How Long Do Cucumber Seeds Take to Germinate? (Speed It Up!)


If you are planning to grow cucumbers this year, you are probably wondering how long they will take to germinate, or sprout.  Even if you have planted cucumbers before, you may want to find ways to make the seeds germinate faster.

So, how long do cucumber seeds take to germinate?  Cucumber seeds take 3 to 13 days to germinate.  Cucumber seeds germinate faster with optimal soil temperature, humidity, and air circulation.  You can speed up the germination process by putting the cucumber seeds in a humidity dome (purchased or homemade) and keeping the soil at 85 to 95 degrees Fahrenheit (29.4 to 35 degrees Celsius).

Of course, there are factors that affect how quickly cucumber plants will grow after germination.  Let’s start by looking at how germination times vary with temperature.  Then, we’ll go over some ways to give your cucumber seeds the optimal environment to grow.

How Long Does it Take for Cucumber Seeds to Germinate?

Cucumber seeds will take 3 to 13 days to germinate.  One of the most important factors that affects time to germination is the soil temperature.

Time for Cucumber Seeds to Germinate by Soil Temperature

According to both Cornell University and the Michigan State University Extension, cucumber seeds will germinate in 3 to 10 days under ideal conditions.  However, it may take a little longer at borderline temperatures on the low end (around 60 degrees Fahrenheit, or 15.6 degrees Celsius).

thermometer
Temperature is one of the main factors that determines whether cucumber seeds will germinate successfully, and how long they will take.

For example, if soil temperatures are lower than 60 degrees Fahrenheit (15.6 degrees Celsius), you may fail to see any germination at all.  If you do, it is likely to take 13 days (close to 2 weeks) for cucumber seeds to germinate at such low soil temperatures.  You will also see a relatively low germination rate (the percentage of planted cucumber seeds that sprout).

In slightly warmer soil temperatures in the 60s Fahrenheit (15.6 to 20.6 degrees Celsius), it will take 6 to 7 days (about a week) for cucumber seeds to germinate.  You should see better germination rates in this case.

Note: if you want to test seed germination rates for an older seed packet, check out my article on seed germination rates.

In warmer soil temperatures between 70 and 80 degrees Fahrenheit (21.1 to 26.7 degrees Celsius), cucumber seeds can germinate in 4 to 5 days.  The germination rate will be much higher in this scenario.

At the high end, with soil temperatures between 85 and 95 degrees Fahrenheit (29.4 to 35 degrees Celsius), cucumber seeds can germinate in as little as 3 days!

For a summary, check out the table below, and for more information, check out this article from the University of California on ideal seed germination temperatures.

Seed
Germination
Temperature
Temperature
(degrees
Fahrenheit)
Temperature
(degrees
Celsius)
Minimum6015.6
Ideal65 to 9518.3 to 35
Maximum10540.6

How and Why to Start Cucumbers Early

Generally, cucumber seeds should be planted directly into the garden in the spring.  Ideally, the seeds should be planted after the soil has warmed to at least 65 degrees Fahrenheit (18.3 degrees Celsius).

If you start cucumber seeds indoors, it may be difficult to transplant the seedlings into the garden without disturbing the roots and harming the plant.  However, it may be worth the risk in a cold region with a short growing season.

If you do decide to start cucumber seeds indoors, there are a couple of ways to keep them warm.  One way is to use a heat mat underneath the seed container.  Another method is to put the seed container on top of your refrigerator (it is cold inside the refrigerator because it gives off heat on the outside!)

For more information, check out this article on starting seeds indoors from the University of Maryland Extension.

If you still want to plant your cucumber seeds directly in the garden, there are some ways to warm up the soil a bit and keep your plants comfortable in the early days.

First, you can cover the soil with black or clear plastic and let the sun warm up the air and soil underneath.  This will let you plant cucumber seeds a bit earlier than normal.

You can also use a cloche for each cucumber seed.  A cloche is a covering (usually made of plastic) that protects seeds or seedlings from cold, pests, wind, and other outdoor dangers in the garden.

glass cloche
A cloche does not have to be this fancy – an empty clear plastic water jug will work fine!

You can use an empty clear plastic milk or water jug as a cloche – just cut out the bottom and put the whole thing over the spot where you planted the seed.  The plant will eventually outgrow the cloche, but that is fine.  By that point, the plant will be large enough, and the weather will be warm enough, that it won’t need the protection any more.

A cloche will help to trap the sun’s heat in the air, and some of that heat will get trapped in the soil as well.  This extra heat will help the cucumber seeds to germinate faster.

A word of warning: don’t let the plant get too hot after it germinates!  You can remove the top of the plastic jug, thus creating an air vent to help cool things down inside the cloche.

How to Help Your Cucumber Seeds to Germinate Faster

Aside from maintaining an ideal temperature, there are some other ways to help your cucumber seeds to germinate faster.

One of the best ways is to keep the cucumber seeds (and the soil you put them in) moist, so we’ll start there.

Keep the Cucumber Seeds and Their Soil Moist

Even with ideal soil temperatures, cucumber seeds will not germinate without enough moisture.  In fact, seeds will die if they dry out too much after the germination process has begun.

spray bottle
A spray bottle is handy to keep soil moist for cucumber seeds that are trying to germinate.

If starting seeds indoors, you can use a spray bottle to keep the soil moist, or let the seed trays soak up water from below.  If sowing directly into the garden, keep the soil moist by watering as often as necessary to keep the soil continuously moist (but never wet enough to wash away seeds or soil).

Keep the Humidity at the Right Level

Humidity is another important factor to consider when germinating cucumber seeds.  If the air is too dry, then the soil will dry out faster, and the seeds will have trouble germinating – they may even die!

If the air is too humid, then the soil will stay too wet, especially if you over water the seed tray or garden soil.  This can lead to damping off, which occurs when mold or other pathogens affect seeds or seedlings.

Damping off is more likely with high humidity levels, in moist soil, and at cooler temperatures.  For more information, check out my article on damping off of seedlings.

If you find that you have trouble keeping the air and soil humid enough, you do have some options.  One possibility is to use a humidity dome.

A humidity dome traps moisture in the air and soil so that seeds have the humid environment they need to germinate properly.  A humidity dome will help your seeds to germinate faster, increase germination rates, and cut down on the time and effort needed to keep soil moist.

For more information, check out my article on humidity domes.

Keep the Soil Aerated

Seeds need air, just like seedlings and established plants.  If the soil is too wet and there is too little air circulation, it can spell death for your seeds before they even have a chance to sprout.

To keep your seeds from suffocating due to lack of air, there are two key actions you can take.

First, keep the soil moist, but not wet.  Do not over water the soil, and consider using a humidity dome (indoors) or a cloche (outdoors) to help you to get the right soil moisture and air humidity levels.

Second, keep the soil loose.  Do not compact the soil by pushing down hard on it either before or after planting your seeds.  When there is more space between soil particles, there is more space for air and water, both of which are necessary for seed germination.

Use Newer, Younger Cucumber Seeds

For best germination results, use new cucumber seeds, rather than old ones.  Newer seeds will have a higher germination rate, while older seeds may fail to germinate at all.

seed package
Use newer seeds if possible – they will have a higher germination rate.

Generally, cucumber seeds will last about 3 years.  After that, their germination rate starts to decrease rapidly.  For more information on the lifespan of cucumbers and other seeds, check out my article on how long seeds will last.

Can You Germinate Cucumber Seeds in a Paper Towel?

Yes, you can germinate cucumber seeds in a paper towel.  The paper towel holds moisture and allows the seeds to breathe, serving as an alternative growing medium.

paper towel
Yes, you can germinate seeds in a moist paper towel.

To germinate cucumber seeds on a paper towel, wet the paper towel until it is damp (not soaking wet).  Then, lay out the cucumber seeds so that they are separated (not touching).

Be sure to keep the paper towel and seeds in a warm place, to encourage faster germination and higher germination rates.

The only drawback of this method is that you will need to transplant the sprouted seeds into soil by hand, since they will soon need nutrients from the soil to grow and establish stronger roots.  Be gentle when handling the tiny sprouted seedlings!

How to Help Your Cucumber Plants to Grow Better After Germination

If you get a few key things right, then your cucumber plants will grow much better after germination.  These key factors are planting time, seed spacing and thinning, watering, and fertilizing.  Let’s start with planting time.

Choose the Right Time to Plant Your Cucumber Seeds

As mentioned above, soil temperature has a huge impact on the time it takes for cucumber seeds to germinate.  If you plant too early, a hard frost can kill the seeds.

frosted leaf
A frost will kill cucumber plants – wait until a couple of weeks after the last frost date to plant them outside!

Even after the danger of frost has passed, cucumber seeds will germinate slowly – or not at all – if soil temperatures are too cool (below 60 degrees Fahrenheit, or 15.6 degrees Celsius).

According to the University of Georgia Extension, cucumber plants grow best in warmer temperatures, between 75 and 85 degrees Fahrenheit (23.9 and 29.4 degrees Celsius).

So, when is the right time to plant cucumbers?  If there is still snow on the ground, you will have to wait!

According to Burpee, cucumber seedlings should be around 5 to 6 weeks old before transplanting outdoors.  Generally, you should start the seeds 3 to 4 weeks before the last spring frost date.

The soil will not be warm enough to transplant cucumber plants outdoors until at least two weeks after last frost date.

For more information, check out this frost date calculator from the Old Farmer’s Almanac.

Use Proper Plant Spacing and Seed Depth for Your Cucumber Seeds

Cucumber seeds should be planted about 0.5 inches (1.25 centimeters) deep.  The seeds should be spaced 2 inches (5 centimeters) apart.

The rows themselves should be 2 to 3 feet (0.6 to 0.9 meters) apart, to allow enough space for watering, weeding, fertilizing, and harvesting.

Once germination occurs and seedlings begin to emerge, thin them so there are 8 to 12 inches (20 to 30 centimeters) between plants.  For more information, check out my article on why you should thin seedlings and how to do it.

An alternative planting method is to build up mounds of soil in the garden, and plant 3 to 4 seeds close together.  These mounds should be spaced 5 to 6 feet (1.5 to 1.8 meters) apart.

For more information, check out this article on growing cucumbers from the University of Minnesota Extension.

Water Your Cucumbers Properly

Cucumber plants need plenty of water, especially after fruit sets.  Cucumbers have a shallow root system, so be sure to give them a deep watering as often as necessary.  Keep the soil moist, but not soaked.

watering can
Keep your cucumber plants well watered, especially after fruits have formed.

You may need to check them frequently during hot, dry weather.  For more information, check out this article on cucumbers from Clemson University.

https://hgic.clemson.edu/factsheet/cucumber/

Fertilize Your Cucumbers Properly

For best results, the soil pH should be between 6.0 and 6.5 when growing cucumbers.  You can improve the soil structure and nutrient content by adding compost or decomposed manure in spring or fall.

For more information, check out my article on how to make your own compost, and my article on where to buy compost.

compost bin
You can make your own compost from yard and kitchen scraps to feed your plants!

You can also try a balanced fertilizer, such as 10-10-10, to provide extra nutrients.  If you are not sure what this means, check out my article on NPK ratios.

Before adding fertilizer to your garden, get a soil test to be sure that you really do need it!  Otherwise, you may be over fertilizing your plants, which can burn them.

For more information, check out my article on how to do a soil test.

Conclusion

Hopefully, this article gave you a sense of how long it will take your cucumber seeds to germinate (3 to 13 days).  You should also have some good ideas on how to speed up the process.  Remember that temperature and moisture are two of the key factors in getting cucumber seeds to germinate well.

I hope this article was helpful – if so, please share it with someone who can use the information.  Now get back to gardening!

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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