Ageratum Growth and Care Guide

Ageratum is a charming annual flower known for its soft, fluffy clusters of blooms that resemble little clouds of color. Also known as Floss Flower, this flowering Annual comes in shades of blue, lavender, pink, and white. Ageratum brings a cool, calming touch to garden beds, borders, and containers. This Plant Guide will walk you through everything you need to know about growing and caring for Ageratum. We also highlight the top varieties and how to best use it in the garden. Lets dive in!

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By: Reggie Meehan (6/21/2025) -- Last Updated (2/4/2026)

Introduction to Ageratum (Floss Flower)

Ageratum is one of those plants that’s been around forever, but can still surprise you when you use it the right way. I’ve always loved it for those soft, fluffy blooms and colors that lean gentle rather than loud—blues, purples, pinks, whites. It's incredibly useful in mixed plantings where you want texture without stealing the show. Most of what we grow and talk about today falls under Ageratum houstonianum, a workhorse species that holds its color well and behaves nicely in beds, borders, and containers.

It’s worth noting that a different plant, Conoclinium coelestinum, is sometimes referred to as "Hardy Ageratum" due to its similar-looking flowers. That plant, better known as mistflower is a native perennial that blooms later in the season and belongs to a completely different genus than Ageratum. It’s a good plant in its own right, but it’s not what we’re talking about here. When I say Ageratum, I mean the annual, dependable, sun-loving plant that keeps blooming through the heat of Summer. 

I have regularly planted annual Ageratum in my gardens, pots, and hanging baskets as it provides a long lasting true periwinkle blue color. In recent years, the newer varieties not only provide a more resilient plant, but also provide a larger selection of bloom colors. Their resilience and ease of care make them a top pick for gardeners of all skill levels. This coming year, I will be welcoming the breakthrough variety, Monarch Magic Ageratum, to my gardens.

Characteristics of Ageratum

Ageratum is compact, dependable, and blooms far longer than you’d expect from something so tidy. Once established, it doesn’t ask for much, but keeps showing up day after day looking the same as it did weeks and months earlier. Beyond looks, it pulls its weight ecologically too. Bees and butterflies are regular visitors, especially during the heat of summer when other flowers start to slow down. It’s the kind of plant that fits easily into a garden—pretty, useful, and low-maintenance all at once.

Size and Growth Habit

Ageratum comes wide range of sizes, which is part of what makes it so versatile. Depending on the variety, plants can stay as short as 6 inches or stretch closer to 30 inches tall. Compact types tend to top out around 8-12 inches tall and wide, forming neat, mounded plants that stay right where you put them. I like using these along walkways, at the front of beds, or in containers where scale really matters.

Taller varieties can play a completely different role. Reaching 24 to 30 inches, they bring height and airiness to the middle or back of the border without feeling heavy or stiff. The flowers sit well above the foliage on sturdy stems, adding movement and a soft vertical layer that pairs beautifully with other medium-height plants. Choosing the right type of Ageratum—short or tall—makes a big difference in how a planting comes together.

Leaves and Flowers

Is Ageratum Annual or Perennial? 

Ageratum is typically grown as an annual in most regions, including USDA Hardiness Zone 8A here in South Carolina, where it cannot survive Winter frosts. It performs best in warm months and may occasionally self-seed, though it rarely overwinters in cooler areas. In tropical climates, particularly USDA Zones 11–12, species like Ageratum conyzoides can behave as short-lived perennials. These varieties thrive in year-round warmth and may bloom continuously in humid environments. Beware A. conyzoides often grows wild and can spread aggressively, even becoming weedy in some areas.

Best Varieties of Ageratum

Over the years, I’ve grown a lot of ageratum—some that impressed me right away, and others that looked good on paper but didn’t hold up once summer set in. The varieties I come back to are the ones that stay neat, bloom consistently, and don’t need constant attention to look good. The selections below are the ageratums I recommend most often, based on how they perform in our climate, how useful they are in real garden designs, and how reliably they deliver color season after season.

Monarch Magic™

This Ball Floral introduction in 2024 is receiving the #1 rating based it is true to its tagline, “A one-of-a-kind spreading Ageratum that monarch butterflies can’t resist!” In sum, 'Monarch Magic' is amazingly unique as it both spreads and trails (and mounds). We recommend Ageratum adjacent to your orange blooming Butterfly Weed so the Monarchs will be drawn to it and can feed on your Asclepias so that we can have more Monarch butterflies!!! And the blue and orange combo will POP in your garden!

Does this variety have the impressive numbers to be #1? No. It is not the most planted Ageratum, nor the most researched, nor the most in demand, YET. But it will be. So, #1 it gets. And, did we mention it ranked 5.0 in the plant trials in 2024 and that it is so good that Proven Winners sells it as a Proven Selection?

Aloha Series

The most popular Ageratum in local garden centers. Aloha Blue has been around for decades so there is no trial data. Since it originates from seed, it can be found in less expensive flats. It is relatively compact and works well as a groundcover or grown as a filler in larger containers including hanging baskets. Aloha White is far less popular, and generally are only available by seed. Again, true blue colors are rare and this soft periwinkle blue is as versatile as it is pretty. Plus, it is easy to grow, and flowers all season.

Blue Horizon

Ageratum 'Horizon Blue' is a larger Ageratum (18-30” tall) that not only received a 5.0 trail ranking in 2024, but it was also the first Ageratum found to be “suitable” for cut flower use. This Ageratum it can be dried for use in dried flower arrangements. The sky's the limit with Horizon Blue.

How to Grow and Care for Ageratum

Ageratum gives you a lot back for very little effort, which is why I recommend it so often. Once it’s planted in the right spot, it tends to take care of itself, blooming steadily from late Spring right up until frost. The key is getting the basics right; good spacing, decent soil, and enough sun.

Planting Ageratum

Ageratum should always wait to be planted well after the danger of frost has passed. It is intolerant of cold conditions (40°F or lower) and rushing it rarely pays off. I space plants about 6 to 12 inches apart depending on the variety, which gives them room to fill in without competing for air or light. That spacing also helps prevent disease later in the season, especially when summer humidity rolls in.

If you like starting from seed, ageratum is very cooperative. Seeds can be started indoors 6 to 8 weeks before your expected last frost date, or you can simply plant young transplants once the weather settles. Either way, choose a spot with good drainage and decent airflow. 

Sunlight Requirements

Ageratum does best in full sun, and that’s where you’ll see the most flowers and the best plant shape. That said, it’s more flexible than people expect. In hotter climates, a little afternoon shade can actually help plants hold their color and avoid stress during peak summer heat. I usually aim for at least six hours of sun a day, with morning sun being especially valuable. Too much shade, though, and you’ll start to see stretching and fewer blooms.

Soil Requirements

Good drainage matters more than rich soil when. It prefers a well-draining garden soil that doesn’t stay wet for long periods. While Ageratum performs best in moderately fertile conditions, it’s surprisingly adaptable and will still do fine in less-than-perfect soil as long as water doesn’t sit around the roots. A slightly acidic to neutral pH—somewhere between 6.0 and 7.5—keeps it happy and growing steadily.

Watering Needs

Ageratum likes consistent moisture, but it does not like wet feet. I water regularly, especially during dry spells, but I always let the top inch of soil dry out between waterings. Once established, it’s more drought-tolerant than people realize and bounces back well after short dry periods. Container-grown ageratum needs a little more attention since pots dry out faster, especially in Summer. Check moisture often, but don’t fall into the trap of watering every day just because it’s hot.

Fertilizer Needs

Ageratum isn’t a heavy feeder, but it does appreciate a little help. I like to use a balanced, slow-release fertilizer at planting time, then supplement lightly during the season if needed. Monthly feeding is more than enough. Too much fertilizer will give you lots of leafy growth and fewer flowers, which defeats the whole point of growing it in the first place.

Pruning and Deadheading

You’ll often hear that modern Ageratum hybrids don’t need deadheading, and technically that’s true. Modern varieties are "bred to cover their dead,” meaning new blooms hide the older, fading ones. That said, in real gardens, things don’t always line up perfectly. If older blooms start showing through or looking tired, a little deadheading goes a long way toward freshening the plant back up.

Older series and some compact types, like Aloha Blue and Blue Hawaii, benefit most from occasional cleanup. For taller varieties, such as Blue Horizon, a mid-season trim can be helpful if plants start stretching or losing their shape. A light cutback encourages fresh growth and keeps the plant looking intentional rather than worn out.

Overwintering

Ageratum is not frost-hardy, so in most climates it’s grown as an annual. Once frost hits, it’s done. In frost-free regions, plants can sometimes be cut back in late Fall and allowed to regrow the following season, though results vary. For most gardeners, it’s easiest—and most reliable—to replant fresh each Spring.

Common Pests

One of the many things I appreciate about Ageratum is how little trouble it has with pests. It’s generally ignored by deer and doesn’t attract many problem insects. Occasionally, you might see aphids, whiteflies, or thrips, but serious infestations are rare. Spider mites can show up during hot, dry weather, but they’re easily managed with neem oil or insecticidal soap if caught early.

Common Diseases

Ageratum isn’t especially disease-prone, but problems can show up when plants are crowded or kept too wet. Botrytis, root rot, and leaf spot are usually tied to poor air circulation or soggy soil, especially in flats or densely planted beds. Giving plants space, watering properly, and removing any affected leaves quickly will prevent most issues before they spread.

Common Mistakes

The biggest mistake I see with Ageratum is assuming it never needs any maintenance at all. While it’s true that modern varieties hide their spent blooms better than older types, they don’t always do it fast enough to stay picture-perfect. A little cleanup now and then keeps plants looking fresh.

The other common issue is not enough sun. Ageratum that doesn’t get at least six hours of light a day will stretch and lose its tidy shape. Give it sun, don’t overwater it, and resist the urge to overfeed—and you’ll be rewarded with steady color and a plant that behaves itself all season long.

Common Misconceptions

A common misconception about Ageratum is that it only flowers in blue. It also blooms in white, pink, and purple varieties but these varieties may be less available. Another misconception deals with the perennial or hardy Ageratum being confused with the annual ageratum, Ageratum houstonianum. The perennial Conoclinium coelestinum, which is also commonly referred to as hardy Ageratum, is not an Ageratum and it is not the same species. Finally, Ageratum is NOT Edible. It contains toxic compounds and should not be eaten by humans, pets, or wildlife.

Using Ageratum in the Garden

Ageratum is one of those plants that earns its keep in just about any setting you put it in. It’s adaptable, steady, and easy to work with, which makes it a great choice whether you’re planting your first garden or refining a space you’ve been tweaking for years. I like it because it plays well with others—it fills gaps, softens edges, and brings consistent color without demanding constant attention. From clean borders to pollinator-focused beds and containers, Ageratum does its job well.

Borders and Edging

This is where Ageratum really shines. Compact varieties, like the Aloha Series, are ideal for edging because they grow evenly, stay low, and don’t wander out of bounds as the season goes on. I use them to line walkways, frame garden beds, or create a clean transition between different planting areas. The flowers add color without blocking sightlines, and the plants hold their shape even in the heat of Summer. When you want a border to look intentional from Spring through Fall, Ageratum is one of the easiest ways to make that happen.

Pollinator Gardens

Ageratum is a pollinator magnet, with its nectar-rich blooms attracting bees, butterflies, and other beneficial insects. It’s a perfect addition to eco-friendly landscapes that prioritize biodiversity. Planting Ageratum alongside other pollinator-friendly species creates a thriving habitat that supports your garden’s ecosystem. Don’t forget that Monarch Magic Ageratum is the #1 Ageratum for a reason … It actively attracts Monarch Butterflies!

Container Gardening

Varieties like Ageratum Artist Blue and Ageratum Bumblebee (in Blue, Silver, Rose & White) are perfect for container gardening, adding vibrant pops of color to patios, balconies, and small garden spaces. Their compact growth habit and continuous blooming make them easy to maintain in pots or hanging baskets. Ageratum pairs beautifully with other container plants, offering a cheerful and long-lasting display. Even Aloha Blue and Blue Hawaii can be used as fillers in containers and hanging baskets.

Ageratum Blooms All Season!

Looking to grow Ageratum in your garden? At Garden Delivery, we offer premium Ageratum plants, known for their soft, tufted blooms and rare true-blue color. Our varieties are carefully selected from trusted growers and bred for exceptional garden performance. Ageratum is ideal for borders, edging, and containers, thriving in sunny spots with long-lasting blooms from spring through fall. Plus, it’s a pollinator favorite! We provide detailed plant information and performance rankings to help you choose with confidence. Add Ageratum to your garden today and enjoy season-long color and charm with minimal effort.