Stop Early-Season Sowings from Failing – 5 Steps for Strong, Reliable Seed Starts

Sowing seeds early in the year is not without any risk; there is no sure-fire guarantee of success. I’d love to tell you there was, and that all your early sowings would work out, but I would be doing you a disservice. It is something that divides opinion. You’ll see social media flooded with cheery gardeners sowing seeds in January, while other experienced heads will tell you to wait, as they see early-season sowings as a folly.

The facts are that yes, you can sow seeds in January. Indeed, here on Homes & Gardens, we published recent articles on flowers you can sow in January and vegetables to sow in January. But in those articles, we explain that early sowings will require additional warmth and light to have any chance of germinating and developing into healthy plants.

For many years, I worked as a professional gardener and always started sowing vegetable seeds in January. I sowed year-round in roles where I was growing crops for restaurants, and I still do early sowings for my home vegetable plots. I have experienced many successes and struggles with winter sowings. Taking all that I’ve seen into consideration, here are my five essential steps to successful early-season sowings.

5 Essential Steps to Successful Early-Season Sowings

In short, the essential steps to successful early-season sowings include ensuring seeds and seedlings get the right amount of warmth and light. And you need to care for and water them properly early in the season to keep them healthy.

Your chances of success with early-season sowings will depend on where you can sow them. A greenhouse is always best, but a warm windowsill will suffice, and you may need extra equipment such as heat mats and grow lights.

You can get complete sowing kits, such as this one at Amazon, that come with a seed tray, heat mat, grow lights, and a humidity dome, and can help improve your chances of success with early-season sowings.

1. Sow at the Correct Time

One of the often overlooked essential steps to successful early-season sowings is timing. As with many aspects of life, timing is key.

Sowing seeds indoors at the correct time of year gives them the best chance of germination and keeps them healthy. Get it wrong, and you run the risk of poor (or no) germination, leggy seedlings, and stressed plants that are susceptible to pests and diseases.

It is important to know the frost dates in your climate so you can get the timing right for transplanting seedlings. This ensures they don’t sit in trays or pots for too long, getting unhealthy and root-bound, and take up space in your greenhouse or cold frame.

All seed packets will reveal information about timing. They will show when to sow the seeds, both indoors and outdoors, and give other tips on planting depth and soil temperature. Seed packets are the best source of sowing information, and you can easily find this information in books or online.

Make a seed sowing schedule at the start of the season. Using the guidance on seed packets and working backwards from that crucial last frost date, you can plan your sowings and start flower and vegetable seeds indoors at the right time.

2. Give Seeds and Seedlings Sufficient Heat

For most growers, except those in the warmest US hardiness zones, early-season sowings will take place indoors. The lower natural levels of heat and light mean that the opportunities to sow seeds outdoors are limited.

You can start sowing seeds as early as January indoors, such as long-season crops like eggplant, peppers, tomatoes, and onions, as well as flowers like verbena, nicotiana, and Icelandic poppies.

These sowings must be done undercover, such as in a greenhouse or on a warm windowsill, and giving them sufficient heat is critical for success. This can be why many gardeners wait until at least early spring to start sowing seeds.

The minimum greenhouse temperature for seedlings varies, but for many crops it is around 45°F to ensure they stay alive. For germination, however, the requirements are much higher, and many seeds need a temperature of 64-75°F.

Over the years, I have used heated propagators, heat mats, and fan heaters (like this greenhouse fan heater with thermostat at Amazon) to provide crucial warmth to early sowings. This extra warmth increases your chances of fast, strong germination, rather than sorry results, especially for warmth-loving crops like eggplant, tomatoes, and chili peppers.

Heat mats are the most cost-effective way to provide essential bottom warmth to seed trays, such as this seedlings heat mat at Burpee, which can provide seedlings with a 10-20 degree increase in temperature.

In late winter and early spring, there are the first opportunities to warm up the soil with plastic sheeting, cloches, or portable cold frames and make the first outdoor sowings of cool-season crops, including beets, carrots, and spinach.

These crops can sprout in soil temperatures as low as 45°F, but you’ll have much more success if you can warm the ground in advance and keep the seedlings protected from dropping temperatures.

Again, seed packets are always a useful source of information as they tell you the specific temperatures required for germination and the timings for when to sow indoors and outdoors.

3. Light Is Crucial – so Get It Right

Once seeds germinate, they also need light for strong growth, as well as warmth. Getting the levels of light right is one of the most essential steps to early-season sowings, as a lack of light can mean weak, leggy seedlings that grow tall and thin as they stretch towards any available light.

As natural sunlight is shorter and weaker during the early months of the year, grow lights supplement natural levels to ensure seedlings grow strong and healthy. Any sowings before March will benefit from additional light, especially if they grow on window sills, from which point the levels of natural light start to increase at a rate.

LED grow lights are energy-efficient and affordable. Lights with a blue spectrum are useful for seedlings, but using full-spectrum lights that mimic natural sunlight is often helpful, as they provide different wavelengths to encourage strong growth. An example of such a grow light is this full-spectrum grow light with a timer at Amazon.

Use these grow lights for 12-16 hours a day, placing them 6-12 inches above the seedlings and increasing the height of the levels as the seedlings develop. Consistency is important, and not keeping such a cycle is a grow light mistake that can affect seedlings.

Some grow lights come with timers; otherwise, getting a programmable timer is recommended. Like this digital timer, also available at Amazon.

4. Keep Seedlings Well-Ventilated

Warmth and light understandably take most of the headlines when gardeners think of the essential steps to successful early-season sowings, but don’t overlook the importance of air circulation.

The early stages of a plant’s leaf are fraught with potential problems, and that includes damping off, which can kill your seedlings.

Damping off is a common disease that affects seedlings, causing them to collapse and die. The seedlings rot where the stem meets the soil and collapse over. There are several causes of damping off, including overwatering, but one common culprit is poor airflow and high humidity.

If you see mold on seedlings (either green or white) and collapsed plants as a result of damping off, remove any infected seedlings to stop the spread.

Good air circulation helps to reduce humidity and strengthen your seedlings. It is always advisable to remove humidity domes (you can get humidity domes at True Leaf Market to cover seed trays) from trays and pots for extended periods. And to open doors or vents on bright days to ventilate a greenhouse or cold frame, to allow air movement.

You can also use small fans, such as this greenhouse fan with adjustable speeds from Amazon, to improve air circulation and help to keep your seedlings healthy.

5. Be Careful With Watering

Watering is always a balancing act with seedlings; you don’t want too much or too little. Early in the year, there is an increased risk of seedlings rotting if you overwater them. This is because the soil dries out more slowly in cooler temperatures, but there are some sure-fire ways to avoid overwatering plants and prevent issues like damping off.

I always water from the bottom rather than the top when dealing with seeds. I use this technique for two reasons: it prevents the seeds from being dislodged by overhead watering and ensures the soil absorbs the necessary moisture without becoming oversaturated or waterlogged.

To water plants from below, place seed trays or pots in a large tray filled with water, such as these shallow plastic trays at Amazon, and leave them for at least 10 minutes to soak up moisture.

To test how often to water seedlings, a simple trick is to pick them up. If the trays feel heavy, they are moist. If the tray feels light, it is short of water and is best put into a tray of water to rehydrate it.

Don’t let trays of seedlings completely dry out, as they will collapse, and it is not guaranteed they will recover through watering.

Another point worth mentioning is that it is advisable to avoid using cold water to water seedlings, as it can shock them. In the early part of the season, keep a watering can of water in the greenhouse so it is at room temperature and won’t stress your seedlings.

Another important aspect to ensure any success when sowing seeds is to use the right soil. The best soil to start seeds is always a potting mix designed for seeds and cuttings.

Such a product, like this Burpee seed starting mix made from coconut coir, is specially formulated for the needs of seeds, having a finer texture than other soils, containing fewer nutrients, and can hold onto water efficiently.

You don’t want to use garden soil, as it holds onto too much moisture and risks seeds and seedlings rotting.