Garden Timeline: When to Plant in Zone 9b

If you are trying to figure out when to plant in zone 9b for your vegetable garden, you’ve come to the right spot! I will share some resources I have found helpful, as well as some specifics for when I plant in my zone 9b garden.

I am currently gardening on the north end of the Phoenix metro area. We have a moderately sized raised bed garden in our backyard, and we do our best to capitalize on the space, and grow as much as possible for as long as possible. Learning how to time my planting has made a big difference in the productivity of our garden.

When it comes to figuring out timing for when to plant in zone 9b, two great resources I’ve used are:

• Planting guide from Native Seeds SEARCH
• Vegetable planting calendar from University of Arizona

I’ve also gotten a lot of help, tips and tricks from several other gardeners local to the Phoenix area. One such reference is Angela from Growing in the Garden. She has a great website full of resources, and an active Instagram feed as well.

While I can share guidelines, and what works well for our garden, a lot of the ideal growing conditions will still depend on your specific growing space. For example, we have a lot of shade in our yard, and our garden tends to be in partial shade on and off throughout the day. Which is great during the hot summer! But, I have found that for many things it means longer growing periods before I can harvest. I have had to learn to be a little more patient than the exact numbers given on the backs of the seed packets. But as I’ve learned I’ve been able to adjust when and what I plant to optimize what works best for us in our garden.

I hope you find some useful information here that will help you along in your own gardening journey!

Consider Starting Seeds Indoors

One trick that I have found invaluable, is starting seeds indoors – both for my spring garden as well as my fall garden. This allows me to get around some of our hottest temps, and extend my growing season by a few months! If you’re curious about starting seeds indoors, check out my How-To article. The timelines I share below are primarily focused on when to start seeds indoors and when to transplant.

Because of the hot summers here in the Phoenix area, we end up with a short spring growing season. It is shortened by the summer temps rising too high for plants to produce well. (Or survive at all, depending on the variety.) Getting a jump start by starting seedlings early helps me extend my spring growing season. In addition, winters and early spring are cold, and not ideal for germinating seeds directly in the ground. But once seedlings are started, there are many varieties that will grow really well in the cool weather. Early spring is the BEST time of year for lettuce, kale, chard, collards, radishes, broccoli, peas… The list goes on!

I also start seeds indoors to get an early start on our second fall growing season. When the temps “drop” to about 100F, that is the time to get started with new fall seed starts. If I were to direct sow new seeds outside, they would whither and fade away due to the still-hot temps. Instead, if I start these seeds indoors, by the time the temps drop to good growing weather (70s and 80s), I have well established seedlings to transplant. Leveraging this jump start, I can get productive growth from these plants for months!

Calendar Guide to Plant in Zone 9b

These recommendations by month assume some average temperatures, as noted. If you are experiencing different weather, adjust accordingly. This is the timing that I have so far found to work best in our garden. In pretty much every case there is some flexibility to start things a few weeks earlier or later, as you will notice when looking at planting ranges in other calendars.

Guidelines by Variety for when to Plant in Zone 9b

Leafy Greens

I typically grow my leafy greens and brassicas during the fall/winter growing season. This gives me the longest period to grow and harvest these wonderful veggies. This is also during a time when our garden is relatively pest free, so it is a much more carefree time to garden. As noted, some of these varieties will grow well into the spring. In some cases (like with Kale and Swiss Chard), I may start a second set of seedlings in early spring to plant out in March/April, and get a second round of leafy green harvest later in the spring. The more delicate greens like lettuce, spinach, and arugula will all bolt as soon as the temps hit the 80s.

Lettuce and Spinach

• Start seeds indoors for lettuce in the fall as soon as temps start to hover around 100F, typically in late August. Transplant 6-8 weeks later, once day time temps are consistently in the 80s, typically towards the end of October.
• You can follow the same plan above for Spinach. I have also had good success direct sowing Spinach in the garden along with the Arugula, when the temps are consistently in the 70s to 80s in the late fall or early spring.

Arugula

• Directly sow seeds in the garden in late fall or early spring, when the temps are consistently in the 70s to 80s, typically around November or late January.
• I have yet to try starting arugula seeds indoors (you need a lot of plants to get much harvest so direct sowing is easiest). But I would time it with the lettuce and spinach if you were to test it out 🙂

Brassicas like Kale, Collards & Broccoli

• Start seeds indoors for brassicas in the fall as soon as temps start to hover around 100F, typically in late August.
• Transplant 6-8 weeks later, once day time temps are consistently in the 80s, typically towards the end of October.
• These varieties are cold hardy and will grow well through the winter without any harm from frost.
• Kale and collards will also grow well into the late spring.
• In fact, kale will grow all summer if protected from the hot summer sun. It is susceptible to aphids as the weather warms, so if you don’t want to deal with those pests your best bet is to just pull it out when they become too much of a problem. I’ve tried spraying with neem oil consistently to keep the aphid problem low, but if it is a bad season for them it’s not usually worth it for me to try and keep the kale growing.

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Swiss Chard

• Grow swiss chard with the same timing as the brassicas above. It is also cold hardy and will not be harmed from frost.
• Swiss chard also lasts pretty long into the spring for us – it is usually one of the last leafy veggies we pull out. The flavor gets more bitter as the temperatures warm, so you may prefer it as a cooler season green, but test it out and see what you like!

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Fruiting Varieties

When it comes to the fruiting varieties like tomatoes, peppers, chiles, eggplants, cucumbers, squash, etc – they enjoy warmer weather and will last into the early summer. If well watered and protected from the hottest summer sun, many of these will continue growing through the summer, although they typically stop producing fruit during the hottest time. But, if they survive the summer, they will produce amazing bumper crops to harvest in the late summer and fall! It is worth it to try and keep these plants growing through the summer, as often the fall harvest is even more bountiful than the spring harvest.

Tomatoes, Peppers, and Chiles

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• Start seeds indoors for tomatoes and peppers in early to mid December. These you will likely need to plant up twice before transplanting to the garden. The tomatoes especially grow pretty quickly, but the bigger the transplants you have the more productive the spring harvest!
• Transplant tomatoes in mid February. Valentine’s day is a good guideline, as we don’t see any frost after this point in the season.
• I usually wait a few more weeks to transplant the peppers and chiles, as they like a little warmer weather. Aim for planting when the day time highs are consistently in the 70s. This usually happens in early to mid March.
• *You have a second growing season for these varieties – you can plant out transplants during monsoon season, so typically in July/August. To have transplants ready to plant in July, you would want to start from seed at the beginning of May.

Eggplants, Cucumbers, Summer Squash

• Start seeds for eggplants and cucumbers in mid February. You can wait until you have planted out your tomatoes, if you are tight on space and need those to be off your grow station to make room for more seedling starts.
• Transplant eggplants and cucumbers once your day time highs are getting into the 80s much of the time. This is typically early to mid April, about a month after you have planted out the peppers and chiles.
• In my experience the squash starts will grow faster than the cucumbers and tomatoes, so I typically plant them into the garden a few weeks sooner – end of March as a ballpark.
• *You also have a second growing season for summer squash – follow the same instructions as above for tomatoes/peppers/chiles.

Notes on a few other varieties…

Peas

• Directly sow seeds in the garden in early January.
• Pro tip I recently discovered for peas – plant them really dense! a row of 3-5 plants under a trellis, repeated every 2-3 inches the length of the trellis.

Rooted Veggies like Carrots, Radishes, and Beets

• Directly sow seeds in the garden in late fall, once day time temps are consistently in the 80s. This is typically at some point towards the end of October.
• You can also start beet seeds indoors in the fall at the same time you would start the brassicas.
• Transplant 6-8 weeks later, once day time temps are consistently in the 80s, typically at some point in October. You can see that if you have transplants started, you plant those out about the time you would direct sow the seeds, giving you a 1-2 month jump start on your growing season!

So there you have it! This is by no means an exhaustive list, but is a starting point for the vegetable varieties we have grown, and what has worked well as a timeline for us to plant in zone 9b. I hope you’ve gleaned some helpful nuggets! I wish you luck on your gardening journey 🙂