A seed starting kit bundles the tray, the cells, and the dome so you can sow seeds the day it arrives. Some add a water reservoir. Some add a light. The best kit for you depends on how many plants you want and where the tray will sit. Here are the kits worth buying, and one you can put together yourself for less.
Every kit on this list works with any seed. Fill it with Botanical Interests or True Leaf Market seeds and you are set. See my notes on the best seed companies if you want more options.
Best self-watering kit: Burpee seed starting kit
The Burpee XL self-watering seed starting kit has 32 extra-large cells that sit on a capillary mat over a water reservoir. Fill the reservoir once a week and the mat wicks water up into each cell. The cells never dry out and never sit in a puddle. The clear dome holds humidity until the seeds sprout.
This is the kit I point beginners to first. Uneven watering kills more seedlings than anything else, and the mat takes that job away. The big cells carry tomatoes and peppers right up to transplant size, so there is no potting up. Burpee also sells its own coconut coir seed starting mix that swells up in the tray with warm water.
Best budget kit: Jiffy peat pellet greenhouse
The Jiffy greenhouse kit is the classic, and it comes as a two-pack. Compressed peat pellets sit in a tray under a dome. Add warm water, the pellets swell, you poke a seed into each one. There is no mix to buy and no cells to wash. When the seedling is ready, the whole pellet goes in the ground.
The trade-off is that pellets dry out fast under lights and the netting around each pellet does not always break down in the soil. Tear the netting before planting. It works well for cucumbers, squash, melons, and sunflowers, which hate having their roots disturbed. It is less good for slow crops like peppers that sit in the pellet for two months.
Best all-in-one kit with a light: AC Infinity humidity dome kit
The AC Infinity humidity dome kit includes the tray, the cells, a tall dome, and an LED grow light built into the lid. Add the matching seedling heat mat with a thermostat underneath and you have a full germination station on one square foot of counter. The tall dome gives seedlings room to grow for a few weeks before the lid comes off.
This is the kit for a kitchen, an apartment, or anyone who does not want to build a shelf. It is also the best choice for a classroom or a kid who wants to see the whole process in one box. The light is bright enough for seedlings but not for growing lettuce to full size, so move plants under a bigger light or outside once they fill the dome.
Best kit for a lot of plants: a 72-cell tray under a strip light
For a full tray of tomatoes from seed to transplant, pair a Burpee 72-cell tray and dome with a 4-foot Barrina LED strip hung from a shelf. The strip covers two trays side by side, so one light and two trays handle 144 seedlings. Two shelves of this cover a family vegetable garden, and the parts last for years.
Best no-soil kit for herbs: Click and Grow
The Click and Grow smart garden is a different animal. It uses pre-seeded pods, a water tank, and a built-in LED light. There is no soil, no mess, and no watering for three weeks at a time. It is a good pick for basil and lettuce on the counter through the winter. It will not start a flat of tomatoes for the garden, but it grows herbs and greens to eat, year round. The code HHARVEST takes 31 percent off from November 3 to 30. Read my full Click and Grow review for the pros and cons.
The DIY kit that beats most of them
Buy the parts and you get sturdier gear for about the same money. Here is the list.
One Bootstrap Farmer 1020 tray with no holes, to hold water. One set of 6-cell inserts or a 72-cell tray with a dome. One bag of Espoma seed starter mix. A pack of plastic labels and a Garden Marker pen. A heat mat with a thermostat if the room is cool. A clip-on grow light or a strip light for the shelf.
The Bootstrap Farmer trays are thick enough to carry one-handed when full, and they last for a decade instead of a season. That alone makes the DIY kit the better buy for anyone who plans to start seeds every year. My seed starting supplies checklist goes through each piece.
How many cells do you need
Count the plants you will set out, then add a third for the ones that fail or get eaten. A family vegetable garden with six tomatoes, four peppers, a dozen lettuces, a dozen onions, and a row of flowers needs about 50 cells, so one 72-cell kit covers it. A bigger garden with a cutting bed and a second planting of greens needs two or three trays. Buy one kit the first year. If every cell gets used, buy another the next.
Cell size matters as much as cell count. Small cells in a 72-pack are fine for lettuce, onions, and flowers that go out at four weeks. Tomatoes and peppers sit indoors for eight weeks and want a bigger cell or a move into a 3 inch (8 cm) pot halfway through. A kit with 32 big cells, like the Burpee XL, skips that step.
How to use any seed starting kit
Moisten the mix or pellets with warm water before sowing. Sow two seeds per cell and snip the weaker one later. Keep the dome on and the tray warm until the first sprouts show, then take the dome off and turn the light on. Water from below once the surface dries. Pot up or transplant when the seedlings have two sets of true leaves. Harden off seedlings for a week before they go in the garden. My post on the best temperature to germinate seeds explains why the heat mat matters so much for peppers and tomatoes.
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