Croton Fertilization Guide

[TropicalRob]

GOAL: I want to know how many ounces of fertilizer i need to add to my Croton in a container.

So i have been googling around for how to "properly" fertilize my crotons,
and i found this..

http://edis.ifas.ufl.edu/ep106

from University of Florida Extension - "Croton Production and Use"

The fertilization paragraph states:

Fertilization: Crotons grown in ground beds require less fertilizer per unit of surface area than plants grown in pots. Soil pH should be in the range of 4.5 to 6.5. Adjust soil pH with dolomite or sulfur. Fertilizers with a ratio near 3-1-2 (N-P2O5-K2O) produce excellent plants, and either liquid or slow release forms may be utilized. Pot-grown plants require 1,500-2,000 pounds (lb) nitrogen (N)/acre (A)/year (yr) [1,680-2,240 kilograms (kg) N/hectare (ha)/yr] from a 3-1-2 ratio fertilizer while 900 lb N/A/yr [1,000 kg N/ha/yr] is adequate for bed-grown plants. Excess fertilizer will reduce intensity of foliar coloration, reduce root system size and possibly lead to nutrient runoff into surface waters and/or leaching downward into ground waters.

so.. Crotons like a 3:1:2 ratio NPK fertilizer.
1500-2000 Lbs of Nitrogen, for every acre, per year. I believe that range is based on light levels and temperature.

I want to know how many ounces of fertilizer i need to add to my Croton in a container.

Lets do the math..

1 Acre is 43560 square Feet.
lets use the low range of 1500 lbs of Nitrogen.

so we need 1500 Lbs of Nitrogen, for every 43560 square feet , per year.

lets say our imaginary nursery was 4356 feet by 10 feet. which will match with the 43560 sq feet (ONE ACRE).

lets also assume our container pots are 8" inch SQUARE, Vertical sides, for easy math.

lets convert our nursery measurements from feet to inches, to determine how many pots we have.

4356 x 12 = 52272 inches / 8 = 6534 8" pots
10 feet x 12 = 120 inches / 8 = 15 8" pots

our nursery can hold 6534 x 15 = 98010 pots. 8" wide, back to back.

A fertilizer with a stated NPK of 3:1:2, will have
3 lbs of Nitrogen (per 100 lb bag)
1 lb of P (per 100 lb bag)
2 lbs of K (per 100 lb bag)

to get 1500 lbs of Nitrogen, we will need (1500/3) 500 bags of fertilizer. each bag 100 lbs.
or (500*100) or 50,000 lbs of fertilizer to cover our 98,010 pots

16 ounces in 1 pound. 50k x 16 is 800k.

thats 800,000 ounces of fertilizer to cover our 98,010 pots.

800,000 ounces / 98,010 pots = 8.16 ounces

8.16 ounces of fertilizer per pot per year.
this is using a fertilizer bag stating a NPK of 3:1:2

looking at the florikan website for fertilizers they sell...
http://www.florikan.com/nitrogentab.html

they sell the Florikote NPK 19:6:13, and 18:6:12, both roughly the 3:1:2 ratio.
using the 19:6:13 blend.
this has 19% N, 6% P, & 13%K for every 100 lb bag of fertilizer.

so quickly..
to get 1500 lbs of Nitrogen.. we need 78 bags of fertilizer.
we need LESS bags of fertilizer, since each 100lb bag contains
a lot more pounds of N, P and K.
78 * 100 = 7800 lbs of fertilizer.. 124,800 ounces of fertilizer.

124,800 ounces of fertilizer / 98010 pots = 1.26 ounces of fertilizer per pot.

1.26 ounces of fertilizer per pot per year
this is using a fertilizer bag stating a NPK of 19:6:13

can someone verify that what I'm doing is correct?
also, if i fertilize twice a year.. do i then divide by dosage by 2?
if i fertilize 4 times a year, divide the dosage by 4?
or just do the "pour-thru" method, and if the TDS is low, add
another 1.26 ounces?

thank you in advance.
-rob

 

[Bullwinkle]

Lamar this is in your sweet spot,but I will try and answer,it depends on what type of fertilizer.Do you plan on using slow release (osmocote harells etc)??Once you get back to me I will try and share what I do with my 3 gallon size plants.

 

[VeroKarl]

Lamar this is in your sweet spot,but I will try and answer,it depends on what type of fertilizer.Do you plan on using slow release (osmocote harells etc)??Once you get back to me I will try and share what I do with my 3 gallon size plants.

Actually, while your on the topic of fertilizing crotons I have another question. All of my crotons go in the ground, but I would love to know how often and when you fertilize. I sometimes use the 10-10-10 fast release and other times the slow release depending on the season. Let me know what has worked best for you. Once we get to the rainy season fertilizing is off limits in my county (I live close enough to the canal leading to the lagoon that I want to be careful to avoid an influx of nitrogen into it). I usually do slow release in the fall and fast release in late winter/early spring. I just broadcast around the gardens. Thanks.

 

[Phil Stager]

Everything here except the cycads gets palm special (8-0-12+ 2 Mg and minors) - controlled release, 3 or 4 times per year. Almost anything with P in it is probably a waste; has anyone ever seen a plant in the ground suffering from a P deficiency? I doubt it. I may hit everything with some KMag during the rainy season, more for the palms than the crotons - but we've not had a real soaking rainy season here in the S. Pinellas desert for a good while. What kind of soil do you have? Soils can vary considerably throughout the state.

 

[VeroKarl]

Everything here except the cycads gets palm special (8-0-12+ 2 Mg and minors) - controlled release, 3 or 4 times per year. Almost anything with P in it is probably a waste; has anyone ever seen a plant in the ground suffering from a P deficiency? I doubt it. I may hit everything with some KMag during the rainy season, more for the palms than the crotons - but we've not had a real soaking rainy season here in the S. Pinellas desert for a good while. What kind of soil do you have? Soils can vary considerably throughout the state.

Phil, The soil varies considerably around the yard. I have some areas that you dig down six inches and you hit either rock fill, cement, or limestone (not positive because part of the yard had been a drainage field for 20 or so years until it was moved into a new location in 2005 after the property had some upgrades because of hurricane damage). Other areas are very sandy and are missed by the irrigation so end up being desert like, and there are a few areas that I assume were filled with a thick layer of crap top soil because it seems like clay loam and holds the water to the point of being almost constantly saturated. At the end of the property I have a large storm drain with a grate that I assume empties directly into the canal. It can form a small temporary pool after a heavy rain, but nothing is there aside from lawn.

I think my first year I used the palm fertilizer for everything and switched to the 10-10-10 and the slow release all purpose after someone had recommended it. We usually get some pretty solid rains in the summer, but that has varied yearly since I have been in Vero. I thought higher P levels help plants that are newly planted get their roots established quicker especially in crappy soil, and I am still constantly putting new plants in at this point so usually look for a relatively high middle number. I have a little bit of everything when it comes to plant varieties so probably should be applying different fertilizers accordingly, but things seem to be doing well for the most part. Why don't you use the palm special on the cycads, I have some and just use the same fertilizer I give to everything else (granted my cycads have not exactly thrived so I am probably completely screwing up their needs)? I will give that palm special a try for my final fertilizing in May and see how the plants do this summer. Thanks.

 

[Phil Stager]

I use the cycad special (high N) on the recommendation of Tom Broome; I also want mine to grow as fast as possible. If one is in no hurry, cycads can go with little fert. The Cycad Society web site probably has a lot more info on the topic. Cycads do require excellent drainage, esp. the south African ones.

 

[TropicalRob]

Lamar this is in your sweet spot,but I will try and answer,it depends on what type of fertilizer.Do you plan on using slow release (osmocote harells etc)??Once you get back to me I will try and share what I do with my 3 gallon size plants.

I do plan on using a slow release fertilizer. As for what brand? have not decided yet. Maybe ill get a bag of each and do a test. Diamond R has their brand as well as Florikan. And Harrells is an option too.

Reading the labels on Florikan and Osmocote slow release, its essentially a coating around the nutrient that slowly dissolves over a set time period. 60 days, 90 days, 270 etc. And the speed of dissolving
is based on amount of water and temperature. So in the hot wet summers, when plants are thriving, they get a more rapid dosage of fertilizer, and in the colder dryer winter it slows down the release.

And if thats the case, would the plants OVER DOSE in the pouring rains of South Florida's summers? Lots and lots of water, and high day/night temperatures?
or would the massive amounts of water just leech it all out the bottom? hum.

Reading another thread on this site, they talk about using a low N, and high Potassium fertilizer in Aug to help fend off any possible cold damage.
From what i recall, use of low N, is so you get no/little new baby growth, which can be easily damaged in the cold.
and high potassium/sugar to act as an "anti-freeze".
August was a cut off point, so that the plant has time to soak up all the nutrients and harden off.
Googling around indicated some mixed results, and some called it a myth.
I guess its MythBusters time, and perform a test.

So as for timing, if i were to fertilize now,
i would use a 90 day 3:1:2 fertilizer to get me to August.
Then in August, use another fertilizer, low in N and high in K to prepare the plants for a possible cold winter?
then in Spring, use a 6 month (180 day) fertilizer to get me back to Aug.
wash and repeat.

But if it is true, that the summer rains/heat will dissolve the fertilizer at a super rapid rate,
would it be, in the best case scenario, and assuming labor/time is not a factor, to fertilize with a 30 day fertilizer, once a month for 6 months, instead of using a 6 month fertilizer?
This would essentially give me a better distribution of nutrients over time.

Sorry for being all over the place..the more i think about this, the more questions that keep popping up.
its fun! thanks!
-rob

 

[Bullwinkle]

If you are using slow release fertilizer then I recommend 3 oz of per 3 gallon pot three times yearly.I use the 120 day Harrells 20-4-11 product and it works great.

 

[Native son]

Wow, I spent 35 years trying to please the Turf industry in this area. It boiled down to keeping a good record of your applications, and be willing to change when the weather forces a change. I like the 3/1/2 thought it is good science from a great U. F. group. I have moved up the food chain a little bit,with irrigation even controlled released material will run thru a cycle faster. I blend 18-3-17---14-4-14---20-4-11---5-4-0(sludge) at 4 or 5 applications per year. If you total this you see 57-15-47 which is on the same line as the 3-1-2. The soils we all work with are so variable it is very easy to over think this. A few of you have been here and know how over planted we are the Palm number has climbed past 50 the croton number is past 600 in the ground and 100 plus containers. Final word anything I say must be taken with a grain of salt(I also have 90+in the misty house). Stop by you might find something like.

 

[TropicalRob]

If you are using slow release fertilizer then I recommend 3 oz of per 3 gallon pot three times yearly.I use the 120 day Harrells 20-4-11 product and it works great.

Thank You Moose!

To Re-do the math, using the higher range of Lbs of Nitrogen. 2000 lbs of N , per acre, per year.
and with 3 gallon. 10" pots.

Calculate number of 10" pots in an acre.
LENGTH: 4356 feet = 52272 inches / 10 = 5772.2 pots
WIDTH: 10 feet = 120 inches / 10 = 12 pots.

69266.4 pots (10") in an acre, back to back, square, vertical.

Using the Florikote 19:6:13.. to get 2000 lbs of N per acre, we need to use 105.2 bags (100lbs each).
105.2 * 100 = 10526. lbs of Fertilizer, which is 168420.8 ounces.

168320 ounces/69266 pots = 2.43 ounces of fertilizer per 10" pot.

if we punch in Harrels 20-4-11 fertilizer,
we need 100 bags of fertilizer (100 lbs each) to reach the 2000 lbs of N per acre.
100 bags * 100 lbs = 10,000 lbs of fertilizer = 160,000 ounces of fertilizer.

160,000 / 69266 pots = 2.3 ounces of fertilizer per 10" pot.

http://www.florikan.com/labels/16-4-12-120.pdf

The Florikote 16-4-12, 120 day top dress, has a chart for gallon pots and grams of application.
for 3 gallon (HIGH) is 75 grams= 2.6 ounces
for 3 gallon (HEAVY) is 90 grams = 3.17 ounces

125 bags * 100 = 12500 lbs= 200000 ounces
200000 / 69266= 2.8 ounces per 10" pot.

Ok..the math seems to be roughly panning out, at least with the Florikan chart.

And I'm sure, as with cooking receipes, "SALT TO TASTE". People use different soil,
different daily shade/light, have different water (well/city), different water cycle frequency,
length, pressure, sprinkler nozzle types, etc..

Thanks again for letting me vomit my thoughts on your forum
-rob

 

[VeroKarl]

If you are using slow release fertilizer then I recommend 3 oz of per 3 gallon pot three times yearly.I use the 120 day Harrells 20-4-11 product and it works great.

I remember Ron mentioning Harrells as well. Where is this sold? I don't remember seeing it available, but have not specifically looked for it. I want to continue to experiment with different brands and N-P-K ratios. Thanks.

 

[VeroKarl]

I use the cycad special (high N) on the recommendation of Tom Broome; I also want mine to grow as fast as possible. If one is in no hurry, cycads can go with little fert. The Cycad Society web site probably has a lot more info on the topic. Cycads do require excellent drainage, esp. the south African ones.

Thanks Phil, I will see if I find the cycad special as some of mine have been very slow to put on new growth.

 

[Native son]

TRob Slow down on getting so fine tuned smaller amounts on a regular schudule weather adjusted will win the race. If you are a nurseryman with a large operation you must fine tune it for profit and control As many as I have I still do this as a lawn project. Take a beverage an ENJOY!

 

[Phil Stager]

For cycad special, contact Tom Broome at cycadjungl@aol.com

 

[TropicalRob]

I remember Ron mentioning Harrells as well. Where is this sold? I don't remember seeing it available, but have not specifically looked for it. I want to continue to experiment with different brands and N-P-K ratios. Thanks.

http://www.harrells.com

Looks like they have locations all over the US.

Heres a South Florida address:

1120 NW 7th St
Homestead FL 33030
(305) 247-8663

 

[VeroKarl]

http://www.harrells.com

Looks like they have locations all over the US.

Heres a South Florida address:

1120 NW 7th St
Homestead FL 33030
(305) 247-8663

Thanks Rob, I will check the website or give them a call to see if the product is available closer to Vero. It may be something the independent garden centers carry.

 

[Moose]

Went to Harrell's this past Friday. Could not for the life of me recall the blend Mike was using (see above). I ended up with a slow release 16- -11 with minors, 6 month formula which will last realistically 5 months with the elevated temps of the growing season. Should be good until November when all the crotons will get dressed up only with Slow release K-Mag for the winter.

I need to piggyback on Lamar's orders of fertilizer. His pricing is way better then mine due to his long term relationship with Harrell's.

 

[Moose]

The formula from Harrell's for the crotons is 16-6-11. Tried to edit my previous post but the 15 minute edit window had expired. Thought Dean was going to alter the software to extend the edit time to 30 minutes.

The micronutrients listed are as follows:

Magnesium 1.3 % water soluble
Copper .077 % water soluble
Iron .32 % Chelated slow release
Manganese .13 % water soluble
Molybdenum .011 %
Zinc .077 % water soluble

Since I have many established palms, the roots are often at or near where croton fertilizer is applied. So the minors are important for the palms and may be beneficial to the crotons.

 

[Native son]

We have so many variables in soils in south Florida it is very hard to say XXX is the one to use. When going into the "Winter" yes there is a proven formula but all the rest of the year control release materials on a regular schudule seems to work out well.