Welcome to Top of the Crops. Today, you will learn about growing beautiful marigolds in your polytunnel. From knowing when, where, and how to grow marigolds, you will soon have these gorgeous flowers decorating your garden or polytunnel in no time. Don't forget to also check out our insightful blog for more gardening tips at Polytunnel Gardening.
Marigolds are among the most useful and attractive flowers to grow in a polytunnel garden. One of the reasons that they are so useful is that these are particularly valuable companion plants for a wide range of common crops.
Not to be confused with calendula, sometimes called 'pot marigolds', marigolds are members of the Tagetes genus.
The most popular varieties are perhaps those of the species Tagetes patula, otherwise known as French marigolds. These are the most commonly grown in the UK and there are many cultivars to choose from.
But there are also other species that you might grow, including Tagetes erecta, called African marigolds, Tagetes minuta, called southern marigold or Muster John Henry, Tagetes lucida, sweet mace or sweet-scented marigold, and Tagetes tenuifolia, or signet marigolds. There are also plenty of hybrids between some of the above.
We'll take a closer look at some species and varieties to grow later in this guide.
The common names of these plants are extremely misleading, since in fact, Tagetes marigolds are native to the Americas – just one of the interesting facts about these plants to discover.
When choosing marigolds for your garden, it is of course essential to consider the conditions that they prefer and require.
Marigolds generally need:
A sheltered site in full sun.
A moderately fertile, moist but well drained or well drained soil or potting mix.
They can grow well in the ground or raised beds but many will also be suited to container cultivation.
To grow marigolds in your garden you will need:
Marigold seeds, plug plants or bedding plants.
A suitable growing location. (A prepared bed or container filled with free-draining peat-free potting mix.)
Seed trays, small pots or soil blocks etc. if growing from seed.
Facility to water your plants as needed.
Secateurs or garden scissors for deadheading.
Organic mulch materials.
Marigolds should be grown in a sunny location, either in the ground, raised beds, or containers. As well as making sure that the basic growing needs of the marigolds you have chosen to grow have been met, you should also consider how the marigolds will fit in to your overall garden plans.
One important thing to consider is how marigolds can be beneficial to other plants growing close by. We'll take a closer look at companion planting and why marigolds can make good companion plants a little later in this guide.
Marigolds can be easy to grow, as long as you consider the needs of the specific type and variety you have chosen to grow.
It is relatively simple to grow marigolds from seed, though many will choose instead to purchase plugs or small bedding plants to plant out in their gardens as these are quite affordable and readily available.
Marigolds should be planted out in spring, once all risk of frost has passed where you live. You will be able to plant out a little earlier in a polytunnel or other protected space than you will outdoors as the temperatures will warm a little sooner.
Indoors sown marigolds should be hardened off before they are planted out into their final growing positions. Before planting out marigolds, prepare your planting area.
Make sure the area is free from weeds and add organic matter to enrich the soil and ensure good drainage. If you are planning to grow marigolds in a container, prepare this container, and fill it with a suitable free-draining peat-free potting mix.
Plant spacing will depend on which type and variety of marigolds you have chosen to grow, since some types grow much larger than others.
After planting, water your new plants in well, and add a mulch of homemade compost or other organic material around but not touching the plants.
Removing all the spent flower heads from marigolds may not always be practicable if you are growing a lot. But it can be beneficial to deadhead marigolds not only to keep your garden neat but also to encourage the production of more flowers.
It can also be a good idea to pinch out the heads of taller types to encourage them to take on a bushier form.
Tagetes marigolds are tender plants and will usually die back and be discarded at the end of the growing season.
However, note that in the right setting they can sometimes self-seed readily. So do not deadhead too zealously towards the end of the flowering period if you wish for them to do so, or wish to collect seed to sow next year.
Marigolds flowers may also be harvested for use in your home.
Several Tagetes species give edible yields used to make drinks, as pot herbs, essential oils for food flavouring. The petals are also sometimes used for edible colouring (like saffron) and natural dyes.
Marigolds are also sometimes used in herbal medicine, either fresh or dried and stored for later use. The essential oil is sometimes also used in perfumery.
Of course, marigolds might also be used for floral displays inside your home.
If you do decide that you would like to grow marigolds from seed rather than purchasing plants, this is a wonderful idea. Propagating marigolds from seed is pretty easy and straightforward, and it is the more eco-friendly choice since you will not bring more plastic pots into your home.
You can either sow marigolds indoors in early spring, or sow them outside in late spring, directly where they are to grow.
Sowing indoors gives earlier blooms. Sow the seeds in a warm location, pricking out and potting up the seedlings or putting them into soil blocks once they are large enough to handle. Grow them on in a warm and bright spot indoors before hardening them off and planting them out into their final growing positions once all risk of frost as passed.
If you choose to direct sow outdoors, do so in late spring, into a prepared bed or container. Thin the seedlings to the required spacing for the particular type and variety of marigold that you have chosen to grow.
Marigolds don't require a great deal of care. The key things to remember are that you should water well throughout any dry spells in the growing season, but not overwater nor allow waterlogging to occur as good drainage is essential.
Remember that marigolds growing in pots will need watering more frequently than those growing in the ground.
Marigolds in the ground or raised beds won't usually need feeding. But those in containers should be given a potassium-rich organic liquid plant feed every week or two from midsummer onwards.
Deadheading and pinching back as mentioned above are the only other care elements to consider.
When choosing which marigolds to grow, it is important to think about what different types can provide, as well as how different types differ in their appearance and growing needs and which might be best suited to a particular location.
Some key Tagetes marigold species to consider include:
French marigolds are bushy annuals that grow to around 30cm in height and width. They have aromatic, deeply-divided foliage and can bear single or double flowers that can have a range of hues from summer into early autumn.
Some highly regarded AGM cultivars of Tagetes patula include:
Bonanza Flame
Fireball
Honeycomb
Queen Sophia
Tiger Eyes
To name just a few examples.
African marigolds grow much taller than French marigolds, with a height of around 50 - 120 cm and a spread of around 20-40cm, and bear larger blooms which can grow to 10cm across.
Named cultivars with an AGM include Discovery, Inca Orange, and Perfection.
This annual grows up to 1.5m tall. It has deeply divided foliage with a strong scent, and has heads of small, white flowers with yellow centres. This plant is more prized for its root secretions, which are said to kill weeds and repel nematodes, than for any ornamental value.
A tender, bushy perennial usually grown as an annual, this marigold also known as sweet mace is used as a tarragon substitute in Mexican cuisine. It has glossy green, linear leaves and bears small yellow flowers in the late summer and autumn.
Signet marigolds grow up to around 45cm tall, and bear an abundance of small, single flowers with vibrant hues. The petals are edible and look lovely scattered over salads.
When deciding where and how to grow marigolds in your garden, companion planting should, as mentioned earlier in this guide, be a key consideration.
It is not so much about finding plants that make good companions for marigolds, but rather about realising the many crops that can benefit from having marigolds planted close by. Since marigold's don't need much help to do well in the right conditions.
Marigolds make excellent companions for many fruits and vegetables you may have growing in your polytunnel or elsewhere in your garden. Marigolds draw in pollinators, while also often repelling, confusing or distracting pest species with their pungent scent.
For example, marigolds can make excellent companions for tomatoes and cucumbers in a polytunnel or greenhouse, in part because they can deter whitefly and aphids.
Certain Tagetes marigolds also release chemicals from their roots that can repel certain harmful nematodes in the soil. Though this is a complex business and not all marigolds will confer benefits in this way, and to be of aid, specific types need to be used in specific ways, to target specific problems in specific areas...
The most common problems to arise when growing marigolds do so because of excessive wet or waterlogging. Free draining conditions are essential, whichever type and variety you have chosen to grow.
Sometimes, African marigold flowers can rot in wet weather. So if you live in a wetter area, grow these under cover where water can be more easily controlled, or grow different varieties.
Marigolds help control pests in a garden and are not typically plagued by pests themselves. These easy plants are also generally not troubled by diseases.
Companion plant widely with marigolds. You can use them to line the front or sides of beds, intersperse them or intercrop them between plants of another crop, or grow them in pots around or near your main growing areas.
Just ensure good ventilation and good drainage and the marigolds should thrive in the warm and relatively dry conditions a polytunnel can provide.
