When to Start Seeds Indoors: A Seed-Starting Guide for Low-Desert Vegetables
Knowing which seeds to start indoors and when to start seeds indoors in Arizona can be confusing. In this article, you will learn which crops are best direct-sown with seeds in the garden and which crops can be started indoors to get a jump on the growing season.
I’ve included a seed-starting guide for low-desert Arizona gardeners to help you know when to start the seeds inside. This chart (at the end of the article) includes dates for beginning sowing seeds indoors so they will be ready for transplanting at the right time. Low desert includes elevations below 3500 ft in the Southwest, such as the Phoenix and Tucson metro areas.
If you are unsure how to start seeds indoors, this article shares 10 steps for successfully starting seeds indoors.
When you learn how to start seeds indoors and start them at the correct time, you can have the advantages of growing from seed combined with the advantages of adding transplants directly into your garden.
Article Index:
Tips for growing vegetables from seed in Arizona
- When to use seeds
- When to use transplants
- Crops that are best to direct-sow in the garden
- Which seeds to sow indoors and transplant outside in the low desert of Arizona
- When to start seeds indoors
- Harden off seedlings before transplanting them in your Arizona garden
6 Tips for Growing Vegetables from Seed in Arizona
1. When to use seeds
Starting garden vegetables from seed has several advantages. Seeds are often much less expensive than purchased transplants. There is also a greater variety of options when starting from seeds. When you grow from seed, you aren’t limited to planting what your local nursery or big box store has in stock.
Arguably, the biggest benefit is that plants grown from seeds can be planted at the optimal planting time for your location. Planting at the correct time is crucial for success.
Are you wondering which seeds to use? I have linked to my favorite seeds for many of the vegetables. Just click on the name of most of the vegetables to go to the seeds.
2. When to use transplants
Planting transplants in the garden has advantages as well.
- Long-season crops like tomatoes and peppers need the head start that planting a transplant provides.
- Transplants are convenient, easy to use, and yield more predictable results than starting from seed.
- Planting transplants give you a harvest sooner.
- Transplants are also more resistant to damage from pests and insects than tiny seedlings.
3. Crops that are best to direct-sow in the garden
Some crops do best when directly seeded into the garden rather than starting seeds indoors and planting transplants. The roots of these crops do best when left to grow undisturbed.
Best direct sown:
Crops like garlic and potatoes aren’t planted from seeds but from actual garlic cloves and sprouted potatoes, so they also do best when directly sown into the garden.
4. Which seeds to sow indoors and transplant outside in the low desert of Arizona
Vegetables with a long growing season are often started indoors and then transplanted outside for the best chance of success.
Here is a link to my favorite seed-starting supplies.
Long growing-season vegetables grown best from transplant:
Still, other seeds are slow to germinate and do best when started under optimal growing conditions inside, such as:
Although some crops have definite preferences about being sown in the garden or indoors, others will grow fine when planted either way.
Vegetables that can be started from seed or transplant include:
- Bok choy
- Broccoli
- Cabbage
- Cauliflower
- Chives
- Collard greens
- Kale
- Kohlrabi
- Leeks
- Lettuce
- Malabar spinach
- Mustard greens
- Okra
- Onions
- Roselle hibiscus
- Spinach
- Swiss chard
5. When to start seeds indoors
When you learn how to start seeds indoors in Arizona and start them at the correct time, you can have the advantages of growing from seed combined with the advantages of adding transplants directly into your garden at the best time.
Use the following chart to determine when to start seeds indoors for your low-desert Arizona garden so they will be ready to plant at the correct time for your growing season.
| Vegetable (days from seed to transplant) | Planting Dates |
|---|---|
| Armenian cucumber* (3-4 weeks) | Start seeds indoors: January 15 – June 15 Plant outside: February 15 – July 15 *does best directly sown in garden |
| Artichoke (8 weeks) | Start seeds indoors: October 15 – January 15 Plant seeds outside: November – Dec. 15th Plant transplants outside: January 15 – March |
| Arugula (4-6 weeks) | Start seeds indoors: September – January Plant seeds outside: August 15 – January Plant transplants outside: October – February |
| Asparagus (10-12 weeks) | Start seeds indoors: August – November Plant outside: November – February 15 |
| Beets* (4-6 weeks) | Start seeds indoors: August – January Plant outside: September 15 – February 15 *does best directly sown in garden |
| Bok Choy (4-6 weeks) | Start seeds indoors: August 15 – January Plant seeds outside: August 15 – January Plant transplants outside: October – February |
| Broccoli (4-6 weeks) | Start seeds indoors: August 15 – December Plant seeds outside: August 15 – December Plant transplants outside: October – January |
| Brussels sprouts (4-6 weeks) | Start seeds indoors: July 15 – October Plant seeds outside: August 15 – November Plant transplants outside: September – November |
| Cabbage (4-6 weeks) | Start seeds indoors: August 15 – December Plant seeds outside: August 15 – December Plant transplants outside: October – January |
| Celery (10-12 weeks) | Start seeds indoors: July – September Plant seeds outside: August 15 – December Plant transplants outside: September 15 – December |
| Vegetable (days from seed to transplant) | Planting Dates |
|---|---|
| Cantaloupe* (3-4 weeks) | Start seeds indoors: January 15 – June Plant outside: February 15 – July *does best directly sown |
| Cucamelon (3-4 weeks) | Start seeds indoors: January – March July 15 – August Plant transplants outside: February 15 – April August 15 – September |
| Cucumber* (3-4 weeks) | Start seeds indoors: January – March July 15 – August Plant outside: February 15 – April August 15 – September *does best directly sown |
| Eggplant (8-10 weeks) | Start seeds indoors: December 15 – January May 1 – June Plant transplants outside: March July 15 – August 15 |
| Ground cherry (6-8 weeks) | Start seeds indoors: December 15 – January May 15 – June Plant transplants outside: February 15 – March July 15 – August 15 |
| Kale (4-6 weeks) | Start seeds indoors: August 15 – December Plant seeds outside: August 15 – December Plant transplants outside: October – January |
| Kohlrabi (4-6 weeks) | Start seeds indoors: September 15 – December Plant seeds outside: August 15 – November Plant transplants outside: October 15 – January |
| Leeks (8-12 weeks) | Start seeds indoors: August 15 – November Plant seeds outside: August 15 – October 15 Plant transplants outside: January |
| Lettuce (4-5 weeks) | Start seeds indoors: August 15 – January 15 Plant seeds outside: August 15 – January Plant transplants outside: September 15 – Feb. 15 |
| Luffa* (3-4 weeks) | Start seeds indoors: January 15 – March 15 July 15 – August 15 Plant outside: Feb 15 – April 15 August 15 – September 15 *does best directly sown |
| Malabar spinach (4-6 weeks) | Start seeds indoors: January 15 – April Plant outside: March – May |
| Mustard (4-6 weeks) | Start seeds indoors: September – January Plant seeds outside: August 15 – January Plant transplants outside: October – February |
| Vegetable (days from seed to transplant) | Planting Dates |
|---|---|
| Onions (8-10 weeks) | Start seeds indoors: October – December 15 Plant seeds outside: October – November Plant transplants outside: December – February 15 |
| Peppers (8 weeks) | Start seeds indoors: December 15 – January May Plant transplants outside: February 15 – March July |
| Pumpkin* (3-4 weeks) | Start seeds indoors: February June – July 15 Plant outside: March July – August 15 *does best directly sown |
| Roselle hibiscus (4-6 weeks) | Start seeds indoors: February – April Plant outside: March 15 – May |
| Spinach (4-6 weeks) | Start seeds indoors: August – January Plant outside: September – February 15 *does best directly sown in garden |
| Swiss chard(4-6 weeks) | Start seeds indoors: August 15 – January Plant seeds outside: August 15 – January Plant transplants outside: September 15 – Feb. 15 |
| Summer squash* (3-4 weeks) | Start seeds indoors: January 15 – March 15 July 15 – August 15 Plant outside: February 15 – April 15 August 15 – September 15 *does best directly sown |
| Tomatillo (6-8 weeks) | Start seeds indoors: December 15 – January May 15 – June Plant transplants outside: February 15 – March July 15 – August 15 *Plant 2 to ensure pollination |
| Tomatoes (6-8 weeks) | Start seeds indoors: December 15 – January May 15 – June Plant transplants outside: February 15 – March July 15 – August 15 |
| Winter squash* (3-4 weeks) | Start seeds indoors: February June – July 15 Plant outside: March July – August 15 *does best directly sown |
6. Harden off seedlings before transplanting them in your Arizona garden
You’ve worked so hard to get your seedlings ready to plant in the garden. Don’t forget this last step. It is very important to “harden off” seedlings before planting them in the garden. This allows them to adjust to the different conditions outside gradually rather than all at once.
To “harden off” seedlings, begin by taking them outside to a shady location during the day and bringing them inside at night. For a few days, expose them to a little bit more sunlight each day. Plants that are “hardened off” correctly adjust better when planted out in the garden.
Would you like the low-desert planting dates for vegetables, herbs, and flowers in a convenient calendar?
*PLANTING GUIDE: Each month has a planting guide (letter boards) for the vegetables, herbs, and flowers to plant in the low desert of Arizona.
*HARVEST GUIDE: Harvest guides are the harvest photos of what it is possible to harvest each month.
Angela, this is incredibly helpful! I was really unsure about how long many of the plants should grow indoors and hence when they should be started in order to plant outside at the correct time. Thanks for the chart!
So glad it was helpful. I found myself wondering and figured others had questions about it as well. Thanks for letting me know. Best of luck with your garden.
Thank you for such a helpful list of when to plant seeds. It can be confusing! I have a question on starting the seeds. I have a large light stand in my garage and am hoping to start the seeds out there but am worried about it still being too hot in September. What are the best temperatures to start the seeds in? P.S. I love your calendar!
So glad it’s helpful. It is too hot in the garage during the summer in Arizona to start the seeds. Indoor temps are much better and some crops like lettuce and onions prefer even cooler weather (60-70F) before sprouting.
Thank you so much! I wish I would have read this before I planted my seeds in my seed trays. I planted cabbage, kale, and collards so I will follow these directions once they start sprouting. I have them in my Arizona room, but at night I’ll move them inside and then in the mornings I’ll water and put them back in the Arizona room. I know I can do this lol.
Thank you so much! I wish I would have read this before I planted my seeds in my seed trays. I planted cabbage, kale, and collards so I will follow these directions once they start sprouting. I have them in my Arizona room, but at night I’ll move them inside and then in the mornings I’ll water and put them back in the Arizona room. I know I can do this lol.
Hi Angela,
Thank you so much for all of this great info! We don’t get back from a trip until July 10th. Do you think it would be too late to start tomatoes then?
It will probably be fine. I’m having the same issue with summer seed starting this year as well. Luckily Arizona Worm Farm said that they will have tomato starts ready to go in late July or August, so that is also an option. Best of luck to you and enjoy your vacation!
I will plant my seeds outside in the next week. Should I put burlap on top of the soil and then add mulch on top of the burlap or mulch first and then burlap?
Generally you use burlap in place of mulch. If you’re going to use mulch, you don’t need to use burlap.