Annual versus Biennial versus Perennial

What's the difference between an annual plant, a biennial plant, and a perennial plant? The distinction lies in the anticipated length of their lifecycles. Let's look at the definitions real quick, and then we'll explore each category in more detail.

ANNUAL PLANTS

Annuals complete their life cycle in just one growing season, going from seed to seed in a short time period. You'll have to replant annuals each year (or let new plants grow where last year's plants dropped their seeds).

BIENNIAL PLANTS

Biennials take two years to complete their life cycle, assuming extreme weather doesn't end this cycle early.

PERENNIAL PLANTS

Perennials can live for years. The word perennial actually means "through the years." These plants either stay evergreen or keep coming back in the spring.

What Are Tender Perennials?

The difference between annuals, perennials and biennials may seem cut-and-dried... until you start taking different locations into consideration. Some plants are capable of living for several years in their native habitats but, when grown in colder climates, will die in the winter because they're just not cut out for the cold. These plants are called tender perennials. Gardeners in colder climates often treat them like annuals and restart them by seed every year. Tropical plants like tomatoes and peppers are tender perennials that can't survive cold winters unless they're moved indoors or into a greenhouse.

Other plants are capable of living for several years in many climates, but the part you might be interested in eating becomes essentially inedible after the first season in the garden. Carrots are a prime example.

So whenever you see a plant's category, just keep in mind its actual life expectancy depends on your climate. If you live somewhere with extremely cold winters, plants that are typically considered perennials elsewhere might not make it more than one year in your garden. Some of the hardiest of perennials might even need frost protection over the winter to make it through.

What Does Annual Plant Mean?

Annual plants are those that complete their life cycles in one year, usually within just one season. These plants are started from seed, grow to maturity in the garden, produce seeds, and then die off. The next year, annual plants start from seed again. So basically they go in, do their thing, and get out.

Some annual plants are so good at dropping seeds that new plants will often pop up the next year (these are called volunteer plants). It might seem like your dill plant is returning after winter, but in reality, it's the second generation of that dill plant.

Annual Vegetables

Some examples of annual plants you might grow in the kitchen garden are lettuces from the Aster family; spinach and beets from the Amaranth family; arugula and radishes from the Brassica family; peas and beans from the Fabaceae family; squash, cucumbers, and melons from the Cucurbit family; and corn from the Gramineae family.

Annual Herbs

Cilantro and dill are two of the most popular annual herbs to grow. There's also cumin, which comes from the same family, the Apiaceae family.

These herbs will spend perhaps 90 to 120 days in your garden before going to seed. They love growing in cooler weather, so when the temps increase and the days lengthen, these herbs will bolt, or go to seed. At the end of their life cycle, they'll produce pretty little flowers that dry and become seeds for next year's plants. It's really easy to save your own cilantro seeds (otherwise known as coriander) and dill seeds to plant for your next cool season.

Annual Flowers

Some of our favorite annual plant flowers to grow in the kitchen garden are cosmos, sunflowers, German chamomile, marigolds, calendula (also called pot marigold), and zinnias from the Aster, or daisy, family. Then there are also nasturtiums, borage, pansies, violas, vincas, and petunias from various other families.

How to Grow Annual Plants

Annuals germinate and grow quickly from seed, so they're typically best started from seed. I direct sow most of my annual plants in the garden as soon as the temperatures are right for them. Annuals will reach maturity quickly, and then as their season comes to a close, they'll focus on seed production.

Because the time annuals will spend in your garden is relatively short, it's best to save your money and avoid buying annuals as small plants from the store when possible. A small spinach plant, for example, might cost a couple bucks at the store. You can buy an entire package of spinach seeds for the same price and have dozens of spinach plants grown to the same size in about 30 days.

Some annuals need to be replanted by seed each year. Others self-sow quite freely if growing conditions have been right for them; when that's the case, you'll have new plants popping up in your garden each year without any effort from you. (Free plants!)

The Benefits of Growing Annual Plants in Your Kitchen Garden

Annuals are typically super easy to grow from seed, and they grow quite quickly. They know their time to reach maturity and then produce seeds for the future is short, so they don't mess around.

A good example of this is radishes. You can sow radish seeds directly in the garden in the spring. They'll sprout and then be ready to harvest in just 30 to 45 days or so. If you leave a couple radish plants in the garden, they'll start to produce a tall flower stalk when the weather grows warmer. You'll get lots of pretty little purple and white flowers, but the radish seeds will actually form in these little green seed pods. You can harvest your own radish seeds from these pods as soon as they dry out.

In addition to being able to watch the complete life cycle of a plant, you can also save your own seeds for annuals like cilantro, dill, marigolds, zinnias, radishes, lettuce, and so many more. When your plants are done, it's nice to be able to clear them out of the garden space and start fresh with plants that will thrive in the current season.

What Are Biennial Plants?

"Bi" means two, so biennials are plants that need about two years (or at least 18 months) to finish their life cycle. They'll typically grow strong stems and roots and lots of leaves in their first year, before going dormant over the winter. Then, at the end of their second year in the garden, they'll produce flowers and go to seed before dying. Biennial plants have turned out to be some of my favorite things to grow.

Some examples of biennial plants you might grow in your kitchen garden include kale, collard greens, Brussels sprouts, and cabbage from the Brassica family (cabbage is, of course, often treated as an annual because it's harvested at the end of its first season, once it's formed a full head). There's also Swiss chard from the Amaranth family and celery and parsley from the Apiaceae family. These Apiaceae biennials well send down long carrot-like taproots into the soil to help them stay for the long haul.

How to Grow Biennials

I typically start biennial plants by seed indoors in late winter so that I can move them outdoors as transplants as soon as the weather is right. These plants will then settle themselves into the garden for a nice, long stay. You can also buy starter plants from your local nursery. Biennials are well worth your money since they'll give you months and months of production.

Now, keep in mind some biennials will need to be treated as annuals in colder climates. My Swiss chard plants could often hang in there after a little light frost in Chicago, but they'd be done after the first heavy freeze or snow if I left them uncovered. You can help these plants make it through winter by using frost cloth or cold frames to keep temperatures around the plants about 10 to 15 degrees warmer during the coldest months. They'll still die back, but then they'll hopefully return in the spring.

In warmer climates, biennials shouldn't have a problem making it through the winter, but they might need some help hanging on during a hot, dry summer. Make sure to keep them well-watered.

If a biennial plant makes it 18 to 24 months without dying from extreme weather, it will produce a tall center stalk and then flowers. Those flowers turn into seeds, and the 2-year life cycle begins anew.

The Benefits of Growing Biennial Plants in Your Kitchen Garden

Biennials have performed really well for me over the years. I noticed one October in my Chicago kitchen garden that biennials planted in March were still looking beautiful and productive, even though they'd been in the garden for longer than six months at that point. My tomatoes, which weren't planted until May, already looked spent and were ready to come out of the garden.

The reason biennials thrive for so long is because they're highly motivated to stay and survive in your garden as long as possible so they can make it to their seed-producing year. This makes them pretty forgiving of less-than-ideal conditions in your garden. And that means more harvests for you, possibly even year round.

Because they last longer in the garden, I feel like I get more for my money and space with biennials. You can harvest kale and Swiss chard leaves in May and continue to harvest them weekly over the next six months at least—long after the spinach has bolted and the peas are ready to be pulled.

What Are Perennial Plants?

Perennials are plants that can last for years in the garden. In warmer climates, these plants can grow and produce throughout the entire year. In colder climates, they'll die back with the arrival of frost and snow. That means their foliage will turn brown and shrivel up, but their roots are still alive. These plants will overwinter in your garden and then pop back up from their roots once spring has arrived and there's no more threat of frost.

Perennial plants range from herbs like rosemary and oregano to fruiting plants like peppers and even blueberries.

Keep in mind that the actual lifespan of a plant will depend on your climate. There were many plants that were perennial in my garden in Houston but that had to be grown as annuals in my garden in Chicago thanks to the cold winters.

Perennial Vegetables

Potatoes, peppers, and tomatoes from the Solanaceae family are all technically perennials, though they're often grown as annuals because they can't handle frost. If you live in an area that doesn't see much cold weather, you can grow these plants for years and years.

Perennial Herbs

These herbs are often called woody herbs, and they keep growing year round in moderate climates until they become bushes or even small trees. My mom has had an oregano plant in her garden for three and a half years, and that thing is huge! In a climate that has frost and snow, a plant like oregano might only grow to about half or a full square foot within the growing season before going dormant. After overwintering in the garden, it'll grow back from its roots.

The majority of the herbs in the mint family are perennials, including lavender, rosemary, oregano, thyme, sage, lemon balm, marjoram, anise hyssop, and mint. Basil is technically a perennial, but it's so sensitive to frost that it's treated as an annual in most climates. Fennel in the Apiaceae family is another short-lived perennial that's often grown as an annual in cooler climates.

My favorite perennial herb is chives. These plants are often the first to pop up every spring, and they'll produce like crazy throughout the growing season.

Because these herbs are in your garden for the long haul, it's worth it to buy well-grown plants from your local nursery. You can also take cuttings and encourage them to grow roots rather than try to start these herbs from seed.

(Learn more about perennial herbs.)

Perennial Flowers

Echinacea (AKA coneflowers), asters, yarrow, and some varieties of black-eyed Susans (AKA rudbeckia) from the Aster plant family are perennials. I love planting perennial flowers in the pollinator garden that surrounds my kitchen garden. It's the ultimate low-maintenance space.

Perennial Fruiting Plants

The Rosaceae family gives us perennial plants like strawberries, blueberries, and blackberries—the berry cousins, as I like to call them. These plants will continue in your garden for many years and fruit from new growth on the plant each year.

These berries can be planted in early spring or early fall. They need time to develop strong roots before winter and will then begin producing new canes and stems as soon as the ground thaws. They will finish their berry production before temperatures begin to drop once more.

How to Grow Perennials

Most perennials are planted in the spring or early fall so that they can settle in before extreme high or low temps. Perennials are often slow to grow from seed (it's like they think they have all the time in the world or something!), so it's worth your cash to buy well-grown starts from your local nursery so that you can enjoy your first harvests much sooner.

In areas where the winter is too cold for more tender perennials, you can overwinter them indoors in the sunniest spot you have. Lavender, rosemary, sage, thyme, and even peppers can be carefully potted up and moved indoors to escape frost. When the ground thaws in spring, these plants can go right back outside. The exception would be the berry cousins, which should be left outside to meet their required chill hours so that they can grow and produce again in the spring.

Some perennials benefit from being cut back in the fall. It's a good idea to do a little research on the type of plant you're growing so that you know its preference.

The Benefits of Growing Perennials in Your Kitchen Garden

It's obviously great whenever a single plant can last a gardener for years and years. Because they're wired to be survivors, perennials are typically pretty low maintenance. They're often resistant to pests and disease and can handle some neglect. Echinacea and oregano, for instance, are both pretty drought tolerant. In fact, some perennials are so good at staying alive and spreading that they're considered invasive in some places (an example of this, sadly, is yarrow). The good news is these perennials can often be kept in check by harvesting from them frequently.

Another benefit is that perennials often begin producing faster than annual plants in the spring. Their roots are already established, and they've grown before, so they know the drill. I always know that spring is about to arrive when my chives pop up to say hello after a long winter's nap.

Are carrots annuals or perennials?

Carrots are technically biennial plants, but that really only matters if you're interested in harvesting carrot seeds. Carrot plants will produce the part you most want to eat, the taproot, within their first season in the garden. If you are after seeds, you'll need to leave some roots in the soil so that they can flower the next year.

By the way, beets are technically the same. I lumped them in with annuals for the sake of simplicity.

Is there such a thing as perennial tomatoes?

Tomato plants are technically perennials in their native South America. Indeterminate tomato vines will basically just grow and produce forever until frost knocks them out. Most gardeners grow tomatoes as annuals during their warmer months, though some gardeners do take steps to overwinter their tomatoes. Personally, I've found keeping tomatoes through the winter to be a pain, and my plants often look tired after they've spent several months growing and producing. I prefer to just start tomato seeds indoors each year and have fresh plants for spring/summer.

Is basil an annual or perennial herb?

Basil is an example of the tenderest of tender perennials. It's what we call a short-lived perennial herb. It will die at the first sign of wintry weather, which is why gardeners in most climates treat basil like an annual and plant new basil each warm season by seed or from cuttings. In very warm climates, gardeners can enjoy growing basil outdoors for several years.

Keep a Mix of Annuals, Biennials, and Perennials in Your Garden for Year-Round Excitement

So there you have it! That's probably more info than you ever wanted to know about the life expectancy of plants. It's good to know the distinction between annuals, biennials, and perennials, so that you can plan out your kitchen garden and have a mix of all three growing. That way, you'll almost always have something growing and producing. It keeps things interesting!

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