March Planting Guide By Zone

Written By Lara Wadsworth

March is the month that most people equate to spring, or at least the promise of spring. Temperatures are steadily warming up (whatever that means for you), and while the northern zones are likely to experience lots of cold and even snow in the month of March, the gardening season is fast approaching. March is prime planting time for most zones to ensure a long, fruitful growing season.

What Hardiness Zone Am I In?

In 2023 the USDA came out with an updated zone hardiness map that was created using a greater set of data for a more accurate representation. In a nutshell, the USDA Zone Hardiness map assigns a number to each region of the USA based on the average winter low temperature that the area experiences each year. Therefore, this number is often used to determine what seeds you can grow where because it is consistently correlated with what plants can be grown in a region. So, if you determine what growing zone you are in, you can find out what types of seeds you can grow, when to start your seeds indoors, and other similar information. Visit the USDA's website and put in your zip code to discover what zone you are working with! For the sake of simplicity, I will ignore the subclasses of ‘a’ and ‘b’ as they won’t make a huge difference when it comes to seed starting.

Last Frost Dates

Knowing your zone is a great place to start, but what is even more important to seed starting is being aware of when your last frost date is and how many weeks away it is. You can easily find out what the typical last frost date is for your area by contacting your local extension office or using the Climate.gov interactive map tool. Then, looking at the calendar, count backward in weeks from that day to plan your earliest planting dates. On most seed packets, if a seed needs to be started indoors, it will say something like “Start seeds indoors 6-8 weeks ahead of time.” When that time frame comes for you, you know what to do! It can be helpful to have your plan settled ahead of time and then write on a calendar when what seeds need to be started and when. That is why I have also listed the typical weeks to planting time frame under each zone for the month of March, just in case your particular area is different. Use these two numbers and any local recommendations or resources you have to determine your planting schedule.

Basic Seed Starting Supplies

Getting the right supplies to start seeds indoors can make or break your spring garden. I recommend getting seed starting trays or cells of your choice (I like using the 12-cell seed starting set). You will also want to get a seed-starting soil mix like coconut coir and perlite. Avoid using garden soil, as it’s often unsuitable for indoor seed starting. While those are the basics, light and heat are often overlooked. Placing seed trays by a window might provide light, but it can also make the seeds too cold, and windowsills usually don’t offer enough light for delicate seedlings. Using heating mats and grow lights solves both problems! When I finally upgraded my setup to include adequate heat and light, I saw a major difference in the vigor of my seedlings. Grow tents are also a fantastic tool.

Zone 3

Zone three represents the coldest regions in the U.S. and includes areas in Alaska,Montana, North Dakota, Minnesota, Maine, and Vermont. In March, these regions are still experiencing winter, and temperatures are unlikely to rise above freezing much, if at all.

• Approximate Weeks Until Last Frost: 10-12
• Last Frost Date Window: Mid May to early June
• Seeds to Start Indoors: Cool-season flowers like pansies and petunias (if you haven’t already). Cool-season crops that can be planted out before the last frost include hardy vegetables like celery, radicchio, and endive. Early Brassicas like broccoli, rhubarb and cool-season herbs like parsley, chives, and mint can also be planted indoors during the month of March.
• Seeds to Sow or Transplant Outdoors: The ground is still too frozen to plant outdoors.

Zone 4

Zone 4 covers regions such as parts of Alaska, Montana, North Dakota, South Dakota, Michigan, Wisconsin, New York, and Maine. These areas experience extreme winters, and March brings a few welcome days above freezing. Yet, this is a critical time to start some cool-season vegetables indoors, as they need a good chunk of time to develop before being planted outdoors.

• Approximate Weeks Until Last Frost: 8-10
• Last Frost Date Window: Mid-April to Late-May
• Seeds to Start Indoors: Warm-season flowers like marigolds, nightshades like tomatoes and eggplants, Brassicas like broccoli, cabbage, and Brussels sprouts, and Alliums like onions and leeks. Asparagus seeds should also be started about now.
• Seeds to Sow or Transplant Outdoors: It is likely too cold for outdoor sowing unless you have a heated system or are using season-extending tools like a greenhouse, cloche, or floating row covers.

Zone 5

In Zone 5, which includes parts of Alaska, Idaho, Montana, Wyoming, Utah, Colorado, Nebraska, South Dakota, Indiana, Illinois, Wisconsin, Michigan, New York, Vermont, New Hampshire, and Maine. By March, these areas are on their way to a good thaw, but there are still plenty of days below freezing, which makes it dangerous for most tender plants to be outside. Providing proper protection can make it possible to grow some cold-hardy crops, but unless a seed needs cold stratification, it shouldn’t be planted outside yet.

• Approximate Weeks Until Last Frost: 6-9
• Last Frost Date Window: Mid-April to Late-May
• Seeds to Start Indoors: Brassicas, such as cauliflower; Crucifers, such as collard greens; Nightshades, like tomatoes; Cucurbits, such as cucumber, gourds, and melon; and any cool-season crops, like spinach and endives, that you want to give a head start.
• Seeds to Sow or Transplant Outdoors: If you have access to row covers or cold frames, you can start directly sowing cold hardy vegetables such as spinach and lettuce. March in zone 5 is the perfect time to broadcast sow wildflower seeds outdoors, as the cold period will improve germination rates once the frost has passed.

Zone 6

Zone six includes parts of Washington, Oregon, Nevada, Idaho, Utah, Arizona, New Mexico, Colorado, Kansas, Nebraska, Missouri, Kentucky, Illinois, Indiana, Michigan, Ohio, West Virginia, Maryland, Pennsylvania, New York, New Jersey, Connecticut, Rhode Island, Massachusetts, and New Hampshire. March is one of those major transition months for Zone 6. Depending on your location, you could have 50-60 F weather or snow! That’s why it is best to keep most plants indoors this time of year, but the hardiest varieties can be planted outside if March is looking more temperate for you or if you are using protective covers like winter grow tents or cloches.

• Approximate Weeks Until Last Frost: 5-8
• Last Frost Date Window: April to Mid-May
• Seeds to Start Indoors: Frost-hardy greens like chard and kale; Crucifers like artichoke; Kohlrabi, Okra; Cucurbits like pumpkin, summer squash, winter squash, watermelon, and other slow-growing annuals that need a good head start on spring.
• Seeds to Sow or Transplant Outdoors: Cool-season crops like spinach, endives, celery root, beets, and spring radishes, as well as umbels such as parsnip, arugula, and turnip, can be directly sown with minimal protection. March in zone 6 is also the best time to sow a spring cover crop if you’re not using all of your garden this year or won’t be growing anything until you transplant your summer vegetables like tomatoes, squash, and peppers.

Zone 7

In Zone 7, which includes areas like Washington, Oregon, Idaho, Nevada, Utah, Arizona, New Mexico, Texas, Oklahoma, Kansas, Arkansas, Missouri, Tennessee, Kentucky, North Carolina, Virginia, Maryland, Delaware, and New Jersey. These areas still experience winters, but by March, things are well on their way to thawing out. The last risk of frost is early April, so March will have lots of back and forth above and below freezing, with nights being the most dangerous time for tender plants to be outdoors. If you have started other seeds indoors ahead of time in January or February, late March is the time to start hardening them off slowly in preparation for being transplanted into the garden. Just be sure to keep a close eye on the changing temperatures.

• Approximate Weeks Until Last Frost: 2-5
• Last Frost Date Window: Mid-March to April
• Seeds to Start Indoors: Summer vegetables including tomatoes, peppers, eggplant, and Cucurbits like squash, melons, cucumber, and pumpkins, as well as warm-season herbs such as basil.
• Seeds to Sow or Transplant Outdoors: Cool season crops such as celery, endives, and spinach. Root vegetables such as beets, parsnips, carrots, rutabaga, and potatoes. Whatever you plant, it must be able to handle light frosts, as this is still very possible in March for zone 7.

Zone 8

Zone 8, which includes parts of Washington, Oregon, California, Nevada, Arizona, New Mexico, Texas, Arkansas, Louisiana, Mississippi, Alabama, Georgia, South Carolina, and North Carolina, sees mild winters; therefore, March brings little to no frosts. The ground is almost completely thawed and will be quite workable in general. This is the time of spring when you can plant out most plants while watching the weather to provide protection if a frost is imminent.

• Approximate Weeks Until Last Frost: 0-2
• Last Frost Date Window: March to Mid-April
• Seeds to Start Indoors: Any seeds you want to give an optional headstart to or begin in a more controlled environment, such as Melons, Herbs, flowers, and anything else that could quickly be transplanted outdoors.
• Seeds to Sow or Transplant Outdoors: Legumes such as peas, beans, and cover crops like vetch. Cool-season crops, such as spinach, spring radishes, and kale can handle a light frost and will mature quickly.

Zone 9

Zone 9, including parts of Washington, Oregon, California, Arizona, Texas, Louisiana, Mississippi, Alabama, Florida, and Georgia enjoys mild winters. These areas might get frosts sometime in January, but all risk of frost has passed by late February. With row covers, these areas can benefit from year-round gardening!

• Approximate Weeks Until Last Frost: 0 Plant this month!
• Last Frost Date Window: February to Mid-March
• Seeds to Start Indoors: It is unnecessary to indoor sow any plant in March in zone 9 unless you want the benefit of a more controlled seed-starting environment.
• Seeds to Sow or Transplant Outdoors: By March, you can plant anything outdoors. The frost has passed, but the intense heat of the summer is not yet here, making this month the beginning of one of the best gardening months (in terms of weather) for these regions.

Zone 10

Zone 10, which includes parts of California, Arizona, Texas, Louisiana, and Southern Florida experiences very mild winters. While most of the growing zones in the United States plan their gardens around winter weather, zone 10 gardeners have to plan around intense summer heat. You can largely garden year-round in these regions but should prioritize cool-season crops in the early spring and winter months, as these varieties will not survive the heat of June-August. Consider growing heat-tolerant varieties for greater success.

• Approximate Weeks Until Last Frost: 0 Plant now!
• Last Frost Date Window: Does not typically experience frosts.
• Seeds to Start Indoors: During March, it is unnecessary to plant seeds indoors in zone 10 unless you want a controlled environment.
• Seeds to Sow or Transplant Outdoors: Focus on planting cool-season crops that cannot handle intense heat, such as spinach, carrots, and arugula; Brassicas, such as kale and turnips. March is a great time to fully plant your garden. Consider adding the ability to hang shade cloth in your garden for the hot summer months. This will allow you to grow cool-season vegetables for a few weeks longer than you otherwise could (leafy greens tend to bolt/flower and become bitter).

No matter what zone you are in, March is the time to get excited about gardening. Every zone in the US has some amazing vegetables, herbs, and flowers they can start growing to get a jump start on the growing season this year. I am in zone 6, and March is the month that I finally get to start taking some tangible action steps on my dream garden. By using your zone’s frost date to guide your planting, you can ensure that your seeds will grow into strong, healthy plants at the right time. March is the perfect month to plan ahead and start seeds that will flourish over the coming months!

Lara Wadsworth, True Leaf Market Writer

I am a native of Southwestern Michigan, where I also reside, and I love all things plants! I got a Bachelor's Degree in Horticulture and found the first work-from-home job I could get. Now, I spend my days writing for TLM, playing with my dog, eating delicious food with my husband, and plotting my next landscape or gardening move. I believe everyone should get down and dirty in the soil now and then. Happy Gardening!