Starting seeds indoors during the cold and dark of winter might be one of the greatest joys for a gardener. It means that greener, sunnier times are coming. Starting seeds indoors isn’t difficult, but there are a few tricks of the trade. Here’s everything you need to know to start seeds indoors and care for your seedlings successfully. 

Gather Supplies & Calendar

To start seeds indoors, you need a few basic supplies. You’ll need a shelf or table, containers, seed starting mix, lights, and a waterer. It’s easiest to have a good setup before you begin. You’ll also need to know the appropriate times to start seeds in your area. It’s a good idea to have or make a calendar for this. 

Earlier in our basics series, we covered what you need to start seeds and when you should start seeds. Please refer to those posts for complete details. 

Follow Planting Recommendations

When starting the seeds you purchased, follow the package instructions or the growing guide. 

Look at planting depth. Some seeds need light to germinate, and you’ll need gently press them into the soil’s surface, while other seeds need to stay moist and dark, and you should plant them at 1/4 inch deep or more.

Try using the tip of a pencil to make holes in the seed starting mix for your seeds.

Consider additional requirements. Some varieties need a bit of extra attention before sowing. Watch for seeds that should be soaked overnight or stratified before planting. 

If you have seeds you got from a friend or seed swap without directions, do a little digging about what that variety needs to thrive. 

Keep Moist

Your containers should have drainage, and you should avoid over or under-watering. Seedlings should be kept moist but not soggy. If the roots sit in water, your plants will fail to thrive. 

A pump-up water mister or sprayer can make watering much more effortless. Using a fine spray can help dislodge tiny seeds and seedlings, and you can swap to a larger traditional watering can as plants grow larger.

The larger your seedlings get, the more water they’ll use, so be sure to take extra care to check them as they grow. Using warm lights or heat maps can also increase your need for watering. 

Adjust Lighting

You’ll also need to adjust your lighting as your seedlings grow. As discussed in our previous post about supplies, you’ll need to provide your seedlings with auxiliary lights hanging above them. 

Keep these lights 2 to 4 inches away from the tops of the seedlings. As your seedlings grow, you’ll want to raise them, so they don’t burn the tops of the plants. However, if you notice your seedlings getting tall and spindly, you should lower your lights.

Fertilize

Seed-starting mixes are great for starting seeds but only provide a few nutrients. If your seedlings grow in containers for an extended period, you’ll need to give them fertilizer. 

The easiest way to give seedlings a boost is to add liquid fertilizer to the water. Liquid kelp is an excellent organic option, and just a tablespoon or two added to a gallon of water goes a long way. Some folks also choose to water with compost tea. 

For liquid kelp or other purchased fertilizers, follow package instructions when available. You should cut the amount in half if the instructions are for mature plants. 

Pot Up as Needed

Your seedlings may outgrow your containers before you’re ready to transplant them. It’s a good idea to have a few larger containers on hand, about an inch or two wider than the existing containers. 

Potting up provides fresh soil and space. If left in small containers, seedlings can become root bound where the roots wrap around the inside of the pot, and can take longer to begin growing after you transplant them. 

You should repot most seedlings so that the stem is at the same level as in the initial pot. Tomatoes can be repotted deeper, with soil covering the stem up to just below their leaves, as they will grow new roots from the stem. 

It’s almost February! In the Southeast, we’re ready to start seeds indoors, and you probably are too. Follow these tips to start seeds indoors and care for them until spring for a bountiful garden in the coming season.

Depending on your USDA Hardiness Zone, you’ll want to start seeds indoors soon! In zone 7a in Virginia, we begin by starting onions, and by the end of January are sowing celery, celeriac, broccoli, cabbage, and cauliflower. Come February, we’ll be starting trays of tomatoes, artichokes, and more at the beginning of March. Starting transplants from seed is fun and allows you to access more varieties, but you need a few seed starting supplies. 

Seed Starting Supplies You Need

Containers

What you use for containers is mainly personal preference, but there are a few things to keep in mind. First, your containers should offer good drainage. Seedlings don’t do well if they’re soggy. 

Flats

One of the most common choices is plastic flats. These are easy to use, and if you buy decent ones can be used for several years. Their uniformity allows you to organize your seedlings easily.

UpCycled

Especially if you’re only starting a few seedlings, you may want to upcycle containers. Yogurt cups are a common choice; just make sure to poke holes in the bottoms for drainage and find trays to place beneath them. 

Soil Blocks

Soil blocks are wonderful because they’re easy to transplant, and they “air prune” the plants’ roots. This means that soil-block plants won’t become root-bound like in typical pots where the roots grow around the inside of the pot because the roots won’t grow out into the open air. To use this method, you’ll need a small tool called a soil blocker and trays to place the blocks in. 

Additionally, they’re an excellent option for transplanting crops that don’t like their roots disturbed. You won’t have to fight to get them out of a tray and potentially damage the roots. 

Compostable Pots

There are also compostable pots like peat pots, or you can make compostable pots from newspapers. These make transplanting easy, but it can be pricey if you have to buy a lot of peat pots. When translating, ensure you don’t leave part of the pot sticking above the soil; it can wick moisture away from the roots. Tear the tops off before transplanting if needed.

Depending on the size of your containers and how long your seedlings need to grow indoors, you may need to pot up your seedlings. Plants like tomatoes thrive when potted up. 

Seed Starting Mix

Many gardeners and farmers use a seed starting mix to sow seeds indoors. Seed-starting mixes have the advantage of being sterile, meaning your seedlings will be exposed to fewer bacterial and fungal issues while they’re first getting started. Seed-starting mixes also hold adequate moisture for seeds without getting soggy. 

If you don’t want to purchase a seed starting mix, you can make your own or use finished compost. Most ordinary garden soil isn’t a good option because it doesn’t drain well. 

If you’re looking for something organic, you want to look for a seed-starting mix or ingredients with the OMRI (Organic Materials Review Institute) label. You can find comprehensive lists of certified products on the OMRI website if you want to browse different brands. 

Lights

A common mistake among beginner gardeners is to plop seedlings in front of a window and not provide any additional supplemental light thinking they’ll grow like houseplants. Unfortunately, most houseplants can tolerate partial shade. In contrast, most vegetable crops, herbs, and garden flowers require full sun, which they won’t receive in a window, particularly in winter. If your seedlings don’t receive supplemental light, they’ll probably become “leggy” or tall and spindly as they reach for the light. 

A quick Google search will turn up several options available for supplemental lights. One of the most affordable options is to use simple shop lights. LED bulbs are the most efficient, but you can use fluorescent 

The lights should be about 2 to 4 inches from the top of your seedlings. It’s best to have a setup that allows your lights to be easily adjusted as the plants grow. If your plants look leggy, they need to be closer but don’t move them too close, or it can burn them. 

Most seedlings do well with 12-18 hours of supplemental light daily. If you can get one, a timer will make managing this much easier. 

Seed Starting Surface

You’ll need a place to put all of your precious seedlings! This is another choice that’s mainly up to personal preference. Some people use work benches or old tables. Large wire shelves, like those meant for storing tools, are one of my favorites. You can easily hang and adjust lights from each shelf.

Optional Seed Starting Supplies

Heat Mat

Your house may feel warm, but many crops benefit from extra heat. Tomatoes, for example, require soil temperature in the range of 75-85 degrees F for good germination. Heat mats can improve the quality of tomatoes and other heat-loving seedlings like peppers and eggplants. 

Fertilizer

Most seed-starting mixes are designed to get plants started, not provide them nutrients long-term. If they’re in a container for a long time, you may need to give your seedlings a little boost. You can do this with liquid fertilizer. A bit of liquid kelp or compost tea, a tablespoon or two, added to a gallon of water is a good option. 

Coldframe or Hoophouse

If it’s an option for you, building a coldframe, hoop house, or setting up some other form of season extension can help you harden off seedlings and provide extra space. 

Buying transplants isn’t as satisfying as watching your own begin from seed long before spring arrives. Gather these seed starting supplies for success with growing transplants.