CORVALLIS, Ore. — So, your vegetable garden is growing lush and fruitful — or not. If it’s the latter, your plants may need a nutritional boost.
Chip Bubl, retired associate professor and horticulturist with the Oregon State University Extension Service, has offered vegetable gardening advice for many years. He shares these tips for midsummer feeding of garden plants.
Most vegetable gardeners begin the season by applying a balanced fertilizer worked into the soil prior to planting. For light-feeding crops, this may be sufficient to carry them through to maturity.
Nitrogen is the nutrient most often re-applied after crops are up and growing. There are several reasons to do this:
- Nitrogen leaches from soils during winter, so little remains at the start of each growing season.
- Nitrogen is essential for vigorous plant growth. A deficiency results in pale green or yellowish foliage and stunted plants.
- Nitrogen is highly soluble and can quickly move from the soil surface to plant roots when watered in after application.
Gardeners often side-dress crops in midsummer using one of the following per 10 feet of row:
- 1 cup of ammonium sulfate (21-0-0)
- 1⅓ cups of calcium nitrate (15-0-0)
- ½ cup of urea (46-0-0)
Scatter fertilizer near the base of plants and water it in. Most crops will respond within two weeks, often showing a noticeable improvement in color and vigor. Corn, onions, members of the cabbage family and squash are particularly responsive.
Organic fertilizers such as blood meal and alfalfa pellets also work well, though they take longer to show results. Lightly work them into the soil and apply early if nitrogen appears to be lacking. Fish emulsion is another option but must be applied more frequently. Always follow label directions for dilution and application rates.
Well-timed side-dressing generally results in higher yields and improved vegetable quality.
Timing guidelines for side-dressing
- Cabbage: 30 days after transplanting
- Cucumbers: When vines begin spreading rapidly
- Winter squash: Same as cucumbers
- Summer squash: When fruit set begins
- Peppers: Same as squash
- Potatoes: When vines reach 8 inches tall
- Beets: When 4 inches tall
- Lettuce: Same as beets
Peas and beans are light feeders if seeds were inoculated at planting with nitrogen-fixing bacteria. Without inoculation, they may need additional nitrogen during the growing season.
Tomatoes are moderate to heavy feeders, but excessive nitrogen can lead to vigorous shoot growth and increase the risk of blossom-end rot. If needed, apply nitrogen lightly.
One more tip
If you've added a lot of organic matter to your soil, or are using a soil mix high in organic material, be aware that:
- Organic matter typically contains little available nitrogen early in the season.
- Microorganisms that break down organic matter require nitrogen, potentially reducing availability for your plants.
In these cases, nitrogen side-dressing during the growing season becomes especially important for healthy crop growth.
Previously titled Fertilizing vegetables midsummer gives plants a boost
