Five signs of a nitrogen deficiency in garden plants

A nitrogen deficiency causes slow plant growth and reduced fruit production.

It's that time of year when nutrient deficiencies begin to cause problems in the garden. While most of us have given our plants a good start with starter fertilizer, many plants need supplemental fertilizer during the growing season. One of the most common nutrient deficiencies in a typical Maine garden is nitrogen. Without adequate nitrogen your plants cannot  build the nucleic acids and proteins they need for healthy growth and fruit production. A lack of nitrogen is often misdiagnosed as a lack of (or too much) water or attributed to the weather.  if your plants are looking a little pale and don't seem to be growing as they should, check them closely for these signs of a nitrogen deficiency.

1. Old leaves turn pale green and may eventually yellow and fall from the plant. Some yellowing of old leaves is normal, but if more than a leaf or two on your plant suddenly begins to yellow it is a good indication that your plants are suffering from a nitrogen deficiency.
2. New leaves are paler green than existing leaves and appear to be smaller than normal. Young leaves should be a rich green and should grow rapidly. If they are tiny and fail to increase in size within a few days, they may need a boost of nitrogen.
3. Plant growth slows or stalls. This should not be confused with plants that have reached their mature size. If the plant has not reached maturity or fails to produce new leaves and branching ceases, the culprit may be a nitrogen deficiency.
4. The underside of leaves may take on a red or purple hue. Although this depends on the type of plant you are growing, leaves that discolor on the underside may be a sign for you to add nitrogen to the soil.
5. Wilting easily under normal weather conditions. Plants suffering from a lack of nitrogen wilt quickly at the first sign of stress. If your plants are wilting when it is not excessively hot or they are not suffering from excessive dryness, a nitrogen deficiency may be causing them to wilt under stress.

Replenishing the usable nitrogen in the soil often produces rapid results. You may notice increased growth and richer color with a few days. You can add nitrogen by adding compost, well-rotted manure, fish emulsion or commercial fertilizers.

Water-soluble fertilizers designed as foliar feeders can be mixed and sprayed onto the plants. Allow adequate amounts of fertilizer to penetrate the soil. Look for mixtures that are high in nitrogen, denoted by the first number in the formula. Always follow the directions included on the container to avoid over feeding and damaging your plants.

Note: A soil test meter is  a great investment for monitoring the pH and nutrient levels in you soil. It only takes a minute to complete the test and takes the guess work out of troubleshooting problems with your plants.