Green beans need warmth to grow and produce their crop of delicious beans. Low temperatures, either early in the planting season, or towards the end of the growing season will damage your bean plants.
What temperature kills green beans?
When the temperature drops down to 33°F (1°C), the cold and frost will kill your green beans – Source: Texas A&M AgriLife Extension
There are a few things you can do to help protect bean plants from cold temperatures, and I’ll go over those strategies in this article.
And, to help you get a bean harvest at other times of the year, I’m going to tell you about a different type of bean that isn’t fazed by cold temperatures at all.
What Climate And Growing Conditions Do Green Beans Need?
Green beans – french (snap) beans, runner beans – need warm temperatures; 8 – 10 hours of sunlight a day; shelter from strong winds; fertile, freely draining soil; and regular watering.
If you provide all of those things for your bean plants, your bean plants will give you a bumper crop in return.
Preparing your growing site and waiting for the right planting conditions makes a huge difference to the growth of your plants.
It’s tempting to rush out and start planting when spring sunshine finally chases away the last of the winter chill, but even though the days can seem warm enough for bean plants, nights will still be far too cold.
Seed won’t germinate, and young plants will sit around, struggling to make any new growth.
It’s much better to wait until early summer (May) to plant beans, and because the weather will be just what they need by that time, they’ll hit the ground running.
Eight weeks later, providing you’ve taken care of your beans, you’ll get your first harvest.
What Temperature Range Do Green Beans Grow In?
The ideal temperature range for growing green beans is 65°F (18°C) to 85°F, (29°) – Source: University of Georgia Extension
For optimal seed germination, your soil temperature should be at least 55°F (12°C). You can plant in slightly cooler soils, but germination will take longer.
When days turn very warm, in mid summer, excessive heat can cause blooms to drop off the plants. Since the bean pods grow out from these blooms, if the blooms drop, you’ll get a lower yield.
Keep an eye on your weather forecast for temperatures 85°F (29C) and over, and if it’s practical, set up some shade cloth to keep your beans a little cooler during the hottest part of the day.
Should You Direct Sow Outdoors Or Start Bean Seed Indoors?
The roots of a bean plant can be damaged during planting out, so it’s common practice to direct sow the seed outdoors.
But if you’re careful when you transplant the young plants, you can germinate the beans in pots indoors, and in some case you might need to.
We almost always sow our bean seed in pots for transplanting, because if we direct sow, mice will gobble up most of our seed.
Even though we’ve got two cats who are great at catching mice, we would often end up with lots of gaps in the row when the plants came through the soil.
The trick to sowing in pots and then transplanting, is to transplant while the plant is still small, before the roots have reached the edge of the root ball.
Bean plants grow fast once they germinate, so you need to be ready to plant them out when they need transplanting, rather than waiting until it’s a more convenient time for you.
When Can Green Beans Go Outside?
Transplant green beans when outdoor temperatures reach 65°F (18°C). If you use a floating row cover made from horticultural fleece, you can plant out a little earlier, once temperatures reach 60°F (15°C).
How To Protect Green Beans from The Cold
Sometimes (often, actually), you’ll get bad luck with the weather when you garden.
Spring is moving along, the weather seems fine, temperatures are good, it’s the right month for planting, your beans have been growing happily for a couple of weeks, and then boom, along comes a late cold snap to lay waste to your tender plants.
During the first few weeks, when the weather can still turn too cold at night, have horticultural fleece to hand, so you can cover your plants if the forecast looks like temperatures will drop into the 30’s.
You can leave the fleece in place if the days are on the cool, side. Plenty of light will still get through the fleece.
If you want to give plants even more protection from the cold, you can set some mini heat reservoirs under the fleece along your bean rows.
These are simple to make. Just take some old plastic milk jugs or other suitable containers and fill them with hot water from your tap.
Place them close to your plants underneath the fleece. They will slowly release their heat and keep your beans a little warmer.
Another way to use these reservoirs is to paint the jugs black and leave them outside with your beans where the sun will warm up, then at night they’ll release their heat around the beans.
The micro-climate created by the fleece and the mini heat reservoirs will make a huge difference to young plants when the temperature drops.
Fleece can easily protect bush beans because they are small plants, but pole beans will be harder to cover up adequately if cold weather hits once they’ve reached any significant height.
A good strategy is to plant bush beans as your first harvest, and wait until the end of May before you plant your pole beans. That way you can easily use fleece to protect your beans.
A Cold Hardy Bean You Can Grow For An Early Crop
Beans aren’t just for summer. And there’s a bean you can grow that will give you an early harvest of beans.
Broad beans, or fava beans, are a shelling bean with a lovely fresh flavor and they’re a real treat in late spring/early summer when no other beans are growing in your garden.
You can sow them in the fall and plant them out to overwinter, or you can sow them late winter and plant them out once the ground can be worked.
Green beans need warm weather to grow. Don’t plant them too early because you risk losing your plants if a cold snap hits. A temperature of 33°F (1°C) will kill your beans.
Plant bush beans which are easy to cover with protective fleece for your first crop.
Keep an eye on your weather forecast and your outdoor thermometer, and if the temperature is dropping into the 30’s, cover your plants and set some mini heat reservoirs under the fleece.