How to Grow Cucumber Indoors

The term “cool as a cucumber” actually comes from the cucumber’s ability to cool the temperature of the blood. It can also kill the bacteria that are responsible for causing bad breath.

Timing

Sprouts in 1-2 weeks. Harvest from Month 3+ on.

Full sun

Equivalent of 7+ hours of direct sun [DLI of 21+ mol/m²/day].

Care

Beginner friendly. Once it’s producing – you’ll have to harvest it every couple of days.

Best Cucumber varieties to grow inside.

There are two types of cucumber that you will see: picklers (stubby & bumpy) and slicers (long & smooth). Here is a list of the top 4 most popular cucumber varieties:

Socrates

Slicer

It is regarded as one of the best-tasting cucumbers on the market today.

Amazon

Tasty Jade

Slicer

Delicious, long Asian cucumber. It is an excellent slicer and perfect for salads and gourmet dishes.

Amazon

Supremo

Pickler

Perfect in salads or as a snack. Great disease resistance. Exclusive.

Amazon

Parisian

Pickler

This dark-green cucumber with firm, thick flesh and inconspicuous seeds is suitable for pickling or slicing

Amazon

Best Setup for Cucumber Plants

You’ll need:

Planter: 

Ceramic Self Watering Planter (preferred) or pot that is at least 12″ / 5 gal.

Soil: 

Standard Potting Mix

Plant Food:

Herb Blend. This should be high in nitrogen (with NPK numbers like 10-5-5). 

Grow Light:

A strong grow light that can give the equivalent of 7+ hours of direct sun [DLI of 21+ mol/m²/day].

Jump to: Our product recommendations

Preparing your Planter & Watering Schedule for Cucumber

Cucumber plants do well in moist soil conditions. If the soil dries out completely the roots will die back and it will be tough for the plant to recover. On the other hand, if the roots are exposed to standing water for too long, they can rot.

A Ceramic Self Watering Planter filled with a standard potting mix self-regulates to keep the soil at consistent moisture for your plant to thrive (and no watering guesswork for you). 

To set one up:

  1. Fill up the planter with dry soil from the bag, gently tamping down the top.
  2. Dump the soil into a large mixing bowl and add water until the soil is moist, but not sopping wet (about ½ Cup)
  3. Mix in 1 tablespoon of the Herb Blend Plant Food.

If you are using a regular pot instead, it should be a little bit bigger (at least 12″ / 5 gal and will need drainage holes to prevent it from being over watered. Let the top of the soil dry out between watering.

Starting your Cucumber: Seed vs Propagate

Cucumber plants are best to start from seed in the area they will grow to their full size (known as “direct sowing”). They’re not practical to propagate from cuttings & they don’t handle transplanting well. Fortunately starting from seed is simple and they sprout quickly!

How to Plant Cucumber seeds

Cucumber grows quickly from seed. Plant 2 sites in a 12″ / 5 gal container. In larger containers, space sites 8″ apart. For each site plant, 2 seeds 1″ deep. Keep the soil warm ( 60-90°F, ideally 80°F). Sprouts typically appear in 7 days but can be as quick as 3 days or as long as 10 days depending on your conditions. To speed things up, you can soak them in water for 12-24 hours before planting.

To speed things up, you can soak them in water for 12-24 hours before planting.

Why starting Cucumber from Stem doesn’t make sense

Cucumbers are short-lived plants and prone to root rot. Even under perfect conditions, they lack the genetic makeup to readily produce roots from their stems.

Where to grow your Cucumber plants

Cucumber plants have the highest light needs of any plant – so unless you have a totally unobstructed southern-facing window and plan on only growing in the summer – you’ll need a grow light. We still recommend taking advantage of your bright window (sunlight is free and great for plants!) and supplement it with a grow light. For an introduction to grow lights, head over to our post on grow lights for indoor gardeners. We’ve also got a buying guide for screw in types, but to keep things simple in this guide, we’ll just provide directions for the 24W Screw in Bulb by Sansi, which we think is a good middle-of-the-road option.

How bright should your grow light be? 

Cucumber plants need the equivalent of 7+ hours of direct sunlight [DLI of 21+ mol/m²/day] to grow their best. In order to provide an equivalent amount with a grow light, it needs to be pretty bright! The 24W Sansi bulb should be placed 6 inches away from the top of the plant. This will give your PPFD (the standard measure of brightness) of 500 μmol/m²/s.

How many hours per day do your Cucumber plants need under a grow light?

Cucumber plants are what’s known as “day-neutral” so can grow under a range of daylight lengths. In order for them to get enough light, we recommend setting up a timer to leave it on for 14+ hours per day.

Cucumber Plants Grow Faster in Warmer Temps

Cucumber plants are called “warm-weather crops” and like temperatures right around 80. They will grow fine in conditions between  70 and 85°F but can lose their fruit if it drops below 40. On the other hand, if they are too hot, they will drop their blossoms, wilt, and stop ripening.  Most homes are in a good range – and a south-facing sunny window can help get a plant the extra heat if needed.

Week 1-2: Check for Sprouts

You could see seedlings in as little as 3 days (though 7 days is more typical). If it’s been 10 days and you still don’t have any sprouts, it’s likely that your setup is too cold.

Week 3: Thin Your Seedlings

Thin your planter to only have 1 seedling per site –  leaving the largest plant. If you are using the reccomended planter (at least 12″ / 5 gal) this will mean you’ve got 2 plants after thinning.  By getting rid of the smaller seedlings, you’re allowing the biggest and strongest one to flourish by reducing its competition for water, food, and space. 

If your seedlings are under 2 inches, stretching out, or folding over, it’s likely that they don’t have quite enough light.

Month 1: How to Prune & Trellis Cucumber Plants

Cucumber plants are vines that will continue to grow and grow – so a monthly trim will be a necessary part of your care routine.  You’ll make your first cut at about the second month, or when you have 5 branches and a growing tip, cut (or just pinch) off the main stem above the 5th branch. By removing the growing tip, you’re having the plant focus its energy on those 5 branches. There are several support options, ranging from cages to stakes, but we like to train those 5 branches up a fan trellis with plant clips.

After this, pruning and trellising is more of an art (fortunately an art that’s hard to mess up) but the general things you’ll want to look of for when:

  1. Little leaves grow out of the “V” where a branch meets the main stem. Snap these “suckers” off right at their base.
  2. The main stem is going past your grow area. Pinch of the growth tip where you want it to stop.
  3. A heavy cluster of Cucumber starts to form. The weight can snap the vine, so clip right above the cluster to the trellis to avoid this (mildly heartbreaking) event.
  4. The plant is getting so dense that light and air can’t get in. Keep up with interior pruning to have a tidy “bonsai” Cucumber plant.

Month 2+: How to Pollinate Your Cucumber Flowers

We only recommend self-pollinating Cucumber, because it’s a bit of a pain to pollinate them otherwise (you would need to find a “male” and “female” flower that would have happened to open at the same time). Assuming you are using one of the self-pollinating varieties – wait until the flowers open then just give them a slight shake or “rub the nose” of the flower.

Month 3+: How to Harvest Cucumbers

The rule for these is to “pick um often and pick um all.” Cucumbers are at peak crispness for a short time, so you need to pick often to catch the small window of the best flavor. When vegetables start to form it’s helpful to experiment a bit to find out what they are like at peak flavor for you. If you miss a single cucumber (and they’re good at hiding!) and it grows to maturity then these plants end their life cycle early. By preventing the plant from finishing that last step of making seeds, you are able to keep it producing vegetables for much longer. 

Month 12+: End of Life

Indoor zucchini plants can last for up to a year, but eventually, they’ll tire out. Once you seed a big drop in productivity, in spite of giving it sufficient plant food it’s time to start over.

Shop This Blog

The right supplies can take the guesswork out of caring for your plants – and turn care from a daily to weekly routine. Through our grow tests, we’ve found these products to produce the best indoor Cucumber (and also have simple maintenance).  Plants are adaptable and can grow in many different conditions, so they are by no means necessary if you already have other supplies.

Best Containers for Cucumber: Ceramic Self Watering Planters

Plants thrive on consistent moisture but can suffer if they’re waterlogged. A semi-porous ceramic self regulates ideal conditions. Our favorite is the COSWIP planter. Runner up is XS Self Watering Planter by Wet Pot.

Best Soil for Cucumber: Standard Potting Mix

Cucumber likes a rich and moist root zone – so you are best off with a standard potting mix – we like this Organic Mix by Espoma

Best Nutrients for Cucumber: Herb Blend

Cucumber likes nutrients that are high in nitrogen (with NPK numbers like 10-5-5). For a Herb Blend, we recommend: Joyful Dirt All Purpose

Best Light for Cucumber: DIY or Soltech

There is a very small chance that you have the bright windows needed to grow these without a grow light. If you are looking for a higher-end option – we love the Aspect Light by Soltech. For a more affordable option, a DIY setup using a 24W Screw-in Bulb by Sansi with a Clamp Light and Mechanical Timer works well too.  Check out our complete guide on a DIY setup for less than $40 or our buying guide for screw in bulbs.

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