Solanum tuberosum L.
Potatoes are often seen growing as casuals on tips and waste ground but it is the volunteer potatoes found in arable fields that are the weed problem. These arise from seeds, tubers and tuber pieces that remain in the soil following an earlier potato crop. After potato harvest there may be as many tubers left in the soil as were planted originally. Volunteers that grow from missed or ground-keeper tubers develop vigorously and are difficult to eliminate in poorly competitive crops like leeks and onions, particularly from within the crop row. Where a berry producing potato cultivar such as Maris Piper has been grown, volunteer potatoes that develop from the seeds can be a problem.
The foliage and green tubers of potatoes are poisonous to livestock. Potato berries and stem pieces can contaminate pea and green bean crops harvested for processing.
All potato cultivars flower but many produce flowers that drop off soon after pollination. Some cultivars, however, form berries each containing 200-300 seeds. Potato berries are produced in large quantities by the cultivars Vanessa, Cara, Desiree, Pentland Ivory, Maris Piper, Maris Peer and several others.
Potato seedlings emerge from May to late-June and may continue to appear until September. Plants from seedlings that emerge up until June may produce small tubers that remain in the soil as ground-keepers over winter.
Persistence and Spread
Once shed, potato seeds can remain viable in soil for 3-9 years. The seeds will also remain viable for long periods in dry-storage at low temperatures.
After potato crop harvest, over ten times more tubers can survive following ploughing compared with shallower cultivations. Cultivation with tines is more likely to leave tubers near the soil surface where they can be killed by exposure to frost. However, this may not be effective in a mild winter and even a moderately hard winter is unlikely to eradicate the entire volunteer population.