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How to Fertilize Your Lettuce Plants for the Best Harvest Ever

Raised garden bed with wooden slats separating sections of leafy green vegetables

Lettuce is a great crop for any gardener because it grows rather quickly, and there are tons of varieties to choose from. Lettuce, because of its delicate leaves and shallow roots, does require some extra TLC in comparison to other garden vegetables. Lettuce plants particularly need frequent watering and plenty of fertilizer. So what’s the best fertilizer to make your lettuce garden thrive? Keep reading to find out how to fertilize your lettuce plants for the best harvest ever! 

What is the best fertilizer for lettuce?

Lettuce is relatively easy to grow and has a fast payoff, with plants fully developing in as little as 30 days. Because of this rapid growth, lettuce absorbs tons of nutrients from the soil quickly. Lettuce is also unique in that leaves can be cut away from the crown and new leaves will continue growing back in their place throughout the growing season. This is another reason why lettuce plants need such fertilizer-rich soil in order to provide the plant with enough nutrients to constantly grow. 

Like most plants, lettuce has a preference for certain vitamins and minerals, and fertilizers rich in their preferred nutrients will perform better than others. Lettuce plants do their best in nitrogen-rich soil, so a fertilizer that packs a strong punch of nitrogen will help lettuce grow at its highest potential. Lettuce is also sensitive to low pH soil, and a nitrogen-rich fertilizer will also function to slightly raise the pH level of the soil. 

1000 Parris Island Cos Romaine Lettuce Seeds - Heirloom Non-GMO USA Grown Vegetable Seeds for Planting - by RDR Seeds

Before adding soil amending ingredients like nitrogen-rich fertilizers such as fish emulsion, blood meal, or lime[3], you should test the pH levels of your soil with a soil test kit. If your soil is already rich in nitrogen, your lettuce plants will do just fine with a more balanced fertilizer. A fertilizer with a ratio in which the three hyphenated numbers are equal or close to equal (for example 10-10-10) “represents the percentage of nitrogen, phosphate, and potassium”[2] and is, therefore, a balanced fertilizer.

What is the best way to fertilize lettuce plants? 

The first step to fertilizing your lettuce plants is to properly amend your garden soil before planting. Lettuce grows its best in fast-draining soil, that is rich in nutrients, and has a slightly acidic pH. If your soil isn’t draining properly, and the soil is not properly prepared your lettuce seedlings will have more difficulty rooting and growing. Throwing some fertilizer on top of some unprepared soil won’t save your lettuce plants. 

Before you plant your lettuce seeds or seedlings, you should aerate your ground soil, loosening any packed dirt, and removing any large obstructions like rocks or sticks. This will improve drainage, as well as allow you to more easily till the soil by adding organic compost. Using a raised garden bed for your lettuce plants will improve the drainage even more so. You should further prepare the soil by mixing in around “1 to 3 inches of compost into the top 6 to 8 inches of soil to improve its fertility and texture”[3]. A great addition to your compost is coffee grounds, which are rich in nitrogen, but not so much that they will seriously affect the pH of the soil. 

"Parris Island" Romaine Lettuce Seeds, 1000+ Heirloom Seeds Per Packet, (Isla's Garden Seeds), Non GMO, Botanical Name: Lactuca Sativa

After your soil is properly aerated and enriched with compost, you can test your soil. If the pH of your soil is low, adding lime is a great way to make it slightly more acidic. It is recommended to add gardening lime to your soil if the pH is under 6.0[3]. The best fertilizers for lettuce are fish emulsion fertilizer, and blood meal as they are organic, decompose rather quickly and contain high levels of nitrogen. They should be added to the soil a few weeks before planting your lettuce seeds or seedlings

As your lettuce plants grow into mature plants they can benefit from a dose of fertilizer every once in a while. Once your lettuce plants start to pop up out of the soil, use a well-balanced fertilizer “with equal parts nitrogen, potassium and phosphate”[1]. You can use a granular, or water-soluble fertilizer, and it should be applied following the manufactures recommendations, and in a quantity that matches the size of your lettuce garden. Typically, you will only need to apply fertilizer to your lettuce garden once as it grows so fast. You should apply the fertilizer only when your lettuce plants are about 2 inches tall[1]. 

Overhead view of garden full of green lettuce plants

Is granulated or liquid fertilizer best for lettuce plants?

There are two main types of fertilizer, granular and water-soluble fertilizer. Granular fertilizers are scattered on top of the soil, whereas water-soluble fertilizers are mixed with water and then used to water the soil. So is granulated or water-soluble fertilizer best for lettuce plants? 

Granular fertilizer takes longer to be absorbed by the soil, whereas water-soluble fertilizer can very quickly penetrate the soil. Water-soluble fertilizer also comes with the added convenience of multi-tasking watering and fertilizing at the same time. However, if your lettuce plants are already overwatered, this could be causing more harm than good. Lettuce likes lots of water, but it also has very shallow roots. If lettuce plants are overwatered, excess moisture can collect on the top of the soil, and potentially cause root or crown rot in your lettuce plants. Therefore if your lettuce plants are thirsty for a drink, water-soluble fertilizer is a great choice. However, if you’re lettuce plants are looking overwatered, you should opt for a granular fertilizer instead. 

Winter Density Lettuce Seeds, 1000 Heirloom Seeds Per Packet, Non GMO Seeds, Botanical Name: Latuca Sativa, Isla's Garden Seeds

When using granular fertilizer, you should avoid applying the granules directly on top of the seedlings. After applying the granules you should water the soil so the granules can more easily absorb into the soil. 

When using a liquid fertilizer, you should soak the soil surrounding the lettuce plants but not the lettuce plants themselves. Soak the soil about 4-6 inches away [3] from the lettuce heads. The roots will still drink up the nutrients without waterlogging or irritating the lettuce heads. 


Article Sources:

  1. Backyard Vegetable Gardening. “Fertilizing and Watering Lettuce
  2. Gardening Channel. “What is the best fertilizer for lettuce?
  3. SFGATE. “The Fertilizing Needs of a Lettuce Garden