Seed Starting Supplies Checklist: What You Actually Need

Seed Starting Guide | 8 min read

Look, I'm going to save you some money and frustration right now. You don't need half the stuff that seed starting articles tell you to buy. After years of starting seeds—both successfully and, let's be honest, with some spectacular failures—here's what actually matters.

The seed starting world's full of gadgets and "must-haves" that mostly just collect dust in your garage. What you really need? It's way simpler than you think. Let me break down the actual essentials that'll give you healthy seedlings without breaking the bank or cluttering up your space.

The Non-Negotiables: What You Absolutely Need

These are the things you can't skip. Try to start seeds without them and you're setting yourself up for disappointment.

1. Proper Seed Starting Mix (Not Regular Soil)

This is the big one. Regular potting soil is too dense and heavy for seeds. It holds too much water, doesn't provide enough air to tiny roots, and often harbors fungi that cause damping off disease.

You need a light, sterile seed starting mix that holds moisture without getting waterlogged. Good seed starting mix usually contains peat moss or coco coir, perlite or vermiculite for drainage, and sometimes a bit of compost. The light texture lets those tiny roots spread easily, and the sterile nature prevents diseases from taking hold before your seedlings get established.

2. Containers with Drainage

Seeds need consistent moisture, but they'll rot if they're sitting in water. Whatever container you use needs drainage holes. That's non-negotiable.

You've got options here. Seed starting trays with individual cells work great because you can pop seedlings out easily when it's time to transplant. Those biodegradable peat pots? They're convenient but can be tricky—sometimes they don't break down well in the garden and end up restricting root growth.

Honestly, you can use clean yogurt cups, egg cartons, whatever small container you've got lying around. Just poke drainage holes in the bottom. The container size matters less than you'd think—most seedlings'll be fine in a 2-inch cell for 6-8 weeks.

3. A Light Source

Here's where people get hung up. Do you need grow lights? Well, if you've got a south-facing window with at least 6 hours of direct sunlight, you might get by without them. But honestly? Most homes don't get enough natural light in late winter when you're starting seeds.

Seedlings'll get leggy and weak stretching toward inadequate light. They'll flop over, and you'll end up with weak plants that struggle when you transplant them outside. A basic LED grow light doesn't have to be fancy or expensive—just position it 2-4 inches above your seedlings and keep it on for 14-16 hours a day.

4. Water Source (Obviously, but There's a Trick)

You need to water your seeds and seedlings—duh. But how you do it? That actually matters more than you'd think. A regular watering can might work once seedlings are established, but for newly planted seeds, the force of water can wash them around or bury them too deep.

Use a spray bottle for the first week or two after planting. Just mist the surface gently. Once seedlings emerge, you can switch to bottom watering—set your containers in a tray of water and let them soak up moisture from below. This encourages deeper root growth and helps prevent damping off disease.

The Game-Changers: Not Essential, But They Make Life Easier

These aren't absolutely necessary, but they'll significantly improve your success rate and make the whole process way less stressful.

Heat Mat (For Warm-Season Crops)

Most seeds germinate just fine at normal room temperature (65-75°F). But tomatoes, peppers, eggplants, and other warm-season crops germinate faster and more reliably with bottom heat. A seedling heat mat keeps soil temperature around 75-80°F, which can cut germination time in half.

Is it necessary? No. Will it save you from the frustration of waiting three weeks for pepper seeds to sprout? Absolutely.

Liquid Organic Fertilizer

Here's something a lot of seed starting guides skip over—when do you actually start feeding seedlings?

Seed starting mix typically has little to no nutrients. That's fine at first because seeds have their own food supply packed in. But once your seedlings develop their first set of true leaves (the second set that appears, not those initial rounded seed leaves), they've burned through the nutrients in the seed.

That's when you need to start feeding them. A gentle liquid organic fertilizer gives seedlings the nitrogen they need for leaf growth without the harsh salts and chemicals in synthetic fertilizers that can torch tender roots.

Labels

You'll absolutely forget what you planted where. I don't care how good your memory is—it's gonna happen. Use labels. Popsicle sticks work fine. Write with a Sharpie or pencil—ballpoint pen fades.

Humidity Dome or Plastic Wrap

Seeds need consistent moisture to germinate. A clear plastic dome or even just plastic wrap over your containers traps humidity and keeps the soil surface moist. Remove it as soon as you see sprouts, though—seedlings need air circulation to prevent damping off disease.

What You Probably Don't Need (Despite What Pinterest Says)

Let's talk about what you can skip, at least when you're starting out.

Expensive Seed Starting Kits

Those all-in-one kits look super convenient, but they're often overpriced and include stuff you don't actually need. You're better off buying components separately so you get exactly what works for your space and budget.

Specialized Seed Starting Tools

Seed dibbers, soil blockers, fancy watering wands—these are fun if you're really into it, but honestly? A pencil, your finger, and a spray bottle do the exact same job.

Individual Grow Chambers

Unless you're starting hundreds of seeds, you don't need those mini greenhouse chambers for each plant. A simple plastic dome over a tray works just as well and costs way less.

The Step-By-Step Process (Now That You Have Your Supplies)

With the right supplies gathered, here's how it actually works:

Fill your containers with moistened seed starting mix. Don't pack it down—keep it fluffy. Water it before you plant seeds so you're not washing them around.

Plant seeds at the right depth. General rule: plant seeds 2-3 times as deep as they are wide. Tiny seeds like lettuce barely get covered. Bigger seeds like beans go deeper.

Cover and wait. Put on your humidity dome or plastic wrap. Place containers somewhere they'll stay warm (on top of the refrigerator works in a pinch). Check daily—you want the soil moist but not soggy.

Remove covering when seeds sprout. As soon as you see green, take off the covering and move seedlings under lights or to your brightest window. Keep lights close—2-4 inches above the tops of seedlings.

Start feeding after true leaves appear. Once you see the second set of leaves (the ones that actually look like the plant, not those initial rounded seed leaves), start weekly feedings with diluted liquid fertilizer.

Harden off before transplanting. A week before transplanting outdoors, start taking seedlings outside for increasing amounts of time each day. This toughens them up for the transition to the garden.

Common Mistakes (That I've Definitely Made)

Let me save you some heartache by sharing what doesn't work:

Starting too early. More time indoors doesn't equal bigger plants. Seedlings that sit around too long in small containers get root-bound and stressed out. Count backward from your last frost date—most vegetables need 6-8 weeks indoors, not 12.

Using garden soil. I know, I already said this, but it's such a common mistake it's worth repeating. Garden soil's too heavy and may contain diseases. Always use sterile seed starting mix.

Insufficient light. Leggy, weak seedlings? Almost always a light problem. If seedlings are stretching tall and thin, they need more light—either stronger light or lights positioned closer.

Overwatering. This kills more seedlings than anything else. Soil should be moist like a wrung-out sponge, not dripping wet. If you're not sure whether to water, wait another day.

The Bottom Line on Seed Starting Supplies

You really don't need much to get started. Quality seed starting mix, containers with drainage, adequate light, and a way to water—that's your foundation. Add a gentle organic fertilizer once seedlings are growing, and you're good to go.

Everything else is nice to have but not essential. Start simple, see what works for your space and routine, and add tools as you figure out what you actually need.

The best part about starting your own seeds? You get to grow varieties you'd never find at the garden center. That weird heirloom tomato you read about? That purple cauliflower? That lettuce mix with six different colors? All yours to grow from seed.

Frequently Asked Questions

What's the most important thing for successful seed starting?

The right seed starting mix, hands down. Regular potting soil's too dense and heavy for seeds. You need a light, sterile mix that holds moisture without getting waterlogged. A quality seedling mix gives you the perfect balance for germination and early root development.

Do I need grow lights to start seeds indoors?

If you've got a south-facing window with at least 6 hours of direct sunlight, you might get by without them. But honestly? Most homes don't get enough natural light in late winter. Seedlings'll get leggy and weak stretching toward inadequate light. A basic LED grow light makes a huge difference.

When should I start feeding seedlings?

Start feeding once your seedlings have their first set of true leaves (the second set that appears, not those initial seed leaves). That's when they've burned through the nutrients in the seed and need external food. Use a gentle liquid organic fertilizer diluted to half strength at first.

Can I reuse seed starting trays?

Yep, but clean them thoroughly first. Wash with hot soapy water, then sanitize with a diluted bleach solution (1 part bleach to 9 parts water) or hydrogen peroxide. This prevents damping off disease from carrying over to your new seedlings.

How long can seedlings stay in seed starting trays?

Most seedlings can hang out in 2-inch cells for 6-8 weeks before they need transplanting. Watch for roots growing out the drainage holes—that's your sign they're getting root-bound and need more space.

What temperature do seeds need to germinate?

Most vegetable seeds germinate well at 65-75°F. Warm-season crops like tomatoes, peppers, and eggplants prefer warmer temps (75-80°F) and benefit from a heat mat. Cool-season crops like lettuce and spinach actually germinate better at cooler temperatures (60-70°F).

Ready to start your seeds the right way? Check out our complete guide to starting seeds indoors, or grab some seed starting supplies to get everything you need for healthy seedlings.