You spent ages preparing your seedlings and now, weeks later, there’s not a sweet green shoot to greet you. I know how devastating that feeling is!
Frankly, this 11 point list is a role-call of all my seedling failures to date. But I’m here to help you, so that next time you push seed into soil, you are rewarded with many happy healthy plant babies!
1. Old seeds
Fresh is best for food and for seed. Stored seeds can become stale quickly, which will result in diminished seed viability, or worse, no seed strike at all.
Some seeds, like citrus and apple, lose viability almost as soon as they dry out. Other seeds, like beans and tomatoes, will last for years when stored in a consistently cool, dry, dark place.
- Aim to acquire seeds that are both fresh and local. Pay attention to the expiration date and make plans to sow them promptly.
- In cases where seeds might be somewhat old, increase your chances of successful germination by planting multiple seeds in each seedling cell.
- For older seeds, consider soaking them in water overnight. This can soften their hardened outer shell, potentially enhancing germination rates.
2. Planted too deep or to shallow
As a rule of (green) thumb, a seed should be planted to double the depth of its size. So if your seed is 1cm in diameter, plant it at least 2cm deep. Plant it too much deeper, and you risk your baby plant will use all it’s stored energy trying to reach the soil surface and perish before it makes it.
But if you plant a seed too shallow, you risk the seed washing away when you water it. Or, worse, the seed dries out too quickly and fails to germinate.
- Apply the double rule to guarantee correct seed planting depth.
- If you struggle with spatial measurements, repurpose an old chopstick marked with measurement indicators as a dibbler.
- For sowing small seeds, create a seed tape to prevent them from being dislodged during watering and to maintain soil moisture.
3. Wrong season
Trying to grow warm-season vegetables like chilli’s or tomatoes at the beginning of winter means your seed will unlikely germinate. Best-case scenario, your errantly timed seed will just wait patiently and germinate when its time comes. Or, it may rot in the soil or be eaten by insects before it gets the chance!
- Sow seeds outdoors in spring when it is warm enough.
- Avoid sowing seeds outdoors in fall, winter and in the heat of summer.
- In winter, sow seeds indoors only.
4. Not enough light
Some (but not all) seeds need some exposure to light to germinate. Poppy, lettuce and many weed seeds need some light which is why they seem to pop up when the soil is disturbed for spring planting! Generally speaking, once seeds break the surface of the soil, they need some light so they can begin photosynthesising.
- Provide the seeds with at least a few hours of light.
- If it is not possible to provide sunlight, use LEDs.
- Avoid placing the seeds in total darkness.
5. Not warm enough
Spring and early-summer sowed seeds like beans, tomatoes, eggplants and many others don’t like it cold and will only germinate when the soil temperature is warming up.
I once dumped a batch of ungerminated carob seeds into my composter when they didn’t sprout, thinking they had just failed. But about a week later, just as I was about to tumble the compost, I noticed they had all sprouted! I suspect the heat of the compost tumbler was much more agreeable to them than the milder temperature in the greenhouse.
- Provide the seeds with a temperature of 60-70°F
- If seeds are sown in a tray, move them to a greenhouse or house to provide enough warmth.
- If the seeds are sown outdoors, create a transparent dome over them. This will increase the temperature inside the dome and speed up seed germination.
6. Too much water
No judgement here, because I too have killed a fledgeling seedling with too much water love. I have to be particularly restrained around peas and beans, which will rot in protest of too much water. You need your seed raising mix moist, not waterlogged!
Unless you are in a particularly hot climate, once your seeds have been planted in your damp seed raising mix, they can take a few days of rest before you water them again.
- Keep the soil with the seeds slightly moist but not waterlogged.
- Avoid watering every day.
7. Not enough water
Insufficient watering can kill seedlings that may have sprouted in the soil but have yet to reach the surface. Commercial seedlings enjoy periodic watering via timed misting systems.
- Do not let the soil dry out until the seedlings emerge.
- Use a sprayer to moisten the soil surface.
- Place a transparent plastic dome over the soil to reduce soil drying.
One season, I was baffled as my fresh, perfectly sowed, warmed and watered sesame seeds failed to germinate. Too late, I found the culprit. Ants! They had infiltrated my seedlings and made off with almost all of my sowed sesame seeds.
On another occasion, snails and caterpillars laid in wait of my seedlings and scoffed them as soon as they broke the surface, leaving tell-tale snail trails and caterpillar poop as evidence of their crime.
- Keep your seedlings as protected as possible, and check daily for signs of pest issues.
- Lay traps and be prepared to defend your seedlings.
9. Special needs seeds
Some seeds need some unique treatment before sowing, like time chilling in the fridge, or a good soak in warm water, inoculation with fungus, or rough treatment with some sandpaper before they can be coaxed into emerging from their seedling pots.
- Research your seeds and follow sowing instructions.
- Some seeds require stratification and if this is your case do so.
10. Wrong kind of seed mix
Seed raising mix should be friable enough to let delicate new roots penetrate, and needs to hold enough water to ensure the soil and seeds don’t dry out. If you are planting seeds from soil scooped out of your garden beds, it may be too clay-ish, or too sandy-ish, instead of being just right.
- Use a sterile and well-drained seed substrate. This can be purchased at any garden center.
- Never reuse this substrate.
- Always sterilize the trays and pots in which you sow seeds.
11. Different seeds need different amounts of time to germinate
Some seeds, like radish, psyllium husk and cress are quick to germinate and pop up in a matter of days. Other seeds like henna, take their time. One year, I gave up on a few pots of asparagus seeds and they lay, neglected on a back shelf of the greenhouse. Three weeks later, I found them, growing beautifully! I have since learned that asparagus seeds like to take their time.
- Research your seeds, if they need extra time, be gracious and give them a comfortable position where they can take their sweet time to germinate.
- Slower than usual germination rates can also be due to colder temperatures, so make sure they are warm enough too.
Once you have mastered sowing from seed, you will never want to go back to expensive purchased punnets from the nursery. Do you have any seed raising tips? I would love to hear from you! Leave a comment below…