Potatoes grow best when they have at least 8 hours of sunlight every day. They don’t need full sun to thrive and too much heat is not ideal – discover the facts in this article..
Spring is here! It’s time to begin planning your vegetable patch. Careful planning is crucial for the success of any garden.
Some plants need more or less light than others. Some can tolerate drought while others require moist soil. Some grow best in temperate climates and others love the heat.
Though potatoes may seem like a simple crop to grow, they can be quite tricky for the budding horticulturalist.
On top of the risks of insect infestations or devastating diseases like blight, it can be hard to create the ideal growing conditions for this staple starchy vegetable.
How to grow potatoes
If you would like more information about growing your own potatoes, please read my article How to grow potatoes. This covers everything you need to know from planting, preparing seed, growing, harvesting and storage and more about this great vegetable.
What are the ideal conditions for potatoes?
To successfully grow potatoes, you’ll need to provide them with the right requirements: soil conditions, nutrients, water and sunlight.
Potatoes grow best where the summer temperatures are between 18°-21°C (65°-70°F) but they can handle slighter warmer climates. They are considered a cool-season crop so it’s best to plant them when the soil reaches 4°C (40°F).
Tubers prefer a well-drained soil with about an inch of evenly distributed water per week.
Mulching will help retain the soil moisture and shield the tubers from direct sunlight.
Do potatoes need light to grow?
Potatoes, like all root vegetables, produce edible tubers under the soil.
But the leafy portion of the plant above ground needs light; almost all vegetables use sunlight for photosynthesis – the process through which they convert nutrients into the starches that will feed the plant.
The tubers, need protection from sunlight as any light will cause them to turn green and produce solanine, which is a toxin. A green potato is referred to as “sunburned”.
Solanine can make people very ill – or if consumed in large enough quantities, may even be fatal.
It’s produced by a member of the nightshade family of plants, which includes other veggies such as eggplants, tomatoes and peppers.
Even prolonged exposure to artificial lights, like those in the grocery store, can turn potatoes green.
Hilling your potatoes – burying the tubers under a heap of soil – will protect them from over-exposure to sunlight.
You should hill your plants when the leaves sprout, and keep the hills intact throughout the growing season. The last hilling should be done before the potato plants bloom, when they’re about 6” tall.
It’s best to hill plants in the morning, before the heat of the day causes them to droop. Just hoe the dirt up around the base of the plant, supporting the stem and covering the tubers.
How much sunlight do potatoes need
When considering how much sunlight plants require, a good rule of thumb is to think in terms of leaves, fruit, and roots.
Crops that we grow for their fruits – such as tomatoes – need full sun, those that we grow for their leaves (spinach, lettuce, etc.) or roots (carrots, beets, or potatoes) can tolerate shady conditions.
So when we talk about sunlight, daylight is sufficient to grow potatoes and is actually better than full sun, as this can lead to the plant requiring extra watering and if the sun is strong enough it will scorch the leaves which will damage the plant.
Potatoes that receive at least four to five hours of daylight will do fairly well, but you may need to wait longer for your crop to mature. When your potatoes get 8 hours of daylight you should expect a decent crop with a normal maturing date.
So while potatoes do – of course – need sunlight to grow properly, the plants can still grow in partial shade. That’s an area that is shady but still bright – it could be shaded for part of the day and sunny for the rest, or receive filtered sunlight for the entire day.
And though light shade can protect tubers from exposure to sunlight – preventing solanine production – it may also impact the crop yield.
Less sun exposure on the leaves will decrease the rate of photosynthesis. This means that the plant creates less nutrients which can result in fewer edible tubers.
Types of sunlight
It’s important to understand what is meant by the amount of sunlight required by a plant. Generally speaking, there are three basic sunlight conditions that are used to describe the daily amount of sun during the prime growing season:
Full sun areas will receive direct sunshine for at least 6 hours per day – typically between the hours of 10 am and 6 pm. In northern climates where the sun is weaker, plants requiring full sun should get at least 8 hours of sunlight per day.
The terms partial shade or partial sun both refer to areas that obtain between 3-6 hours of sun per day. Partial sun areas will receive 3-6 hours of direct sunlight (usually near midday) but are shaded the rest of the day. Partially shaded spaces are either moderately shaded during part of the day or they receive filtered or dappled sunlight all day. That’s when the light is filtered through the leaves of trees before reaching the plant.
Full shade areas don’t receive any direct sun or reflected light during the day. An area with deep shade is not a good place for growing vegetables. Or anything – for that matter! All plants need at least some light to grow.
Learn to embrace your individual microclimates
Most yards contain at least one or even several microclimates. These are small areas where the climate differs from the area around it. It could be a partially shaded area that could extend your cool-season crops – such as potatoes – into early summer.
Try not to see shaded areas as obstacles to avoid, but rather as new planting opportunities. Trees or buildings may cause shifting patterns of light and shade depending on the time of day – or the season.
While this may make it difficult to choose a location for your garden, it can also create microclimates that are favourable for potato growth.
It’s not only while your potatoes are growing that you’ll need to keep the tubers away from light sources.
When storing potatoes, you’ll also need to keep them in a cool, dark place – at around 4°C (40°F) to prevent them from developing “sunburn”.
If you notice any exposed areas turning green, it is perfectly safe to just cut away the green areas and eat the rest of the potato – although normally its just easier to put it into the compost and pick another good one.