USDA Zone 12: Where is it? What to Plant? Tips to Success
When it comes to establishing a vibrant and successful home garden, getting familiar with your USDA hardiness zone is essential.
And for gardeners living in zone 12, there is plenty to learn. This zone consists of some of the hottest temperatures in the US – so hot that it does not appear in the continental US, even in the southernmost states. Zone 12 is warm all year round, with minimal typical winter weather and no frosts.
Keep reading for more information on hardiness zone 12, including temperature ranges, growing schedules, and growing options for the people who reside there.
What is USDA Zone 12?
USDA Zone 12 is one of 13 plant hardiness zones, also called growing zones, as established by the United States Department of Agriculture and detailed on the USDA Plant Hardiness Zone map. These zones are defined by their minimum average winter temperatures, which gardeners can use as a guide for what can and cannot grow successfully on their property.
All 13 zones appear across the United States, including Alaska, Hawaii, and Puerto Rico. They extend mostly latitudinally across the continent. The further north a zone is, the lower its zone number will be, and the lower the minimum average temperatures will be in that region, and vice versa.
Zone 12 is a hot, tropical zone, hence why it isn’t found in the continental US. The hottest zone seen in the continental US is zone 11. The majority of plants that survive and thrive in these regions are tropical plants that love heat and can typically survive high humidity.
In Kauai, Hawaii, which falls under zone 12, summer temperatures typically reach as high as 84 degrees F.
This zone only appears in Hawaii and Puerto Rico, both of which experience very little typical “winter” weather, instead experiencing a warm and mild to hot climate year-round.
Where is Zone 12?
This zone is the second hottest to cover any US territory, and naturally, it is only found in a select few regions that experience the highest temperatures. It is prevalent in both Hawaii and Puerto Rico.
In Hawaii, zone 12 is found on every single island, both major and minor. On the Big Island (Hawai’i) and Maui, it is found around the entire coastal strip of both islands. On O’ahu and Kaua’i, and the smaller islands of Moloka’i, Lāna’i, and Ni’ihau, it covers almost the entirety of these land masses.
In Puerto Rico, it is the most prevalent hardiness zone. Zone 12 makes up the bulk of inland Puerto Rico and the entirety of the land-locked Porta Cordillera region.
Minimum Average Temperatures in Zone 12
All USDA hardiness zones are defined by the minimum average temperatures that occur in winter in these zones. These minimum average temperatures come within a range of 10 degrees F.
Each zone is split into two subzones, A and B.
- Zone 12: covers minimum average temperatures of 50 to 60 degrees F.
- Zone 12a: this subzone covers minimum average temperatures spanning from 50 to 55 degrees F.
- Zone 12b: this subzone covers minimum average temperatures spanning from 55 to 60 degrees F.
These minimum average temperatures help you to better understand the temperature ranges you will be planting in. However, they are not set in stone. Average temperatures can fluctuate in these areas if microclimates change or unexpected weather patterns occur.
Frost Dates in Zone 12
Another environmental factor that goes hand in hand with minimum average temperatures is frost dates. Frost dates explain when the first and last frosts of the year will pass, and in turn indicate when you should begin preparing and planting in your garden, and when you should stop.
- Last frost dates: N/A
- First frost dates: N/A
Because of its consistently warm temperatures, zone 12 experiences no true frosts throughout the year. As such gardeners in this zone technically experience a year-round growing schedule, though many crops cannot be grown in the sweltering summer period.
Zone 12 States
Every USDA hardiness zone extends to more than one state or territory, and every state (with the exception of Delaware) falls under multiple zones.
In the case of zone 12, only one state and one territory fall under this growing zone, much like zone 13 after it. These include:
- Puerto Rico
Both subzones 12a and 12b appear in these regions. Zone 12 is the most prevalent region in Puerto Rico, and one of the most prevalent in Hawaii.
When to Plant in Zone 12
Planting schedules in zone 12 depend on whether plants are warm-season or cool-season crops, and on the planting requirements of each individual species.
Most vegetables that can be grown in zone 12 are warm-weather crops and can be grown at various points of the year. However, vegetables such as sweet potatoes, tomatoes, and peppers should not be planted until spring, or at least until temperatures have reached 60-70 degrees to ensure that soil is warm enough to suit their needs.
Most warm-weather crops will make it through the hottest points of a zone 12 summer. However, you should still make sure you know the temperature limits of everything you plant to ensure that you can provide adequate heat protection, via equipment such as shade sails or grow tunnels, to plants that need it.
Cool-season crops that are compatible with zone 12 such as cabbage, spinach, and lettuce, typically grow best in temperatures below 70 degrees F. Each of them will grow well in the milder winter months, so make sure to get them in the ground in fall or winter at the latest (depending on their maturation dates), so they have plenty of time to reach harvest before temperatures heat up in spring.
Tips for Gardening in Zone 12
While understanding the average temperature range in your area will help your garden immensely, there are a few smaller strategic things you can do to help your trees, plants, and crops thrive.
- The most crucial element you have to contend with when gardening in zone 12 is the high temperatures. It’s essential to ensure that your plants and trees are fully protected from any harsh heat and sun, particularly in the summer months. This also applies to cold-weather crops that may still find the fall and winter months too hot. Heat protection can be applied via mulching, consistent watering, shade cloths and sails, and tactical planting (planting your crops in the shade of trees and taller plants).
- Most zone 12 climates are either humid or arid. In arid environments, prep any dry, poor-draining, and nutrient-deficient soil by turning soil and adding compost or simply building raised beds. In humid environments, be sure to prioritize plants and trees that can tolerate those humidity levels.
- Some regions that fall under higher average temperatures, particularly dry areas, can experience water restrictions. If this applies to your property, consider species with below-average water requirements so you can safely ensure sufficient watering through even the driest parts of the year.
- Climates with no frosts or cold winter weather often face a higher population of insects and other pests. Consider planting in a greenhouse or using row covers if this applies to your area.
- When purchasing seeds, consult your seed packets for extra planting information. Seed packets often provide planting and harvest dates and requirements for soil type, water, temperature range, etc.
Choosing Plants for Zone 12
As the second-hottest climate zone in the territorial US, there are more limits on what you can grow compared to many of the lower zones. That being said, you still have a range of plants, trees, and vegetables to choose from. So where do you start?
The first place to go is your local garden center or plant nursery. These places typically stock the widest range of plants and trees that grow well in your area, and often employees will have some degree of useful knowledge about local gardening.
Otherwise, you can seek out gardening advice from friends, family, and acquaintances who have experience gardening in your region. Some may be local experts with years worth of experience who can advise you on local weather patterns and microclimates, and help you choose the perfect plants for your property.
When you are purchasing seeds don’t forget to consult the backs of seed packets, which will likely have information on harvest times, temperature and soil requirements, and more that will help you to choose the right plants. Seed companies may also provide more detail through their websites.
For beginner gardeners, you can make this process easier by choosing compatible native trees and perennial plants to grow in your garden. Native trees tend to be very low-maintenance and adaptable growers. Perennials only need to be planted once and can be enjoyed for years to come.
What to Grow in Zone 12
Now that you understand the minimum temperature ranges, frost dates (or lack thereof), and approximate planting schedules for zone 12, it’s time to figure out what you can grow!
Here are some of the most popular trees, vegetables, perennial flowers, and herbs that will grow and thrive in your zone 12 garden.
Trees for Zone 12
Unsurprising given its locations and climate, many conventional fruits grown and sold in the US will not survive the zone 12 heat. Instead, zone 12 gardeners have a selection of delicious tropical and sub-tropical fruits to choose from.
- Dragon fruit: When it comes to exotic fruit trees, you can hardly do better than the standout dragon fruit plant. The dragon fruit cactus is small to a medium-sized fruit tree that thrives in warm, sunny spaces and is native to south and central America. They are exceptionally unique plants, with long jagged foliage that is more like separate blades than leaves, bright pink ‘scaled’ fruits, and enormous white and yellow flowers that only bloom at night. Unlike other cacti, dragon fruit trees need plenty of water to ensure a bountiful harvest.
- Plantain: The plantain is grown throughout Puerto Rico, as it suits the zone 12 climate well. These herbaceous perennial “trees” and fruits look very similar to the banana, as both are part of the genus Musa. For centuries plantains have been a staple in many food cultures around the world, but the plantain tree also has plenty of ornamental value, due to its enormous glossy leaves and velvety purple flowers. Maricongo and Superplatano plantains are two varieties that grow well in zone 12.
- Jackfruit: In recent years this enormous and unusually shaped fruit has gained significant popularity in the west due to its versatile uses as a meat substitute for vegan and vegetarian meals. It can also be used in more conventionally “fruity” dishes as sweet food. The jackfruit tree thrives in hot tropical climates and is a fast-growing evergreen that bears large green, pink, and yellow flowers in fall. With enough warmth, sunlight, and moisture, the jackfruit tree grows relatively easily with minimal issues with pests or disease.
- Other fruit trees: West Indian sour cherry, common guava, rose apple, rambutan, soursop, bananas such as Cavendish, Fe’i, Gros Michel, and Red Banana, Washington Navel oranges, Satsuma tangerines, mangosteen, pomelo, Yellow Hawaiian papaya, abiu, durian, egg fruit, avocado tree, mango.
Of all trees you can plant in zone 12, flowering trees add the most color and appeal, particularly in spring and summer. Here are some of the best flowering species compatible with zone 12.
- White Frangipani: also known as plumeria, Hawaiian lei flower, and a host of other names, the white frangipani is a small tropical tree with incredibly ornate and stunning flowers that are usually white and yellow but can also be grown as pink and red. This tree and flower are so significant in zone 12 Hawaii that they are most famously associated with the cultural lei flower garlands made from these flowers. The trees are fairly low-maintenance, able to thrive with little attention as long as the climate is suitable.
- Flame of the Forest: aptly named for the unusual clusters of flame-colored flowers that bloom for several weeks in late winter to early spring, the flame of the forest tree is a small-medium deciduous tree native to south and southeast Asia. These trees will light up any property and capture attention wherever they are planted.According to the Singapore Government National Library Board, their flowers bloom best when rains return after a long period of dry weather. Flame of the forest trees reach up to 35-40 feet tall, and with their unique umbrella-like canopy and brilliant flowers, they do well as ornamental trees.
- Hawaiian Hibiscus: Another native flowering tree closely associated with Hawaiian culture is the Hawaiian hibiscus, the official state tree of these tropical islands! These small evergreen trees are known for their lovely, showy blossoms and delicious fragrance. While Hawaiian hibiscus flowers are typically white, there are seven species of native hibiscus that can be yellow, pink, red, orange, and purple. This hibiscus makes a dramatic accent tree, specimen, and even flowering hedge or privacy screen. They can also be grown in containers for those who want to enjoy them in cooler climates.
- Other flowering trees: Royal Poinciana, Hawaiian Gardenia, Geiger Tree, Ohia Tree, Angel’s Trumpet, African Tulip, Hau Tree, Orchid Tree, Cassia Shower Tree, Yellow Tabebuia, Puakenikeni Tree
Evergreen trees also add color and texture to your garden, with their year-round foliage keeping your property bright even during the winter months. There are plenty of hardy evergreens that grow well in zone 12.
- Coconut Palm: anyone who lives in or has taken a trip to either Hawaii or Puerto Rico will recognize these trees. In zone 12 climates coconut palm trees grow like weeds! They are hardy, and useful, and make a graceful image in any landscape. Heat and humidity are key to growing this iconic evergreen successfully, as well as full sun throughout the year and consistent watering twice a week. They also need plenty of fertilizer – without adequate nutrients, any coconut palm you grow will be stunted.
- Banyan Tree: Part of the mulberry family and native to the Indian subcontinent, this unusually shaped evergreen has been considered sacred by the Hindu religion for many centuries. The banyan tree is frost-sensitive and thrives in consistently warm weather, such as what can be found in zone 12, and is quite common in Hawaii. These trees can reach 100 feet tall and tend to have very large canopies, so if you want to plant them on your property, make sure you have the space to accommodate them.
- Cook Pine: Often confused for the Norfolk pine, the cook pine is the most common evergreen of the Araucaria genus that is grown in Hawaii. It is most recognizable for its unusual leaning growth habit, depending on where they are planted. The cook pine can grow up to almost 200 feet tall and has a spire-like crown and evenly spaced horizontal branches. The foliage of this tree has a cord-like appearance and texture, with very short needles. Its wood is strong and lightweight and is often used for lumber and in reforestation projects.
- Other evergreens: Parana Pine, Ponytail Palm, Hawaiian Hibiscus, Geiger Tree, Arizona Cypress, Eucalyptus Tree, Koa, Noni, Alexandra Palm, Coast Banksia, Ironwood, Cabbage Tree, Sweet Pittosporum, Eugenia Woodburyana, West Indian cherry, Breadfruit, King Palm, Royal Palm, Areca Palm, Bamboo
Native trees are incredibly useful, as their compatibility with the local climate and ecosystems makes them highly adaptable and easy to grow. Consider these native trees for your backyard.
- Geiger Tree: Native to Puerto Rico and other islands in the Caribbean, the geiger tree is a small, evergreen tree that is part of the cordia genus. These attractive trees thrive in zones 10-12 and make a perfect choice of native for gardeners living in coastal areas, due to their high tolerance to salt spray and salty, sandy, and even dry soil. They bear bright orange flowers and small edible fruits with a history of medicinal usage. Geiger trees are low-maintenance and slow-growing trees that add a burst of color all year round.
- Hawaiian Gardenia: Another truly exceptional flowering tree that is treasured on the Hawaiian islands is the Hawaiian gardenia, also known as the nānū or nāʻū. They are small native trees that produce beautiful creamy white flowers and pale green fruits. They are tolerant to drought and wind, and their wood and flowers are valuable resources for making tools and lei. Unfortunately, according to the University of Hawaii Native Plant Propagation Database, these beautiful trees are endangered in their native habitat, but they can still grow and thrive in a domestic landscape.
- Ceiba: Also known as kapok, the ceiba pentandra is the national tree of Puerto Rico, and native to the rainforests of the Caribbean, Central America, and northern South America. This tree is fast-growing and can reach over 170 feet in height, and every few years it will bloom with thousands of flowers and fruits. The ceiba is widely cultivated throughout Asia for its seeds, fiber, and floss, which can be used to make oil, fertilizer, and insulation, amongst other products.
- Other native trees: Coast sandalwood, Candlenut, Geiger tree, Hawaiian gardenia, White Frangipani, Koa
Vegetables for Zone 12
Growing a vegetable garden is the best way to make practical use of your backyard and gardening skills. Here are some of the tastiest vegetables that can thrive in zone 12 temperatures.
- Serrano Peppers: in the same family as the bell pepper and jalapeno is the serrano pepper. These mild, flavorful peppers are excellent for gardeners who like to add a kick to their meals without being overpowered by spice. Heat and humidity are a must for these peppers, and they will grow well once night temperatures reach 55 degrees and above. They are relatively long-growing and take three months to reach harvest. Serrano’s are most often green, but can also be grown as red, yellow, orange, and even purple and brown!
- Spaghetti Squash: One of several varieties of squash, the spaghetti squash is a popular vegetable that is packed with nutrition and has fairly simple growing requirements, making it a perfect choice for beginner gardeners. Despite being a winter squash it enjoys warm weather and should not be planted until the soil has reached and maintained temperatures of atleast 60 degrees F or higher. Squash vines tend to take up a lot of space, so consider planting them vertically to take up as little growing room as possible.
- Sweet Potatoes: These useful tubers have been grown in Hawaii for centuries. Both orange and purple sweet potato varieties can be cultivated in a zone 12 garden since the warm temperatures and near-constant sun provide perfect growing conditions for the plants. Sweet potatoes need soil temperatures of 70 degrees F or higher, and only take six weeks to reach harvest once planted. Once in the ground, sweet potatoes need relatively little attention, aside from weeding, occasional watering, and occasional mulching to keep the soil warm (though this shouldn’t be necessary for zone 12.)
- Other vegetables: taro, squash, peppers, tomatoes, peas, eggplant, cucumber, beans, cabbage, cauliflower, corn, ginger, okra, green onions, honeydew, spinach, swiss chard, lettuce arugula, carrots, radishes, chili peppers, yam, pak choi
Perennial Flowers for Zone 12
These beautiful perennial flowers will light up any part of your property, and only need to be planted once. Some will flowers several times a year, or even year-round in the tropical zone 12 heat!
- Kangaroo Paw: Though their flowers may not look like conventional blossoms, the Australian native kangaroo paw is an interesting perennial that adds color and texture to any flower garden. The flowers of the kangaroo paw have a tubular shape and are covered in a thin layer of small, fuzzy hairs. Their nectar has a tendency to attract small birds. Keep in mind that kangaroo paw prefers a hot, dry climate, and though it can tolerate some humidity you should check humidity levels in your area before purchasing these plants.
- Birds of Paradise: Gardeners who live in tropical climates will likely be familiar with the colorful and unique birds of paradise perennial plants. They are a very well-known and popular tropical plant due to the shape of their flower heads and orange petals, which resemble a tropical bird of paradise. Their large glossy leaves are also very appealing, adding to the overall ornamental value of the plant, and making it a focal point of any garden. They can be grown indoors or outdoors, and tend to flower in late winter or early spring.
- Anthurium: Native to South America, this colorful perennial is very popular as a houseplant in cooler climates but will grow well outdoors in zone 12. With its heart-shaped leaves and glossy red flowers, the anthurium flower will look striking in any garden, and they can even bloom year-round with appropriate care. When grown outdoors this flower needs consistently moist, warm, and rich soil to thrive and produce flowers consistently. Keep in mind that these plants are highly toxic to cats and dogs.
- Other perennials flowers: Scarlet Pimpernel, Flamingo Flower, Begonia, Jasmine, Amaryllis, Brazilian Heart begonia, Amaryllis, Desert Willow, Ivy Geranium, Lantana, Moth Orchid, Portulaca, Scarlet Sage
Herbs for Zone 12
Herb gardens provide useful culinary ingredients and plenty of ornamental appeals. These are some of the best herb plants that can be grown in zone 12.
- Rosemary: This evergreen herb is not only highly useful as a cooking ingredient, but it’s also an appealing addition to your zone 12 garden with its slender branches, narrow silver-green leaves, and tiny purple, blue, or white flowers. They also have a delicious pine fragrance and attract local pollinators, adding extra attractive elements to your garden. Rosemary prefers warm and mildly humid environments and can be planted both outdoors and in containers. They should be pruned semi-regularly, and new plants should be propagated rather than grown from seed.
- Basil: An exceptionally cold-sensitive herb, basil loves hot weather and thrives in a warm, dry climate. This popular herb is an annual plant that dies off each year before winter in cooler climates, but in zone 10 and higher, it can be grown perenially. Basil can be grown well both outdoors and in containers. In warm weather, basil can be harvested within six weeks, and the tops of the plant can be pinched to prevent blooming and also encourage the plant to grow in a wider and bushier shape.
- Cardamom: This south Asian native herb has played an important part in shaping the cuisine of countries in this part of the world, and is becoming more commonplace in pantries around the globe. For gardeners who are interested in cultivating cardamom, zone 12 is an excellent climate zone for this sweet, fragrant herb. Cardamom is a perennial that grows well in warm tropical climates and can reach up to 10 feet tall. They have lance-shaped leaves and delicate, tiny flowers that produce the pods that are used to create cardamom spice.
- Other herbs: rosemary, sage, mint, hyssop, basil, thyme, lavender, chamomile, dill, catmint, lemongrass, cardamom, fennel, poppy, borage, cinnamon, marjoram, nutmeg, savory, cilantro
The Zone is Only Part of the Story
Learning more about the USDA hardiness zone you live in is a great help when you are planning your perfect garden. It helps you to better understand the climate and temperature ranges you are working with, and how those factors influence what and when you can plant on your property.
But the growing zone is only part of the story! There is plenty more to learn regarding your local weather patterns and microclimates, as well as the soil types in your area and the growing requirements of the plants you’ve chosen for your property.
Once you understand more about the environment you live in and the plants you’re growing in zone 12, your home garden and landscape will thrive in no time.