How Much "Plant Tonic" Should I Apply to My Bushes?

Q. We fertilize our bushes early spring and mid fall with a "plant tonic", a 5-10-5 liquid.  Hopefully this isn't too much nitrogen.

A. Actually, I would not worry so much about the nitrogen, the first number, as I would about the middle number, phosphorus. I usually apply fertilizers with a high middle number to flowers, flowering trees and shrubs, fruit trees and vegetables that produce fruits such as tomato, pepper, eggplant, melons, cucumbers, beans and peas. If I want leaf and stem growth I use a fertilizer higher in nitrogen.

This is labeled a 'Starter Fertilizer" or "Starter Fertilizer" because it is high in phosphorus, the middle number, which promotes root development in seedlings and transplants. Use it whenver you are planting anything. Because it is high in phosphorus it can be used for promoting flowers as well even though it is marketed for "starting " plants. It retails 15 lb for $18.00

Phosphorus also encourages more root development in plants. So it is a good thing to apply when planting seeds or transplants. In some soils, phosphorus can concentrate with frequent applications and cause  problems over time. So applying fertilizers that contain phosphorus over and over and over may cause problems. Apply phosphorus a week to two weeks before it needs it.

This is a water soluble fertilizer (granular that dissolves in water) which has 16% nitrogen, 16% phosphorus as an oxide  and potassium as an oxide. It is called a 16-16-16 water soluble fertilizer.$6.65 as of July, 2015. It makes about 100 gallons of fertilizer solution. Promotes growth, flowering, rooting and general health. So it is considered an "all around" fertilizer.

 I usually apply a phosphorus fertilizer only once during the growing season just before flowering or planting and then supplement frequently with small amounts of nitrogen the rest of the season.

Those three numbers, 5-10-5, represent the percent nitrogen, phosphorus and potassium present in this "plant tonic". It may be called a "Plant Tonic" but the word "Tonic" is a marketing term and not based on any science. It is supposed to give you a warm fuzzy feeling for a conventional fertilizer.

This is an interesting water soluble fertilizer because it contains no nitrogen but focuses on phosphorus (roots, flowers, fruit) and potassium (general health). This is a water soluble concentrate that pushes flowering or rooting but relies on the nitrogen already present for growth. Used in hydroponic growing for encouraging new cuttings or seedlings or pushing flower development. Hence called "Grow Bloom". Sells for $8.00 and makes about 150 gallons or more.

Nitrogen doesn't last very long after an application and doesn't cause the problems phosphorus can. Nitrogen is either picked up by plant roots, bound onto soil particles, washed through the soil below the roots or escapes into the atmosphere when converted to a gas. Nitrogen is really good at pushing new growth of leaves and stems and creating dark green color. If there is not enough nitrogen, the lower leaves will yellow and may drop from the stems creating plants that look weak, yellowish with poor growth. Applying too much nitrogen at one time can cause the leaves to burn around the edges and, in some cases, even kill them. Nitrogen fertilizers have a high salt content.

Lack of nitrogen causes plants to grow slowly, appear in poor health and, in particular, have the older leaves turning yellow or dropping from the plant. Use a high nitrogen fertilizer on this plant with low phosphorus since you are not expecting it to flower or produce fruit.

Always adjust your phosphorus according to the needs of the plant. Heavy bloomers and new plants require more phosphorus. Plants that don't bloom and are established require very small amounts.

Always add potassium when possible. Apply high phosphorus fertilizers or "tonics"two weeks before  bloom or immediately before planting. The rest of the time concentrate on high nitrogen and low phosphorus fertilizers.

Two fertilizers are all you need in most situations unless there are some special problems. One should be a high nitrogen low phosphorus fertilizer. The other should be a lower nitrogen and high phosphorus fertilizer. Potassium levels should be medium to high in all fertilizers whenever possible.

Green-Up is an 8-4-4 fertilizer that has a higher percentage of nitrogen which will help plants "green up" and grow leaves and stems. 10 lb bag is $7.95. 20 lb bag is $14.95.

Take a look at our fertilizers on our website and now practice which fertilizers can be used on what.
Click here to visit our fertilizers arranged in alphabetical order.

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