Why Aren’t My Seeds Sprouting?

Having trouble getting your seeds to sprout or your seedlings to survive? It’s almost always one of three problems. Here’s how to diagnose and fix them

Seedlings off to a good start in the greenhouse

So, when the soil just sits there and nothing sprouts, or, worse, when they do sprout and then the seedlings die, it’s frustrating – especially if you think you did everything right.

Fortunately, the most common reasons seeds and seedlings fail can usually be reduced to just three reasons. If you avoid these pitfalls, you can also avoid the disappointment that comes with them.

Reason 1: The soil isn’t warm enough

Seeds of all types are designed to keep the seed germ safe until conditions are right for sprouting. For most seeds, that means soil that is warming, which is a sign spring is on its way. Some vegetable seeds — carrots, broccoli, cauliflower, cabbage, onions, and some flowers — will sprout in soil around 60° F (16° C), but most prefer soil that’s around 68° to 74° F.

If you’re starting seeds indoors, it’s pretty easy to keep the soil warm without any real effort. Just keep the seeds in a warm place until the seedlings sprout (they don’t need sunlight at this point).

If your house is cooler than 68° or you want to start seeds in an unheated area such as the garage, shed, or protected outdoor area (e.g., a patio, greenhouse, coldframe, etc.), use a seed warming mat. A mat doesn’t have to run all the time, just when there’s not enough heat to keep the soil warmed to the right temperature. You can use a light timer or smart plug, to turn the mat(s) on and off as needed.

Once the seedlings have emerged, place them in a brightly lit area where they get at least 4 hours of direct sunlight, or 6 hours of indirect sunlight each day. If you don’t get a lot of sunlight, you can use a grow light. The new LED models are relatively inexpensive and very energy efficient compared to the old incandescent types. Here are a number of good choices at Amazon.com and Walmart.

Reason 2: The seed is too old

Most flower and vegetable seeds will remain viable for at least a couple of years. After that, the germination rate will decline.

Click to enlarge chart

If you purchased your seeds, the packet should have a date with the year for which they were packaged. If you collect and save your own seed, make sure to mark the date on the container so you don’t forget!

If you want to know if your seed is still viable, use this printable chart, which will give you the average storage life of a variety of fruit, vegetable and flower seeds.

You can also check the viability of older seeds with a simple germination test.

Germination test: place 5 – 10 seeds in a moist paper towel and place the towel somewhere warm and out of sunlight. Keep the paper towel moist and check for germination regularly. The number of seeds that sprout within the expected germination period (e.g., 7 days, 14 days, 21 days, etc.) is the estimated germination rate of all of those seeds.

If your seeds have a germination rate lower than 50%, it’s probably time to get new seed.

Reason 3: Too much water

While seeds do need water in order to germinate, too much water is detrimental. Plants actually require equal amounts of air and water in the soil in order to grow. When the soil is too wet, it prevents the seedling’s roots from absorbing nitrogen and carbon dioxide, both of which are required for growth (click here for more about good garden soil).

Soil that’s too wet is also a breeding ground for fungi which can lead to damping off disease – a condition where the seedling’s stems shrivel and die at the soil line.

The best way to avoid overly wet soil is to bottom water – i.e., placing the water in the bottom of the seed tray and letting the soil sponge it up. That will keep the top level of the soil dry and help prevent soil saturation and damping off disease.

If you can’t bottom water, only water your seedlings when the top of the soil feels dry to the touch after pressing it lightly with a finger.

Ensuring good seedling growth

Once your seedlings have emerged, help them get a strong start by ensuring they’re getting enough light. If you notice them getting long and leggy, growing weak stems, and/or looking pale green-to- yellow (referred to as “etiolation”), move them to a sunnier spot or increase the amount of light they’re getting.

Also, once they’ve grown their first set of “true” leaves (usually the second set of leaves after the seedlings emerge), make sure to thin them to the right spacing as noted on their packet.

Like all young living things, seedlings eat a lot and need space to grow. Ensuring the little plants have enough room to spread their roots and leaves will also ensure plenty of food and good air circulation, both of which lead to strong and healthy plants.

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