Sowing Seeds

Understanding Sowing Dates on Seed Packs

Always read over any seed packet before you sow! Ill.: &

So, you’ve bought a few packs of seeds: annuals, vegetables, herbs, etc. and you’re back home, excited to get started sowing them. Before doing so, though, read the information on the back of the pack. It has all sorts of important details: how deep to sow, how to space the seeds, etc. and, perhaps most importantly, when to sow the seeds it contains.

Seeds You Sow Outdoors

Sometimes it will indicate you should sow the seeds directly outdoors, where the plant is to grow. There will likely be a precision like:

• Sow as soon as the ground can be worked: That means sow outdoors early in the spring, after the ground has not only thawed out, but is no longer soaking wet.

• Sow when the soil warms up: Unless other details are given, assume this means when the soil reaches 65˚F/18˚C.

• Sow after all danger of frost is past

• Sow after final spring frost

• Sow after average last frost

• Sow after the danger of spring frost

• Sow after last frost

These terms all mean the same thing, but do not refer to the average last frost date that your local weather station might give you … or at least, should not. Remember that “average” means there’ll be a frost after that date about every second year. (That’s what average means!) What you need is the “frost-free date,” one at which there is little to no risk of frost, probably at least 2 weeks after the average last frost date. Ask your local garden center or garden club when they consider all risk of frost to be over for the season … but always be ready to adapt to any special weather conditions. An extra cold spring would mean delayed sowing for many seeds, for example.

Seeds You Sow Indoors

Alternately, the seed pack may indicate you should start the seeds indoors. Then, after they’ve sprouted and grown for a while, you would then transplant the resulting seedlings into the garden … usually “when all danger of frost is past” (see above) or “when the soil warms up” (see above). This gives slow-to-mature plants a head start on the season.

This packet suggests you can sow outdoors (“Direct Sow”) or indoors and gives an idea when to do so in both cases. Photo: Nan Schiller,

Explaining when to sow seeds indoors is usually done in the form of a statement like:

“Sow indoors xx weeks before last frost.” 

So, pull out a calendar. You need to find the frost-free date for your locality (see above), then count backwards the number of weeks mentioned to determine when to sow indoors. 

Simple, but…

Sometimes, a range is given, as follows: 

“Sow indoors xx to xx weeks before last frost.” 

This may seem like the seed supplier is giving you a bit of a choice, but there is actually a hidden meaning behind the use of two dates. 

If you sow your seeds inside your home where warm temperatures are the norm, the lesser of the two dates will give the best results (i.e. if the packet indicates 6 to 8 weeks, choose 6). 

If you sow in a greenhouse, where lower night temperatures are likely, choose the greater of the two dates. 

And there you go! All you have to do is remember to apply the information!

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

1 comment on “Understanding Sowing Dates on Seed Packs

  1. One of the advantages of a mild climate is that we can sow just about anything directly into the garden. I only start a few seedlings inside, and only to protect them from snails.

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