Many gardeners love gladiolus because it has tall spikes of bright summer flowers. Gladiolus plants are usually put outside in the spring, and they flower in the middle to end of summer. But did you know that you can start gladiolus corms indoors before the plants sprout outside?
Growing gladiolus indoors also known as forcing glads allows you to enjoy their gorgeous blooms 4-6 weeks earlier than normal outdoor planting time. Starting glads inside is a great way to get a jump on the season, especially if you live in an area with a short outdoor growing season.
In this complete guide, we will cover everything you need to know about successfully growing gladiolus indoors, including:
Why Start Gladiolus Indoors?
There are several advantages to getting a head start on gladiolus by planting them indoors first:
Enjoy flowers earlier – Glads started indoors can bloom up to 1-2 months sooner than outdoor planting
Lengthen bloom time – By staggering indoor plantings, you can have glads blooming over a longer period.
For short-season climates that are prone to early frost, forcing glads indoors helps make sure they bloom.
Test new varieties – Grow new corms indoors first to evaluate them before planting outdoors.
Add indoor color – Use forced glads as temporary living decor in the home.
When to Start Gladiolus Indoors
Timing is important when forcing glads indoors. Follow these tips:
Start glads indoors 4-6 weeks before your average last spring frost date.
Allow sprouted bulbs to grow indoors for 4-5 weeks before moving outside.
Transplant sprouted glads outdoors when nighttime temps remain above 60°F.
Supplies Needed
A few basic supplies are needed for starting gladiolus indoors:
Gladiolus corms – Purchase new corms or use stored corms from the previous season. Select large, healthy corms.
Container – Shallow trays, pots, or buckets work well. Make sure container has drainage holes.
Growing medium – Use a well-draining potting mix made for starting seeds/bulbs indoors.
Water – Use room temperature water for indoor forcing.
Light – A sunny window or grow lights to provide bright, indirect light.
Step-by-Step Growing Guide
Follow these simple steps for successfully forcing gladiolus corms indoors:
1. Prepare Corms
Select plump, blemish-free corms that haven’t sprouted yet.
Optional: Soak corms in room temperature water overnight to pre-sprout.
2. Plant in Containers
Fill container with moist potting mix.
Plant corms 2-3 inches deep and 1-2 inches apart, pointed end up.
Water soil until moist but not saturated.
3. Provide Warmth & Light
Place containers in warm spot (65-75°F) with bright, indirect light.
A sunny window or grow lights work well.
4. Monitor Moisture & Growth
Check soil moisture daily, water as needed to keep damp but not wet.
Watch for sprouts emerging in 2-3 weeks.
5. Harden Off & Transplant Outdoors
Gradually introduce to outdoor conditions over 7-10 days.
Transplant sprouted glads outdoors when soil is above 60°F.
Growing Medium Options
You have a choice of starting gladiolus corms in soil or water:
Soil – Plant in pots/trays filled with moist potting mix. Provides stability & nutrients. Requires more space than water.
Water – Place corms close together in shallow water, just covering base. Simple & space-saving but water must be changed frequently to prevent rotting.
Troubleshooting Common Problems
Here are some potential issues and how to prevent them:
Leggy growth – Caused by insufficient light, move to a brighter spot or use grow lights.
Rotting corms – Usually caused by overwatering, allow soil to partially dry between waterings.
Floppy stems – Tall, weak stems need support, stake stems to keep them upright.
Few or no blooms – Likely due to inadequate chill period, be sure to store bulbs properly after digging.
Deformed blooms – Can be caused by extreme temperature changes, keep growing area stable.
Growing Gladiolus Year-Round
By starting glads at strategic intervals, you can have gladiolus blooms nearly year-round:
January – Force bulbs for mid-late spring blooms.
March – Start bulbs for early summer blooms.
May – Plant outdoors for mid-late summer blooms.
July – Start bulbs for late fall blooms indoors.
If you plan ahead, you can bring colorful gladiolus blooms into your home during the winter months when garden color is limited. Forcing gladiolus indoors is simple and rewarding. This year, give it a try and enjoy the beautiful early glads!
Yes, gladiolus can be grown successfully in pots, provided the containers are large and deep enough to accommodate their root systems and tall stems.
Are gladioli indoor plants?
If you can’t wait for spring to get started, starting gladiolus indoors will give you the leg up you’re craving.
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How to Start Gladiolus Indoors
To be clear, gladiolus have corms, not bulbs. But many gardeners refer to them as “bulbs,” so we’ll being using the terms interchangeably in this guide.
Spring can’t come early enough, as far as I’m concerned. So let’s not wait one minute more!
Four to six weeks before the last predicted frost date in your area, prepare the corms.
Whether you purchase new bulbs to plant or you’re restarting some that you lifted in the fall and kept in storage, you need to prepare them for planting.
Some retailers won’t carry gladiolus during the off season but others have them in stock, so if you’re buying new, it pays to shop around.
Eden Brothers, for example, carries a fantastic range, from the tricolored pink, pale yellow, and creamy white ‘Mon Amour’ to the blood-red ‘Black Star.’
Or maybe you want a mixture of colors. If so, visit Burpee for a Glamini mix in yellow, red, purple, and white.
Brush off any dirt from the overwintered bulbs with a soft, dry brush. Divide up any large clumps. Purchased bulbs should be clean and already divided up for you.
You can optionally set the corms in water overnight to encourage them to open up and start growing.
Either submerge them entirely or just set the base in the water. This just speeds up the sprouting process, but it’s not essential.
Fill a flat or a container that’s at least eight inches deep with fresh, water-retentive potting mix.
If you have lots of gladiolus corms, consider using a large storage bin – 18-gallon or larger. Just remember to put it in place before you start filling it up, because it’s going to be heavy to move.
If you don’t have anyone to help you move the container, you might want to put it on wheels or in a wagon.
Plant the corms approximately two to four inches deep, depending on the size, as you’ll want them twice as deep as the length of the corm. Make sure the pointy end is facing upwards.
Water the medium well so that it’s moist but not soaking wet or soggy.
Put the pot somewhere warm and sunny inside that gets at least six hours of direct sunlight every day. Make sure the soil stays moist.
You can also use supplemental lighting if you don’t have an area with enough exposure.
Allow the top inch of the soil to dry out between watering.
Be cautious if you’re using a large storage container, because it’s easy to add too much water to the point where the soil starts becoming soggy at the bottom of the container, which can lead to rot.
Within a few weeks to a month, you should see new growth popping out of the soil.
The gladiolus plants can go outside as soon as it’s at least 60°F at night and they have at least three leaves.
Before you can put them in the soil and soak up the beauty, you need to harden the plants off as they’re used to the easy life of an indoor environment.
To harden them off, take the growing container outside and set it in or near the spot where the gladiolus will eventually be planted. Leave the pot there for an hour and then bring it back inside.
The next day, leave it out there for two hours before bringing it in.
You’re going to need a helper with a strong back if you used a large storage container! You can probably skip ab day after the workout you’re going to have.
Keep adding an hour each day until the plants can stay outside for a full eight hours.
At this point you can transplant your gladiolus (or leave them growing in their pots).
Prepare the planting area by digging enough holes for all your corms. It’s better to dig a larger hole than you think you’ll need so you don’t have to try and wedge the corm into it.
Gently push your hands into the soil and dig down underneath the roots of each plant. You can also use a trowel, but I like to use my hands because I can really feel the root system and it helps to avoid damaging the roots.
Lift the gladiolus out of the soil and place it in the ground. The corm should be sitting at the same depth as it was in the growing container. Repeat until all your corms are in the ground.
Firm the soil up around the corms and water in well. You might need to add a little more soil if it settles.
Visit our comprehensive guide to growing gladiolus for tips on how to grow and care for this ornamental beauty.
Growing gladiolus indoors
FAQ
How to grow gladioli inside?
Press the gladiolus corm into the ground so that only half of it is in the ground. The pointy end should be facing up. Water the soil and gladiolus corms so that the soil is damp, but not soaked. Keep the soil damp while the gladiolus are indoors. Place the container of gladiolus corms in a location with bright, indirect light.
Can gladiolus live indoors?
Trying to keep one plant blooming nonstop indoors won’t work well, but you can stagger plantings in cycles to get near-continuous blooms. You can grow them indoors only, but it’s best if you can move them outside in the summer and bring them inside in the winter.
Do gladioli do well in pots?
Yes, gladiolus can be grown successfully in pots, provided the containers are large and deep enough to accommodate their root systems and tall stems.
Are gladioli indoor plants?
Starting gladiolus indoors will give you the boost you need if you can’t wait for spring to come.
