Judging the size of a plant can be tricky when all you have to go by is a seedling, especially if the plant is a gift from a friend or a cutting from a neighbor's garden. These plants don’t always come with helpful little care instructions or varietal information like size, which can make choosing a place in your garden or home a little tricky.
Here are some common plants that get bigger than you expect, from herbs to indoor ornamentals, so that you don’t get taken by surprise.

Comfrey

Comfrey flowers

Comfrey is an herb with a history of healing attributes. It can be used as a compress, salve, or drank as a tea to treat a variety of illnesses and wounds. Comfrey also makes a great addition to compost piles, adding nutrients and acting as an activator, and some gardeners use it as a mulch and fertilizer.

I have received comfrey from multiple friends who were dividing up their herbs, and it didn’t take me too long to figure out why comfrey divisions were so popular. Before you add this powerhouse of a plant to your herb garden, there is something you should know—comfrey gets big. Comfrey matures at three to five feet tall and two to four feet wide, making it more like a shrub than an herb, which is wonderful if you use it on a regular basis, and a bit overwhelming if you imagined something a little more tame.

Rosemary

Growing up in the northeast, I always assumed that rosemary was one of the more petite herbs, as I rarely saw it grown outside of containers. You can imagine how surprised I was when I moved south and discovered that rosemary is frequently grown as a hedge and can reach three feet in height and stretch up to five feet in diameter unless regularly trimmed.

Perennial Hibiscus

If you live in zone 5 or higher, you might be tempted to plant the alluringly tropical hibiscus. However, this is no tender hothouse bloom. Perennial hibiscus produces flowers up to a foot in diameter, and the stems can grow to seven feet tall. This spectacular plant is a real eye catcher in the garden, but you might not want to plant it below a first floor window.

Black Eyed Susan

Black Eyed Susan always puts me in mind of summer, but certain varieties can grow up to six feet tall. This makes them ideal for filling in the back of the garden border and for cut flower arrangements, but it can come as a surprise to gardeners expecting a medium-sized flower.

Mint

Mint plant

If you are not already aware of mint’s tendency to spread, consider this fair warning! Mint may only grow to be about two feet tall, but this opportunistic herb can take over an entire garden in a season. If you love mint, consider growing it in a container; it is incredibly difficult to eradicate once established.

Aloe Vera

Aloe vera, like comfrey, is a plant with a long history of medicinal use. This succulent does well in the ground and in containers and is famously easy to grow. What you might not realize is that aloe vera can get surprisingly large. Single plants can grow up to two feet tall and over 14 inches wide, and clusters of aloe can grow to over 10 feet in diameter. If you live in a warmer climate, keep an eye on your aloe vera, as it has a tendency to spread and you will quickly end up with more aloe than you know what to do with.

Bamboo

Equating the giant bamboo jungles of Asia with the little bamboo plants sold as house plants in stores is difficult, but this perception can be dangerous. Bamboo is big, it grows quickly, and it is also invasive. There are many different species, and while some mature at only a few inches tall, others can reach towering heights of over 100 feet; most fall somewhere in-between. If you cultivate bamboo in your garden, be sure to control the spread of this prolific plant.

Jade Plant

Jade plants (Crassula ovata) are one of the more popular indoor succulents. These trees are charming, adaptable, long-lived, and can grow up to ten feet tall under the right conditions. Many gardeners grow jade in containers, which limits their growth, but trimming your jade plant will also keep it a more manageable size. If you let it grow unchecked, however, you might be in for trouble.

Bird of Paradise

Bird of Paradise flower

Another popular house plant, Bird of Paradise produces the spectacular flowers that give the plant its name. What you might not know is that the plant can grow up to eight feet tall, making it a truly impressive centerpiece and a domineering presence in the room.

Bay Laurel

Bay laurel is an evergreen shrub grown as an ornamental plant and as an herb. The leaves of the bay laurel (bay leaves) flavor soups and stews, and as such, it is a popular container plant. It is relatively hardy, especially when grown in the ground, but if left untrimmed, this attractive tree can grow up to 20 feet tall, taking up a considerable amount of real estate in your yard and garden.

Doing a little research is always a good idea before planting. Not only can some common plants get a lot bigger than you expect, but knowing their light and soil requirements can help you find the perfect place in your garden for them to thrive.