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.

Low desert includes elevations below 3500 ft in the Southwest, such as the Phoenix and Tucson metro areas.

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

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Disclaimer: This post may contain affiliate links. See my disclosure policy for more information.

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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.

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6 Tips for Growing Vegetables from Seed in Arizona

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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 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. 

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 vegetables to go to the seeds. 

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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 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. 

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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:

• Beans
• Beets
• Carrots
• Corn
• Cucumbers
• Melons
• Parsnips
• Peas
• Pumpkin
• Radishes
• Rutabaga
• Squash
• Turnips

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. 

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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.

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

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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

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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.

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