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Understanding why Beans won’t Germinate or Set Pods

Who doesn’t love a fresh green bean grown in the garden, picked and eaten straight from the bush! Beans come in all shapes, colours and sizes, and are a simple and easy crop to grow if the environmental conditions are right. But sometimes issues arise that can be confusing if you don’t know what to look for.

I have composed a list of issues that may help you understand the reason your beans won't germinate. Some of these issues are quite common and although it might seem a bit intimidating, don’t let it put you off trying to grow beans at home. Most years you should have a trouble-free experience growing fresh beans, occasionally you may come across an issue that can be frustrating, to say the least.

Various Problems with Germination
Various Problems with Germination

Why won't my beans germinate

I get asked this question on a regular basis and there are several possible causes for this such as

  • The soil might be too cold: Beans are definitely a warm season crop and if the soil is too cold, the seeds won’t activate their germination triggers and will rot in the ground. To avoid this, delay planting until the ground reaches at least 17-18ºC.
  • The soil might be too heavy: Soil that is heavy in clay that crusts up can prevent the new seedling from pushing through. This can be overcome by adding plenty of compost to the garden bed before planting and covering the seeds with a light compost or potting mix.
  • Seeds planted at the wrong depth: Seeds planted 5cm deep in the cool of the spring will have trouble germinating because the soil may be too cold to germinate and rot. The deeper you plant the colder the soil will be. Later in the year the seeds may dry out too much at a shallow depth and will die from lack of moisture. General rule is in early spring, plant at maximum 2.5cm, early summer plant at a deeper depth of 5cm as the soil will be a lot warmer as well as the soil’s ability to hold more moisture at this depth.

Seedlings appear to be cut off, wilt and fall over at ground level

Cutworm
Cutworm

This is the work of cutworms,  these little pests are grey grubs that are found at the base of your seedling. While it is good to mulch and add organic matter into your garden beds, unfortunately, it is also providing a home for these pests. If you have an issue with these pests, you will need to remove and keep your garden beds clean of debris and plant matter as well as keeping your garden free of weeds for a few months then try again.

Seedlings are deformed or have no growing tips or leaves when they emerge

The pest that is responsible for this is called a corn maggot. These small yellowish larvae are the offspring or larvae of small grey flies. The way to fix this problem is to clean the garden bed of any debris and to cultivate the soil to expose the larvae and disrupt the breeding cycle. Try planting again when the weather warms up a bit more.

Corn Maggot
Corn Maggot

Seeds that rot, or the seedlings collapse with dark water-soaked stems not long after they appear

There is a condition that most gardeners have heard of called damping off. This is a fungal disease that lives in the soil, particularly when it is hot and in high humidity weather conditions, to overcome this issue do not plant in cold wet soil and make sure that you have ample drainage.

Damping Off Disease
Damping Off Disease

Stunted seedlings that don’t want to grow

Chilly weather and unfavourable cold soil will limit and weaken your young seedlings. You will run into problems if you plant too early in the season. Conditions, where the temperature is consistently below 16-17 C, are not suited for beans.

Stunted Bean Seedling
Stunted Bean Seedling

Bean plants that flower then the blossoms drop

There are many reasons for this to happen

  • Night time temperatures drop below a threshold of around 14C
  • Day time temperatures get too high, if the temperatures go above 34C and strong wind of which there is no cure there is not much you can do about that.
  • Too much smog/smoke in the air can cause significant issues, it can help by tapping the flowers daily to assist in pollination.
  •  Excessive nitrogen in the soil, fertilise with a low nitrogen fertiliser.
  • Too shady, beans require full sun for at least 6 hours daily.
  • Planting too early in the season as the early flowers won’t set fruit.

Early flowers won’t set pods

there are several reasons that can cause this to happen

  • Your garden may not be fertile enough, fertilise with a low based fertiliser or add plenty of aged compost to the garden bed and work it well into the soil.
  • Too much nitrogen in the soil, this will result in good foliage growth at the expense of pods, by adding decent quality aged compost before planting is equivalent to adding a complete fertiliser of 10-10-10, if you don’t have excess to aged compost, use a fertiliser that is low in nitrogen for beans
  • Not harvesting beans regularly, this will stop the plant from setting new pods

Buds and flowers drop, mature beans are pitted and blemished

This may be caused by the Lygus bugs, these insects can be green, straw coloured with a green triangle on their backs, these little nasties have piercing and sucking mouthparts that feed on the leaves and young pods. Keep the garden free of weeds and handpick and destroy the insects.

Bean pods begin to develop then shrivel up

There are two reasons for this to happen.

  • Lack of moisture is the first thing that comes to mind, If the seed in the pod starts to develop and then the pod starts to shrivel up, check what moisture the plants have. If the soil is dry, give the beans a good soaking so the moisture goes down at least 15cm, mulch well and water again in a few days, keep moisture levels up by digging a small hole in the garden bed to check that the moisture is going down to where it is needed.
  • Tarnish bugs and nymphs may be feeding on the plants. Tarnish bugs are a brown insect with mottled coppery , yellowish, or red markings , while Nymphs are yellowish green and are wingless. Both these pests are small only growing around 7mm long. The best control method is to spray with an insecticidal soap.
Tarnish Bug
Tarnish Bug

Sunburn

Pods are streaked or spotted reddish or pale brown, sunburn is the result of overexposure to the hot sun, to prevent this issue it is best not to prune the bean plants that are above the developing beans and shade the bean plants over the hottest parts of the day.

Sunburnt Bean Pods
Sunburnt Bean Pods

Like I said before, all though it might seem a bit intimidating, don’t let it put you off trying to grow beans at home. Most years you should have a trouble-free experience growing fresh beans, occasionally you may come across an issue that can be frustrating, to say the least.

Some of the beans available in the shop

Understanding why Beans won’t Germinate or Set Pods

Happy gardening

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