Marigolds (Tagetes) both French and African, are great additions to your polytunnel. Not only will the bright blooms bring cheer during the summer months, the marigolds will also be useful to the other plants in your polytunnel. They are one of the very best companion plants and should be spread throughout a vegetable garden in order to repel some common pests, including whitefly and others. Marigolds are more than just an ornamental – the flowers are edible and can also be used to colour food or as a natural dye. Sown once, marigolds will contribute an insecticidal secretion that can remain in the soil for a long time, even after the plants are gone and can help surrounding plants stay pest free.
The French Marigold (Tagetes patula) and African Marigold (Tagetes erecta) should not be confused with the other useful and attractive flower for your polytunnel, Calendula. Calendula are not related, though are often called Pot Marigolds.
French and African marigolds can both be started from seed around 4-6 weeks before the last frost date in your area and will usually germinate within 1-2 weeks. Many people, however, choose to pick up the inexpensive plants available at many garden centres in the spring. These popular bedding plants are not bad value for money and should provide you with plenty of seeds to sow the following year, should you wish to make your growing efforts more self-sufficient.
French marigolds are low growing, while African marigolds are much taller. Both, however, will very much appreciate the sunny warmth inside your polytunnel. French marigolds are perfect for planting in front of your beds or borders, creating an attractive look and attracting wildlife while helping your crops in a number of different ways. You should have blooms from around 8 weeks after planting, all through the summer and right up to the first frosts. These useful plants are also fairly drought tolerant, so should be a great plant if you are looking to save on water used in your garden.
These edible flowers can be picked and sprinkled onto salads or used to colour other recipes at any time. Tagetes patula used in refreshing drinks, and Tagetes species yield an essential oil that is sometimes used in food flavouring. A dye made of the the petals is sometimes also used to dye textiles. All in all, both when in the ground and when used as cut flowers or for other uses, marigolds can give great value for money when planted in your polytunnel.