Planting Potatoes in Oregon: A Guide for Successful Growth

Image: Potato Field

Potatoes are a versatile and delicious vegetable that can be grown in a variety of climates. In Oregon, where the weather can be unpredictable, it’s important to choose the right time and method to plant potatoes for a successful harvest. While many gardeners opt for traditional planting methods, there is a growing trend of using potato towers to save space and increase yields.

A New Approach to Potato Planting

Growing potatoes in towers has gained popularity among gardeners seeking to maximize their potato harvests. The idea is simple: build a structure using wood, wire, or a pot, and plant the potatoes in the bottom. As the plant grows, add more soil to accommodate the growth. This method allows for a higher potato yield in a smaller space.

However, it’s important to note that keeping the towers evenly watered can be challenging. The success of this method depends on careful attention to watering and not building the towers too high. Despite the challenges, potato towers can be a great way to save space in your garden.

Understanding Potato Growth

Potatoes originated in South America and have been bred into hundreds of varieties that grow worldwide. Different varieties have different growing seasons, making them suitable for various climates. Planting seed pieces deep enough (at least 6 inches) is crucial to allow for rhizome development, which is essential for tuber formation.

Tubers typically form between five to seven weeks after planting, coinciding with flower formation. However, some varieties never flower. During tuber development, it’s important to provide adequate moisture and fertilizer, as the developing tuber competes with leaves and shoots for nutrients.

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Certain potato varieties produce fewer but larger tubers, while others set potatoes further up the stem, resulting in a mix of large and small tubers. The choice of variety influences the watering and fertilizing needs during the higher temperatures of July and August, as uneven watering can lead to bumpy tuber formation.

Finding the Perfect Temperature

Potatoes are considered cool-season vegetables but are sensitive to hard frosts. The optimal temperature range for shoot emergence is between 68 and 72 degrees Fahrenheit, while tuber formation thrives in the 50-60-degree range. Tuber set is reduced when night temperatures exceed 68 degrees Fahrenheit and inhibited when they surpass 84 degrees Fahrenheit.

In the Willamette Valley, it’s best to plant potatoes when daytime temperatures range from 55 to 60 degrees Fahrenheit. For the Eugene/Springfield area, this translates to late March or early April, with average daytime temperatures between 55-60 degrees Fahrenheit and night lows from 36-39 degrees Fahrenheit. Rainfall during this period is typically between 2-2.5 inches per month, ensuring adequate moisture supply.

To warm the soil and encourage proper drainage, consider covering the ground with plastic a couple of weeks before planting. Protecting emerging plants from insect attacks and frost can be achieved by using a row cover, either Remay or plastic, at night.

Starting Strong with Certified Seed Potatoes

Image: Tubers

When planting potatoes, it’s crucial to start with certified seed potatoes, which can be purchased at local garden centers. One pound of large potato seed stock can yield up to 10 pounds of potatoes, while one pound of fingerling potato seed stock can yield up to 20 pounds.

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Cut the seed potatoes into egg-sized pieces, ensuring each piece has at least three or more eyes. Allow the cut side to seal over and develop a smooth, dry surface before planting in well-amended, well-drained soil. If using a tower or pot, begin by placing 6 inches of soil in the bottom, then cover the seed pieces with 6 inches or more of soil. Space the seed pieces 12 inches apart and add more soil as the plant grows, leaving the top 6 inches exposed.

When using a wire bin, pile straw, leaves, or sheets of newspaper around the edges to prevent soil from falling through the sides. Keep tower height between 2-3 feet, as taller towers are more challenging to water evenly. It is important to monitor watering closely as potatoes grown in towers or pots tend to dry out more rapidly.

Potatoes thrive in slightly acidic soils with a pH of around 6. Regular fertilization every two to three weeks with a balanced granular or liquid emulsion fertilizer, with NPK numbers around 4-6-6, can help support healthy growth.

Harvesting and Varieties

Potatoes should be harvested after the tops have died down. Gently dust the soil off the skins and store the potatoes in a cool, dry place.

Potatoes are categorized based on the number of days needed to reach maturity. Very early earlies (early, early summer) take around 75 days, early varieties take 90 days, mid or maincrop varieties take 110 days, and maincrop to late maincrop variants take 135-160 days.

It’s important to choose a variety suited to the local climate. For growing in towers, opt for mid- to late-season varieties, as they continue to produce rhizomes and form tubers later, allowing for the desired layered effect. However, closely monitoring watering and fertilizing during the higher temperatures of July and August is essential to avoid bumpy tuber formation.

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Sources and Certified Seed Potatoes

For more information on potato cultivation, you can refer to reliable sources such as Washington State University, Oregon State University, and Cornell Extension.

To purchase certified seed potatoes, consider reputable online sources like Seed Savers Exchange, Johnny’s Select Seeds, Gurney’s, Irish Eyes Seed, and Eagle Creek Seed Potatoes. Additionally, local garden centers may also carry certified seed potatoes, so be sure to inquire about their arrival dates.

Remember, the mention of specific products and services is for illustrative purposes only and does not constitute endorsement by the Oregon State University Extension Service.

Image: Ames Farm Center

For a wide selection of certified seed potatoes and reliable gardening expertise, visit the Ames Farm Center. They offer a variety of high-quality seeds and supplies to help you achieve a successful potato harvest.

By following these guidelines and choosing the right planting time and method, you can enjoy a bountiful potato harvest right in your own garden. Happy planting!