USDA Zone 13: Where is it? What to Plant? Tips to Success
If you are looking to establish your home garden, understanding the USDA hardiness zone you live in will help immensely. These zones establish the temperature ranges in your region and the kinds of trees and plants that grow best there, among other things.
And for gardeners in zone 13, the hottest growing zone in the United States, there is plenty to learn. With blazing heat at the peak of summer and warmth all year round, understanding how to grow plants and crops successfully here isn’t always straightforward.
Let’s look at minimum average temperatures, planting schedules and options, and more for your zone 13 garden.
What is Zone 13?
Zone 13 is the last of the 13 plant hardiness zones, as detailed by the US Department of Agriculture and included on the USDA Plant Hardiness Zone map.
Each hardiness zone, also known as a ‘growing zone’, is defined by the minimum average temperatures that occur in their regions, and these minimum average temperatures indicate when gardeners can begin growing certain crops, and when the growing season ends.
These 13 zones are present in every part of the United States, including Hawaii, Alaska, and Puerto Rico. Almost every zone runs latitudinally along the continental US, from east to west, with the exceptions of zones 1, 2, 12, and 13.
Zone 13 is the hottest growing zone in the US states and territories, with no frosts, a year-round growing season, and near-constant warm weather. Summers in zone 13 can get extremely hot, and as a result, these regions are home to tropical plant species that are quite exotic compared to lower-growing zones.
In Ponce, Puerto Rico, which falls under zone 13, daily summer temperatures regularly reach 90 degrees F. Maximum temperatures can creep as high as 93 degrees during this period.
Both Puerto Rico and Hawaii are the only regions of the US where zone 13 appears.
Where is Zone 13?
As the hottest zone in the US and its territories, zone 13 only exists sparsely in two countries. It can be found in both Puerto Rico and Hawaii, though it is most prevalent in Puerto Rico.
In Puerto Rico, zone 13 conditions can be observed around most of the outer coastal strip of the island. Several of the most populous cities, including Puerto Rico, Carolina, and Ponce, are included in zone 13.
In Hawaii, zone 13 can only be found in very small pockets of these islands, such as on the eastern coast of the island of O’ahu.
Minimum Average Temperatures in Zone 13
Each USDA hardiness zone is defined by the minimum average temperatures that occur in these zones at the coldest points of the year.
Minimum average temperatures cover a range of 10 degrees F and are split into two subzones: A and B.
- Zone 13: covers minimum average temperatures of 60 to 70 degrees F.
- Zone 13a: this subzone covers minimum average temperatures spanning from 60 to 65 degrees F.
- Zone 13b: this subzone covers minimum average temperatures spanning from 65 to 70 degrees F.
These minimum average temperatures indicate which plants and trees will grow well in zone 13. But it’s important to understand that these temperatures are not fixed. They can fluctuate from year to year depending on spontaneous weather patterns and local microclimates.
Frost Dates in Zone 13
Frost dates are another regional feature that is taken into account when establishing growing zones. These dates tell us when the first and last frosts of the year occur. And in turn, they show gardeners when to begin planting frost-sensitive plants and when to stop planting.
- Last frost dates: N/A
- First frost dates: N/A
As the hottest zone in the US, zone 13 does not experience any frosts as temperatures in these regions do not dip low enough. The weather is warm all year round, meaning that zone 13 gardeners have a year-round growing schedule.
Zone 13 States
Most growing zones appear in more than one state and/or territory in the US. And of course, most states contain more than one zone – for example, Hawaii, which contains zones 9a to 13a.
Like zone 12 before it, zone 13 only appears in one state and one territory. These are:
- Puerto Rico
However, zone 13 is far more prevalent in Puerto Rico than Hawaii, with both zone 13a and 13b covering approximately 1/3rd of the island. In Hawaii, on the other hand, it only appears in very small pockets on the coastline of certain islands.
When to Plant in Zone 13
Planting schedules are one of the trickiest components of starting a garden in an unfamiliar climate. Every plant, whether it is a cool or warm-season crop, has individual planting requirements that dictate when they should be grown. So make sure to familiarize yourself with the changing soil temperatures in each season.
There are general rules on when warm and cool-season crops should be planted in zone 13. Cool-season crops that can survive the zone 13 heat, such as lettuce, kale, and celery, can be grown without heat protection during a short window, from mid to late fall through to the end of winter.
Once temperatures begin to exceed 80 degrees F you will need to apply proactive strategies, such as grow tunnels and row covers, to keep these vegetables cool and protected from the sun and heat. You can also purchase starter plants to get a head start in the growing season.
Some warm-season crops in zone 13, such as tomatoes, eggplants, cucumbers, etc can be planted in winter due to the minimum average temperatures sitting above 60 degrees F. However, they should be planted from spring through to fall to ensure ideal temperatures. In the highest points of summer, some of these warm-season crops may also need plenty of irrigation and protection during the hottest parts of the year.
Tips for Gardening in Zone 13
Learning more about your USDA hardiness zone and local climate is very helpful, but there are a number of things you can do to ensure your garden has the best chance of flourishing in the hot, sometimes humid zone 13 climate.
- Intense heat is the biggest obstacle you will face in this zone. Protecting your more heat-sensitive plants and trees in all seasons is imperative. You can provide shade via tactical planting (planting near trees/taller plants that provide natural shade), shade sails/covers/nets, and grow tunnels. Mulching helps to keep the soil cool and retain moisture, and irrigation lines also provide consistent moisture.
- Regions in zone 13 are often either humid or arid. To combat humidity, prioritize tropical plants and trees that thrive in humid conditions. To combat poor-draining, nutrient-deficient soil in arid environments, turning the soil and adding compost or building raised garden beds will help.
- Consistently warm, frost-free climates (such as those that occur under zone 13) often experience higher rates of pests and insects that can damage crops and other plants. If this affects you, planting in greenhouses and using floating row covers are just two ways you can mitigate potential damage.
- If you live in an area with imposed water restrictions during the summer months or other times of the year, prioritize planting species with low water requirements to ensure you have sufficient irrigation during the hottest months of the year.
Choosing Plants for Zone 13
When it comes to planning your garden, choosing your plants tends to be the most exciting part. But if you’re preparing to develop your garden in a new growing zone and climate, it isn’t always easy. Where do you start?
The first and easiest step to take is to visit your local garden center or plant and tree nursery. These businesses will offer a wide range of species that are well-suited to your area, and some employees will have specialized knowledge of local planting conditions.
Otherwise, if you are purchasing seed packets for planting, these packets often contain useful basic information on each species and variety – including harvesting times, and requirements for temperature, water, soil, and more. These seed companies may also provide extra information on their websites.
You can also contact local friends, family members, and acquaintances with experience gardening in your region. Some of these people may prove to be local experts with vital information regarding local soil conditions, microclimates, and consistent weather patterns that may be hard to find elsewhere.
For beginner gardeners in zone 13, focus on finding ways to make your gardening journey easier. For example, prioritize planting native and perennial species. Most natives are hardy, and adaptable, and should thrive in your area with minimal effort. Perennials only need to be planted once, saving you from having to pull and replant your herbs and flowers each year.
What to Grow in Zone 13
Now that you understand more about the zone 13 climate and how it affects your landscape and growing schedule, it’s time to choose the perfect plants for your garden.
Fortunately, there are a number of tropical species you can choose from that will thrive in the warm zone 13 climate.
Trees for Zone 13
If you want a beautiful tree that also provides abundant fruits every year, there are a number of delicious and exotic zone 13 fruit trees to choose from.
- Mamey Tree: Native to Puerto Rico and other areas of the Caribbean and West Indies, the tropical mamey tree is an exotic and little-known fruit tree elsewhere. The Mamey tree bears large leathery fruits with orange flesh that can be eaten raw or cooked in various ways and is an important food source and commercial fruit in its native countries, according to the University of Florida extension. These trees are also often grown in landscaping, where they are used as ornamentals, windbreaks, and shade trees. They can grow as high as 70 feet tall and are sometimes compared to magnolia trees due to their dark evergreen foliage and large white flowers.
- Avocado Tree: many avocado trees are grown domestically and commercially in Puerto Rico, particularly in coastal areas which fall under zone 13. Avocado trees are tall and evergreen with bright, thick foliage, small yellow, and green flowers, and smooth, glossy fruits. These trees can self-pollinate, but it is often better to grow two trees to ensure successful pollination and fruiting. Avocados can also take as long as 13 years to develop fruits when grown from seed, so consider purchasing saplings if you want to harvest avocados as soon as possible.
- Soursop: Sometimes known as guanabana, the soursop is a large green fruit with slightly spiky skin and sweet flesh that has a custard-like texture and consistency. The soursop tree is a fast-growing, medium-sized, evergreen, tropical species that typically grows to 30 feet tall and grows well in both coastal and elevated areas. It does not have a particularly high yield, typically only growing around two dozen fruits per year. The soursop is native to Puerto Rico and other countries throughout the Caribbean and the Americas.
- Other fruit trees: Banana, Mango, Plantain, Tamarind, Carob, Papaya, Soursop, Tahiti Currant, Cocoplum, Ausubo, Pineapple Guava, Starfruit, Breadfruit, Rose Apple, Sintenis Guava
For a burst of brightness and color, consider planting one of these appealing flowering trees on your property.
- Royal Poinciana: Also known as the Flamboyant, this magnificent flowering tree is popular in Puerto Rico and highly recognizable for its bright, blazing red-orange blossoms and delicate, feathery leaves. It is one of the most colorful species in zone 13 and a must-have for gardeners who want to make a statement. The royal poinciana is not only a focal point in any landscape but also does well as a shade tree during the hottest times of the year. They are quite low-maintenance, but their shallow root system can be disruptive.
- Maga: This next flowering tree is a common native and one of the most beloved flowering trees in Puerto Rico. It is so iconic, in fact, that its flower, the flor de maga, is also the official national flower of PR. The maga is a small tree that is largely favored for its ornamental value due to its appealing dark foliage and beautiful, delicate red and pink flowers. They are also sometimes cultivated for timber and can be found growing wild in wetlands and areas with high humidity.
- Puerto Rican Magnolia: While this beautiful flowering tree is native to Puerto Rico, it is endangered in its native habitat in the wild and rarely found in the wild. Regardless, it’s a fantastic species to cultivate domestically, being a magnolia species that is unique to Puerto Rico and the zone 13 climate. With its bright, glossy green leaves and large creamy white flowers it makes an excellent ornamental and shade tree on any zone 13 property, provided you have the space for it.
- Other flowering trees: Plumeria, Hibiscus, Orchid Tree, Manchineel Tree, Blue Mahoe, Capa Jiguerilla
With their year-round foliage, evergreens will add some much-needed color and texture to your surroundings during every part of the year.
- Calabash: an unusual evergreen, the calabash tree is a small tree that produces textured green and white flowers and large, round, green fruit that are toxic to humans. Their flowers are pollinated by bats, and they can produce flowers and fruits at any time of year. Because of their flowers and long, lance-shaped evergreen leaves, they make an interesting ornamental tree in tropical climates. Be wary of their fruits, however, which are hard and heavy enough to injure people when they ripen and fall from the tree.
- Caribbean Pine: This Caribbean evergreen is a hardy conifer often grown in plantations in low-lying areas. These pines have fissured, reddish-brown bark and dark green needles and can grow to over 100 feet in height. Caribbean pines are often grown and used commercially, to produce timber, pulpwood, and resin. The seeds of these trees spread very easily and regenerate quickly after wildfires, so in some countries, such as Australia, it is considered an aggressive invasive species.
- Macaw Palm: Native to the Caribbean, the macaw palm is a spiny palm with dense, fountainous foliage that erupts from the top of the 20-30 foot evergreen. It is named for its small red fruits which macaws often eat, and also produces small white flowers that grow on long inflorescences. Its thin trunk is covered in distinctive spiky thorns that may prevent some from adding it to their garden, which is a shame since they are otherwise very appealing palms. Additionally, they cannot be grown in containers or indoors.
- Other evergreen trees: Bamboo, Acrocomia Media, Mangrove, Puerto Rican Hat Palm, Sierra Palm, Royal Palm, Coconut Palm, Calabash, Ausubo, Cook’s Holly, Mamey Tree, Soursop, Higuero De Sierra, Dahoon Holly, Oiticica, Puerto Rican Magnolia, Mountain Cabbage Palm, Sintenis Guava
For adaptable trees that will fit seamlessly into your local ecosystem, these zone 13 native trees are an excellent choice.
- Puerto Rican Hat Palm: The stately, handsome Puerto Rican hat palm is an excellent choice of native evergreen for zone 13 gardeners who have the space for them. Though they are somewhat slow-growing, the fronds of these palms can soar up to 14 feet above their columnar trunks, and the trunks themselves can grow to be 4 feet across. So ensure that your property can accommodate these palm trees before making a decision to purchase them. These palms love intense heat and need plenty of sunlight and consistent moisture to thrive.
- Cocoplum: The tropical cocoplum is a beautiful yet hardy native tree or shrub, with a high tolerance to drought and salt spray. This tree is often grown as an ornamental, due to its compact size, lovely multi-colored foliage, and consistently flowering white-green blossoms, but it can also be used in hedging and foundation planting. The cocoplum fruit, which is a small red and purple drupe, is also edible and can be enjoyed fresh or used in jams, jellies, and other kinds of cooking.
- Ausubo: Another fruit tree native to Puerto Rico is the evergreen ausubo, which has a long and significant history as the most important source of timber for the Puerto Rican economy. These impressive natives can grow up to 150 feet tall and live as long as 400 years. They are mostly found growing natively in coastal areas, low-lying mountainous areas, and limestone forests in the island territory. It also produces edible yellow fruits and its sap is also extracted and used to create a rubber-like latex.
- Other native trees: Puerto Rican Hat Palms, Ceiba, Cocoplum, Ausubo, Mamey Tree, Soursop, Maga, Acrocomia Media, West Indian Walnut, Oiticica, Puerto Rican Magnolia, Jacana, Mountain Cabbage Palm, Sintenis Guava
Vegetables for Zone 13
One of the best ways to put your garden to work is with a thriving vegetable garden, and thankfully there is a large variety of crops you can plant in the zone 13 climate.
- Yautia: A very popular root vegetable in Puerto Rico that is cultivated all across the Mediterranean and West Indies, the yautia is often confused with the taro as they look quite familiar, though yautia is more elongated in shape. They have a significant presence in the national cuisine of this zone 13 island. These perennial plants are very low-maintenance, needing only partial sunlight, moderate watering, and well-draining soil. They should be planted in soil temperatures of 68 degrees or higher.
- Cucumber: Warm, sunny weather is the best friend of the cucumber plant. Cucumbers are widely popular around the world and are easy to grow and adaptable to varying climates. There are countless varieties of cucumber and even more ways to enjoy them. They are summer crops, typically planted in spring when soil temperatures have reached 65 degrees. Fruits are harvestable after approximately 60 days. Though they enjoy the heat, when temperatures are higher than 95 degrees F they should be granted partial shade protection.
- Corn: Though it’s typically associated with larger-scale farming, corn can grow well in a home garden. It is also a warm-weather crop, needing soil temperatures of 60 degrees or higher before it can be planted. Corn needs full sun and loamy, neutral to acidic soil. Depending on the variety, it usually takes 80 to 120 days before they reach harvest. Consider the available space in your garden before planting, as you will likely need to grow more than ten plants to ensure a decent harvest.
- Other vegetables: Tomatoes, eggplants, beans, zucchini, cucumber, bell peppers, chili peppers, yautia, okra, cabbage, carrots, sweet potato, yams, cassava, potatoes, onions, lettuce, kale, celery
Perennial Flowers for Zone 13
For stunning flowers that will return to your garden year-to-year, consider planting some of these attention-grabbing perennials that can brave the heat of zone 13.
- Beehive Ginger: Named for their curious bracts that grow in unique geometric formations that somewhat resemble a beehive, these tropical flowers are some of the most eye-catching perennials that bloom in zone 13. Not only do their red, orange, and yellow bracts add lovely color, texture, and height to your flower garden, but they are also very easy to grow, with high tolerance to pests and varying soil conditions. These plants thrive in warmth, sunlight, and humidity. There are plenty of cultivars too if you prefer pink, peach, or brown flower hues.
- Heliconia: Another spectacular tropical plant that is sure to light up your garden is the heliconia, which looks somewhat similar to the popular bird-of-paradise flower. Heliconias are fast-growing perennials with pink and yellow flowers, or bracts, that resemble birds’ heads that grow on stalks that can reach up to 15 feet tall, emerging from large glossy leaves similar to banana leaves. In cooler climates, they are often grown indoors as houseplants, though a large percentage of varieties will only grow outdoors in their natural environment. According to the University of Wisconsin Horticulture Extension, there are up to 200 species of heliconia.
- Petunia: A more traditional non-tropical perennial flower that grows well in zone 13 is the petunia, which is one of the most popular flowers in the world. Petunias can be perennial or annual but are perennial in warmer climates. Their flowers bloom in prolific clusters, and in warm climates, they can even flower year-round. There are many different varieties of petunia that can be divided into five groups, which are typically divided by flower size, flower color, and growth habit. In zone 13, these flowers may need protection from extreme heat and harsh sunlight.
- Other perennials: Dahlia, Anthurium, Lantana, Lotus, Petunia, Forsteronia Portoricensis, Brugmansia, Smoketree Spurge, Salvia Splendens, Bird of Paradise
Herbs for Zone 13
Whether you want to grow them for their ornamental appeal or their culinary value, these herbs have plenty to offer for your home garden.
- Borage: Often grown as both a herb and a flowering plant, borage is most recognizable for its bright blue flowers and hairy stems, as well as its light flavor which tastes similar to cucumbers. It grows well in vegetable, herb, and flower gardens, and tends to bloom throughout the summer months. While it is technically an annual herb, borage self-seeds prolifically so will usually pop up every year with enough space. It is a relatively unfussy plant, able to grow in varying soil types and in containers.
- Anise: Anise is a pretty annual herb that is grown for its strongly-flavored seeds, which are often used in cooking and baking, and its beautiful ornamental white flowers and delicate leaves. It grows up to 2 feet tall and needs plenty of warmth and sunlight to thrive, and will also attract many pollinators and other beneficial insects to your garden. These herbs don’t transplant well, so if you are considering growing anise it is recommended to grow them from seed.
- Cilantro: In terms of climate, cilantro is one of the most adaptable herbs available, able to grow in USDA zones 2 all the way to 13. Its leaves, stems, and seeds are very useful in cooking, and it is very easy to grow needing only regular watering and well-draining soil. These plants can be harvested within just 30 days of planting. Keep in mind that excess heat and sunlight can cause cilantro to bolt, so consider planting yours in the fall and winter months before the weather grows hot.
- Other herbs: Sage, Basil, Cilantro, Rosemary, Borage, Savory, Anise, Mint, Red Mint
The Zone is Only Part of the Story
Understanding the USDA hardiness zone you live in will help you to better understand what you can grow in your climate and when you can grow it, based on minimum average temperatures, frost dates, and more. But there are plenty of other things you must learn if you want your future zone 13 garden to flourish and become both beautiful and productive.
Growing zones are only part of the story, and it is just as important to learn about your local weather patterns and microclimates. You should also learn about the soil type and quality in your area, and the requirements of the trees, plants, and flowers you want to grow. Figure out the obstacles you are dealing with, such as salt spray, drought, urban pollution, etc, and which plants can tolerate them.
These factors will go a long way in helping you to build a healthy and thriving garden on your zone 13 property.