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Broad beans are frost hardy annual vegetables that can be planted in autumn, winter or spring, and will germinate outdoors at temperatures as low as 2oC (36oF). Once germinated they will, in theory, tolerate anything down to -10oC (14oF).
Also known as fava beans, these deliciously earthy pulses are incredibly easy to grow, but also incredibly easy to kill. In this article I want to run through some of the basic needs of broad beans, and some examples of common mistakes we all make as gardeners.
In particular, we want to make some important clarifications that go beyond what it says on your seed packet. Most importantly, broad beans are more frost-ignorant than frost-hardy (I’ll explain in a moment).
When to plant broad beans
Broad beans can be planted from late autumn to early summer, but don’t like extreme high or low temperatures. In most mild climates, you can sow broad beans anywhere between October and June.
The table below sets out when to sow broad beans according to different climates:
When to sow broad beans according to different climates
While it’s possible to grow broad beans anywhere in the world, they won’t crop at temperatures above 24oC/75oF, and the plants will die off at temperatures below -10oC/14oF. So, in extreme parts of the country, you need to moderate the growing conditions by growing broad beans in winter to avoid overheating, or sowing in summer to avoid the risk of deep freezes.
|When to sow broad beans, depending on climate*|
|1a – 4b||(no equivalent in Europe)||—||—||May – June|
|5a – 5b||H7||—||February||April – June|
|6a – 7b||H6-H5||October / November||January / February||April – June|
|8a – 9b||H4||November||February||—|
|10a – 13b||H3 – H1a||—||February||—|
(*This table is accurate for any growers in the Northern hemisphere, but for vegetable gardeners south of the equator, invert these months using August as the start of the growing year)
Do broad beans need protection?
Broad beans don’t need protection against frost, but it does help. The frost won’t kill them, and even cutting broad beans back to encourage stronger pods is a natural part of their growing cycle. The biggest risk for broad beans is heavy snow.
Broad beans don’t have the thick sturdy stems of leeks or broccoli, so they are probably the most physically fragile plant in the winter vegetable garden and heavy snow will quite likely snap their stems, but as our editor noticed this year, her broad beans recovered amazingly after at least a foot of snow.
Can you sow broad beans in June or at a later date?
In milder climates, you can grow broad beans as late as June, providing the summer temperatures don’t stay above 24/75oF. A sudden snap up to 30oC/86oF will be ok, but if extreme temperatures persist for over a week, your broad beans will really suffer, so try not to plant them in the first two weeks of June – otherwise you’ll be fighting the heat in late August when they’re starting to crop.
Will frost damage my broad beans?
Frost will damage your broad beans, but it won’t ruin them. By planting broad beans in autumn, before the first frosts, you get a head start on broad beans planted in spring when the ground warms up. There’s no point planting them in frozen soil, as they only germinate above 2oC/35oF, so if you miss autumn sowings, it’s best to sow them indoors over winter.
We regularly experience frosts below -8oC/17oF here in winter (usually feeling more like -12oC/10oF thanks to coastal winds) and while our overwintering broad beans will inevitably turn black, they recover with vigor in spring and crop at least two weeks earlier than crops planted in February.
Can you over winter broad beans?
Broad beans can be planted outdoors in autumn or early winter (as long as you leave at least 3-4 weeks between sowing and the first frost) so they can germinate and start establishing roots. This allows them to over-winter effectively in climates that don’t drop below -10oC/14oF.
They will be visibly damaged by the cold weather, but will continue growing when the frosts thaw. If you’re really worried, or the lowest temperatures are near -10oC/14oF., its best to fleece them just to be safe.
Will heat damage my broad beans?
However, warm temperatures can be devastating for broad bean crops, as they are a cool-weather vegetable. Unlike almost every other vegetable we grow here, they just won’t crop at temperatures over 24oC/75oF. It doesn’t matter how much water you give them, or even if they’ve had a cold snap leading to it, they hate hot summers and will flower, but without enough pollen to effectively fruit.
How to harden off broad beans if starting indoors
Broad beans can survive frosts at any stage after growing two sets of true leaves. By this point they are usually around 6-7” tall and will have four two symmetrical sets of lobed leaves. There should already be fine roots visible at the base of their nursery pot too (that goes for broad beans planted directly in the soil in autumn too).
If you start broad beans indoors, they are slightly more susceptible to frost damage when you plant them out, simply because of the cold shock, so it’s best to harden them off for a week before planting.
To harden off broad beans, move them outside for 2-3 hours in the afternoon for a few days, and increase their time outside by 2-3 hours each day. As long as the earth isn’t frozen, you can plant them in the ground after a week of hardening off.
Broad beans are one of the most versatile crops in the kitchen. It’s pretty hard to convince kids to try them because their most common experience is school meals with steamed or boiled broad beans (and the soggy cardboard texture that goes with that). But food doesn’t get much better than broad beans cooked in butter on a high heat in a frying pan, with chopped seasonal herbs, tossed through fresh pasta – perfect at any time of year.
The reason I mention that dish is that it’s indicative of how long your potential cropping window is for broad beans. Broad beans planted in October are ready to harvest in early April, with broad beans planted in June ready to harvest in mid-September. So next year, when someone asks you “are broad beans frost hardy?” you can show them a plate of beans in early-spring, and tell them, resoundingly, “Yes.”