Now, I don’t know about you, but, in my experience, knowing when to harvest your potatoes can be a bit of a tricky undertaking. There’s a bit of a mixture of information on the internet talking about when exactly they are ready to be dug up, so I thought I’d put together an article discussing everything you need to know about potato plants and when to harvest them.
Table of Contents
What do potato plants look like?
Potatoes grow under the soil so it can be difficult to know they are ready to be dug up. Here are 4 key points to look out for:
- The flowers have developed and gone for at least 2 weeks
- The plant has begun to shrink and the foliage has holes or looks patchy
- The leaves are starting to turn yellow
- You should uncover full-size potatoes when you start scraping at the soil
The growth stages of potatoes
A potato plant typically goes through 4 growth stages. The first stage is when the potato seed germinates. This is followed by tuber initiation, tuber bulking and finally maturity:
- Potato germination – when the potato seed sprouts and a small plant begins to grow.
- Tuber initiation – when the potato plant starts to develop small tubers. These tubers can be found under the soil around the main stem of the plant
- Tubers bulking – when the potato plant starts to grow larger tubers. The tubers will continue to grow in size until they reach maturity
- Maturity – when the potato plant has stopped growing and is ready to be harvested. At this point, the tubers will have reached their full size and will be firm to touch
Potato growth stages timeline
- Potato plant sprouts through the soil
- a smaller plant measures only 1 foot/30 cm in height.
- A medium-sized plant measures 2 feet or 60cm high
- Fully grown plant measures 3 feet or 90cm high
- Plant starts to grow flowers with green foliage
- Flowers die
- The Potato plants’ heights gradually shorten to 2 feet 60cm, and the leaves turn from green to yellow. There are patches of all-yellow
- Potatoes have yellow leaves that turn black and fall onto the soil
- The plant has started to die back and now it’s time to harvest
I have found that planting potatoes in wood chips not only allows me to add a layer of protection from the elements but also provides nutrients and aeration that potatoes need to thrive. This method has resulted in bigger and healthier potato plants for me.
Usually, I start this process off in March (if you’re based in the UK) and the main crop will be ready for September. I always make sure to get my seed potatoes from a reputable seller and I ensure that they are certified as disease-free. I have found that the supermarket ones aren’t as good quality and often have diseases which will infect my other plants.
When your potato plant is ready to harvest
So as mentioned above, as the potato plants start to reach maturity it starts to produce flowers. The flowers are a sign that the plant is starting to produce tubers (Solanum tuberosum). Now don’t jump the gun too early, just because your potato plant has started to flower, doesn’t mean your potatoes are ready to be harvested (not unless you want teeny-tiny ones).
You’ll also notice during the potato’s growing period that the plant starts to produce fruit that looks very similar to tomatoes, these are known as the “true potato seeds“. Amazingly, you can grow potatoes from these seed pots but it does require some processing and a little bit of elbow grease! If this doesn’t sound like something you’d want to do then I would recommend growing them straight from the tuber as it’s far easier.
Many gardener pals over the years have advised me to wait until my potato plant has really started to die down before harvesting my potatoes. I wouldn’t suggest this because when the plant totally dies, pests like slugs and wireworms emerge, which might severely damage your potatoes growing underneath the soil.
I would suggest waiting for your potato plants to “show the first indications of starting to die back” before you start harvesting them. This way, you can ensure that your potatoes are of a good size and haven’t been damaged by pests.
New potatoes and harvesting early
As I’m sure you’re aware, new potatoes are harvested before the plant has reached full maturity. This is because they are smaller in size and have thinner skin, which makes them more delicate. Remember, the earlier you harvest your potatoes the quicker they will start to go stale and soft – so don’t harvest more than you will use.
If you want to harvest some of your potatoes early then I would recommend doing so when the plant foliage is starting to turn green. You can gently dig around the plant with your fingers (I call it the potato tickle) to feel for any small potatoes and then carefully pull them out. These are best used straight away as they won’t last very long.
Key points to note about your potato plants’ color
Although your potato plant may change color, it does not necessarily mean that it is ready to be harvested – let’s look at the reasons why this may be:
If your potato plant is starting to turn yellow before flower development then it could be a sign that it’s getting watered too frequently or it’s not getting enough nitrogen. This is common in potatoes grown in sandy soils as they tend to lose nutrients quickly. The best way to combat this is by adding a nitrogen-rich fertilizer (such as blood meal or composted manure) to the soil around your plants.
Diseases and pests
If your potato plant’s leaves start to turn yellow and/or brown and there are no flowers present, then this is a sign that your plant may be diseased or is being eaten by pests. The most common diseases in potatoes are early and late blight, both of which can be fatal.
As for pests, the most common ones are wireworms, cutworms, white grubs, and Colorado potato beetles. If you suspect that your plant is affected by any of these then I would suggest taking immediate action as they can quickly destroy an entire crop.
Aphids are tiny little pests that can cause big problems for your potato plants. These sap-sucking insects will not only damage the plant by taking its nutrients but they can also spread diseases. If you notice any aphids on your plants then I would recommend spraying them with a Natural Aphid Vinegar Spray which I have written an article about how to make.
So, what have we learned about potato plants in this article? Well, we’ve looked at the different signs that may indicate that your plant is ready to be harvested. We’ve also looked at some of the reasons why your plant’s leaves may start to turn different colours and what you can do about it. Let’s summarise:
- The flowers have bloomed and died for at least 2 weeks
- The plant is gradually getting smaller and the leaves have holes or look unkempt
- The leaves are beginning to yellow.
- When you start scraping at the soil, you should uncover full-size potatoes.
- Potatoes have 4 growth stages – germination, tuber initiation tuber bulking and maturity
- You can grow potatoes in wood-chips which helps with nutrition retention and aeration
- The best time to harvest potatoes is when the plant shows “early signs of dying back” – this prevents pests from being attracted