When to start seeds indoors (2024)

Are you eager to start your garden this year, and wondering when to start seeds indoors? It all depends on what you’d like to grow and when your last frost date will be in order to determine which plants are best suited for indoor sowing.

This blog post provides insight into what types of seeds should be started 10-12 weeks before the last spring frost; 7-9 weeks before; 5-6 weeks before; and 4-5 weeks before – so grab a pen and paper (or open up that note-taking app.) as we explore how you can start seeds indoors at just the right time.

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When to start seeds indoors depends on your last frost date

If you want your garden to thrive, it’s important to know when to start planting. The key factor in deciding when to start seeds indoors is knowing your local last spring frost date. And if you’re not yet sure which seeds to start indoors and which ones to direct sow, here’s a chart showing which common vegetables to direct sow or transplant.

Your local last spring frost date can vary significantly from year-to-year, so it’s important that you check the weather forecast each year around the estimated date for a more real-time estimate of when the danger of frost has passed. This will help ensure that your plants are not damaged by cold temperatures or late frosts after they have been planted outside.

Knowing your local last spring frost date also helps determine how long before the last spring frost you should begin starting seeds indoors. Generally speaking, most vegetable and flower seedlings need 4-6 weeks of indoor growth before they can be safely transplanted into the garden beds outside without fear of damage from cold weather or late frosts.

When to start seeds indoors (1)

Seeds you can start indoors 10-12 weeks before the last spring frost

When it comes to starting seeds indoors, timing is everything. Knowing when to start your seeds can make or break a successful garden. If you’re in North America, the key factor for determining when to start your seeds indoors is knowing what the last spring frost date is for your area.

If you live in an area with a long growing season and mild winters, then 10-12 weeks before the last spring frost date may be ideal for starting some of your favorite vegetables and flowers from seed. Some examples of plants that do well when started 10-12 weeks before the last spring frost include celery, eggplant, leek, onion, pepper, and lisianthus.

Celery takes about 70 days from planting until harvest time so plan accordingly if you want fresh celery on hand during summer months. Eggplants need around 80 days from planting until they are ready to pick while leeks take around 90 days so both should be planted early enough that they have plenty of time to mature before summer heat sets in. Onions also need at least 90 days but many varieties will take up to 120 days so plan ahead if onions are part of your garden plans this year. Peppers usually require between 60-90 days depending on variety and lisianthus needs around 100 days from sowing until bloom time so keep these timelines in mind when planning out your indoor seed starts this winter.

Starting seeds indoors 10-12 weeks prior to the last spring frost gives them plenty of time to get established before being transplanted outdoors into their permanent home once all danger of cold weather has passed. This way, you can enjoy homegrown veggies earlier than ever and reap the rewards of your hard work.

Seeds you can start indoors 7-9 weeks before the last frost

Starting seeds indoors 7-9 weeks before the last frost date gives plants plenty of time to germinate and grow strong enough for transplanting into the ground or larger containers when temperatures are warm enough.

Lettuce is one of the most popular vegetables that can be started indoors during this timeframe. Lettuce grows best in cooler weather, so getting them established early will give you a head start on harvesting crisp greens throughout the season. While loose-leaf varieties are generally direct seeded outdoors, types that form a head are generally started in flats and transplanted out. If you harden off the lettuce seedlings, they can usually go outdoors well before the last frost.

Globe artichoke is another vegetable that does well with indoor seed starting 7-9 weeks before the last frost. It takes some patience as these large plants take up to two years from planting until harvest but they are worth it. Parsley also does well when started indoors at this time and makes a great addition to many dishes both fresh and cooked.

For those looking for more color in their gardens, coleus, petunias, and salvia all make beautiful additions with vibrant blooms lasting through summertime heatwaves if cared for properly. Coleus comes in many varieties ranging from bright reds and oranges to deep purples while petunias come in almost every hue imaginable – perfect for creating unique combinations within your flower beds or container gardens. Salvia has long been used as an ornamental plant due to its tall spikes of purple flowers which attract pollinators like bees and butterflies making it beneficial for other parts of your garden too.

When to start seeds indoors (2)

Seeds you can start indoors 5-6 weeks before the last frost

Starting seeds indoors five to six weeks before the last spring frost can be a great way to get a jump start on your garden. It’s important to know which plants you should start at this time, and how best to do it.

Tomatoes are one of the most popular vegetables that can be started indoors five or six weeks before the last frost date. Tomato seedlings need about 10-12 hours of light per day, so if you’re using artificial lighting make sure it’s bright enough for them. When planting these seeds, use a soil mix specifically designed for starting seeds and keep them moist but not soggy until they germinate. Once they have sprouted, thin out any weak seedlings. Here’s a guide on when to plant your tomato seedlings outdoors.

Cauliflower is another vegetable that can be started indoors around 5-6 weeks before the last frost date. Plant cauliflower seeds in a well-draining potting mix and keep them moist until germination occurs in 7-14 days. After germination, provide plenty of light – either natural sunlight or artificial lighting – for 12 hours each day while keeping temperatures between 65°F and 75°F during the day and 55°F at night. When transplanted outdoors after all danger of frost has passed, give cauliflower plenty of space as it needs room to grow without competition from other plants nearby.

Starting seeds indoors 5-6 weeks before the last spring frost is a great way to get an early start on your gardening season. With just a few simple steps, you can be well on your way to having healthy plants ready for transplanting in no time. Now let’s take a look at which seeds you can start indoors 4-5 weeks before the last spring frost.

Seeds you can start indoors 4-5 weeks before the last spring frost

It’s time to start thinking about your garden. If you want to get a jump on the growing season, it’s important to know when and what seeds you can start indoors 4-5 weeks before the last spring frost. Starting seeds indoors is an easy way for any gardener, beginner or expert, to get a head start on their gardening projects.

Basil is one of the most popular herbs that can be started indoors 4-5 weeks before the last spring frost. Basil has many culinary uses and adds flavor and color to dishes like pesto, salads, soups, and sauces. Planting basil from seed will give you more variety than buying plants from a nursery or store. When starting basil from seed indoors make sure you use a well-draining soil mix in individual pots or trays with drainage holes as they don’t like soggy roots.

Cucumbers are another vegetable that can be started indoors 4-5 weeks before the last spring frost date. They do well when direct seeded vs seeded indoors, but in cooler climates may be sown indoors. Cucumbers are relatively easy to grow but require warm temperatures so starting them early gives them enough time to mature before summer heat sets in. Make sure your cucumber starts have plenty of light as this helps encourage strong stem growth which leads to healthier plants overall when transplanted outdoors later in the season after all danger of frost has passed.

When to start seeds indoors (3)

FAQs aboutwhen to start seeds indoors

What month do you start seeds indoors?

The best time to start seeds indoors depends on the type of plant you are growing and your local climate. Generally, most vegetable and flower seeds should be started 6-8 weeks before the last expected frost date in your area. This will give them enough time to grow large enough for transplanting outdoors when temperatures warm up.

If you’re unsure about when this is, check with your local garden center or extension office for more information. It’s important to remember that different plants have different needs so it’s always a good idea to do some research before starting any seed indoors.

Can you start seeds inside too early?

Yes, it is possible to start seeds inside too early. This is called “rushing the season”, and is very common! Starting seeds too early can lead to a small jungle growing inside your home. Seedlings may need to be potted up into bigger containers several times before they go outdoors for good. Additionally, if temperatures outside are still too cold for young plants, they may not be able to survive transplanting into the garden.

What seeds should not be started indoors?

It is generally not recommended to start seeds indoors that do not transplant well. These include corn, squash, and pumpkins. It is best to wait until the weather warms up before planting these types of seeds outdoors directly in the garden bed. Finally, it is important to remember that starting certain trees or shrubs from seed may take several years before they are ready for transplanting into the landscape.

What temperature should you start seeds indoors?

The ideal temperature for starting seeds indoors is often between 18-21°C (65-70°F). Here’s a chart showing the optimal temperature range of some common vegetable seeds for their germination.

It’s important to keep the soil at a consistent temperature, as fluctuations can cause poor germination. Additionally, keeping the soil moist but not overly wet will help ensure successful seed growth. To maintain an even temperature, consider using a heat mat or other heating device. With proper care and attention to detail, you can give your seeds the best chance of success.

Before you go…

Starting seeds indoors is a great way to get your garden off to an early start and ensure you have the best possible harvest. It’s important to know when to start seeds indoors based on your last frost date, as well as which types of seeds are best suited for each time frame. With some planning and research, you can easily learn how to start seeds indoors with success. So don’t be afraid – get out there and give it a try. You’ll be glad you did when you see those beautiful plants growing in no time at all.

Resources

  • The best garden catalogs for seeds, live plants, tools, and supplies
  • Best seeds for winter sowing
  • Winter sowing guide for planting seeds outdoors in cold climates

References

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When to start seeds indoors (2024)

FAQs

When to start seeds indoors? ›

As a general rule, seeds are started indoors about six weeks prior to your last frost date. During a cold spring, it's better to delay sowing a little to ensure the soil temperature is warm enough than to jump the gun and get disappointing results.

How early should you start seeds indoors? ›

When should you start seeds indoors? Start seeds six to eight weeks before the last frost in your area. 2 Most plants are ready to go outside four to six weeks after you start the seeds.

Is February too early to start seeds indoors? ›

Even if the last thing you're thinking about in January or February is the garden, it's actually a great time to start seeds indoors for frost-hardy leafy greens and for slow-to-get-started herbs.

How warm does it need to be to start seeds indoors? ›

The closer the temperature is to the optimum, the quicker germination will occur. Most seeds germinate when the soil temperature is between 68° and 86°F. Once germination occurs, the optimum growing temperature for the seedling is about 10°F cooler than the optimum germination temperature.

How many seeds per hole when starting seeds indoors? ›

Most seeds prefer a depth of about 2 times their length. The tiniest seeds can be sprinkled directly on the surface. Cover the seeds with a thin layer of soil. Plant about 3 seeds per hole (more if using older seeds) and once they germinate, thin down to leave only the strongest seedling.

Is March too early to start seeds indoors? ›

It's also a great time to sow a variety of seeds indoors so they'll be ready for early planting. Believe it or not, once you've prepared beds for them, you can start sowing seeds for many cool season veggies in March, along with broad (or fava) beans, which are some of the hardiest vegetables out there.

What happens if you start seeds indoors too early? ›

A fresh pile of seed packets makes gardeners yearn to get growing. But hold tight! If you start too early, you might end up with leggy, overgrown plants that need babying until the frost disappears and the soil warms.

Is January too early to start seeds indoors? ›

First there is too little light at this time of year – If you rely on a sunny windowsill to start your seeds, you want to wait a little longer to start seed sowing. Most plants need at least 10 hours of light in order to grow well, and in January, much of the Northern Hemisphere receives less than that.

Can I start seeds indoors in January? ›

Yes, you absolutely can start seeds indoors in winters. It's a great way to give seedlings a head start versus direct sowing outside in spring. I do this with peppers and tomatoes every winter. Yes that's the point.

Is it too late to start seeds indoors in April? ›

April is a great time to start to sow your flowers indoors so they can be ready for summer blooms!

What is the best way to start seeds indoors? ›

How to Start Seeds Indoors in 4 Easy Steps
  1. Fill a large bowl with seed-starting mix and mix in a little water to evenly moisten the soil. ...
  2. Place your seed tray inside the drip tray and fill each cell to just below the top with soil.
  3. Sow your seeds. ...
  4. Cover the tray and place it under your lights on the heat mat.
Feb 10, 2023

How cold is too cold for seed starting? ›

This means that the temperature is not dipping below 70 degrees Fahrenheit at night. If you live where the temperatures are getting down into the 30s, 40s, 50s, or even 60s at night, the soil is too cold to germinate these types of vegetable seeds.

How long can seedlings stay in egg cartons? ›

But you also can't leave your seedlings in their egg cartons for too long, waiting for the weather to heat up. Seedlings should be moved to the garden once the roots reach the bottom of the tray, but before they start to grow into a circle.

Does 1 seed equal 1 plant? ›

In general, two to three seeds should be planted per hole. Seeds do not have 100% germination rates, so not every seed planted will sprout. Overseeding holes, cells, or pots will help ensure that the number of plants you desire will grow (or more. Don't exceed three seeds per hole.

Do I plant the whole packet of seeds? ›

If only a few plants are needed, it is not necessary to plant all the seeds in a packet.

Can you use potting soil to start seeds indoors? ›

It is too dense for the job and contains weed seeds and possibly pathogens. If you grow a lot of seedlings and also do container gardening you might want to invest in a large bag or compressed bale of commercial soilless growing media. It is cheaper than buying the same amount in small quantities.

Can I start seeds in January? ›

Look through your catalogs and find the vegetable seeds for your garden. Some flower varieties should be started in January. In a warmer environment you can plant certain vegetables, but must be ready for a frost. Indoor herbs are always great to grow in a sunny windowsill.

Should you soak seeds before planting indoors? ›

Soaking can accelerate germination and increase the proportion of seeds that successfully germinate. Seeds have evolved a protective coating around the embryo so the embryo can survive being dispersed by some means. The coating protects the seeds until they find themselves in a suitable place to grow into a new plant.

Should you start all seeds indoors? ›

Though some plants prefer to be direct sown (like squash and cucumbers), almost anything can be started indoors as transplants, if done right, including root crops like beets, radishes and turnips. The main exception are vegetables with long taproots like carrots and parsnips, which need to be direct sown.

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