When you sow seeds, you’re putting a little bit of hope in the soil. Then you watch with anticipation, checking each day to see if the sprouts have popped up. If it’s not happening, you may begin to wonder why. Seeds might not germinate for one of several reasons. Here are common causes and what you can do to help.
Plant Type
Each type of plant has its own timeline for emerging from its seed. Lettuce, for instance, begins to show in as little as two or three days, while carrots can take up to three weeks. Be aptient, check your seed packets and other reasoruces to find out what the expected time of germination is for the plants you’re growing. Always allow a few extra days beyond that window before confirming that none of the other causes are a factor.
Watering Mistakes
- Too Dry: As seeds absorb water, their outer coat breaks open and the seedlings emerge. They need consistent moisture as their stems unfurl and they begin growing roots. When the soil is fully dry, the seedlings may fail before they break through the soil or they could wilt after they poke up. Keep the soil consistently damp to provide the seeds with just the right amount of water.
- Too Wet: When the soil is soggy, seeds don’t sprout or they drown quickly. Lightly moisten the soil—avoid soaking it—and keep it damp until the seedlings have all come up and begin producing leaves. In wet conditions, seedlings also become susceptible to damping off, a fungal disease that can wipe out seedlings right as they emerge from the soil.
Wrong Temperature
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Too Cold: Check seed packs for the ideal temperature for sowing each type of plant. Early vegetables, such as peas, can sprout when the nighttime low is 40 degrees F. Most others won’t begin germinating until temperatures exceed 50 degrees F during the night. If the soil temperature is less than ideal, seeds may take a few days longer to come up.
Summer crops, such as tomatoes and cucumbers, typically don’t come up until the overnight temperatures are above 55 degrees F. For that reason, many gardeners start these seeds indoors while it is still too cold outside. A heat mat and thermostat allow you to keep the soil the exact temperature for each type of seed. - Too Hot: Spinach, kale, radishes, carrots, and other cool-season crops can be grown in the fall in many areas of the US. But sow them after temperatures are consistently below 60 degrees F at night, or they may not survive the heat.
Incorrect Planting Depth
Some seeds germinate only in the dark, while others require light to begin growing. Seeds planted too deep may not be able to emerge because they’re not getting enough warmth and light. Seeds planted too shallow may dehydrate before they have a chance to grow. Before starting, review the seed packet information so you know exactly how deep to plant. A tool with measurements that guide you to just the right level, such as the Burpee American Cast Dibbler, can help you get your seeds to the proper depth.
Poor Soil Quality
Seeds have the nutrients they need to sprout, so you can plant them indoors in a soil-less mix such as Burpee’s Organic Coconut Coir Concentrate. When the seedlings have their second true leaves, you can begin feeding them with a dilute liquid organic fertilizer like Neptune’s Harvest Fish and Seaweed Fertilizer. These nutrients will keep the seedlings growing strong after sprout.
When sowing seeds directly in the garden or containers, be sure the soil is loose and well-drained. Heavy clay soil can be too dense for sprouts to extend their roots outward and may hold onto so much moisture that seedlings drown before they emerge. Mix in compost before planting to help loosen the soil. Sandy soil, on the other hand, doesn’t hold enough water or nutrients to get seeds off to a healthy start. Add Burpee’s Organic Vermiculite to aid in retaining moisture and nutrients.
Insufficient Light
Many varieties sprout in the dark, but all seedlings need light almost immediately after emerging. If you sow the seeds directly in the garden, overcast conditions and shade from nearby structures or trees may slow down their growth. When sowing seeds indoors, place the tray of sprouts under lights as soon as half of the seeds have come up. Burpee’s grow light set-ups make it easy for you to keep them as close to the seedlings as can be without burning them.
Old Seed
If you buy good quality, fresh seeds, more than 90 percent of them will germinate. You can try to plant the previous season’s seeds, but the germination rate will have dropped significantly, below 80 percent. If you are storing seeds from one year to the next, keep them in airtight containers away from moisture and direct sunlight to preserve viability. If seeds become too dry, their germination rate is likley to be very low. But don’t worry, Burpee updates its seed catalog annually at the start of every January, when new seeds are available for the year.
Pesky Wildlife
Rabbits, voles, groundhogs, deer, squirrels, and birds may eat or tear out your new seedlings before you even see the sprouts. Block these pests by covering the bed with floating row cover after planting. This light, woven fabric allows water, air, and light to reach the seedlings but keeps nuisance animals out.
Indoors, mice may dig in the soil or feed on your sprouts when they emerge. Try to set your seed-starting trays where mice can’t easily access them. You might also try setting up a barrier around the trays using cardboard boxes or other material.
For more resources on germinating seeds for your garden, check out Burpee's handy gear and supplies.