As gardeners we’re all familiar with black plastic plant pots of all sizes being used at every stage of a plant’s development. But have you ever stopped to think why they are mainly black in color – what’s the reason behind this?
Black plant pots absorb more heat that lighter colors, meaning plants that need more heat to grow, or plants growing during the winter – can all benefit from black plant pots to keep their roots warm. However, black pots are not so good on hot sunny days when they can dry out soil and bake roots.
In this blog post we’re going to discuss the relative merits of black plants pots, and compare them to other types of planters to see which colors are best for different plants, seasons and circumstances.
How Black Pots Benefit Plants & Their Roots
Black pots do benefit plants and their roots – but not always.
We all know that different colors absorb or reflect light in different ways. Black absorbs light. Red does too, but not as much. White and light colors are reflective.
Let’s take a roof for example. Studies have shown that on a sunny day with an outside temperature of 90° F, a white roof’s temperature will be about 110° F. A black roof on the same 90° F day will be around 150°. That’s – a lot.
In summer, a white roof helps keep the house cool, but in winter, a black roof will help keep you toasty. What to do? Here’s an interesting idea for a color-changing roof.
Luckily for gardeners, the solutions are easier. Container gardeners can change the pot, change the location of the pot, or change the pot contents.
Just like on your roof, the temperature difference between a black pot and a white pot, both sitting in the sun on your patio, is significant. The temperature of the pot transmits to the soil, then on to the roots.
Roots can be fussy about temperature. They are like Goldilocks – not too much and not too little. Here’s the scientific paper that everyone quotes.
Soil temperature affects plant health because soil temperature affects root health. When roots get too hot – or too cold – it puts stress on the plant. Stressed plants don’t grow as well, flower as well, fruit as well and they are more susceptible to insects and diseases.
Black pots absorb heat. That’s a good thing if your black pots are in the full sun in spring and fall – maybe even in a mild winter.
Black pots are a great idea when your plant needs a little warmth boost – like seedlings do in early spring. They are a great idea for a cool greenhouse in the winter. Black pots are a great idea if you have a succulent fixation.
Black pots full of moisture-loving, flowering plants in the full sun on a hot summer’s day is not a good idea.
Just like the roof, black pots are good when the plant needs a little help to stay warm. Glossy white pots are better, though, on hot, sunny, summer days. Tan pots may be a great compromise.
Can Black Planters Get Too Hot & Cook Roots?
Absolutely yes. You can turn black pots into tiny ovens.
Studies show that glossy white pots are better at reflecting light than any other color. Flat white is next best, then silver, red, orange, yellow, green, blue, violet and finally black, is hottest.
Not only does the pot color affect the soil temperature, but pot material and its size does too. Metal containers conduct heat readily. Terra cotta pots are heat neutral. Concrete is an insulator. Wood, plastic, fiberglass, pressed paper, and coir are insulators.
Pot size matters too. Generally, the smaller the pot, the larger the temperature problem.
Your patio material will also affect pot temperatures. Wooden decks will stay cooler than tiles. Light colored cement will reflect light – and absorb less heat.
How Do I Keep My Black Plant Pots Cool?
Sometimes, you’ve just got to have black. We get it. If you just have to have black pots, there’s a solution. The solution is shade, and wheels.
Gardeners are naturally attuned to the climate – and the microclimate. Microclimates are climates in the small spaces around your house and in your garden. There’s a big microclimate difference between the sunny, south-facing cement patio and north-sloping, tree-shaded lawn.
Take some time to get to know your microclimates. Where and when is your patio shady or sunny? Invest in a temperature gun (loads of fun), then draw a map. Plan out where your black pots will get shade during high noon in summer. Got a gazebo? Here are more tips.
Consider a seasonal patio rotation schedule. In the spring and fall, black pots can be happy in the full sun. In the heat of the summer, at high noon to around 2 pm, find a spot that your black pots can have some shade.
To minimize lugging heavy pots around, invest in some wheels for your pots.
Setting pots in groups will also help with over-heating. Big pots offer shade for smaller ones. Or consider putting your black pots into trays filled with gravel. Water evaporating from the tray will cool the plants.
If you just can’t stop yourself from buying black pots, consider buying ones with thick walls. The thicker the walls, the more insulation they will provide. You can also DIY a solution with actual insulation – foam boards. Of course, this will only work with square or rectangular planters.
Many garden tips are about insulating pots in the winter, but the reverse applies as well. Insulation is insulation.
Finally, you can change the type of plants in your black pots. Not all plants hate heat. How about succulents? Flowering plants that love it hot include marigolds, salvia, geraniums, sedum, sunflowers, lemon verbena and lantana.
Are White, Clear & Light Colored Pots Bad For Plants?
The answers here are maybe, maybe, and maybe.
White and light-colored pots, particularly glossy ones, reflect light and heat. Anyone who has gardened in a greenhouse in summer knows – keep it reflective. For plants that need to keep cool, those are the best colors for planters.
If you have few microclimate choices other than sunny (like on a balcony), try white and light-colored pots. Then, set the white pots on a reflective, white surface.
If you live in a cool and cloudy place – even in summer – or you love plants that love heat, white and light-colored pots may not be a good choice. They will be too cold. Go darker.
Clear pots are not a good choice for plants that like to grow in soil. But not all plants do. Orchids are a great example of a plant that does not need soil – only light and air.
For plants that naturally live in soil, clear pots offer no root protection at all from UV rays and heat. Also consider the soil in a clear plastic container. There are lots of microscopic critters that live in healthy potting soil that will not tolerate direct light.
But in certain cases, experts say that clear pots can help, even with plants that live in soil. Instances when clear pots work well are generally temporary, to help boost root growth. Clear pots also allow gardening geeks, and newbies, to observe root growth and understand plants better.
Clear pots can boost root growth in new transplants. For a transplant, the key is to get the root system thriving as soon as possible. A transplanted plant’s roots will grow to the edge of the pot and stop. Clear pots for transplants lessen the shock when the plant goes in the ground.
Is Tan The New Black When it Comes To The Best Plant Pot Color?
Maybe. We all know that black goes with – everything. But tan isn’t half bad at coordinating with other colors. And you won’t bake your roots.
On the color spectrum, tan and black are very different. Almost at opposite ends. If you live in a sunny climate with hot summer days, tan pots will be several degrees cooler than black ones.
For sunny climates, UV rays bake many pot materials (and patio furniture in general). Tan pots will last longer than black ones.
Keeping container gardens watered is always challenging. For black containers, water will evaporate faster because the temperature is higher. Tan pots will help a little in the fight to keep pots watered.
So there you have it – black plant pots are black in color to increase the heat around the roots of growing plants, or plants growing during the colder months. They absorb more heat precisely because they are black.However, when the sun comes out and the temperature increases, unless you’re prepared to wheel your black plant pots around the yard to find pockets of shade during the day – you’re better off putting many plants in glossy, light colored pots that reflect the heat.
Good news for succulent fans though – you can leave them in a black plant pot all year round and they’ll love it. 🙂