Figuring out what’s wrong with the plants in our garden isn’t usually cut and dry, which is why it’s always good to have a soil test done before the season starts and to keep track in a garden journal what amendments and fertilizers you have added. It’s also important take into consideration other environmental factors, like cold snaps or heat waves, too much water or not enough. Once you’ve ruled out those problems, you may have a nutrient deficiency or a nutrient in excess. How do you correct it?
Keep in mind, nutrient imbalances may be invisible for quite some time. That plant may be suffering from a deficiency or toxicity for a while before symptoms become visible. So, you may not be able to fix the problem as quickly as you’d like.
For deficiencies, start slowly. You don’t want to dump a bunch of nutrients onto a plant and cause the balance to swing the opposite direction and shock the plant. Always check the soil pH to be sure it’s at the right level for your plant first. The wrong pH can cause the plant to be unable to take up the nutrients it needs, even if it’s abundant in your soil. Also make sure the plant has adequate water. Once you know those things are in check, begin adding nutrients.
If the deficiency is one of the ‘big 3”, nitrogen, potassium or phosphorous, then add a balanced fertilizer with a higher level of the particular nutrient that is lacking. If you’ve done a soil test and you know for sure which nutrient is missing, you can apply an amendment that contains only that nutrient. But always, always, always apply at the rate stated on the package. Just because the soil is depleted doesn’t mean you need to dump twice as much into the ground or the pot. That’s how you get toxicities and it’s also how fertilizers leach into ground water. The plant can take up only so much at one time. So, follow the amount and schedule on the package to slowly and safely adjust your nutrients.
If we’re talking about one of the secondary or trace nutrients, your best bet is to work in more compost or other green organic matter and a layer of mulch. Most of these secondary and trace nutrients aren’t needed in large quantities and organic matter usually has enough to take care of the needs of the plants. Also make sure your other nutrients are in balance because a deficiency or abundance of one can cause a problem with others.
When it comes to toxicity, the approach is straightforward. First, be sure all the other nutrients associated with that toxicity are in balance and your pH is correct. Second, stop using any fertilizers or amendments that contain that nutrient. Thirdly, try to keep the plant and surrounding soil very well-watered for a few weeks without adding anything. This is especially effective in pots and raised beds, but can work for in-ground plots, too. The idea is you are washing those nutrients further away from the root zone and making them less available to the plant. If you feel you need to take drastic measures because a soil test has shown you the level of nutrients are off the chart, you can also dig out some of the soil surrounding your plant and replace it with a garden soil or potting soil that is more neutral. That’s extreme, but it does work in a pinch. It works best with plants in pots.
Your Friend in the Garden,
