Best Seed Starter Kits

Updated September 2020
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BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We buy all products with our own funds, and we never accept free products from manufacturers.Read more 
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Why trust BestReviews?
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We buy all products with our own funds, and we never accept free products from manufacturers.Read more 
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We purchase every product we review with our own funds — we never accept anything from product manufacturers.

37 Models Considered
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We purchase every product we review with our own funds — we never accept anything from product manufacturers.

Buying guide for best seed starter kits

Last Updated September 2020

If you live in an area with long, cold winters, starting vegetable seeds indoors and then transferring the seedlings outdoors once the weather warms up is a great way to get a jump on the growing season. By having seedlings ready to plant as soon as spring permits, you gain several weeks of growing time, which often means an additional few weeks of crops in your vegetable garden. 

Even gardeners who live in mild areas often like to start seeds indoors, as careful timing can mean an additional round of crops. Plus, starting your garden from seed is very economical and lets you choose from the widest selection of plant varieties.

While it’s not necessarily more difficult to start seeds indoors than it is to sow them directly in your garden, it does require know-how and a few pieces of equipment. Buying that equipment in a kit is easier, and often more economical, than buying pieces separately. Here’s what you need to know to choose and use the best seed starter kit.

You can gain weeks of growing time by starting seeds indoors and then transplanting them into your garden.

Considerations

For seeds to germinate, they need the right combination of water, oxygen, and warmth. Once sprouted, the seedlings also need light and a nutrient-rich medium where their roots can spread. A good seed starter kit makes it easy for you to provide all of these requirements right in your living room.

Growing tray

All seed starter kits include some sort of growing tray. In the most basic kits, the tray is made of plastic and divided into small compartments or pods. The compartments may be round, square, or hexagonal. There are trays with as few as 10 compartments and as many as 100. A good seed starter growing tray is heat-resistant so it can be placed on top of a warming mat to speed up germination.

You’ll need to fill your tray with soil or seed starting mix before sowing your seeds. Once the seedlings are ready to transplant, slip them carefully out of the growing tray and plant them in your garden. The downside to these types of trays is that the risk of injuring seedling roots while transplanting is fairly high.

Trays with peat pots
Some growing trays are designed for use with peat pots. With these trays, you place a small peat pot in each compartment, fill it with soil, and sow your seeds. Once the seedlings are large enough, you can plant the entire peat pot in your garden. Here it will decompose and provide nutrients to growing plants. Peat pot trays are an excellent choice for crops that don’t like to have their roots disturbed and in situations where you want to let the seedling grow a little larger than usual before planting it outdoors.  

Trays with peat pellets
Some growing trays use peat pellets in place of soil. In these kits, you place a small peat pellet, which resembles a miniature hockey puck, in each of the growing tray’s compartments. No need for soil; simply sow your seeds directly onto the peat pellet, which will swell considerably once watered. When it’s time to transplant your seedlings, the peat pellet goes with them into your outdoor garden. The roots are not disturbed, and the peat provides nutrients as it decomposes in the soil. Peat pellet trays are a good choice for crops that transplant while still fairly small, like lettuce.
 

Tray stability and size
Whatever type of growing tray is included in your kit, it should be made of sturdy plastic with sides high enough to prevent spills and enough compartments to start your desired number of seedlings. The size of the compartments is also important. As a general rule, the more compartments in the tray, the smaller they are. When starting larger crops, such as tomatoes, squash, pumpkin, or melons, you’ll have the most success with a tray with fewer (but larger) compartments. Typically, 2 x 2 inches is a good size for these larger plants. 

That said, the majority of popular backyard crops, including peppers, cabbage, cauliflower, vining crops, and herbs, do fine with smaller compartments of 1.5 x 2 inches. There are also trays with compartments as small as 1 x 2 inches. These are suitable for plants you’d transplant while still quite small, which is especially common for gardeners in milder climates. 

Dome

All seed starter kits include a lid, usually made of clear plastic and shaped like a dome. The lid acts something like a greenhouse to keep in moisture and warmth. It should fit securely over the growing tray; many clip in place. It should be tall enough to allow your seedlings to reach full transplant height without bumping against the plastic. The best seed starter kits have domes that let you open or close small vents to control the humidity.

Seed starter medium

While a few kits include seed starter medium, many require you to purchase that separately. You can use regular potting soil, but if you want the best results, use a seed starter mix that’s specifically formulated to encourage germination and healthy growth of seedlings. Seed starter soil is light and fluffy, allowing plenty of oxygen to reach the baby roots while preventing moisture buildup, which can lead to rot.

Kits that use peat pellets instead of soil generally include the pellets, although you’d need to buy replacements each growing season.

Warming mat

Not every seed starter kit requires a warming mat, and few include one. If you have a sunny window and keep your home quite warm, it’s possible that your seeds will sprout without an additional heat source. If your kit doesn’t come with a heating mat and you are hoping for the best results, however, it may be worth buying a mat separately. 

Never use a medical heating pad for your seeds. Not only are heating pads not designed to operate in moist conditions, they also get too hot. A garden heating mat has a water-resistant cover and only warms up to around 80°F or so, which is sufficient to germinate seeds. A seed-warming mat should be large enough so the entire growing tray can sit on top of it. If your kit includes a mat, it will be the right size, but check dimensions if you are purchasing it separately.

Grow light

A grow light is another accessory that isn’t usually included with seed starter kits and is not always needed. You can do without a grow light as long as you have a sunny window that receives at least 12 to 16 hours of light per day but doesn’t get too hot. Unfortunately, most would-be gardeners don’t have an accommodating window and so need to use some sort of grow light to encourage seed germination. 

The best grow lights are full-spectrum LED bulbs that encourage healthy plant growth. Some less-expensive grow lights have fluorescent bulbs which stimulate plant growth, albeit not as effectively as full-spectrum LED light.

Seeds

Very few seed starter kits actually include the seeds, but a few specialty types typically for herbs, tomatoes, or flowers do come with packets of seeds. For many gardeners, however, the freedom to choose the specific varieties of seeds they want to grow rather than relying on the small selection of nursery starts available in the local home improvement center is one of the main reasons for using a seed starter kit in the first place.

EXPERT TIP

As a general rule, start your indoor seeds six weeks before the last frost date for your area.


Staff  | BestReviews
EXPERT TIP

Situate your seed starter kit in a location with plenty of light and warmth.


Staff  | BestReviews

Seed starter kit prices

The price of a seed starter kit largely depends on what it includes.

Inexpensive: For under $25, you can get a basic seed starter kit that includes one or more growing trays and matching lids. Simple grow-light setups that are suitable for most gardeners looking to get a head start on their vegetable gardens usually cost between $30 and $50. Note that if you’re buying a warming pad separately, you’ll need to add another $20 and $35 to your expenses, depending on mat size.

Expensive: Kits that include a grow light or a heat mat cost much more upfront. You can expect to spend between $50 and $100 for these more complete kits.

DID YOU KNOW?

Many popular flower and vegetable seeds do well when started indoors.

Tips

  • Know which seeds should not be started indoors. Some vegetables thrive indoors, but others do best when sown directly into the ground. As a general rule, root crops, including carrots, onions, potatoes, radishes, parsnips, and beets, resent being transplanted. These seeds do best when planted directly in your outdoor vegetable garden at the appropriate time of year. Other crops that do best when planted directly in the garden include corn, peas, green beans, celery, and squash.

  • Know which seeds do well when started indoors. Many seeds are more likely to thrive if you give them an indoor boost. This includes lettuce, Swiss chard, eggplant, pumpkin, peppers, watermelon, kale, broccoli, cabbage, tomatoes, Brussels sprouts, and cauliflower.

Starting seedlings indoors is a great way to introduce children to gardening.

FAQ

Q. When should I start my seeds indoors?
A. While different crops have different recommended planting times, as a general rule, you should start your seeds indoors approximately six weeks before the last average frost date for your area. For example, if you live in an area where freezing temperatures are likely until the middle of April, you should start your indoor seeds around the beginning of March.

Q. Can I start flowers indoors?
A. Although most gardeners use seed starter kits for vegetable and fruit crops, there’s no reason you can’t use the kit to germinate flower seeds as well. It’s a great way to get a jump on the growing season, and you’ll be able to enjoy colorful blossoms for several weeks longer. A few popular flowers that do well when started indoors include:

  • Snapdragons

  • Petunia

  • Lobelia

  • Salvia

  • Coleus

  • Coreopsis

  • Ageratum

  • Nicotiana

  • Zinnia

  • Lupine

  • Cleome

  • Impatiens
     

Q. Why do my seedlings keep dying before I can transplant them?
A. There are several reasons why seedlings die before they are ready for transplanting, but one of the most common is a fungal condition called damping off. Once the fungus gains hold, it can quickly wipe out all of your seedlings. The best way to prevent damping off is to avoid the conditions that encourage its growth in the first place: poor air circulation, insufficient light, overly damp soil, and low temperatures. Signs of damping off include slow or spindly growth, white fuzz on seedlings, mushy stems, collapsed stems, wilting leaves, and pale or discolored leaves.

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