Growing your own tomatoes from seed doesn’t have to be intimidating. I recently switched to starting all my vegetables from seeds. It’s extremely rewarding, but you have to know when and how to plant your seeds, when to transplant, etc.
It’s not hard, but there are some guidelines to follow to increase your chances of success.
Sow tomato seeds indoors 4 to 8 weeks before your last frost date, or when you plan to transplant them outside. Transplant tomato seedlings outdoors when night temperatures are at least 50°F (10°C), as colder temperatures can stunt their growth.
2 Reasons to Start Tomatoes from Seed Indoors
Many gardeners, including myself, always start my tomatoes indoors instead of sowing them outside.
1. The main reason home gardeners start tomatoes indoors is to get a head start and harvest more tomatoes in their growing season. The earlier you plant your tomatoes, the sooner you’ll get blooms and tomatoes.
Tomatoes seem to take forever to grow to those first few feet. But once they reach a critical size, they just start exploding with growth, and you quickly end up with more tomatoes than you can eat.
I get maybe four good months of tomato growing weather, from June through September, but even when starting my tomatoes indoors, I don’t taste my first ripe tomato until the end of June or sometimes early July. If I sow my tomato seeds directly, I would get my first tomatoes in August. The huge beefsteak tomatoes I like to grow would take even longer.
2. The other reason why some people always start tomatoes from seed indoors instead of direct sowing is because transplanting tomatoes allows them to plant tomatoes deeper and let their plants grow a stronger root system. Because of this, even if you live in a place like Texas with a long growing season it’s still a good idea to start your tomato seeds indoors.
Direct Sowing Tomatoes Outside – Yes, It Can Be Done
That said, if you have a long growing season or you don’t mind waiting longer to get tomatoes, you can absolutely sow the seeds directly.
Directly sow tomato seeds only after the threat of frost has passed and your soil temperatures are at least 50°F (10°C). Higher is better, as seeds need warm conditions to germinate. You can cover the ground in clear plastic to warm up the soil even more, but remove it once the seeds sprout, or you might end up cooking your seedlings on a warm day.
When (and How) to Plant Tomato Seeds Indoors
You can start tomato seeds anywhere from 4 to 8 weeks before your average last frost date (find out when your last frost date is here or here) or before you intend to transplant them.
The more time before you transplant, the larger the pot you need for your tomatoes. I like to plant my tomato seeds about 4 weeks before transplanting, and my tomato seedlings have plenty of room in pots that are slightly more than 4 inches deep and 3 inches wide. If you are planting 8 weeks in advance, you may need to move up to a larger pot before transplanting outside.
Plant tomato seeds about 1/8 to 1/4 inch deep, and keep the potting mix evenly moist but not soggy until the seeds sprout. To guarantee success, plant 2 or 3 seeds in each hole and then thin out to one seedling afterward.
You can keep tomatoes under grow lights (even a fluorescent or CFL grow light will work) until they’re ready to transplant.
When and How to Transplant Tomatoes Outside
No matter where you live, always transplant tomatoes when nighttime temperatures are at least 50°F (10°C). Temperatures below 45°F (7°C) can stunt the growth of your tomato plants.
In some places, that means planting soon after your last frost date. In my case, that means waiting possibly as long as two weeks until the nights warm up.
Choose a final home for your tomatoes that is sunny with rich, well-draining soil. Avoid transplanting along a north-facing wall, as it will be shady for most of the day.
When planting tomatoes, many gardeners prefer planting them deep.
I’ve already written about planting tomatoes deep, but briefly, it means digging a deeper planting hole and partially burying the tomato stem, leaving the top leaves above the ground. All along the stem, tomatoes readily sprout new roots, so by planting your tomatoes deep, you are increasing the potential root mass which means your tomato plants will be healthier, be able to take up more nutrients, and be more resistant to drought.