In this post, you will learn exactly how to start cucumber seeds indoors easily. If the growing cucumber seedling has been intimidating you and you were buying them from the store instead, trust me you're just wasting money. It's much easier than you can imagine!
Cucumbers are a highly versatile and popular vegetable, enjoyed in salads, sandwiches, and other dishes around the world!
Growing cucumbers from seed can be an incredibly rewarding experience for gardeners of all levels, providing delicious homegrown produce. With just a few simple steps, you can create your own thriving cucumber seedling crop easily!
Cucumbers are warm-weather plants and the soil temperature has to be 60 F (16 C) or warmer and with a daytime temperature of at least 70 F (21 C) or warmer.
Since I will be planting these cucumber plants in my greenhouse, I'm starting cucumber seedlings way earlier than if I were to plant them outside.
If you are planning to plant the cucumber seedlings outside then you need to start planting them indoors about four weeks before planting.
I like to speed up the process of cucumber germination by soaking the seeds before sowing. Read more about it in my complete guide to soaking seeds before sowing. Seeds soaked in water for 48 hours germinate in 5 days after being planted!
Table of Contents
Why Consider Growing Cucumber Seedlings Indoors?
Growing cucumber seedlings indoors is a great way to start your garden early and get a head start on the season.
Not only does it give you an opportunity to enjoy fresh cucumbers earlier, but it can also help protect your plants from certain pests and diseases early on when your seedlings might be too vulnerable.
Plus, it even helps extend your growing season! In many climates, the growing season for cucumbers is relatively short. By starting seedlings indoors, you can get a head start on the growing season and enjoy fresh cucumbers earlier in the year.
When starting cucumber seedlings indoors, it's easier to control the growing conditions. This allows you to control the temperature, humidity, and lighting conditions when the seedlings need the most amount of care.
This can help ensure optimal germination and growth, leading to healthier and more productive plants later!
Supplies You'll Need to Start Cucumber Seeds Indoors
You only need three simple supplies to get the best cucumber seedlings growing indoors:
1. Organic Cucumber Seeds:
I personally order all the seeds from Nikitovka Seeds, and I highly recommend you check them out. They stock a huge variety of cucumber seeds at really affordable prices!
2. Seedling Starter Kit
There are a variety of containers suitable for use as starter trays. You can purchase seedling trays made of plastic or biodegradable materials.
Alternatively, you can also use egg cartons, paper or plastic cups, or almost any other shallow container that can hold your potting mix.
Whichever container you choose to start your seedlings in, make sure it has proper drainage.
3. Starter Soil Mix
Cucumber seeds can be sown in either potting soil or a soilless starting mix.
But before you begin, check the packaging to ensure that it is sterile. If you plant your cucumber seeds in regular garden soil that has not been sterilized, their health may be at risk.
That's why, it's important to get high-quality potting soil. I prefer to purchase mine at Costco because the price is much lower!
How to Start Cucumber Seeds Indoors (Step by Step)
Step 1: Know When to Start Your Cucumbers
Planting cucumber seeds outdoors should begin about two weeks after the last expected frost date. Cold and frost can hurt cucumbers, so the weather needs to warm up a bit before they can be planted safely.
But starting your cucumber seeds indoors will give you a head start on the growing season since you can easily control and manage the temperature indoors! And this is why it's my preferred way of doing it.
Your cucumber plants will have plenty of time to grow and mature inside if you start your seeds around four weeks before the final expected frost date. Also, it ensures that they will be ready for transplanting about the time you would often begin planting cucumbers.
You can, however, start them even early if you like. But keep in mind that the earlier you start, the more time you will have to devote to indoor care before you can transfer them outside.
Step 2: Fill Containers with Seed Start Mix
Now let's start growing our seedling cucumbers from scratch!
First things first, fill the container with seed starter mix or use organic potting soil mix. I personally get it from Costco for fraction of the cost and I highly recommend you do that as well.
Make sure not to use garden soil which often drains poorly and may carry disease. Gently press the soil to remove air pockets.
Step 3: Sow Cucumber Seeds and Water Lightly
Next, use your finger to poke small holes about a quarter-inch deep for each seed. Place one seed in each hole. Then sprinkle additional soil to cover the holes with seeds about a half-inch thick.
Once again gently firm the sprinkled soil mix and water lightly. It's highly important to make sure not to flood the container with water.
Step 4: Place Container in a Warm Place
Finally, place a container in a warm, sunny spot that receives full sunlight. I personally prefer to place my starter trays on the window sill. Ensure that the temperature is at least 70 F (21 C) to 80 F (27 C).
Alternatively, you can also place them on a seedling heating mat in a place that's free from drafts and make sure to maintain the temperature I've mentioned above, which is 70 to 80 degrees Fahrenheit (21 to 27 degrees Celsius).
Step 5: Monitor and Check Daily
Cucumber seeds can take up to 7-14 days to germinate. Monitor the soil moisture level as you wait for the seedlings to emerge.
Check daily to keep the planting mix moist but not saturated. Once you see the first sprout keep the seedling at high light exposure or set it on the window sill that gets lots of direct sunlight.
Continue keeping the planting seed moist but not soggy.
Five days later after planting the white seeds, cucumbers sprouted and the green-coated ones did not.
Nine days later after planting the longer cucumber plants were the white seeds and the shorter ones were the green-coated seeds.
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How to Start Cucumber Seeds Indoors (Step by Step)
Ingredients
You will need
- Organic Cucumber Seeds
- Seedling Starter Kit
- Starter Soil Mix
Instructions
How to Start Cucumber Seeds Indoors (Step by Step)
- Step 1: Know When to Start Your Cucumbers
- Planting cucumber seeds outdoors should begin about two weeks after the last expected frost date. Cold and frost can hurt cucumbers, so the weather needs to warm up a bit before they can be planted safely.
- But starting your cucumber seeds indoors will give you a head start on the growing season since you can easily control and manage the temperature indoors! And this is why it's my preferred way of doing it.
- Your cucumber plants will have plenty of time to grow and mature inside if you start your seeds around four weeks before the final expected frost date. Also, it ensures that they will be ready for transplanting about the time you would often begin planting cucumbers.
- You can, however, start them even early if you like. But keep in mind that the earlier you start, the more time you will have to devote to indoor care before you can transfer them outside.
- Step 2: Fill Containers with Seed Start Mix
- Now let's start growing our seedling cucumbers from scratch!
- First things first, fill the container with seed starter mix or use organic potting soil mix. I personally get it from Costco for fraction of the cost and I highly recommend you do that as well.
- Make sure not to use garden soil which often drains poorly and may carry disease. Gently press the soil to remove air pockets.
- Step 3: Sow Cucumber Seeds and Water Lightly
- Next, use your finger to poke small holes about a quarter-inch deep for each seed. Place one seed in each hole. Then sprinkle additional soil to cover the holes with seeds about a half-inch thick.
- Once again gently firm the sprinkled soil mix and water lightly. It's highly important to make sure not to flood the container with water.
- Step 4: Place Container in a Warm Place
- Finally, place a container in a warm, sunny spot that receives full sunlight. I personally prefer to place my starter trays on the window sill. Ensure that the temperature is at least 70 F (21 C) to 80 F (27 C).
- Alternatively, you can also place them on a seedling heating mat in a place that's free from drafts and make sure to maintain the temperature I've mentioned above, which is 70 to 80 degrees Fahrenheit (21 to 27 degrees Celsius).
- Step 5: Monitor and Check Daily
- Cucumber seeds can take up to 7-14 days to germinate. Monitor the soil moisture level as you wait for the seedlings to emerge.
- Check daily to keep the planting mix moist but not saturated. Once you see the first sprout keep the seedling at high light exposure or set it on the window sill that gets lots of direct sunlight.
- Continue keeping the planting seed moist but not soggy.
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Thank you this was very helpful.
I have planted my seeds twice now and it has still not sprouted, am getting frustrated.
Am using seeds from the cucumber plant I got from the market, I think maybe that's why it's not growing.
Yes, that is why the cucumber seeds aren't germinating. The seeds in the cucumber were not fully mature before the cucumber made it to the market. The cucumber needs to be on the cucumber vine entire time for it to be fully mature, I mean to get to yellow or orange color. Then you remove fully mature cucumber from the cucumber vine and then remove the seeds. Dry them by placing them onto a cloth or a paper towel (you cannot rinse the seeds). And then if planed the following year they may not even germinate, usually, they will germinate the year after. I'm planning to make a post about it sometime in the future. But for now, I hope your question got answered. Thank you for asking!
So you plant them in one large container and then do you just split when you put them into the garden? I couldn't find info on that. I hope I didn't just miss it.
No, that is not correct. I plant the seeds into one large container for them to germinate. As soon as they reach about 1 to 1.5 inches tall, I repot them into individual containers. I have a separate post with a video on how it's done. I hope this is helpful.
Hello Valya, I really enjoyed reading your article about starting cucumber seeds indoors, I found it very helpful. Thank you, Richard.
I'm happy to hear that. Thank you for an amazing review!
Ok what am I doing wrong when I have the seeds in a jiffy seed starter tray an my plants are growing tall an thin then dying. With only a little leaf at the top
There could be multiple reasons. Not enough soil inside of those individual starter containers for the roots to expand and grow. Growing thin is not enough light. I personally never trusted those starters and prefer doing it exactly how I made a post about it. I hope it helps. Thank you for your comment!:)
It appears that your container for starting the seeds does not have holes in the bottom. Can any container be used? I watched your very informative video for repotting the seedlings. I’m excited to get started! My cucumber seeds never did grow last year when I planted them directly in my garden - multiple times. Thanks for your gardening help. I love growing our own food!
It does not matter in what container you start growing the seeds. But it's important to repot cucumber starter plants into containers that do comes with wholes. See How to Repot Cucumber and Tomato Seedlings post for more info. Thank you for an amazing review!
I planted seeds in my small greenhouse. Cukes came up in 3 days -then the stem wilted and plant died! Not enough sun??
The greenhouse should have enough light. It could be due to the temperature. It was probably too cold for the plants.
Thank you for your helpful tips. It really helped since this is my first time planting anything.
You are most certainly welcome!
Getting ready to plant cucumber seeds indoors and so happy to read your comments on proper way to do so. Seems it was being done correctly. Thx! 🙂
I'm happy to hear that! Good luch!
Would you have any Idea why a burpless cucumber plant grown in a professional nursery would get yellow spots on the leaves? We start our own but buy a few from a local greenhouse to get an early start. 2 years ago we were picking at least 100 cukes a day for our produce stand. Last year our whole cucumber crop got infected. It was a hot dry summer in Central PA so we had to water often but we used soaker hoses instead of spraying. Is there a problem with diseased cucumber seeds from some suppliers? Thank You for any advice you may have.
Those seeds were probably infected. The leaves will have yellow spots and if you look under or on the other side of the leaf you will see very small microscopical bugs on them. They eat the nutrients from the leaves which makes them leave turn yellow and the plant will dry out eventually. I'm sorry. That happened to me in the past as well.
Hi, I'm wondering if there is any difference on which end of the seed i put first in the soil? Is there any difference at all?
Thank you.
It depends on the seed. If you're referring to a cucumber seed then there is no difference. I hope this helps. Thank you for asking!