How to Grow Marigolds: A Practical Guide from Seed to Flowers

Marigolds are straightforward flowers to grow from seed and are hard to beat when you want plenty of colour without too much fuss. They flower for months, grow happily in pots and borders and you will be suprised with the different types that you will find.

There are two main types you may have seen. French marigolds tend to be shorter and bushier, making them ideal for pots, edging and filling gaps. African marigolds are generally taller, with much larger flowers that can make quite a statement in a border.

Both are grown in much the same way.

Marigold seeds germinate readily and the young plants grow quickly once conditions warm up. Give them plenty of sunshine, reasonable soil and regular water while they're establishing and they'll largely get on with flowering.

They're also useful plants to have around the vegetable garden. We often grow marigolds amongst other crops, particularly tomatoes, although they're worth growing for the flowers alone.

When to Sow

Marigolds are best started under cover from February to April.

You can sow in February if you have somewhere warm and bright to grow the seedlings afterwards, but I don't think there's much advantage in planting early. March and April are particularly good months because increasing daylight helps produce much stronger young plants.

If you don't get around to sowing until late April, that's absolutely fine. Marigolds grow quickly and later seedlings soon catch up once the weather warms.

Both French and African marigolds need warmth to germinate. A heated propagator is useful for early sowings, but somewhere comfortably warm indoors will usually do the job.

African marigolds can be worth starting slightly earlier because they generally take longer to reach flowering size than the smaller French types.

You can sow directly outside later in spring, but we prefer starting marigolds in pots or trays. It gives the seedlings a head start and means you're planting reasonably sturdy plants rather than hoping tiny seedlings survive slugs and unpredictable spring weather as well as any weeds.

How to Sow

Marigold seeds are easy enough to handle and usually germinate easily

Fill a seed tray, small pot or modules with seed compost and sow the seeds thinly over the surface. Cover them with a light layer of compost, roughly 0.5–1cm deep, then water gently.

Put the tray somewhere warm. Keep the compost moist but don't leave it soaking wet.

In good conditions, seedlings often appear within a week or two.

Once they've germinated, move them into plenty of light. This is important. Marigolds kept somewhere warm but gloomy soon become long, thin seedlings leaning hopefully towards the nearest window.

If you've sown several seeds together, move the seedlings into individual pots or trays once they're large enough to handle and have developed their first proper leaves.

Hold seedlings by a leaf rather than the stem when moving them. 

Keep them frost-free and pot them on if necessary while you're waiting for conditions outside to improve.

Growing Seedlings On

Marigold seedlings grow fairly quickly once they've got going.

Keep them somewhere bright and water when the compost begins to dry. There's no need to keep them permanently wet, and young plants won't appreciate sitting in cold, soggy compost.

As the plants develop, you'll start seeing the difference between the types. Compact French marigolds naturally begin making bushier plants, while taller African varieties need more room as they grow.

If seedlings become crowded, pot them on rather than leaving them fighting for light and root space.

Before planting outside, harden them off for a week or two. Plants that have spent their lives in a greenhouse or on a windowsill need a little time to get used to wind, cooler nights and direct sunshine.

Put them outside during the day in a sheltered position and bring them back under cover at night, gradually increasing the amount of time they spend outdoors.

Don't be tempted to plant them permanently outside too early. Marigolds are tender and frost can quickly stunt the plants.

Planting Out and Spacing

Plant marigolds outside once the danger of frost has passed, usually from May onwards depending on where you live, In our area it is best to wait until the end of May to plant otu.

Give them a sunny position. They'll tolerate a little shade, but you'll generally get stronger plants and far more flowers with plenty of sunshine.

Marigolds aren't especially fussy about soil. Reasonably fertile, free-draining garden soil is perfectly adequate.

Spacing depends quite a bit on what you're growing. Compact French marigolds may only need around 20–25cm between plants, while larger African varieties can need 30–40cm or more.

It's worth checking the eventual height and spread of the variety rather than assuming every marigold stays small. An African marigold can be quite a different proposition from a little French bedding variety.

Marigolds are excellent in containers too. Compact varieties are particularly useful for pots and window boxes.

Water everything properly after planting.

Keep an eye out for slugs and snails during the first few weeks. Once marigolds are established they're fairly robust, but young plants can disappear remarkably quickly.

Growing On

Once established, marigolds don't need much attention.

Keep weeds down while the plants are small and water during dry weather. As compact varieties fill out, they'll cover much of the surrounding soil themselves.

Some gardeners pinch out young marigolds to encourage branching. You can do this if plants are becoming tall and thin, but many modern varieties naturally make good bushy plants without much help.

Taller African marigolds may need a little support in exposed gardens, particularly once they're carrying several large, heavy flowers. A discreet cane or support is much easier to add before the plant has fallen over.

They dont need much looking after. If they're healthy, growing and beginning to form buds, they're probably perfectly happy.

Remove damaged or yellowing leaves as you notice them and keep an eye on plants growing tightly together. A little airflow around the foliage helps keep them healthy.

Watering and Feeding

Marigolds are reasonably tolerant plants once established, but they'll flower better if they aren't repeatedly allowed to become bone dry.

Water young plants regularly while their roots establish. After that, plants growing in the ground generally only need extra water during prolonged dry spells.

Containers are different. Pots and window boxes can dry quickly during summer, particularly when they're packed with flowering plants, so check them regularly.

Water the compost or soil around the base rather than constantly soaking the flowers and foliage.

In decent garden soil, marigolds don't need much feeding.

Plants growing in containers will eventually use up the nutrients available in their compost, so an occasional liquid feed for flowering plants can help keep the display going. A high-potash feed is useful once flowering is underway.

As with most things in the garden, more isn't necessarily better. Too much nitrogen can encourage plenty of leafy growth when what you really want is flowers.

If the plants look healthy and they're flowering their socks off, there's no need to keep finding extra jobs for yourself.

Flowering and Deadheading

Marigolds usually begin flowering from early summer and can continue right through into autumn until frost eventually finishes them.

Regular deadheading is worth doing.

Once a flower starts looking tired, remove the whole flower head rather than simply pulling away a few petals. This stops the plant putting unnecessary energy into producing seed and encourages it to keep making new flowers.

During the height of summer, I tend to go around the plants every few days and remove anything that's finished. It doesn't take long and keeps the whole display looking considerably better.

If you'd like to save your own seed, leave some of the later flowers on the plants and allow the seed heads to mature and dry.

Marigolds are also excellent cut flowers, particularly the taller African types. Pick them when the blooms are fresh and fully developed.

Keep watering and deadheading and they'll usually carry on remarkably well into autumn. They're often still producing colour when quite a few other summer flowers have decided they've had enough.

Common Problems

Slugs and Snails

Young marigolds can be very attractive to slugs and snails, especially just after planting out.

Keep a close eye on them during damp weather. Once the plants are larger and established, they can usually tolerate some damage, but a small seedling can be eaten almost overnight.

Aphids

Aphids sometimes gather around tender shoots and developing flower buds.

Small colonies can often be rubbed off or washed away with water. Ladybirds, hoverfly larvae and other beneficial insects will usually help too, so don't panic at the first aphid you see.

Spider Mites

In hot, dry conditions, particularly in greenhouses or sheltered areas, spider mites can occasionally become troublesome. Leaves may look mottled or unhealthy and you may notice very fine webbing.

Keep plants properly watered and avoid allowing them to become continually stressed by dry conditions.

Grey Mould and Rotting Flowers

Wet weather can cause large marigold flowers, particularly the big African types, to become soggy and start rotting.

Remove damaged flowers rather than leaving them sitting on the plant. Good spacing and airflow also help.

Lots of Leaves but Few Flowers

If your marigolds look wonderfully green but aren't producing many flowers, check how much sunshine they're receiving and whether they've been overfed.

Too much nitrogen and too little light can both encourage leafy growth at the expense of flowers.

Plants Becoming Tall and Floppy

Some African marigolds naturally grow quite tall, so this isn't necessarily a problem. In an exposed position, give taller plants some discreet support before the weight of the flowers pulls them over.

Marigolds really aren't plants I worry about too much. Get them through the vulnerable seedling stage, give them sunshine and keep the faded flowers coming off, and they'll generally reward you with colour for months. And if you've only ever grown the familiar little orange bedding marigolds, try one of the taller or more unusual varieties — you might be surprised how different they can look.