PTP_2008_12_Fertilize

Plants That Produce

The Scoop On Fertilizers, Part II^‡

By Richard Frost

The nutritional care of plants in home gardens is easiest to understand by considering 5 general categories of flora.

1. Arid and Semi-Arid Ornamental Native Plants. Feed only micronutrients once in the fall and again in spring^a,b. Foliar application is best, or soil drench on large specimens.

2. Outdoor Leafy Vegetables and Herbs plus Non-blooming Ornamentals. These plants want an N-P-K formula that is high in Nitrogen(N), relatively low in Phosphorus(P) and Potassium(K), and contains micronutrients^b.

Example Fertilizers	Application Rates^c
Example Fertilizers	2-5 gal pot	10’x10’ bed	shrub	tree
5-1-1	1 oz/mo	1.25 lb/mo	10 lb/yr	20 lb/yr
30-10-10	.17 oz/mo	3.3 oz/mo	1.7 lb/yr	3.3 lb/yr

3. Outdoor Subtropical Fruits and Ornamentals. Citrus, Palms, Avocado, Guavas, Myrtles, Pineapples, Sapotes, Cycads, etc. can utilize 2/3 to 3/4 pounds of K for each pound of N, a small amount of P^(d) plus micronutrients.

Example

Fertilizers

potted plant

new tree in ground

6’x’6 tree in ground

big tree

0.9-0.3-0.6^*

28 lb/yr

55 lb/yr

111 lb/yr

167 lb/yr

28-8-18

0.9 lb/yr

1.8 lb/yr

3.6 lb/yr

5.4 lb/yr

^*Reasonably dry, composted horse manure.

4. Outdoor Non-tropical Fruits & Berries, Fruiting Veggies, Flowering Herbs, Ornamentals, Bulbs. “Old World” Fruits & Berries, Flowering Annuals & Perennials (esp. Roses), Bananas, Flowering Bulbs, Tomatoes, Peppers, Strawberries, Broccoli, Carrots, Melons, Turnips, etc. utilize 1.5 pounds of K for each pound of N, negligible P^(d), plus micronutrients.

Example

Fertilizers

2-5 gal pot

10’x10’ bed

potted tree

tree^† in ground

8-3-12

5/8 oz/mo

3/4 lb/mo

3 lb/yr

12.5 lb/yr

20-5-30

1/4 oz/mo

5 oz/mo

1.25 lb/yr

5 lb/yr

^†Use half dosage for bush or new tree, 1.5x for large tree.

5. Indoor Plants incl. Tropicals and Hydroponics. These are planted in a soil-less or somewhat sterile soil media. Consequently, the nitrogen source must be Urea-Free. Most have individual needs too voluminous to discuss here^‡.

^aWorm castings contain 0.5% each of N-P-K, several micronutrients, and important non-plant food ingredients. However, they are a poor choice for many southwestern natives and can cause leafy veggies and herbs to bolt.

^bMicronutrients. Excluding N, P, and K, there are about 20 minerals that all plants require or utilize in tiny amounts. A balanced mixture is better than unbalanced liquid kelp.

^cApplication rates. A 3+ year-old tree can utilize 1 lb of N per year, and a 10x10’ bed of annuals 1 oz of N per month. For a 5-1-1 fertilizer, (1 oz) / 5% = 1.25 lb yields 1 oz of N. Similarly for 28-8-18, (1 lb) / 28% = 3.6 lb yields 11b of N.

^dPhosphorus should be placed in soils before planting. Afterwards, quantity is only needed in soil-less media.

^‡For copies of past articles and more information, please see www.plantsthatproduce.com.