When I was a child, I have fond memories of following grandpa through the garden.  He always used a wooden walking stick that had notches carved in the side of it.  Those notches corresponded to when corn, tomatoes, and beans needed fertilized.  So when do various vegetable crops need fertilized?

In the first season of the Keep Growing Podcast, we took an in-depth look at the science behind fertilizers.  You can find out more about the roles various nutrients play in fertilizers in the show notes for that episode.  Also, a couple years ago, I walked through the process of testing and amending garden soil.  If you’re correcting a nutrient deficiency based on a soil test, the time to do that is in early spring, prior to planting.  What we’re looking at in this post is supplemental fertilizer to give your veggies a boost just when they need it.

Plants need the most nutrients when they are growing the most rapidly.  For lettuce and other spring crops, this happens in early spring.  For corn and squash, their peak growth happens in mid-summer, just before they start to produce blooms.  Tomatoes and potatoes will also need a boost from fertilizers mid-season.

For long-season crops, like corn, many gardeners apply fertilizer as a starter at the time of seeding, a larger amount in mid-summer before rapid growth, and then a final application as the ears start to develop.  Hence, grandpa’s walking stick.  When using organic fertilizers, only a single application is adequate because they release their nutrients slowly throughout the growing season.

Always apply fertilizers according to the packaging. Applying them improperly can lead to burning the plant.  As a general rule of thumb, granular fertilizers should be worked into the soil, either over the entire area prior to planting or as a side dressing once plants are established, just be careful to not disturb the roots.  Water soluble fertilizers should never be applied directly after transplanting or when the soil is dry.  This can lead to fertilizer burn.

Overall, fertilizing is an important aspect of vegetable gardening.  You can grow without fertilizers, but your yield might be negatively impacted.  Also, fertilizer helps with the overall health of the plants, helping boost their natural defenses against disease, similar to our own response to taking vitamins to boost immunity.