I am growing 6 German Butterball potatoes in my backyard in downtown Toronto. The plants are very tall, about 5 feet. There were about half dozen white blooms but they only appeared on some of the plants. question: late august and the plants are still healthy. when do I harvest? thanks.


Thank you for contacting the Toronto master gardeners with your inquiry.

Potato varieties are usually classified as early, mid and late season from the time you plant the seed to harvest.  German Butterball potatoes are a late season potato and become mature anywhere from 110-135 days.

In general,  when growing potatoes they prefer loose, fertile, well-drained soil. Make sure to keep your newly planted potatoes good and moist until the sprouts push above the ground, giving them approx. 2” of water per week. Once the plants mature at the end of the season, slow down the watering. Feed your growing potatoes with a fertilizer higher in phosphorous and potassium such as bone meal, to encourage tuber growth.

As the tubers begin to develop at the base of the plant, mound about 5cm of soil over them. This technique is called hilling. Hilling is a technique of mounding up the soil around the plants as they grow, while leaving the top-growth exposed. This technique promotes the production of bigger potatoes, more of them, kills weeds and keeps the sun off of the tubers. You should repeat the hilling process 3-4 times throughout the season.

Harvest late season potatoes after the tops have begun to wilt, and before the first hard frost. Potatoes can endure light frost.

Once you dig up your potatoes, brush off any dirt but do not wash them. Instead, store your unwashed potatoes in a cool, dark place, for two weeks to allow the skins to cure- letting the skins toughen so that they store better. For longer storage, dust off any dirt and place your potatoes into baskets or bins with good ventilation. Cover with newspaper and place them in a cool, dry place where the average temperature is around 5C.

Enjoy your bountiful harvest.