How to Prevent Parsley Bolting and Keep Your Plants Lush and Green
Parsley (Petroselinum crispum) is a biennial plant; thus, it completes its life cycle in two years.
In the second year of growth, parsley plants will produce flowers, and then they will produce seed. This flowering transition process is known as "bolting."
Unfortunately, when herbs such as parsley bolt, their flavor can be impacted. This is because the plant is directing all of its resources towards reproduction. This can often lead to a bitter taste and tough leaf texture.
There are several reasons why your parsley plant could be bolting early.
Bolting early can often occur when the plant is experiencing stress, such as if it has recently been transplanted, or if it is not getting the necessary water and nutrients.
Be aware that Parsley plants prefer a moist soil and regular watering; this may help to minimize stress on the plant.
A further reason for early bolting, is that the plant is receiving too much direct sunlight and/or heat.
Ideally, Parsley plants should be grown in partial shade, it might be worth moving the plant to a shadier location if possible.
As parsley is a cool-season plant, it naturally that prefers cooler temperatures. So if your parsley is subjected to high temperatures, it will be more prone to bolting.
In summary, to prevent parsley from bolting prematurely, be sure to keep the plant well-watered, grow in a partially shaded location, and try to maintain a cooler temperature.
But why do parsley plants need to bolt anyway?
A plant will bolt and produce an inflorescent stem when it shifts into a reproductive growth state.
During this process, a plant wants to shift its energy away from vegetative growth (leaves, stems, and roots) and direct its resources at producing flowers and seeds.
There are both internal and external signals that a plant will use to stimulate this transitional process.
Temperature – Many plants will bolt when exposed to either high temperatures or to fluctuations in temperature (this is one of the main reasons for parsley bolting early). When the temperature rises a plant will often perceive it as a sign to reproduce, as it is unlikely to thrive when it gets too hot.
Day length – Many plants are photoperiodic, and are thus sensitive to the amount and length of daylight they receive. When the days get longer or shorter, the plant may perceive it as a signal to begin reproducing. Parsley is a long day plant.
Water and nutrient stresses – if a plant is stressed due to lack of water or nutrients, it will often bolt in an attempt to produce seeds as quickly as possible.
Age – plants are programmed to bolt after they reach a certain age or size, regardless of environmental conditions.
In many cases, bolting is a natural part of a plant's life cycle, but it can have negative effects on the quality and flavor of the parsley leaves.
Gardeners can take steps to prevent parsley bolting through providing regular watering to keep soil moist, provided adequate nutrients, and growing in an environment with a cool temperature and correct day length.
References and further reading
Royal Horticultural Society- Bolting in Veg: https://www.rhs.org.uk/vegetables/bolting
GrowVeg – How to Prevent Bolting in Vegetable Crops: https://www.growveg.com/guides/how-to-prevent-bolting-in-vegetable-crops/
Oregon State University Extension Service – Understanding Plant Life cycles: https://extension.oregonstate.edu/gardening/techniques/know-life-cycles-plants-annuals-biennials-perennials
University of Minnesota Extension -Growing Cool Season Vegetables, Bolting and other problems: https://extension.umn.edu/yard-and-garden-news/growing-cool-season-vegetables-minnesota
I hope you have enjoyed this article on Parsley bolting and the bit of background information on the uses of herb, you may enjoy some of my other growing guides, such as my guide to growing celery, Fennel, and Galanthus plant.
