9+ Vegetables That Should Be Started Indoors

In the sphere of vegetable growing, some vegetables are fast growers, others take much longer to mature, and some like it considerably warmer than others.  In this blog we’re going to pin down which are the best vegetables to start indoors because of the limiting factors of our central Alberta climate.

Not all vegetables are created equal and not all climates are created equal.  No kidding.  Our Edmonton area boasts of an average of 105 – 115 frost free days, depending on how cranky Mother Nature is in any given year.  Our grandfather, John Wallish, banked on having no more frost from June 9 onward.  We think that’s the day he took of his long underwear!

When To Start Vegetable Seeds Indoors

Take a quick look at our Ultimate Vegetable Timing Chart – this blog will be an addendum to that chart, with specifics about starting garden plants indoors. Each vegetable listed in this chart has information regarding the best time to seed, unique growing tips, common diseases and pests, and their companions and enemies.
In the ‘Timing’ column you will find those that will perform the best as transplants because they have a relatively long maturation time.

Vegetables That Should Be Started Indoors

Broccoli, Cabbage, Cauliflower, Kohlrabi (Cole Crops)

These plants can be started indoors about the 2nd – 3rd week in April so they are ready for planting around the 3rd week of May.  These young plants can take the cool nights & early mornings, but avoid frost.  If it’s looking like there may be a frost, be sure to cover them up.

Related:  3+ Essential Tips For Growing Vegetables And Flowers Indoors


Being tropical in origin, are extremely sensitive to cool weather making them one of the best vegetables to start indoors. These may be started in small 3-4 inch pots around the 1st or 2nd week in May so they are ready to outdoors in June.  We don’t recommend putting cucumbers outdoors until the first or second week of June. Be ready to upsize the pots if they get big. Again, be mindful of cool nights (below 8 C) or frost.  Cucumbers are very happy growing in greenhouses.

Related:  Growing Plants Indoors – Pitfalls to Avoid

Lettuce & Other Leaf Crops

Lettuce and leafy greens can be started indoors, but do well outdoors in successive seedings too. If you’d like to get a jump start on them, start them in the first few weeks of May.  Leaf crops are very fast growers. Be sure to give them plenty of room to grow and keep the temperatures cool in your indoor garden – they will stretch in high temperatures.

Peppers & Tomatoes

These tasty vegetables like it hot and they have a long maturation time. Start seeds indoors the 2nd or 3rd week in April – watch for stretching if the indoor temperatures are too hot.  Transplant seedlings from trays into larger pots when they are about 3 inches tall.  They will be ready to be transplanted in the outdoor garden by the last week in May or 1st week of June, when the threat of frost is diminishing significantly.


Looking at the Veggie Timing Chart, you may find it curious that corn is a long crop, taking up to the middle of August to mature; but yet it isn’t listed as a transplant candidate.  We don’t recommend that you seed corn indoors because it transplants extremely poorly.  We’ve always known this, but because some customers have requested transplants, we tested it and we found the corn stalks to be incredibly short (3.5 -4 feet) producing small cobs about 4 inches long.  We feel that transplanting corn just doesn’t work and the corn doesn’t thrive.  That is why we won’t grow them as vegetable starts in the greenhouse for purchase. Check out the chart for timing and seeding instructions for corn.

Related:  How To Take Care Of Indoor Plants

Looking for more details on seeding?  Be sure to check out our blog and video on seeding!

Feel free to reach out to us with any questions you have be it via emailvoicemail, or in person.  We are happy to help out wherever we can.

– by Sharon Wallish Murphy

About The Author

Sharon Wallish Murphy
Sharon grew up in the Wallish Greenhouse at the heels of her father, Charlie, who mentored her. Sharon’s passion is to share the love for growing and to empower others to find joy in their gardening journey, just like her dad.