Can You Leave Plants In A Car Overnight? (4 Things To Avoid)


Maybe you just bought new plants and you don’t want to bring them in while it is raining or snowing.  Maybe you just finished a long trip and don’t have the energy to move your plants tonight.  Either way, you might be wondering if your plants can survive a night in the car.

So, can you leave plants in a car overnight?  You can leave plants in a car overnight and they will most likely survive – if you avoid common hazards.  The most common ways for plants to die in a car are extreme heat, extreme cold, and dry air.  A lack of light could kill your plants if you leave them in a trunk or in a car in a dark garage for too long.

Of course, if you must leave your plants in a car overnight, there are some ways to protect them from these hazards.

In this article, we’ll take a look at ways to keep your plants a live if you leave them in a car overnight.

Let’s get started.

Can You Leave Plants In A Car Overnight?

You can leave plants in a car overnight and they can survive.

cars at night
Leaving plants in a car overnight exposes them to some hazards, such as extreme heat or cold.

However, if you want to keep your plants alive, there are some hazards to avoid, including:

  • Extreme heat (especially in summer or if the car is parked in direct sunlight with closed windows).
  • Extreme cold (especially in winter or if the weather forecast calls for a frost).
  • Dry air (especially if plants were recently purchased and their soil was already dry).
  • Extended Darkness (especially if the plants are in a trunk or in a car in a dark garage).

A plant that isn’t exposed to these hazards will probably be fine spending one night in a car.  However, if you park in a garage, make sure to get the plant to a well-lit area in short order.

Don’t leave plants in a dark garage for too long unless it is shade-tolerant.

Will Plants Die In A Hot Car Overnight?

Plants can die in a hot car overnight (especially if it is dry weather and their soil was dry to begin with).  Some plants can tolerate temperatures up to 95 degrees Fahrenheit (35 degrees Celsius) or higher.

However, the temperature inside a car can get much hotter than that (especially when the windows are closed and it is parked in the sun).

According to ABC News, the temperature inside a car can reach well over 100 degrees Fahrenheit (38 degrees Celsius) in the sun..

thermometer
The temperature inside a car in the sun with closed windows can reach over 100 degrees in a short time (less than 30 minutes).

The table below summarizes the temperatures that a car can reach inside when left in the heat with closed windows on a sunny day.

Temp
Outside
Temp
In Car
(10
min)
Temp
In car
(30
min)
7089104
7594109
8099114
85104119
90109124
95114129
This table summarizes the
temperatures that a car can reach
inside when left in the heat with
closed windows on a sunny day.

If you leave your plants in the car in the afternoon or evening with the windows closed, watch out!  Even a short period of focused sunlight could heat up the car.

That heat will then be trapped inside (due to the greenhouse effect).  Even though temperatures tend to cool down at night, this extreme heat exposure could still hurt or kill your plants.

To keep your plants from succumbing to the heat, open the windows before leaving them in the car overnight.  Even just opening the windows a little will help to let some of the trapped heat out.

Also, put the plants in a place where they won’t be in direct sunlight.  For example, if the sun is setting and visible through the windshield, put the plant behind the driver’s seat.

Finally, give your plants some water before you leave them in the car overnight.

Will Plants Die In A Cold Car Overnight?

Some plants will die due in a cold car overnight (especially without protection).  The cold tolerance of plants varies, but freezing temperatures are bad news for many plants (especially if they are not hardened off).

What Temperature Is Too Cold For Plants?

The cold hardiness and temperature tolerance of plants varies quite a bit.

Some plants can tolerate freezing temperatures and survive.  Others will suffer from damage in cool temperatures.

frost
Some plants can survive a freeze overnight, while others suffer damage below 50 degrees.

According to the University of Arkansas Extension, many houseplants will suffer damage if the temperature drops below 50 degrees Fahrenheit (10 degrees Celsius).

Some examples of vegetables that suffer from cool temperatures include:

  • Basil
  • Eggplant
  • Pepper
  • Tomato
basil in pot
Basil can sustain cold damage if temperatures drop below 50 degrees Fahrenheit.

Some examples of flowers that suffer from cool temperatures include:

  • Begonia
  • Impatiens
  • Marigold
  • Zinnia
begonias
Begonias are sensitive to cold temperatures.

You can find a more extensive list of vegetables and flowers (along with their cold hardiness) from Purdue University.

How To Keep Plants Alive In A Cold Car

Luckily, there are ways to keep plants alive in a cold car if you have nowhere else to put them on overnight.  Some methods include:

  • Cloche
  • Frost Blanket
  • Cardboard Box

Let’s start with cloches.

Keep Plants Warm In A Cold Car With A Cloche

If the plants are small (for example, tomato seedlings), you can use a cloche to protect them.  A cloche is a clear cover (usually made of plastic) that helps to trap heat in the soil and air underneath.

In a pinch, you can cut the bottom out of a plastic container (such as a gallon water jug).  Use the top to cover the plant and give it a better chance to survive the cold.

water jugs
Cut the bottom out of clear plastic bottles to make a cloche to protect plants from cold.

If a cloche by itself isn’t enough to keep a plant warm, try wrapping a frost blanket around it for added protection.

Keep Plants Warm In A Cold Car With A Frost Blanket

A frost blanket is a good addition to a cloche (or a good option if you don’t have any plastic bottles!)  A frost blanket can really be any blanket (or even a piece of clothing) that you have in the car.

blanket
Wrap some type of blanket around a cloche or cardboard box to insulate plants from cold.

A thin piece of cloth may not provide much protection.  However, even a few degrees of cold protection can make a difference for plants stuck in a car on a cold night.

Keep Plants Warm In A Cold Car With A Cardboard Box

A cardboard box can trap a little heat underneath, at least temporarily.  It will work better if you can drape a blanket over the box to provide better insulation.

cardboard boxes
A cardboard box is another way to keep plants a little warmer in a cold car overnight.

If you use a box with a blanket inside as a liner, put the plant inside, and then cover it with a cloche, it will provide good cold protection overnight.

Will Plants Die Due To Dryness In A Car Overnight?

Your plants will probably be safe spending one night in a car without water.  Of course, if their soil was already dry and the weather is hot, they might succumb to the lack of moisture.

A tell-tale sign that plants are too dry is their soil and leaves.  If the soil is dry, dusty, and “crumbly” and the leaves are wilted, then the plant needs some water.

In that case, give your plants a little water to hold them until morning.

Will Plants Die In A Dark Car Overnight?

A lack of light in a car overnight will not kill your plants.  They are used to dark conditions at night, so being in a trunk or dark car overnight will not kill them.

car trunk
Putting plants in your car trunk for one night will not cause them to die due to darkness.

If you leave your plants in a dark car trunk or garage for multiple days (all through the day and night), they will start to suffer from the lack of light.  No light means no photosynthesis, which means no energy for growth.

Can I Leave Flowers In A Car Overnight?

You can leave flowers in a car overnight if the temperature will be reasonable.  As with other plants, flowers face a few dangers when left in a car overnight: heat, cold, and dry air.

potted flowers
Potted flowers will last longer in a car than cut flowers.

Some flowers can tolerate heat, while others are cold hardy.  This table from Purdue University gives an overview of the temperature tolerance of some types of flowers.

Cut flowers will not last as long as potted flowers in a car (since cut flowers don’t have roots to draw water from soil).

cut flowers tulips
Cut flowers (such as tulips) will last longer in a vase of water.

If you keep the cut flowers with their stems in water, they will last much longer (either inside or outside a car).  For example, according to the University of Vermont Extension, cut tulips can stay fresh in a vase of water for 7 to 10 days.

Will Flowers Die In A Car Overnight Without Water?

If your car is hot, the flowers may not survive the night without water.  Put the stems of cut flowers in a vase or container with water to give them a chance to survive.

For potted flowers, water them so the soil is wet enough to give the roots water to easily absorb.

Conclusion

Now you know what to do (and what to avoid) if you absolutely need to leave your plants in a car overnight.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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