To start seeds indoors you really need six things: seeds, a fine seed-starting mix, small containers with drainage holes, a tray to catch water, plant labels, and a strong light. A heat mat and a small fan make a big difference for tomatoes and peppers. Almost everything else sold for seed starting is optional. This seed starting supplies checklist sorts the must-haves from the nice-to-haves, with cheap swaps for each, so you can get set up before your first sowing date.
Want the basics in one box? Our Tomato Seed Starter Kit and Pepper Seed Starter Kit each include 8 seed varieties, 8 starter pots, 8 soil disks and 8 plant markers. Add a light and a tray and you're ready.
Seed starting supplies at a glance
| Supply | Need it? | Notes and cheap swaps |
|---|---|---|
| Seeds | Yes | Fresh, labeled packets with planting depth and days to sprout. |
| Seed-starting mix | Yes | Fine, light and sterile. Not garden soil. |
| Containers with drainage | Yes | Cell trays, small pots, or rinsed yogurt cups with holes poked in. |
| Waterproof tray | Yes | Any shallow tray or baking pan for bottom watering. |
| Labels | Yes | Plant markers, popsicle sticks or tape on the pot. |
| Grow light | Yes, for most crops | A shop-style LED fixture works. A sunny window alone usually gives leggy seedlings. |
| Heat mat | For peppers, tomatoes, eggplant | Or a warm spot like the top of the fridge. |
| Small fan | Helpful | A gentle breeze gives sturdier stems. Or brush seedlings with your hand daily. |
| Humidity dome | Optional | Plastic wrap works. Remove it once seeds sprout. |
| Outlet timer | Helpful | Keeps lights on a steady schedule. |
| Spray bottle | Helpful | Keeps the surface moist for tiny seeds. |
| Larger pots | Later | 3-4 inch pots for potting up tomatoes and peppers. |
| Fertilizer | Later | Half-strength liquid feed once true leaves appear. |
The must-haves, explained
1. Good seeds
Start with varieties suited to your season length, in packets that tell you depth and days to sprout. Heirloom, open-pollinated seed also lets you save your own seed later. Store leftovers sealed in a cool, dry place for next year (how to store seeds). You don't have to sow a whole packet: see do I plant the whole packet of seeds?
2. Seed-starting mix
Seeds need a fine, loose, sterile mix that holds moisture without staying soggy. Garden soil packs down and can carry disease; heavy potting soil with bark chunks makes it hard for tiny roots. Moisten the mix before filling containers. Compressed soil disks, like the ones in our starter kits, are a tidy option: add warm water and they expand. Details: seed-starting mix vs. potting soil.
3. Containers with drainage holes
Cell trays (about 1-2 inches per cell) save space for lots of seedlings. Small reusable pots are easier to move. Whatever you use, it must drain: standing water rots seeds and causes damping off. Recycled cups work if you poke 2-3 holes in the bottom.
4. A tray for bottom watering
Set containers in a waterproof tray and pour water into the tray, not over the seeds. The mix soaks it up from below without washing tiny seeds out of place. Empty any water still standing after 30 minutes.
5. Labels
Every sprouted seedling looks alike for the first two weeks. Label each pot or row with the variety and sowing date.
6. Light
This is the one most beginners skip and regret. Seedlings on a windowsill stretch toward the glass and grow thin and floppy. An LED shop light or grow light hung a few inches above the plants (check the maker's distance), on for about 14-16 hours a day, gives short, sturdy seedlings. Raise it as they grow. Setup help: how to hang grow lights; running costs: how much it costs to run a grow light.
Worth adding for warm-season crops
- Heat mat: peppers, tomatoes and eggplant sprout fastest with soil at about 75-85Β°F. Peppers can take 2-3 weeks in a cool room and under a week on a mat. Take seedlings off the mat once most have sprouted.
- Fan: a small fan on low for a few hours a day mimics wind, strengthens stems and dries the soil surface, which helps prevent damping off.
- Timer: a plug-in timer for the light means you never forget to switch it on or off.
What you can skip
- Expensive all-in-one systems. A light, a tray and some pots do the same job.
- Fertilizer at sowing. Seeds carry their own food. Start a half-strength feed only after the first true leaves appear.
- Special seed-starting gadgets like soil blockers or self-watering mats. Nice to have, not needed for a first year.
- Starting everything indoors. Beans, peas, squash, cucumbers, carrots, radishes, beets and corn grow better sown straight into the garden. Check our seed starting calendar to see which crops to start inside and when.
A simple first setup
For a typical first garden, like our 4x8 raised bed plan, you'll start roughly 6-12 tomato, pepper and eggplant plants indoors. That fits on one shelf under one light:
- One 2-foot or 4-foot LED light on chains or a shelf, with a timer.
- One waterproof tray holding 8-24 small pots or cells.
- Seed-starting mix or soil disks, labels and a spray bottle.
- A heat mat under the tray if your house is cool.
- A handful of 3-4 inch pots for potting up a few weeks later.
- A tray or crate to carry seedlings outside when it's time to harden them off.
When you're ready to sow, follow our step-by-step guide to starting vegetable seeds indoors. For greens, the Lettuce and Leafy Greens Starter Kit comes with pots and soil disks too. Browse all seed starter kits, or pick your own varieties from our individual seed packets. For a whole garden's worth of seed in one bag, see the Survival Seed Vault Kit.
FAQ
Can I start seeds without a grow light?
You can, but results are hit or miss. A bright south-facing window works for some quick crops like lettuce. Tomatoes and peppers almost always stretch and flop without extra light, especially in late winter when days are short.
Do I need a heat mat?
Only for warmth-loving crops in a cool house. Tomatoes sprout fine at normal room temperature; peppers and eggplant are much faster and more even with bottom heat.
Can I reuse seed-starting trays and pots?
Yes. Wash them in warm soapy water at the end of the season and let them dry fully. Use fresh seed-starting mix each year.
When should I buy seed starting supplies?
Get set up a couple of weeks before your first indoor sowing date. For many areas that means onions and celery in late winter, then peppers, eggplant and tomatoes 6-10 weeks before your last frost.
More questions about our seeds and kits are answered on our FAQ page.
Reviewed by Ryan, owner of Gardeners Basics, an heirloom seed company that ships from Spanish Fork, Utah.
