Sunflowers have long been my favorite flower – not only in the garden but also in the vase. This might be because my favorite color is yellow or because their bright blooms instantly remind me of sunny days. But no matter where I live, I consider sunflowers a must-have.
I didn’t always have the backyard space to grow these surprisingly large plants. I’m sure there are many gardeners in the same boat. Happily, growing in containers offers an alternative for small spaces or urban gardens that lets you enjoy these beautiful plants to the fullest.
There are slight differences in planting and care to grow successful sunflowers in pots or containers. Follow these few tips to get it right.
Start With The Right Size Container
Container size matters for sunflowers due to their extensive roots.
Although growing sunflowers in pots or containers isn’t necessarily any more or less complicated than in the ground, many gardeners forget about the importance of container size. It’s easy to be swayed by the aesthetic appeal of a pot, but for sunflowers, it’s what’s inside (or, rather, the size of the inside) that matters.
Sunflowers have extensive root systems to support their tall stems. The roots grow deep and spread wide, requiring a large container to avoid stunted growth.
Around 8 inches deep and wide is the minimum for a dwarf sunflower. Still, the exact size will depend on the size of the variety you’re growing (especially the super-tall varieties, which often have deeper taproots to correspond with their height).
Width becomes even more critical if you’re tempted to plant multiple sunflowers in one container. But since sunflowers like their personal space and overcrowding can lead to a battle for resources, one plant per container is preferred.
Choose Materials Wisely
Plastic pots lack support and breathability, while porous terra cotta and ceramic pots are preferred for better airflow.
The material of the pot also plays a vital role in determining the plant’s success – although admittedly to a lesser degree than size.
Plastic containers are lightweight and offer more choices in shape and color but typically don’t offer the proper support. The lack of breathability in plastic pots can stifle the roots, requiring additional drainage to prevent rot. Plastic pots can also topple easily when the soil is dry, as sunflowers can quickly become top-heavy.
Porous and well-draining terra cotta and ceramic pots are the first choice for sunflowers. The breathability improves airflow around the roots and helps regulate the soil’s moisture levels, ensuring that the roots don’t drown in excess water or dry out from a lack of it. They are also less likely to be knocked over by the wind, avoiding mishaps in unsheltered areas.
Don’t Forget About Drainage
Proper drainage is vital for container sunflowers to avoid waterlogging and root rot.
If I’m ever asked about the most important things to consider when container gardening, the first answer is always drainage. You can get everything else on this checklist right, but your sunflowers still will not survive without good drainage!
Sunflowers love moisture. However, a balance is required to give them what they need at the right time, especially when growing in containers. Too much water and the roots become waterlogged, leading to root rot. Too little, and they dry out, causing wilting.
Drainage holes allow excess water to escape, preventing the soil from becoming waterlogged and ensuring an early death. Even if you do water earlier than you should on occasion, drainage holes will help remove the excess, allowing air to flow freely around the roots.
While most containers come with drainage holes, some decorative options don’t. Luckily, keeping a drill handy gives you the best of both worlds. Drill a few holes evenly in the bottom of the container, using the right drill bit for your chosen materials.
Choose A Smaller Variety
Dwarf sunflower varieties are ideal for containers and limited spaces, offering vibrant colors and compact growth.
Sunflowers come in an impressive range of sizes, from the majestic ‘Mongolian Giant’ to the more manageable dwarf varieties. When growing sunflowers in limited spaces, these dwarf varieties are your allies. They bring the same vibrancy of their taller relatives to urban gardens – just in a more compact package.
Dwarf varieties, often reaching no more than a few feet in height, are ideally suited to life in a container. They don’t outgrow their space; you won’t have trouble balancing height with container size.
There are many dwarf sunflowers available, allowing you to pick a few varieties that catch your eye without taking over your entire garden. ‘Sunspot’ is an adorable variety that grows to about two feet tall, perfect for containers. For something a little more unique, try the dwarf ‘Teddy Bear’ with ruffled petals.
Choose The Right Soil Mix
Opt for a well-draining potting mix with compost for root health and nutrients.
Soil is the foundation of successful growth, providing the support a sunflower needs to thrive. When growing sunflowers in pots or containers, soil choice becomes even more crucial because you completely control it.
A heavy clay soil that holds onto water too tightly can suffocate the roots, while a sandy mix that drains too quickly can lead to wilting. A well-draining potting mix enriched with compost to improve soil structure and health provides an ideal home for sunflower roots.
The compost will improve moisture retention while adding essential nutrients these hungry plants crave. You can also add a handful or two of slow-release fertilizer to the mix, depending on the quality of the potting mix you’ve chosen.
Although it is a quick fix, don’t be tempted to use garden soil straight from your backyard. Garden soil often lacks the airy texture required for container gardening and can carry existing pests and diseases to your new plants. Instead, invest in a quality potting mix or make your own blend tailored to the sunflower’s needs and your garden environment.
Sow Directly Into The Pot
Once you have your pot and seeds, you can either start seeds in trays or directly sow them in containers.
When you’ve chosen your pot and purchased your seeds, it’s time to get sowing.
You can start your seeds early in trays as you would when planting in the ground. But one of the benefits of growing sunflowers in pots or containers is that you can direct-sow the seeds and keep them protected until they are ready to head outdoors.
These plants are known for their rapid growth, with roots quickly establishing themselves. But they are also sensitive to root disturbance. Transplanting at the wrong time or with the wrong technique can lead to transplant shock, stunting growth, and extending the time it takes for the plant to settle. Sowing the seeds directly into the pot avoids this risk, allowing the sunflower to grow undisturbed from seedling to flowering.
Plant the seeds about half an inch deep and water them gently to encourage germination. As the seedlings emerge, they’ll find themselves already at home, free to establish without the disruption of transplanting.
Add Supports
Sunflowers, with their large size, need support to prevent bending or breaking stems due to the weight of flower heads.
Sunflowers are surprisingly large plants. As the stems begin to stretch, the weight of the flower heads can cause them to bend or even break, particularly if exposed to strong winds or heavy rain. Supports – such as stakes, trellises, or even cages – provide the stability sunflowers in pots or containers need to grow.
It’s best to add these supports early on, preferably when filling the container with soil. Not only does this make installing the stake far simpler, keeping it sturdy throughout growth, but it also avoids the risk of damaging the roots that may have already spread later on.
Place the support close to the stem but not so close that it restricts growth. It should also be tall enough to accommodate the expected height of the mature sunflower, taking the portion buried under the soil into account.
Soft ties, such as garden twine or strips of cloth, are best to secure the stem to the support. They should be firm enough to hold the stem in place but loose enough to allow growth and movement. Hard and rigid ties can cut into the stems as they grow, damaging essential systems and increasing disease risk.
Place In Full Sun
Sunflowers thrive in full sun, needing at least 8 hours of direct sunlight daily for optimal growth.
Sunflowers’ very name speaks of their affinity for sunlight. Full sun is essential for strong growth, even if you’re growing a smaller variety in containers.
Sunflowers are heliotropic in the early stages of growth, meaning they follow the sun’s movement throughout the day. If you have yet to see a timelapse of this interesting process yet, take a look. They do this to maximize photosynthesis and attract more pollinators.
To successfully grow sunflowers, find a spot where they will receive at least 8 hours of direct sunlight daily, preferably more. A south-facing location – free from the shade of buildings, trees, or other plants – is the best option if you have the space.
If you’re growing sunflowers in pots or containers on a balcony or patio, consider the sun’s movement throughout the day and position them accordingly.
Water Consistently
Sunflowers require ample water when grown in containers due to faster soil drying.
Sunflowers use plenty of resources to produce their sunny flowers. One of those essential resources is water, and plenty of it when growing in containers. When placed in full sun, the soil in containers dries out much quicker than in regular beds, requiring careful monitoring to ensure you’re watering at the right time.
Keep the soil evenly moist but not soggy on the upper stratus of the soil as the seeds germinate. A gentle misting or careful watering that doesn’t disturb the seeds is best. As the seedlings emerge and the roots begin to establish, you’ll need to water deeper to push root growth downwards.
Unfortunately, it’s not as easy as watering on a schedule and forgetting about the plant the rest of the time. Environmental factors and growth will influence how quickly the soil dries out and how often you need to water.
Keep a close eye on the soil in the container and water when it just starts to dry out. You’ll need to water more on warm summer days and less with regular rainfall. Ensure the excess moisture drains freely from the bottom of the container and keep the pot in full sun to limit chances of rot.
Avoid Overwatering or Underwatering
Overwatering leads to root rot, while underwatering causes drooping stems and wilting leaves.
The balance between too much and too little water is a daily concern that determines the fate of your sunflower plant.
Although usually done with good intentions, overwatering can lead to waterlogged soil and root rot. Like humans, the roots need to breathe and move freely without what is essentially suffocation.
Excess moisture will fill air pockets, waterlogging the roots and creating a breeding ground for diseases. The signs may be subtle at first – a yellowing leaf or a wilting stem – but you’ll quickly notice the problem spreading if not resolved.
Underwatering is also damaging to these moisture-loving plants. The previously strong stems will start to droop as the cells lack the moisture required to keep them rigid. The leaves will begin to wilt, and the plant will struggle to put out flowers without the resources they need for growth.
The soil’s moisture level guides you on when to water and when to wait. Always press a finger a few inches into the soil before watering. If it feels dry, it’s time to water. If it feels damp, wait a bit longer.
Feed At The Right Time
Container-grown sunflowers need regular feeding due to limited soil nutrients.
Sunflowers are heavy feeders that need additional nutrients throughout the season to maximize growth. Feeding is even more essential when they’re grown in containers where the soil’s nutrient reserves are limited.
In the early stages of growth, additional nutrients are unnecessary soon after planting. The base nutrients available in a high-quality potting mix are usually sufficient to support this initial growth.
But as the sunflower develops lush leaves and long stems, its hunger for nutrients (particularly nitrogen) grows. A balanced liquid fertilizer, applied once per month, can provide the nutritional boost the plant needs to build strong, healthy foliage.
Phosphorous and potassium are most important just before flowering, supporting bloom development and overall health. You can continue with a balanced fertilizer for complete nutrients or adjust the ratios as needed.
Trim Flowers Carefully
Carefully trim sunflowers just above a leaf joint with sharp shears.
Although sunflowers look good in their pots or containers throughout the season, you may still want to trim a few flowers off to enjoy indoors. And if you’re growing these plants for cut flowers, it’s vital to cut carefully to avoid long-lasting damage.
Sunflower stems, while strong in appearance, can be surprisingly sensitive. Unnecessary damage from shears or knocks can quickly lead to disease or decay that spreads throughout the plant.
Use sharp, clean pruning shears or scissors to cut just above a leaf joint. Cut at a slight angle to improve water uptake in the vase. Don’t cut too much at once – leave a few heads on for seed harvesting later.
Watch Out For Pests and Diseases
Pests and diseases like aphids and fungal issues can harm sunflowers in containers.
Like gardeners, pests like aphids, moths, and beetles find a sunflower’s leaves, stems, and even flowers irresistible. These pesky pests feed on all parts of the plant, weakening it and often spreading diseases as they move. Sunflowers confined in pots or containers can accelerate this invasion, with pests finding it easy to move from one plant to another.
Diseases are also a risk, especially in warm and humid environments. Fungal diseases like mildew and rust can spread quickly, leaving masses of discolored leaves and stunted growth.
Choosing disease-resistant varieties, properly watering to avoid waterlogged soil, and regularly trimming dead or diseased leaves are essential prevention methods that apply to container plants just as they do out in the garden.
Regular inspections of the sunflower’s stem, leaves, and flower head to look for signs of discoloration, holes, or unusual growth patterns can help you catch an infestation or infection early. The treatment (natural insecticides, pruning, or adjusting your watering) will depend on the specific problem but should be done as soon as possible to protect the plants from early death.
Avoid Growing Indoors
Sunflowers thrive best in outdoor container gardens.
Sunflowers make showy and healthy container plants with enough space and the right environment. Unfortunately, even though it may be tempting to grow indoors, our homes don’t quite match up to these environmental needs.
Indoors, even in the brightest room of your home, the quality of light does not meet what sunflowers naturally need to grow to their full potential. They may survive, but without the full spectrum of sunlight, they often become weak, leggy, and prone to diseases. Flowering is also unlikely, ending in an incredibly disappointing growing season.
Space is also a consideration. Even dwarf varieties need room to grow above and below the soil. You’ll need plenty of space right in front of a south-facing window or under strong grow lights to successfully grow indoors – not conditions many of us have.
Sunflowers belong outdoors, whether on balconies, patios, or other container garden spaces, where they can bask in the sunlight and maximize flower development. Growing indoors may not be impossible, but it’s also not ideal.
Final Thoughts
Your sunflower-growing dreams don’t have to end with a lack of backyard space! Following these tips, you can easily grow your favorite sunflowers in containers.
