Most amateur gardeners have an intuitive sense about what grows well in their region, but not everyone knows the tricks to a successful harvest. Whether you’re just starting out or have been at it for years, “when to plant” your vegetable garden is a kind of scientific method. This article will help growers of all levels get the timing right for planting in spring for a summer harvest.
Get to Know Your Zone
Knowing your specific growing zone is paramount for getting your planting cycle just right. Find a zone map and search your exact location. Remember, some states are large, and may have a few zones and even sub-zones to navigate. For example, the northern-most part of Alaska is zone 1 but not all of the state is tundra—a very small part of the southern coastal area is actually zone 5. Likewise, the southern-most coastal area of Alabama is zone 9, making it a very different growing region than land-locked northern Alabama, which is a cooler zone 7. The southern tips of Florida and Texas, as well as Puerto Rico and Hawaii range from zone 10-13.
When to Start Seeds Indoors
Proper gardening usually requires that some seeds be started indoors or bought semi-matured from a nursery. For most crops, start seeds indoors about 6–8 weeks before your last spring frost date. This gives the plants plenty of time to grow healthy enough to survive transplanting into the garden.
This isn’t the case for all growing zones. Only those that experience a risk of frost or variable temperatures should follow the frost date guidelines. Some veggies do better when planted directly in either warm or cooler ground, while others need to be mature seedlings with no risk of frost before they go into the dirt. While some may sprout seedlings and even grow into mature plants, their yield potential will depend on their temperature requirements.
Frost Variations Per Zone
Zone 3 is nestled along the northern border and is the coldest mainland garden zone in the United States, also meaning the shortest growing season. While temperatures can fluctuate as winter turns to spring, the last frost date tends to be around May 15, while the first frost date comes around September 15. Alaska is the only state with zones 1 and 2 which will experience an even shorter season between frost dates.
As you travel south, warmer zones will have more time between frost dates, but it doesn’t always follow an exact method. For example, frost can still occur in zone 4 up until June, but has an overall warmer seasonal temperature than zone 3. Generally speaking, the warmer the climate, the longer the growing season, but dates will vary according to weather patterns as well. Getting to know your first and last frost dates of your zone will increase the production rate in your garden.
Cool Season/Early Spring Crops
The lettuce family can be planted directly into the ground in early spring as these leafy plants can withstand a small amount of frost. If you want to get a head start on a short season, start seeds indoors 2-3 weeks before planting, but remember that lettuce seeds won’t germinate in soil that is too warm (80 degrees or more) so keep them in a cool section of your home. Once planted, they take around two months until they are ready to be picked. Arugula grows quicker, usually in just a few weeks.
Snow peas got their name for a reason, as these climbers can take the cold! Start indoors like lettuce and plant seedlings as soon as the soil can be worked, making sure to give them something to grow up or along. They should be ready in 6-8 weeks and are best when picked young.
Spinach is another hardy green that can be planted in early spring, fall, and even winter in some zones that don’t get experience harsh cold. It has similar growing needs to the lettuce family.
Root vegetables don’t transplant well, so it’s best to sow them directly into the ground at the appropriate time. Carrots can be planted early, as can beets (late March or early April for Zone 3). Pick beets before it gets too warm.
Radishes will grow quickly and are a good beginner vegetable because of their success rate. Plant in the very early spring when temperatures are cool and get ready for a quick harvest in 3-5 weeks. For continuous production, plant a row of radish every two weeks throughout the spring and harvest the roots while they’re still small.
Garlic, onions, and potatoes are cool weather crops that can be planted in early spring or late fall and sown directly into the ground as well.
Members of the cabbage family, including: cauliflower, cabbage, kale, Brussels sprouts, and broccoli are all excellent early spring veggies. Most of these crops can be started indoors to get a head start, but are also able to withstand direct planting.
Kale is hardy and can endure frost, especially once established towards the end of the season. Sow directly into the ground as soon as the soil temperature reaches 40 degrees.
Broccoli does best when started indoors (4-6 weeks) and then put into the garden 4-6 weeks before the last spring frost. The plants are frost-tolerant, and in zones 6 and 7, autumn broccoli plants can often survive the winter and produce a second harvest.
Cauliflower is best grown in temperate zones and likes consistently cooler weather in the 60’s—so no risk of frost on either end, but also, any warmer and it will grow in “buttons”, rather than a single large head. Start indoors or sow directly into the ground depending on your zone.
Warm Season/Frost-intolerant Vegetables
Tomatoes, peppers, zucchini, cucumber, green beans, and eggplant must be started from seed indoors early to get a head start on the growing season. Zone 3 and 4 should start them as soon as March or April so that they can be planted in time for a summer harvest. Tomatoes and peppers need at least 6-8 weeks inside before going in the ground, whereas cucumbers and zucchini need 3-4 weeks before transplanting. None of these crops can endure cold weather, so plant them well after any signs of frost have gone.
Starting seeds indoors before your last frost date will give you a jump start on the growing season and knowing when to transplant seedlings outdoors will help to maximize your harvest. Use a planting calendar if you want to organize different types of crops, and remember that soil and light restrictions are important as well. With a little hindsight you can have a variety of crops to harvest through the summer, no matter how long your growing season is.