Are you wondering how to grow gladiolus, those showy flowers with tall, elegant stems? Gladiolus has a super special spot in my heart.

Growing up, my grandpa was the guy with the green thumb in the family. Besides being a full-time farmer, he had this thing for gladiolus. Every summer, his garden was a sea of colorful spikes, and you could always find a bunch of them brightening up my grandparents’ dining room table.

But let me tell you – these flowers aren’t just a sentimental favorite of mine!

In this guide, I’m going to break down the steps to grow gladiolus (aka: sword lilies) in your own garden or even in pots. Plus, we’ll dig into some cool facts about these awesome flowers and tackle common questions.

This is a long post with a lot of detail, so if you just want the cliff note version I’ll break it down right here:

So, if you’re ready to add a splash of color to your garden, let’s roll up our sleeves and get planting!

How to Grow Gladiolus

A gladiolus grows from a type of bulb that is technically referred to as a corm. 

Here’s what gladiolus corms look like:

Corms differ from bulbs in that they have a rounded shape, a pointy growth stalk and tiny outcroppings that signal new growth. Some internal structures also vary from your standard flower bulb. 

Corms differ from bulbs in that they have a rounded shape, a pointy growth stalk, and tiny outcroppings that signal new growth. Some internal structures also vary from your standard flower bulb, making them unique among flowering plants.

If you’re interested in more details, this article from the University of Illinois explains the differences between true bulbs and corms in greater depth. 

But, let’s not get bogged down in the details. Whether you’re looking to plant gladiolus corms or true bulbs, the planting and care process is pretty much the same. You might hear folks commonly use the term “gladiolus bulbs,” so we’ll stick with that to keep things simple.

Now, let’s move on to the gladiolus planting process.

Preparing to Plant Gladiolus

Investing time in the necessary prep work can help you enjoy the best color and yield from your gladioli.

Follow these steps to lay the proper groundwork:

In-Ground or In a Container? You have the option of either growing your gladioli in an in-ground garden (which is the most common method) or using a large container, like a raised bed or a large flower pot.

If you’re using a container, look for one that’s at least 12 inches in diameter and 16 inches deep. 

Here are a couple of options to consider:

• Bloem Ariana 20-Inch Pot
• Foyuee Galvanized Steel Raised Bed

Keep in mind that gladioli need good drainage, so make sure that whatever container you choose has pre-drilled drainage holes.

Raised bed frames, like the one pictured above, have an open bottom that sits directly on the ground, providing plenty of natural drainage. 

Decide on your planting location. Choose a location that gets full sun. Gladiolus will still grow even if it gets shade for part of the day, but the colors will be less vibrant.

And due to their tall height, make sure to place your gladiolus behind shorter plants to avoid obstructing their sun exposure. 

Ensure proper soil texture and keep the soil moist. Gladioli like their soil to be a sandy loam with good drainage, but they also need the soil to be moderately moist.

If you’re looking to plant gladiolus in-ground or in a large raised bed, mix topsoil with organic matter (like compost) in about a 60/40 ratio. To achieve that loose, sandy texture gladioli love, add potting mix to the soil you just blended.

If you’re filling just a few flower pots, you can skip the soil-blending and use commercial potting mix by itself. The Miracle-Gro formula we mentioned above is a great choice. 

Plan for the right planting time. Gladiolus is a summer flower, so aim to plant roughly two weeks before the end of your local cold season and all the way up to July.

However, some varieties thrive even if planted early or late in the season. For a continual show of color, you may want to choose a few varieties with staggered blooming patterns. 

Choose healthy bulbs. For the largest and strongest plants, select gladiolus bulbs that have a rounded shape and are at least 1 ¼ inches in diameter.

Smaller bulbs will typically still germinate and grow, but you’ll likely end up with much smaller blooms.

Don’t use any bulbs that have soft spots, discoloration or have a misshapen, flat bottom. These bulbs may be harboring plant diseases or insect eggs, so discard them. 

To soak or not to soak? Gladiolus growers are divided on this point. Some people are convinced that soaking their bulbs prior to planting leads to faster germination, while others completely skip it. 

Gardeners in both camps successfully raise beautiful flowers, so the choice of soaking or not is up to you.

If you decide to pre-soak your bulbs, do it the day before you plan to plant. Fill a bucket with tap water, and place your bulbs in for about an hour. Then set them on an old towel until planting time. 

How to Plant Gladiolus Bulbs in Pots or In-Ground

After selecting just the right sunny location for your gladiolus plants, follow these steps to settle your bulbs into their new home:

1. Dig a Hole and Plant Your Bulb.

With a hand trowel, dig a small hole about 4 inches deep. Place a scoop of compost at the bottom of the hole for an extra nutritional boost. 

Place the bulb’s pointed end upwards towards the surface; this is where the flower spikes will emerge. Then cover it up with soil and press down on the area firmly. Congratulations, you’ve successfully started to plant gladiolus in your garden!

2. Space Your Bulbs Appropriately

Gladioli get quite large, but they don’t mind growing in close quarters.

Different varieties may need less or more space to grow, but a good general rule is to space your bulbs about 6 to 8 inches apart.

If your primary goal is to raise gladiolus for cut flowers, plant your bulbs in a straight row. This makes it easy to reach the flower stalk for cutting.

Otherwise, if you have a vision for a dense gladiolus patch, plant your bulbs in a grid pattern, like the photo shows:

If you’re planting in a flower pot, it’s better to err on the side of planting fewer bulbs than risk overcrowding. 

So if you choose a 12-inch pot, plant one bulb per pot. If you choose a 16-inch pot, you’ll have a maximum of two bulbs, and so on. 

3. Water Your Bulbs Well

Thoroughly water your newly-planted bulbs, making sure to saturate the soil and keep it moist.

Since gladiolus prefers well-drained soil and only moderate amounts of water, you’ll want to avoid soaking the ground in the future. 

But the bulbs need plenty of moisture to start the germination process, so be generous with the water immediately after planting!

4. Place a Support Stake (Optional)

Depending on the variety you’re growing, you may want to stake your gladioli for extra support, especially as the flower spike begins to emerge. This can be particularly helpful if you plan to cut bouquets. 

You can place your stakes immediately after planting, just make sure that you’re careful not to damage your bulb. 

Where to Find Gladiolus Bulbs

Given the lack of gladiolus in the average home garden, it might be easy to assume that the bulbs are expensive or hard to find.

Not so!

Gladiolus bulbs tend to be about the same price as most other common bulbs, like daffodils or hyacinths. However, some of the more splashy gladiolus varieties tend to cost more. 

But keep in mind that you can replant healthy, well-cared-for bulbs every year, so you may only have a one-time investment. 

Most big chain stores, like Home Depot and Lowe’s, usually have gladiolus bulbs available. Nurseries and other specialty plant shops may also have several different varieties.

And of course, online resources abound!

Blooming Bulb offers an incredible selection of gladiolus varieties in a rainbow of colors and color blends. This can be an especially great option if there’s a particular, rare variety you’re looking for.

Also, Amazon normally has a few varieties to choose from, like this Peaches and Cream mixed set.

Caring for Gladiolus

Most gardeners consider gladiolus to be one of the easier flowering plants to grow.

As long as they get the sun they crave and enough water, gladiolus thrives even with minimal maintenance. And they also tend to be fast growers, so you’ll soon see the rewards!

Here’s what you need to do to keep your gladiolas happy:

Watering

Gladiolus plants needs a minimum of 1 inch of water per week, so make sure to give them a drink if the rain doesn’t take care of it for you. Pay attention to the water needs as the flower spike begins to grow; it’s essential for healthy blooms.

Keep in mind that flowerpots typically dry out faster than large raised beds or in-ground gardens. Check the soil moisture regularly, especially during dry spells or heat waves. 

Fertilizing

We’ve already mentioned adding compost during the planting process, but your gladioli will be glad for a little more nutrition through the summer!

Apply a side dressing of organic, water-soluble fertilizer once your gladiolas are 10 inches tall and the flower spikes start to show. This all-purpose formula from Fertilome works well and is particularly beneficial for nourishing gladiolus bulbs. 

Once the flowers start to show their colors and the flowers bloom, side dress your plants again. This helps keep colors vibrant and long-lasting. 

Overwintering

As a tropical flower, gladiolus is fairly intolerant of cold weather.

If you live in USDA hardiness zone 7 or lower, you’ll need to dig your gladiolus bulbs after the first killing frost. 

Allow your bulbs to cure by leaving them exposed to sunlight for a couple of days. Then store gladiolus bulbs in a breathable container, like a cardboard box or paper bag, and store indoors in a cool, dry place. 

If you live in a warmer areas, your bulbs can safely stay in the ground all winter.

However, some newer gladiolus varieties are more winter hardy and appear to have more resistance to cold temperatures, with some advertising cold-hardiness through zone 4. 

If you’re not sure which zone your area falls into, consult this map from the U.S. Forest Service to find out. 

Potential Problems to Watch Out For

Although gladiolus generally grows problem-free, always keep an eye out for pests and plant diseases. 

Here are the ones that present a particular danger:

Common Harmful Insects

Several kinds of garden pests may attack your gladiolus, damaging your plant’s foliage as they feast on sap and foliage. 

The photos show the most common pests you’ll run across: aphids, whiteflies, mealybugs and thrips.  

Some of these bugs are tiny and hard to see, but white and yellow spots showing up on your gladiolus leaves are a telltale sign. 

To treat any of these pests, spray your plant with a natural pesticide. Pure neem oil is a perfect option.

Keep in mind that neem oil isn’t as strong as commercial chemicals, so you’ll probably have to apply it a few times before your pest infestation completely clears up.  

Mosaic Virus

Various forms of mosaic virus infect many different plants, and gladiolus is susceptible to a couple of different strains. 

Mosaic virus causes leaves to develop yellowed areas, typically along the foliage vein lines. 

Unfortunately, once a plant contracts mosaic virus, you can’t do anything to treat it. Your only option is to remove the entire plant, bulb and all, and destroy it. 

Since mosaic virus can spread to other plants, act quickly to avoid losing your entire gladiolus garden. 

Prevention is the best strategy here. Viruses often live within dormant bulbs, so carefully look over your bulbs prior to planting. An infected bulb will often have discoloration or a crumbly/soft spot, so discard them immediately.  

Final Thoughts

When it comes to a bright rainbow of colors, large blossoms and a strikingly tall height, gladiolus is a true standout! What’s more, they’re low-maintenance plants and make for a long-lasting cut bouquet. 

So take a page from the history books and add a touch of vintage beauty to your garden with gladiolus!

What are your thoughts on gladiolus? Where would you plant them: In a pot, along a sunny fence, or somewhere else?

Share your thoughts in the comments!