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Seed Starting Supplies
Starting seeds indoors takes a seed starting mix, cell trays with a clear dome, bottom heat, a light and a timer. This guide lists 10 supplies checked on the maker or store page on 12 Nov 2026, with the price listed there.
Photo: Newly sprouted corn seedlings in straight rows of bare brown soil. Rémy Sanchez, CC BY 3.0, via Wikimedia Commons
What you need
Seed starting mix
A fine, light mix made for seeds, not garden soil. Bags are sold by the quart or cubic foot.
Cell trays and a dome
Standard 10 x 20 in trays hold 72-cell inserts; a clear dome holds moisture until seeds sprout.
Bottom heat
A heat mat under the tray warms the mix; the one listed here is rated to warm it 10 to 20 degrees above room temperature.
A light
An LED grow light over the trays; the one listed here has an adjustable height and its own tray.
A timer
A plug-in timer turns the light on and off at the same time every day.
Labels and watering
Plant labels for each variety and a can or mister that waters gently.
10 products checked on 12 Nov 2026
Seed starting mix
Burpee Eco Friendly 8 Qt Seed Starting Mix
8 qt bag of coconut coir based mix.
Trays and domes
Burpee 72 Cell Self-Watering Seed Starting System
Two 36-cell trays, a self-watering mat, a dome and 72 growing pellets; the kit is 10 x 20 in.
Bootstrap Farmer 72-Cell Seed Starting Trays
Cells 1.5 in square and 2.25 in deep; 1-year warranty against breaking or warping.
Bootstrap Farmer 1020 Extra Strength Humidity Dome
5.4 in tall with 2 adjustable vents; fits standard 1020 trays.
Bottom heat
Burpee Seed Starting Heat Mat 10 x 20 in
17.5 watts; the maker says it warms soil 10 to 20 degrees above room temperature.
Grow light
Epic Grow Light with Tray
Countertop LED light with adjustable height, a built-in timer and a tray for twelve 6-cell packs.
Light timer
BN-LINK 24-Hour Mechanical Outlet Timer, 2-Pack
Settings in 30-minute steps; rated 15 A, 125 V.
Soil blocks
Johnny's 4-Cell Handheld Soil Blocker
Makes four 2 x 2 x 2 in soil blocks, so no plastic cells are needed.
Labels and watering
Bloem Deluxe 2-Gallon Watering Can
2 gallon plastic can with a removable nozzle, made in the US.
Prices are as listed on the linked store page on 12 Nov 2026 and change often. Amazon buttons are affiliate links: State Gardening may earn a commission at no cost to you. See the affiliate disclosure.
Count back from your last frost date
Seed packets give indoor sowing as weeks before the last spring frost. These pages give the 50% and 10% last frost dates for every county; Pennsylvania calendars also publish start-indoors dates on the what to plant now page.
Seed Starting Supplies: questions
What do I need to start seeds indoors?
Seed starting mix, cell trays with a dome, a light on a timer, labels and a gentle way to water. A heat mat warms the mix.
When should I start seeds indoors?
Count back from your county's last frost date by the number of weeks on the seed packet. Frost dates for every county are on the state frost date pages.
Can I use garden soil in seed trays?
Seed starting mixes are sold for this job; the products here are bagged mixes made for seeds.
What size tray fits a heat mat?
The 10 x 20 in tray size used by most kits matches the 10 x 20 in heat mat listed here.
Where are the prices from?
Each price is what the linked maker or store page listed on 12 Nov 2026. Prices change, so check before buying.
Does State Gardening earn from these links?
The Amazon buttons are affiliate links. Frost dates and planting calendars are not affected by them.
More gear guides
Photos: Newly sprouted corn seedlings in straight rows of bare brown soil: Rémy Sanchez, CC BY 3.0, via Wikimedia Commons; Two hands firming soil around a young green seedling just planted in the ground: Robbieross123, CC BY-SA 4.0, via Wikimedia Commons; Community vegetable garden with chard, squash and staked tomato plants in summer: Gavin Anderson, CC BY-SA 2.0, via Wikimedia Commons; Community garden plots of beans, onions and greens beside flower borders and paths: Mack Male from Edmonton, AB, Canada, CC BY-SA 2.0, via Wikimedia Commons; Raised wooden vegetable bed planted with rows of lettuce and salad greens: Acabashi, CC BY-SA 4.0, via Wikimedia Commons; Dark finished compost filling a wooden compost bin in a garden: Bernard Dejean, CC BY-SA 4.0, via Wikimedia Commons; Freshly seeded front lawn turning green beside bare soil and a garden hose: HA1256, CC BY-SA 4.0, via Wikimedia Commons; Tall corn and other vegetables growing in a fenced backyard garden: Tomwsulcer, CC0, via Wikimedia Commons.