Common purslane (Portulaca oleracea) is a familiar sight in gardens, often leading gardeners to wonder about its enduring presence. Despite its persistent nature, purslane is definitively an annual plant. It completes its entire life cycle within a single growing season, typically germinating in spring and dying with the first hard frost.
Defining Plant Life Cycles
Plants are categorized by their life cycles. Annual plants, like marigolds, complete their entire life cycle—from seed germination, through growth and flowering, to seed production and death—within one growing season. Biennial plants, such as foxgloves, live for two growing seasons; they typically grow foliage in the first year and then flower, produce seeds, and die in the second year. Perennial plants, including hostas, live for more than two years, often returning year after year from their rootstock.
Purslane’s Actual Life Cycle
Purslane is a summer annual plant, meaning each individual plant germinates, grows, flowers, produces seeds, and dies within a single warm season. Its growth begins in late spring and continues until killed by fall frost. While it might seem to reappear endlessly in the same spots, this is due to its effective reproductive strategies rather than individual plants surviving multiple years.
Why Purslane Persists
Purslane’s remarkable persistence stems from several highly effective survival mechanisms, making it seem like a perennial. A single purslane plant can produce a vast number of tiny seeds, with reports of up to 240,000 seeds from one plant. These seeds are incredibly resilient and can remain viable in the soil for many years, sometimes up to 40 years, creating a substantial “seed bank” that continuously replenishes new growth. Seeds often germinate best from the soil surface or very shallow layers, less than 0.25 inches deep, particularly during warm, moist conditions.
Purslane also reproduces from stem fragments; even small pieces of its succulent stems can root and grow into new plants if left on moist soil. This succulent nature also allows pulled plants to remain viable and even mature seeds after being uprooted, if not removed from the garden entirely. Its tolerance for various conditions, including drought and poor or compacted soils, allows it to thrive in many environments where other plants struggle.
Gardening Strategies for Purslane
Managing purslane effectively involves targeting its prolific seeding and fragmentation. A primary strategy is to remove plants before they have a chance to produce and disperse their numerous seeds. Hand-weeding is an effective method, but it is important to remove the entire plant, including any broken stem pieces, to prevent them from re-rooting. Prompt removal is especially crucial when plants are small, as older plants are more difficult to control and can produce viable seeds even after being uprooted.
Applying a thick layer of mulch, ideally 3 inches deep, can significantly suppress purslane seed germination by blocking sunlight. Adjusting watering practices can also help; deep, infrequent watering encourages the roots of desirable plants while discouraging the shallow root system of purslane. Improving overall soil health through aeration and adding organic matter can also reduce weed pressure, creating a less hospitable environment for purslane. Preventing soil disturbance can also reduce new germination by keeping buried seeds from reaching the surface.