Question:
Why is it that I have to replant over half my green and yellow beans every year? Even though I use generally use new seeds, less than half of the seeds germinate. I always end up re-seeding a few weeks later, and those seeds come up just fine.
Answer:
The problem is likely cool soil temperatures. The ideal soil temperature for bean seed germination is 15C to 21C. Germination is slow and poor when soil temperatures are below 15C. Germination may take two weeks or more if soil temperatures are below 15C. Soil temperatures are considerably cooler than air temperature. Cool soils also tend to be the right conditions for seeds to rot, especially if spring is cool and wet. This is why you have better success when you re-plant.
Does this sound familiar? There are many factors that can affect vegetable seed germination in the garden:
Seed viability:
- How old are the seeds? Seed viability varies from plant to plant. For example, parsley seeds are viable for only one year, while other seeds like squash can stay viable for up to 6 years.
- If you are not sure when you bought your seeds, do a germination test:
Seed depth:
- Seeds need to be planted at the correct depth. This information is usually on the seed packet. A rule of thumb is to plant seeds about twice as deep as the seed. Best to check on the packet or check out our growing guides.
- Planting too deeply can cause some seeds to rot.
Temperature:
- Warm season vegetables that are started indoors such as tomatoes, peppers and eggplant need warm soil temperatures for germination. Try putting a heat mat under the plants or place in a warm location until they germinate.
- Other warm season vegetables like cucumbers and squash can be seeded directly outdoors once soil temperatures are above 18°C.
- Cool season vegetables like lettuce and radishes can tolerate cooler soil and can be planted out early.
Water:
- Seeds need to be kept evenly moist as they start to germinate. If the soil dries out during this critical time, seed germinatation may be spotty or