Marigolds are stunning annual houseplants that are popular and primarily grown for their beautiful flowers. These flowers are typically orange, yellow, or red and are typically densely packed on the plant’s shoot or solitary, depending on the marigold species you’re growing. However, like with every other houseplant, you might encounter a few issues getting the plant to grow tall.
To fix marigolds that aren’t growing tall:
- Move the plant to where it can get enough sunlight.
- Ensure you use well-draining soil for the marigold plants.
- Optimize your watering practices.
- Control the amount of humidity around the marigold.
- Check that the temperature isn’t too high.
While marigolds can reach a maximum height of between 6 inches and 5 feet (15 and 152 cm), yours might struggle to grow tall. I wrote this article to serve as a complete guide for gardeners dealing with underdeveloped marigolds, and you’ll learn quick and easy solutions to make your plant thrive.
1. Move the Plant to Where It Can Get Enough Sunlight
All green plants use sunlight to perform photosynthesis and create energy for their life processes. They use this energy provided by the sun to grow deeper roots, bloom, and develop extensive shoots.
However, these plants require this sunlight in specific amounts—too little, and they don’t grow tall; too much, and you risk burning them.
Marigolds need at least 6 hours of sunlight to thrive, and they also prefer to stay under the sun. And while most houseplants prefer to stay in the shade or mild sunlight, marigolds will flourish in the blazing sun.
Therefore, I advise you to move your marigolds to a spot with plenty of sunlight—maybe a porch or an appropriately positioned window—if they’re not growing as much as they should.
You can also use a grow light if you live in a region where you don’t get enough sunlight.
2. Ensure You Use Well-Draining Soil for the Marigold Plants
Plants need soil for support and nutrients, but not every kind of soil is suitable for your plant. Soil deficient in essential nutrients will result in poor plant growth just as much as soggy soil will. So, you must be careful when choosing suitable soil for your marigolds.
Marigolds prefer almost any well-draining soil and you might need to add perlite to potting soil or sand to garden soil before planting them. This material will help improve drainage and ensure you don’t end up with small or underdeveloped plants.
Keep an eye out for the soil pH, as this can also affect the plants. Marigolds generally prefer neutral pH (between 6.0 and 7.0), and higher or lower numbers could lead to severe issues and affect the plant’s development.
I’d recommend you go easy on the fertilizer when keeping marigolds since they’ll flourish in leaner soil. They typically take only two months from seed to bloom, but if it’s been over a month since you’ve planted your marigolds but they’re not growing as fast as you expect, you can use fertilizers.
If you must use fertilizer, opt for organic fertilizers. Marigolds don’t feed heavily on soil nutrients but they grow well with an application of a balanced liquid 10-10-10 NPK fertilizer a week after planting to give them a good start.
On the other hand, applying a phosphorus-rich (5-10-5) liquid fertilizer after 5-6 weeks will promote flowering.
Pro-tip: As soon as you realize your marigolds are growing slowly, check the light, water, temperature, and soil drainage. If you’re confident they’re all optimal, you can apply a balanced liquid fertilizer and observe the plant’s response.
3. Optimize Your Watering Practices
Every gardener knows watering is essential to growing beautiful plants—outdoors or indoors. However, you need to optimize the amount and quality of water you give your plants, just like with sunlight, to ensure the plants thrive.
Your marigold is most likely underwatered if it’s not growing tall. Fortunately, marigolds have somewhat tame needs when it comes to watering, unlike other plants.
In the first two weeks of growth, marigolds need constantly moist but not waterlogged soil. The seedlings need enough moisture to establish healthy roots. During this time, you must keep the top 3 inches (7.6 cm) of soil hydrated to support the shallow roots.
Without enough moisture during this stage of development, your plant will likely struggle to grow to its maximum potential.
Once the roots have grown long enough—approximately 3 weeks from sowing—the plant becomes drought-tolerant. At this stage, you can water the soil 1.5-2 inches (3.8-5 cm) of water per week. This is equal to 1.2 gallons (4.6 liters) of water per square foot (0.09 sqm).
The watering frequency can vary depending on the temperature and soil drainage in your area. You can divide the amount into two watering sessions per week, making sure that the top 8 inches (20 cm) of the soil is adequately hydrated each time.
For potted marigolds, you must water the soil deeply and wait until the top 2-3 inches (5-7.6 cm) of the soil is dry before watering again. Check the soil about 5 days after deep watering to see if the soil is dry enough. If it’s still moist, give it 1-2 more days.
There are some signs to watch out for to confirm if underwatering is the reason for the marigolds’ stunted growth.
A telltale sign of underwatering is dry, faded, or wilted leaves and some parched marigold plants might also have curled leaves.
You should establish a consistent watering routine to fit the marigolds’ needs and use only clean water during the process. However, ensure you take care, so you don’t accidentally overwater the plant.
4. Control the Amount of Humidity Around the Marigold
Humidity and soil moisture content are closely related when keeping plants, and high or low humidity will affect your plants just as much as overwatering or underwatering. And while it’s necessary to keep the humidity of the plant’s growing environment at optimal levels, you must also ensure it’s constant.
So, I advise you to check the humidity levels in your home if you notice your well-watered plant is drying out.
Variations in humidity could stress the plant, resulting in faded leaves, root rot, underdeveloped plants, and an increased risk of disease. Of course, all of these could lead to shorter marigolds.
You should keep the humidity levels between 20% and 50% to ensure your marigolds flourish but take care to keep these levels as constant as possible.
A home humidifier is a great choice to regulate humidity since it’s easy to operate and quiet. But you might need to pair it with a high-grade hygrometer to ensure you keep track of the humidity levels. Alternatively, you can place potted marigolds on a pebble tray with water.
Outdoors, marigolds are sun-loving and have high heat tolerance. You can mist the foliage with water using your garden hose during midday on days you don’t water the plant. This can slightly improve the humidity around your marigolds and the leaves will have enough time to dry out by nightfall.
However, these might not be necessary if you live in a relatively humid region.
5. Check That the Temperature Isn’t Too High
High temperatures can reduce metabolic activity in marigolds and affect their development. These plants are especially at risk of being affected by heat since they prefer full sunlight to thrive. Therefore, it’s necessary to check that the heat isn’t too high to affect the plant’s natural biological processes.
Marigolds generally prefer temperatures between 70 and 90 °F (21 and 32 °C), and they’ll thrive at higher temperatures if they get shade at midday. Growing your marigold plants at these temperatures would be best to improve their growth.
However, scorching summers reaching over 95 °F (35 °C) can stunt your plant’s growth and cause heat stress even to the normally heat-tolerant marigolds.
You can add some water to the soil if the temperature is too high or move potted marigolds to a shadier spot where it’s cooler. However, ensure you don’t overwater the plants in the process. Remember to establish a watering routine that’s consistent with these temperatures.
Check the weather forecast regularly so you can make adjustments for your marigolds and ensure they grow to their maximum potential.
Marigolds typically vary in size depending on species, planter size, and several other environmental factors. However, a plant that’s not growing tall might be a symptom of a problem with the marigold’s growing conditions.
Pay attention to your plant’s symptoms and take proper care of your marigold plants if you want them to grow tall. Fortunately, it’s pretty easy to fix the underlying cause, and you should end up with healthy plants afterward.