How To Grow Cucumbers From Seeds Indoors

Growing Cucumbers From Seeds Indoors is easy when you have the right tools and resources. Cucumbers are versatile vegetables in that they can be consumed fresh, pickled, or even made into relish. 

Growing cucumbers indoors will allow you to have a continuous supply throughout the season with minimal effort and investment.

I like to pickle them and use them in fresh salads. I will go over the steps to grow cucumbers from seeds indoors successfully.

When starting cucumbers from seeds indoors. First, sow cucumber seeds in small pots filled with seed starting mix 3 to 6 weeks before the last frost in your area. Make sure your seedlings get 13 to 18 hours of artificial light per day. Water your cucumber seedlings daily.

Materials For Starting Cucumber Seeds Indoors

• Seed Packets
• Seed Starting Mix or Potting Mix
• Seed Trays
• Plastic Pots or cell packs
• Plastic Cling Wrap 
• Pot to Boil Water
• Plastic Cups to soak seeds
• A fluorescent or LED lighting system
• Labels or masking tape for organization
• Sharpie Marker

Steps to Starting Your Cucumber Seeds Indoors

Step 1: Soak Your Cucumber Seeds in Labeled Cups Overnight

I like to soak my seeds for at least 12 hours or more to ensure the seed is sufficiently soaked for the germination process.

Step 2: Layout your Seed Trays 

Layout your seed trays and put your pots or cell packs in them. For cucumber seeds, I like to use pots. This way I don’t have to transplant them except when they are ready to be transplanted into the vegetable garden outdoors.

I have found over the years that cucumber seedlings can be a little sensitive. They also seem prone to dying if I transplant them from smaller to larger pots before going outside.

Make sure that whatever container you use has drainage to let excess water out.

Step 3: Boil water and pour over potting soil

You will want to pour boiling water over the seed starting mix to kill fungus gnat eggs. I know these little gnats will start to appear once my seedlings start to grow. If you don’t get rid of them they can be a real nuisance!

They make it hard for plants to grow because they feed on plant roots and soil material. These gnats can also cause some weaker plants to die out!

If you don’t want to bother boiling water your seedlings will be just fine most of the time. However, this one extra step will ensure your seedlings grow efficiently.

The soil will still need to be moistened when sowing cucumber seeds indoors.

Step 4: Label Your Pots

I grow a lot of different seeds indoors and I always label my pots so my seedlings don’t get mixed up.

Step 5: Place Soil Mix in Pots

Place soil in pots make and sure it is moist before planting your seeds.

Step 6: Sow Your Cucumber Seeds In the Soil

Put 2 or 3 seeds into each pot. This way if a few don’t germinate you will still get a seedling to grow in each pot. You can cull the excess seedlings or transplant the extras into additional pots.

Step 7: Lightly Water Soil If Necessary

If your soil is a bit dry spray the soil with a spray bottle to moisten the soil further

Step 8: Place Plastic Cover Over Seeds

Using a plastic covering such as cling wrap reduces water evaporation. This also increases warmth and humidity, which helps speed up seed germination.

Step 9: Monitor Seeds For Sprouting

Your cucumber seedlings will not sprout in the first 3 days. Start monitoring your cucumber seeds on the third day. Once some seedlings have sprouted remove the plastic immediately, so they can grow.

Step 10: Set Timer for Lights

You can purchase many types of timers online. Your seedlings need a minimum of 13 to 18 hours per day when using an artificial light source.

Do You Soak Cucumber Seeds Before Planting?

Yes, soak cucumber seeds in labeled cups anywhere from 12-24 hours before sowing in pots indoors. This will ensure your cucumber seeds germinate and then sprout. 

What Is The Best Soil to Start Cucumber Seeds In?

Start cucumber seeds in a seed starting mix or potting soil with a neutral pH. The soil needs to be 68 °F (20 °C) or higher in temperature for the cucumber seeds to germinate properly. The optimal soil temperature for cucumber seed generation is 80 °F (26.66 °C).

How Deep Do You Plant Cucumber Seeds?

You should plant cucumber seeds at a depth equal to two or three times their width. Make a little hole with a pencil and drop 1-3 seeds in the hole.

It is better to plant the seed too shallow rather than too deep. If planted too deep the seed may not have enough energy to break through the top layer of soil.

How Long Does it Take to Grow Cucumber From Seed?

Growing cucumber seeds from germination to harvest takes 55 to 70 days. Germination by itself takes 4-7 days when starting cucumber seeds indoors.

How Do You Get Cucumber Seeds to Germinate?

Soak the seeds for 12-24 hours. After this plant the seeds in a moist seed starting mix or potting soil. Cover the seeds with plastic cling wrap and wait 4 to 6 days. This is the fastest way to germinate cucumber seeds.

How Long Does it Take For Cucumber Seeds to Germinate Indoors?

Cucumber seeds will germinate indoors in 4 to 7 days.

Growing Cucumbers Indoors Under Lights

The type of light bulb you use for starting seeds indoors can affect the health of your plants. Some bulbs are not bright enough or emit a color that is too warm, which can hinder plant growth and flowering.

The best way to start seeds indoors is with a minimum of 5000k for light color and 2100 lumens for lighting intensity. The best lights have 5000k for light color and 3000 lumens or higher for light intensity.

I use cheap T12 fluorescent lights that I purchased years ago from Home Depot. These work great and don’t break the bank. You will want to keep the Flourescent 2 to 4 inches (ca. 10 cm) above your cucumber seedlings for an optimal growth rate.

If you notice light brown spots or a bleached appearance on the cucumber leaves you may want to raise the light 1 to 2 inches (ca. 5 cm) to fix the issue.

You can also use LED lights for your seedlings. Looking for a light with a cooler blue spectrum marked as 5000-6500K (Kelvin). LED lights should be position further above your seedlings at about 8 to 10 inches (ca. 25 cm).

The cucumber seedlings should receive a minimum of 13 to 18 hours a day of artificial light.

Do Cucumber Seeds Need Light to Germinate?

Cucumber seeds do not need light to germinate. Once your cucumber seeds have sprouted they should be given light immediately to ensure optimal growth.

How Many Times a Day Should I Water Cucumber Seedlings?

Cucumber seedlings should be watered once a day. Water the bottom of the seed tray. This will allow the pots or cell packs to soak up the water for the cucumber seedlings.

Do Cucumber Plants Need to be Hardened off?

Yes, cucumbers plants need to be hardened off before transplanting to your garden. You should move them outside for a couple of hours each day for 7 to 10 days.

Start in a spot with shade the first day and gradually move them each day to a sunnier spot. After 7 to 10 days they should be ready to go in the ground.

When hardening off plants make sure you don’t expose them to cold temperatures. Cucumber plants are very sensitive to cold weather.