The Best Fertilizer For Cucumbers

Cucumbers grow easily when they get enough sun, water, and nutrients.

So, to make sure your plants stay healthy and to maximize fruit yield it’s a good idea to use a fertilizer.

Our recommended choice is Lilly Miller Morcrop Tomato & Vegetable Food.

This fertilizer has the right balance of essential nutrients for successful growth. And continues to feed your plants for up to 6 weeks at a time.

The best fertilizer for cucumbers at a glance:

All links lead to Amazon, where you can find more information & customer reviews.

The Best Fertilizer For Cucumbers

Lilly Miller Morcrop Tomato & Vegetable Food

Lilly Miller Morcrop

This fertilizer provides a 5-10-10 NPK formula that works well for cucumber plants. And you can also use it for any other vegetables you’re growing in your garden.

Cucumbers use twice as much potassium (K) than nitrogen (N) as they grow. So this product gives you a great balance.

The nitrogen is provided as both slow and quick release. So you get fast nutrition to your plants and quick growth. But you also get the slow release of nutrients that continues to feed them for up to 6 weeks at a time.

It’s also fortified with 4% calcium. This prevents your cucumbers from developing blossom end rot, a disorder caused by calcium deficiency that spoils the fruit.

The product comes as granules that you mix into the soil surface and then water. Use it when you first plant your cucumbers and then every 4-6 weeks while they’re growing.

Customers report impressive yields. With the only drawback being the smell of manure when it’s first applied.

Pros
  • A good NPK ratio for cucumber plant growth and fruit yield
  • Fortified with calcium to prevent blossom end rot
  • It contains fast-release and slow-release nitrogen
Cons
  • Unpleasant odor when first applied

Espoma Garden Tone

Espoma

This natural fertilizer is ideal for growing cucumbers if you prefer organic gardening.

It provides everything your plants need to grow and bear fruit. With an NPK ratio of 3-4-4. And a full range of essential secondary nutrients and micronutrients. Making sure that your plants won’t suffer from any nutrient deficiencies in the soil.

While the NPK ratio of organic fertilizer is always lower than products containing synthetic fertilizer, it does have other benefits that encourage strong growth.

To start with, it’s great for producing healthy long term soil for your plants to grow in. Improving texture, structure, and aeration.

And the organic material is broken down slowly, providing continuous nutrition over many weeks.

Espoma Garden Tone also contains beneficial soil microbes that increase nutrient availability.

And it’s safe for the environment, with no worries about phosphorus runoff.

Pros
  • Natural & organic
  • Contains all the essential nutrients your plants need
  • Added soil microbes improve the soil health and increase nutrient availability for root uptake
  • Safe for the environment
Cons
  • Strong odor
  • Lower NPK than synthetic fertilizers

Down to Earth Organic Vegetable Garden Fertilizer


Down To Earth is a balanced natural fertilizer with a 4-4-4 NPK ratio. It’s OMRI listed for organic use, making it a good choice for organic gardeners.

It has all the benefits you’d expect from organic fertilizer. It’s slowly broken down by microbes in the soil. Gradually releasing nutrients for your plant to use, without the risk of overdoing it and causing fertilizer burn.

And the soil it helps you build over time is healthy. With a high level of microbe activity, and great supporting structure for your plants.

Like most organic fertilizer it does have a strong odor when first applied. But it goes away after a few days.

Pros
  • All-natural and organic
  • OMRI listed
  • Creates healthy soil with good microbe activity
  • Environmentally friendly
Cons
  • Strong smell
  • Lower NPK than chemical fertilizers

Osmocote Smart-Release Plant Food Flower & Vegetable


Osmocote flower & vegetable food has a nutrient rich 14-14-14 NPK formula.

It comes in slow-release granules that have a special semi-permeable resin coating. When they get wet the nutrients inside dissolve, enabling their gradual release. Feeding your plants for up to 4 months with each application.

Customers are happy with the growth of their plants when using this fertilizer. But some people don’t like the way the resin balls accumulate in the soil without dissolving.

Pros
  • High nutrient content
  • Feeds plants for 4 months
Cons
  • The empty shells don’t dissolve and are left in your soil after they release their nutrients

Miracle-Gro Water Soluble Plant Food Vegetables & Herbs


Miracle-Gro is a well known brand with a successful line of fertilizers. This one is designed for gardening vegetables and herbs.

It’s an 18-18-21 NPK fertilizer that provides quickly available nutrients for everything in your vegetable garden. As well as cucumbers, use it on your tomatoes, carrots, peppers, squash, zucchini, and all Cucurbita, to keep them in good health while they grow and maximize their yield.

It’s easy to use. Just mix it together with water in your watering can each time you water your plants.

And as it’s easily water-soluble, it’s a good choice if you’re growing hydroponic cucumbers.

Pros
  • High NPK
  • Water soluble—useful if you grow cucumbers using hydroponics
Cons
  • It can cause nutrient burn if you don’t follow the instructions carefully

Cucumber Nutrient Requirements

Cucumbers need plenty of the primary nutrients, nitrogen, phosphorus, and potassium to grow. So it’s a good idea to get an NPK (Nitrogen-Phosphorus-Potassium) fertilizer that provides all 3.

In particular, they’re hungry for potassium, and require more of it than the other 2. NPK fertilizer with a ratio of 5-5-10, or 5-10-10 is a good choice to cater to a cucumber plant’s growing requirements. But you can also use a balanced fertilizer such as 10-10-10.

They also need secondary nutrients and micronutrients that are usually present in the soil.

A common nutrient deficiency is a lack of magnesium. This sometimes occurs mid-season and reduces fruit yield. The symptoms include the leaves turning yellow, which is first noticeable on the older, lower leaves.

But adding Epsom salt as a side dressing can correct the problem.

Related: Is Epsom Salt Good For Cucumbers?

What Type Of Fertilizer To Use On Cucumber Plants

The best fertilizer for cucumbers comes in 2 different types: organic and synthetic (chemical). They each have their own advantages.

Organic fertilizer often contains the full range of primary and secondary nutrients your cucumbers need for healthy growth. As well as many essential micronutrients.

It breaks down in the soil slowly, releasing nutrients throughout the growing season (you can also get liquid natural fertilizer that provides faster access to nutrients).

Adding organic matter also helps to build healthy soil for the long term. With good texture, drainage, and aeration.

Synthetic fertilizer has the advantage that it’s usually higher in NPK. But it usually doesn’t have the full range of nutrients that are provided by organic fertilizers.

It comes as a water-soluble powder that provides a fast-release of nutrients to the soil for plant uptake. This leads to rapid growth. But also the need to fertilize frequently as the nutrients are lost from the soil quicker.

You can also get it in slow-release fertilizer granules that break down and release the nutrients over a period of weeks.

Well-Aged Compost For Cucumbers

Another good option for fertilizing your cucumber plants is compost. As it’s organic, it has all the benefits mentioned above.

For best results, try to work it into your soil before you plant your cucumbers.

Making your own compost is easy, and involves combining soft green materials (vegetable waste, grass clippings, etc) with woody material (wood chippings, prunings, dead leaves, and straw) in a compost bin and allowing them to decompose together.

You can also buy bags of compost at some garden centers.

Growing Conditions For Cucumbers

Cucumbers are easy to grow. But fertilizer isn’t the only thing they need. Here are some tips to help you get the most out of your plants and grow the best cucumbers.

  • When planting cucumbers put them in a location where they can get 6 or more hours of direct sun each day
  • They need a lot of water to grow, and do well in fast-draining soils
  • Soggy soil makes it hard for them to uptake oxygen and fungal infections may develop on their roots
  • 1 or 2 deep waterings a week is ideal, wait until the top inch of soil is dry first
  • If you’re growing in containers or pots, make sure they have good drainage holes that allow water to easily run out
  • They like warm conditions and will struggle to grow at temperatures below 60°F with seeds failing to germinate
  • At temperatures below 50°F the leaves start to turn brown and die—so be careful not to plant them outside until nighttime temperatures are sufficient
  • They prefer a soil pH of around 6.8, but they can go a bit higher
  • If you start them inside remember to harden them off for a couple of weeks before permanently moving them into your garden—you can also move them into a greenhouse first

Related: The Best Fertilizer For Tomatoes And Peppers

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