This comprehensive guide covers over 100 flowers and plants. It will tell you exactly when to sow seeds indoors, all you need to know is your average last frost date. Let’s grow pretty things successfully!
When to Sow Seeds Indoors – Complete Chart to Over 100 Beautiful Flowers
It’s important to note that if you don’t see your flower choice on this list, it may not be included because it’s recommended to sow outside. Some flowers and plants just do better when started outdoors.
The example is the sunflower, which I did include because there are so many varieties of a sunflower. But generally, the original flower we think of will do better when started outside after your last frost date.
Please note there is an option below to request these charts below for easy reference.
1. Find your average last frost date
The first step is to find out your average last frost date. Farmer’s Almanac has about the best tool I’ve ever seen for this.
You type in your area, and it gives you the first and last frost date for the year so you can plan accordingly.
No worries if the date isn’t exact, it will be close enough to sow seeds indoors and have them ready in time. This tool hasn’t failed me yet!
2. Gather your supplies
Gathering your supplies before you start seeds indoors will save you unnecessary surprises!
The first year I started, I found myself frantically shopping to get things I didn’t realize I needed. It was almost a disaster!
You really don’t have to spend a ton of money. I’ll put an asterisk by the items I found I needed to successfully sow seeds indoors.
- Planting trays
- Small planter pots*
- Popsicle sticks or labels
- Saran-Wrap or plastic domes*
- Seed starting soil*
- Heating mat
- Tabletop growing light(s)*
- Oscillating fan*
- Light timer(s)
- Quality plant fertilizer*
I know it looks like a lot, but it really isn’t. This list is a bare-bones list. You could obviously purchase many more things like extra growing lights, tiers, or even mini-greenhouses or hoop houses.
These are the things I personally use every year.
If I tried skimping on these things, they only led to seed starting mistakes.
3. Sow 10-12 weeks before
There are other reasons a flower may not be on this list. They may be too invasive to be beneficial, they are on a different time frame list, or I forgot about it!
- Please do use the comment section below if you have a suggestion to add to any of these. I will gladly research it and add it to the indoor sowing guide if it belongs!
- Make sure you also research which seeds need to be cold/moist stratified as well. Seeds that need the stratification won’t grow for you if they miss the mimicking of winter.
My biggest tip to sow seeds indoors is to read the seed packet for planting instructions.
Any quality company will usually have everything you need to know about successful planting!
4. Sow 8-10 before
You may notice when you’re looking for a particular variety, there might be a couple of different names for one flower.
- This may be because they are truly slightly different. An example is the Cottage Pinks and Sweet William flowers. Both are of the genus Dianthus, but the species are different. This may cause them to have slightly different needs.
- Some people are also more familiar with one name over the other, so I sometimes tried to include both. 🙂
You’ll also notice there are perennials and annuals on these lists. Not sure of your growing zone? Check out the USDA Plant Hardiness Zone Map.
5. Sow 6-8 weeks before
As you can see, the 6-8 week time-frame is the most popular time to sow seeds indoors! As I learn of new beneficial and beautiful varieties, I’m sure I’ll be updating this section the most!
(I will continuously update this guide as I find more plants and flowers to include!)
- Another thing to note is some plants don’t like to have their roots interrupted for transplanting, so they are best started outdoors.
- Or, at the very least, sow them in biodegradable peat pots so the whole thing can be planted into the ground.
6. Sow 4-6 weeks before
Another option to consider when planning to sow seeds indoors is if they can be fall sown.
Sometimes this is the easier and more successful option and leaves you with more room for other varieties such as annuals.
I recommend placing a soil marker or small wire fencing around the seeds you may plant in the fall, though, as it’s so easy to forget where they are when spring comes!
I’ve also mistaken them as weeds and pulled them. I’ve learned to always mark my fall sown seeds!
7. Sow 2-4 weeks before
The list definitely gets shorter as we near the average last frost date!
- As with any plant on this list, I will often bring them outside during a warm day, in a sheltered area, to get them used to the elements.
- If they are sun-lovers, I begin my week of hardening off but bring them in at night if the nights are still cool.
I won’t plant them outside until it’s warm enough for them at night. I’ve also had to cover seedlings or bring pots in the garage for surprise frosts or cold nights.
It happens, it’s just a part of gardening, so prepare for that also.
And always prepare for a few losses because unfortunately, even with the best of planning, that can also happen.
I tried to create a comprehensive list of wildflowers, annuals, perennials, and a few plants in this indoor sowing guide. I genuinely hope it will help you take some of the guesswork out of it all as you sow seeds indoors.
It really is a fun, gratifying, money-saving thing to do. It can also be addicting, especially when you see a yard full of flowers that you grew from seed!
What other flowers or plants can be added to this guide? Please comment below and let me know your suggestions!
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