Soil- Best is deep, light and loose loam- but can grow in most soils. One of the vegetables that like a fairly acidic soil-5.2 to 6.8 ph. Best to amend with compost, sulphur to acidify soil, avoid fresh manures they encourage scab, also high nitrogen tends to promote vine growth and reduce tuber production. Potatoes are a great first crop in a new area- especially if lawn has been sheet mulched as they like the organic matter breaking down, are not super tender and with the hilling and mulching, weeds and re growing grass are smothered out.
Planting: Though they like cool weather, potatoes will rot in cold, wet soil. Wait for soils to warm to at least 55 –70 degrees. Make sure soil is not water logged. They are frost sensitive- the above ground part will get killed by a heavy frost, they can regrow but numerous frosts will set plant back. Can plant from mid March to June in Sonoma.
You can presprout the potatoes for quicker emergence- by spreading potatoes in a crate or box, keeping in a warm, medium light spot and sprouting. Allow one or two weeks to sprout. Avoid letting potatoes get long sprouts that easily break off. Perfect seed potato size is about the size of an egg- 2-4 oz. For larger potatoes you can cut the potatoes up with each potato piece having several eyes. People often let the potatoes scab over for a day before planting if they have cut them. Larger potatoes tend to produce fewer large potatoes, and smaller ones more small potatoes.
Multiple ways to plant:
Most common- dig a shallow trench- 6-10 inches deep, plant the seed pieces 12-16 inches apart, unless really small. Cover with 4-6 inches of soil.
Other options- chop down grass and weeds in an area, add a layer of compost, sheet mulch with newspaper and straw. Every 12 inches make a hole in the mulch and nuzzle in a potato.
Container or basket method- if potatoes continue to be mulched or covered partially with soil- they will continue to grow up and produce more tubers along the stem. Start with a large container or wire basket- add 6 inches of soil. Add a potato, when plant is 6 inches tall add more soil or straw mulch to the top of the plant allowing top leaves to show, keep doing this, as long as the plant grows.
Care- Keep beds well weeded, hilling the soil up around the plant. Hint it is easier in the early evening to hill plants because the leaves fold upwards and you can tuck the soil under. After several hillings, mulch to keep soil cool and moist. Potatoes respong well to foliar fed of kelp or maxicrop
Watering- less water makes better tasting and higher protein potatoes, Allow soil to dry out and water long and deep. But you may get smaller yields if you hold back too much on water.
Pests- main problem is gophers- plant in gopher protected areas. Most other pests only make holes in the leaves without doing much damage.
Harvest- once plants are in full bloom there are potatoes forming if you want some yummy early creamers harvest some when in full bloom or just after blooms fade. Wait for plants to start to die back before harvesting main crop. Stop watering them at this stage. Allowing plant to die back, toughens the skins making them better storage potatoes. You can leave them in the soil for several weeks to toughen the skins.