When to Start Sowing Seeds: A List of the Earliest Seeds to Start Indoors

A guide for which seeds can be sown the earliest based on your region’s climate #vegetablegarden #gardeningtips #seedsowing
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A guide for which seeds can be sown the earliest based on your region’s climate. Includes information on last frost dates and hardiness zones and types of vegetable seeds to sow in the weeks before spring officially arrives.

While most gardeners are still poring over their seed catalogs there are always the impatient ones (like me) who want to get growing. Fortunately, there are seeds that can be sown this time of year if it’s done undercover. But take heed, only sow the ones that benefit from being started early or you risk losing your plants, time, and money. These are my tips for sowing the first seeds including which ones can be sown the earliest. There are even a few that benefit from an early start.

A guide for which seeds can be sown the earliest based on your region’s climate #vegetablegarden #gardeningtips #seedsowing

Starting Seeds Too Early Can be Risky

Online, and mainly in Facebook gardening groups, I’ve seen quite a few growers posting photos of seedlings they’ve started early. It’s such an optimistic sight to behold! Young green seedlings stretching out of the compost seeking the sun. Sadly, unless these gardeners are set up with grow lights, it’s quite likely that their precious new plants will keep stretching and stretching. The young plants become ‘leggy’ and sick and most of the time don’t make it.

The fact is, no matter where you are in the northern hemisphere, it’s still winter. The sun could be shining and some days might even feel a bit balmy but don’t be fooled – snow may not be that far from your future. The time for planting crops outside in the garden is still months away so you may want to reconsider sowing seeds too early.

However, SOME plants do benefit from an early start. They include the types listed below in the categories to sow eight to ten weeks before your last frost date. If you have a heated propagator, grow lights, and an undercover place to sow seeds then get sowing. I share tips for starting seeds indoors during winter in another piece.

When should I start Sowing Seeds? A guide last frost dates for your zone and which seeds can be sown the earliest #vegetablegardening #lovelygreens #gardening
Hardiness zones for North America and Britain

When to Start Sowing Seeds

The answer to this question comes down to your region’s climate. Obviously, you wouldn’t sow spring crops in April if you lived in Australia. That’s an extreme case of seed sowing differences though. The main factor comes down to your last frost date. Look into how long it takes for seedlings to develop before they need to be planted out. This will include the days it takes to germinate then the time it takes for them to reach their development point for planting out. Use that time to count back the weeks they need from your last frost date and that’s the earliest you can sow undercover.

Seed packets take this into account when they present information on when to sow. Know though that most seedlings, with optimal conditions, are ready to be planted outside about a month after they germinate. If you wait too long to plant them out, the plants and their harvests will likely be negatively impacted. With seed sowing, being patient with seed sowing pays dividends in the spring and summer.

The information above pertains to starting seeds indoors. If you’re wondering about direct-sowing in containers or the garden then it’s different. Sowing outdoors generally needs to be done after your last frost date and once the soil has warmed up. Sow before then and the seeds might not ever grow, or if they do, the emerging seedlings can be killed by cold and frost.

When should I start Sowing Seeds? A guide last frost dates for your zone and which seeds can be sown the earliest #vegetablegardening #lovelygreens #gardening
Wait on sowing vegetables like beans, squash, and cucumbers until you’re closer to your last frost date

Average vs Safe Frost Dates

Below are the rough guides to the first and last frost dates for different zones in the northern hemisphere. To find the date more specific to your town or region search for them over here: USA & Canada and Britain. Please also be aware that these dates are all average dates and that in an average year they’re correct. Some years you’ll get freakish cold weather in spring though so talk to gardening friends and neighbors about your safe date too. For me, my average last frost date is March 31st. My safe date that I can count on for no more frost is a month later.

If I’m sowing hardy plants, like peas or cabbages, or veg that will be grown in the greenhouse, I’ll tend to stick to the average last frost date. For more tender outdoor grown plants I’ll use my safe date and grow them indoors. If you see “Plant after all danger of frost has passed” on the back of a seed packet, use the safe date, not the average. Plants sown a little later will catch up quickly and you’ll be surer that they’ll survive.

ZoneAverage Last Frost DateAverage First Frost Date
1July 16-31August 1-15
2June 8-21September 8-21
3May 8-21September 21-October 7
4May 22-June 7October 1-15
5May 1-15October 8-21
6April 16-30October 16-31
7April 1-15October 21-November 7
8March 16-31November 1-15
9February 16-28December 1-15
10-13No freezeNo freeze
When should I start Sowing Seeds? A guide last frost dates for your zone and which seeds can be sown the earliest #vegetablegardening #lovelygreens #gardening
Alliums, like onions and shallots, do well to be started from seed a month before your last frost date

Some Crops Benefit from an Early Start

There are plants that will benefit from an early start. If you have a warm conservatory or heated greenhouse then you could start off warm weather veg like tomatoes and eggplant (aubergines) relatively early. It’s important to give these indoor-grown seedlings the correct amount of light, warmth, and humidity so do read up on growing seeds indoors in winter. In many places grow lights are recommended if you are growing seedlings before the spring equinox. Especially tropical seedlings such as tomatoes, chilies, peppers, and eggplants.

Cooler weather veg is best sown in the early part of the year as well. These can deal with a lot less light and warmth and a windowsill can do. An unheated propagator is a good idea in getting these started though. The good news is this means that you can sow kale, cabbage, broccoli, brussels sprouts, and onion seeds undercover without expensive equipment or electricity bills. When they’re large enough, you can then transplant them in your garden after the last frost. Make sure to harden them off properly first and to give them the protection of fleece or a hoop tunnel. Here’s a general guide to when you can begin sowing vegetable seeds. Also, the links take you to where you can purchase the seeds from MIgardener. Use the code LOVELYGREENS to get 10% off your purchase.

Seeds to Sow Undercover up to 10 weeks before the last frost date

Seeds to Sow Undercover up to 8 weeks before last frost date

Seeds to Sow Undercover 6 weeks before last frost date

Seeds to Sow Undercover 4 weeks before last frost date

Seeds to Sow Undercover 2 weeks before last frost date

More Winter Gardening Ideas

In late winter and very early spring, there’s a lot that we can busy ourselves with to get a head-start on the growing year. Here are more ideas that will help you grow a bountiful vegetable garden this year!

11 Comments

  1. I have been trying to find seeds for the 9 Star broccoli for years. I live in Texas in the United States. Do you know of any place that has this seed variety that I can purchase?

    1. I’m sorry but I’m not as familiar with seed companies in the USA. I’d suggest speaking to a seed supplier that supplies Nine Star Broccoli seeds in the UK and see if they know of anyone in the US.

    2. Smallislandseeds company on Etsy. They sell it and it’s in stock free shipping
      Nine Star Perennial Cauliflower/Broccoli Seeds – Brassica Oleraceae – Prolific, Delicious, and Perennial 30 seeds for $3.29 to the US

  2. seed packets always use the last frost date to tell you when to start. I live in the SF bay area where there is no frost. Does this mean I can start flowers indoors at any time?

    1. Hi LaurieAnn, technically your last frost date in San Francisco is February 1st. It doesn’t mean that you’ll have frost until that date every year, but rather the last chance of frost ends on that day. Find out more about last frost dates throughout California and even specific parts of the bay area here.

  3. You CAN use ordinary 40 watt double fixture lights suspended from a chain…I
    did this for many years and raised many seedlings for my expansive garden…

  4. Trying hard not to be drawn into sowing any seeds for a few weeks. Too much temptation online though.

    Those frost dates look a bit optimistic to me. I’m in zone 7 or 8 {Yorkshire UK} We often get a frost in the first week of May, with a below zero degree centigrade temperature. It usually sets my early potatoes back. Maybe I’ve mis-read the tables.

    1. I’d love to see what miniature garden plants and herbs could be cultivated now too — you’re the one in the know Janit :)

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