Growing Beans? Check the leaves

Beans are very good at showing you when they’re not happy – their leaves change very quickly. If you’re growing them at the moment, give them a checkover to make sure they’re okay. (If you’re not growing them yet, don’t worry, there is plenty of time to plant them still!)

What to look for:

Here are some of the more common things to look out for, but any leaves that aren’t a glorious green give an indication of some sort of plant stress.

  • Yellow/pale coloured leaves
  • Mottled leaves – where the veins are dark and the leaves in between are yellow
  • Pale brown papery patches
  • ‘Scorched’ edges – darker brown patches with bright yellow rings
  • Curling leaves – leaves curling at the edges

How to help them recover:

None of the symptoms above are disastrous, and at this time of year, May/June, the most likely problems will come down to temperature, water and nutrients.

Too hot?

Beans do well in the heat, but only if they have enough water and nutrients in the soil to sustain them. If it is hot and sunny, be sure to check the moisture levels in the soil, and water thoroughly if they seem to dry. Equally, don’t drown them – they will struggle just as much with excessively wet soil as they will with dry soil. Think of a bag of compost when you first open it, and that lovely level of moisture that they usually have – not sticky, but not dusty and dry either. This is kind of what you want to aim for in the soil when you are growing beans.

Too cold?

This can be a problem at the start of the season, in April and early parts of May. Cold winds in particular can cause beans stress. If you can protect them with some horticultural fleece or a cloche, this will keep them happy until it warms up a bit. We have, in the past, decided to pull up bean plants a few days after planting to relocate them in pots in a greenhouse due to cold spells!

Too dry?

Again, check the level of moisture in the soil – they need a good amount of moisture (as described above) well below the surface of the soil, where their roots are searching for water and nutrients. If you can, it would help to mulch to try and keep soil moisture a little more consistent.

Too wet?

If the soil is waterlogged for long, the roots of beans can start to rot and then you’ll see leaves turning yellow. It’s not usually a problem, but you may find this is the cause if you are overwatering, especially in pots. Again, check the moisture levels in the soil, and if the soil is sticky, let it dry out a little and then cut back on how often you water.

Not enough nutrients?

This often goes hand in hand with the soil not having enough moisture, as if there is no water for the roots to draw up the nutrients, then they become deficient.  If you’re growing in the ground and you haven’t added any organic matter or manure for a couple of years, this could be a problem and we’d advise using a liquid feed or worm cast tea to top up the nutrients. You can do this as a one off now, and then again when the plants start to flower. The same is true if you’ve reused old compost from last year’s pots as well. However, if you’ve planted the beans in pots of fresh compost, or in rich soil, then nutrient deficiency is unlikely to be the problem.

Other causes?

There are other bacterial or viral infections that can affect beans, but this doesn’t normally happen this early in the season, so we would be surprised if that’s the problem at this point (late May/early June) – further into the summer, you may want to consider things like bean halo blight, mosaic virus, rust and a few others, but we will cover those later in the season!