Plant Doctor Archive

Growing beans

I'm having problems with beans. Some varieties do well, but others are dismal failures. I've tried several times, but Barlotto Fire Tongue has failed to even germinate. The climbing yard-long beans are really slow to grow. They only reached 30cm high, by which time Scarlet Runners and King of the Blues had reached the top of a six foot high fence and produced lots of beans. The seed was bought last year. What am I doing wrong?

A SIMPLE answer is that Scarlet Runner is one of the easiest beans to grow well and usually gives good yields with a minimum of fuss. Other varieties can be variable depending on your conditions. Germination failure can be the result of poor seed being sold, but could also be poor conditions causing the fleshy seeds to rot. And this may affect some varieties more than others.

Ideally, beans need warmish soil (above 15°C) for good germination - if the soil is too cold and wet, they can rot off. Don't be tempted to soak them in water overnight before sowing as this can do more harm than good. Some bean seed comes ready-coated with a fungicide to prevent rot during germination - the label should mention this. If not, you could try dusting the seed with a copper fungicide or Super Sulphur, or watering a fungicide, like Thiram, into the soil around the seeds immediately after sowing. Don't plant too deeply - no more than 3cm below the surface.

Some gardeners find they have best success by starting bean seeds off in pots of free-draining mix on a window sill or other well-lit spot and planting out once they have reached the three or four-leaf stage.

The climbing yard-long beans are a more tropical plant and so need warmer conditions than the others to thrive, with soil temperatures above 20°C. Try planting them against a sunny wall to help maintain warmer night temperatures.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.