Nitrogen is a necessary element for healthy plant growth; fertilizers typically contain a mix of nitrogen, potassium, and phosphorus, but nitrogen is so necessary that you will often find high-nitrogen fertilizers available for plants that are low in just that specific element. Nitrogen is readily available — thank goodness — but you do want to be sure that your plants are actually low in nitrogen and not another element. You don't want to waste money and fertilizer while not helping your plants. 

Yellowed Leaves Are a Major Hint

Nitrogen deficiency in plants usually involves yellowed leaves. These can start off toward the bottom of the plant and work their way up as the plant grows, meaning that younger plants might have yellow leaves on the lower half of the plant only, while older plants have yellowed leaves at all levels. You might see a pinkish or reddish tinge on some of the leaves, but they shouldn't be all red or mottled pink and red; that usually indicates more of a magnesium deficiency.

Everything Looks Smaller and More Spindly

Nitrogen is such a basic element for plant health that a deficiency results in smaller stalks, leaves, blossoms, and fruit. Everything looks more spindly, too; the plant will just look like it's not thriving. Even if you're watering it well, it can look like it's just drying out and becoming weaker by the day. If you add nitrogen to the soil quickly enough, however, you can save the plant; plants are a lot more resilient than many people realize.

The Soil Drains Really Fast

One clue that you're dealing with a nitrogen deficiency isn't so much a symptom you find on the plant as it is a condition you find in the soil: very, very thorough drainage. You do want well-drained soil for most plants, but soil that lets water run through quickly can also lose nitrogen with that water. The element can really drain away. Ensure the soil drains well enough to keep the plants healthy but not so quickly that you end up with poor soil. You may have to amend the soil to make it less drainage-friendly.

Organic fertilizers high in nitrogen come from many sources, and you can either add those sources themselves or buy organic fertilizer that is high in the element. The second option can have more advantages as the amount of nitrogen will be more specific; you won't have to guess how much is in each scoop of fertilizer.

If you need high-nitrogen organic fertilizer, contact a supplier near you.