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When to Start Seeds Indoors: A Seed-Starting Guide for Low-Desert Vegetables

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

To help you know when to start the seeds inside, I’ve included a seed-starting guide for low-desert Arizona gardeners. This chart (at the end of the article) includes dates to begin sowing seeds indoors so they will be ready for transplanting at the right time.

If you aren’t sure how to start seeds indoors, head over to this article that shares 10 steps for successfully starting seeds indoors


Disclaimer: this post contains affiliate links. See my disclosure policy for more information.


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.


6 Tips for Growing Vegetables from Seed in Arizona


1. Sometimes it is best 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 you are 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 thatplants grown from seeds can be planted at the optimal planting time for your location. Planting at the correct time is crucial for success. 

Wondering which seeds to use? I link to my favorite seeds for many of the vegetables. Just click on the name of most of the vegetable to go to the seeds. 

Seed Storage & Organization Tips

2. Other times it is best 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 give you more predictable results than starting from seed.
  • Planting transplants gives you harvest sooner.
  • Transplants are also more resistant to damage from pests and insects than tiny seedlings. 
When to start seeds indoors

3. Learn which crops need to be direct sown 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. Learn which seeds can be sown indoors and transplanted 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:


5. Start seeds indoors at the right time in Arizona

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 into 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. Expose them to a little bit more sunlight each day for a few days. Plants that are “hardened off” correctly adjust better when planted out in the garden.


Gardener's Gift Guide: Garden Favorites​

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. 


If this post about when to start seeds in the low desert of Arizona was helpful, please share it:


Kylene

Tuesday 1st of June 2021

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?

Angela Judd

Tuesday 1st of June 2021

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!

Karlynsia

Thursday 10th of September 2020

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.

Karlynsia

Thursday 10th of September 2020

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.

Melinda Jones

Wednesday 2nd of September 2020

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!

Angela Judd

Wednesday 2nd of September 2020

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.

Hydee

Thursday 23rd of July 2020

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!

Angela Judd

Thursday 23rd of July 2020

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.