiling hooks along the light path.

You can even lay a gravel layer beneath the pots and add covers to shield the pots from water loss. Increase light amounts slowly. Otherwise, leaves would fall off. During this transition, avoid overwatering. Light isn’t adequate to dry out excess water.

If you keep tropical plants, monitor the nighttime temperatures and ensure they stay above 50 degrees Fahrenheit. Else, move them inside. Importantly, ensure the plants are disease- or parasite-free before you bring them back inside. Inspect the soil.

Repot if the pests have burrowed the soil. Treatment can also involve dipping the pot inside lukewarm water for about 10 minutes or so. If you notice legginess after outdoor exposure, it’s a sign of light deprivation. Prune the same amounts of leaves, stems and roots. Before you repot, scrub the pot, add fresh soil, and plant again.

Lastly, give the plants food. A healthy dose of fertilizers will do the trick.

How Long Should a Fan Be On in A Grow Room?

The short answer is: as long as possible. A good grow room air conditioner nourishes plants with artificial winds. Since airflow is inconsistent indoors, fans ensure stable supply. Plants need air to breathe. Inspiration involves inhaling carbon(IV)oxide, which is one of the raw materials plants use to manufacture their own food.

Fans also keep room temperature and humidity in check in a room with lights. Since room light is the only available source of light, when you switch it off, photosynthesis ceases. Light produces heat. So, when you switch it off, room temperature decreases. But this doesn’t mean you have to turn off the fan. Instead, reduce its speed but keep it on till lights switch on again.


With the right conditions of air temperature, humidity and carbon(IV)oxide, plants can thrive. While nature provides a way to fulfill all these conditions, you can simulate it in an indoor environment, especially when you want to keep plants that aren’t indigenous to your area.

If you keep a tropical or subtropical plant in a temperate region, then you need a way to simulate the summer climate. On the other hand, if you keep a temperate plant in a tropical region, you can keep the plants in an indoor environment. Plants suffer when you move them between indoor and outdoor environments. You need to allow them to acclimate to new conditions.

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