10 Tips on How to Improve Germination Success

Rough Up Your Seeds (Scarification)

We don’t condone violence, but a little targeted roughing up could be just what’s needed to persuade your seeds to get a move on!

Here’s another way to breach that tough seed coat.

• For larger seeds like nasturtium, try filing down or wearing down the seed coat, using something like a nail file, or roughening the seeds up between sheets of sandpaper. This process of breaking down the seed coat has got a pretty cool name, scarification. In the wild, this would naturally happen as seeds bump up against rocks or other abrasive things in the soil.
• For flatter seeds like squash seeds, just nick the rounded edge of the seed several times using nail clippers to break off some of that woody outer coating. Take care that you’re only nicking the seed coat and not damaging the interior of the seed. Create an entry point for moisture. Then, soak these seeds and sow them, dramatically hastening germination and reducing the risk of seeds just languishing and potentially rotting away.

For peas and beans, you could nick the seed case with a sharp knife, nicking it at the opposite side to the little eye you can make out here. And once you’ve scarified your seeds and soaked them, you’re good to sow … promptly so they don’t dry out.

Power Up with Peroxide  

An alternative, perhaps unexpected, way to boost germination is to soak seeds in hydrogen peroxide. That might sound extreme—none of us like to use nasty chemicals—but hydrogen peroxide is quite benign, as you can see from its chemical formula, H2O2, which breaks down safely into little more than water and oxygen.

It seems crazy—this stuff is normally used for dying hair or treating wounds—but it’s awesomely effective at treating seeds, too. Let me show you.

I’ve got 2 cups of water here, which is half a liter, to which I’m adding a quarter cup or around 60ml of hydrogen peroxide solution. Make sure what you buy is in the range of about 1–3% concentration, which is normally how it’s sold—you don’t want it any stronger than that anyway. Now stir it all up, add your seeds, then leave to soak for just half an hour. Once the time’s up, continue soaking in plain water for up to 12 hours as usual.

You want this stuff to go far, and a great way to do that is to pop your seeds and hydrogen peroxide solution into ice cube trays—allocating one compartment to one type of seed. Just make a note of what’s in which compartment, or you could get confused and unstuck pretty quickly!

Moisture Matters

Some potting mixes, especially seed-starting mixes, can get dust-dry if the bags they’re in aren’t properly rolled down after each use. Seeds need moisture to germinate, so dried-out mixes need careful preparation before sowing. However, we don’t want to plunge the mix into a bucket and waterlog it either because over-wet soil can cause small seeds to rot.

Some mixes seem to positively repel moisture and stay on the surface without draining through. The simple solution is to pre-moisten dry mixes by spreading out what you need onto a tray and then watering or spraying the mix and massaging all that moisture in till you have a good, consistent moisture level.

Try to match the potting mix you use with the size of the seed you’re sowing. Larger seeds will be fine with an all-purpose potting mix, but you’re best sieving it to leave a finer particle size for smaller seeds.

Potting mixes on heat mats or under grow lights dry out far quicker than those that aren’t, so check pots and trays every single day—no excuses—and be disciplined on keeping everything moist. Remember, if seeds have started to germinate but then can’t get enough water to continue growing, they may well falter and fail, and we don’t want that!

Keep Humidity High Before Sprouting

Covering seeds with a humidity dome or clear plastic wrap is a great way to retain some of that vital moisture, though this needs to be removed once the seedlings are up to reduce the risk of disease taking advantage of the humid conditions.

Use Warm Water

When you do water, use warm water if possible. Water that’s warm to the touch won’t shock your seeds. Particularly for warm-season crops, using warmer water will help keep that soil temperature up, so we’re not checking precious progress by suddenly cooling it with chilly water straight out of the tap. At the very least, draw your water, then leave it to come up to room temperature before using it.

Sow at the Right Depth

Most seeds benefit from light, which means sowing them at the correct depth so enough light can penetrate the soil or potting mix to reach the seeds beneath. In most cases, this means sowing seeds so they’re buried to the equivalent of one seed diameter’s depth. Some seeds, especially tiny ones, must be sown on the surface of the soil. If in doubt, just check the seed packet instructions.

Use Viable Seeds

A seed needs to be viable if it’s going to germinate. Old seeds can give patchy results, especially if they haven’t been stored properly. Check seed packets for packing and sow-by dates, which are usually displayed on the back – if you haven’t accidentally ripped it off when opening the packet!  Learn more about how long seeds last.

If you’re saving your seed, bear in mind how long seeds tend to remain good for – this table will help. 

Viable Seed Chart

Pre-Sprout Seeds

Many gardeners like to use this method to germinate seeds that tend to be tricky to get started, too. Pre-sprouting (also called hitting) seeds like this can improve overall germination rates, giving you tiny, ready-to-go seedlings for planting at their final spacings.

It can be hard to transplant seedlings of things like parsnips, but pre-sprouting means you know how many seedlings you’re growing and can plant them straight away without any transplant shock. It also saves having to sow thickly and then thin out.

This is a popular technique for vegetables, including parsnip, chard, cilantro or coriander, cabbage, and pretty much all warm-season crops like tomatoes, peppers, and squash.

Frequently Asked Questions

What temperature is best for seed germination?

Most seeds germinate best between 65°F and 85°F, but cool-season crops can sprout in soil as low as 45°F, while warm-season vegetables often need 70°F or higher.

Which seeds benefit from soaking before planting?

Large or hard-coated seeds such as beans, peas, beets, squash, cucumbers, and sunflowers benefit most from soaking.

How long should seeds be soaked before planting?

Most seeds should be soaked for 8 to 12 hours. Avoid soaking longer, as this can cause seeds to rot.

Should I leave my heat mat on all the time?

Yes. Leave heat mats on 24/7 until seeds sprout to maintain consistent warmth.

When should seedlings be removed from a heat mat?

Remove seedlings as soon as they emerge, then move them to a bright, cooler location.

Can old seeds still germinate?

Yes, but germination rates decline over time. Proper storage extends seed life, but some crops remain viable longer than others.

We hope this will prove a handy reference as sowing gets underway this spring. If you’re craving even more seed-starting inspiration, see our complete guide on “How and When to Start Seeds Indoors.”