Last week we went over the six macronutrients and six micronutrients (trace elements) all plants need for good health.

There are a variety of fertilisers put out by garden product companies with the backyard fruit-grower in mind. These have been formulated to provide sufficient quantities of the essential macro- and micronutrients needed at every stage of a fruit tree’s cycle — from bud break in early spring to development of healthy leaves and strong branches, through to flower production and fruit set, and finishing with preparation for winter dormancy.

Each brand will differ slightly in exact quantities of these nutrients, but all contain essentially the same things: plenty of the really important nitrogen (N), phosphorus (P) and potassium (K); good amounts of the other three macronutrients magnesium (Mg), calcium (Ca) and sulfur (S); and suitable amounts of the micronutrients iron (Fe), manganese (Mn), boron (B), zinc (Zn), copper (Cu) and molybdenum (Mo).

Some formulations are intended to be given in a largish amount at the beginning of growth for slow release into the soil over several months to promote leaf, branch and root development before another application is given to promote flowering and fruiting. Others are intended for more regular and even feedings over a year to prevent an oversupply of any particular nutrient. Always follow the directions each manufacturer states to ensure best results — as with our own nutritional requirements, too much of a good thing can be as bad as too little of it!

Below I’ll describe three different fertilisers made with fruit and citrus trees in mind, all of which can be used on jujubes, and all of which I have used. None of these are to be taken as an endorsement by me, and I am certainly not being paid or receiving other benefits by mentioning them. This is strictly FYI for those new to this sort of stuff, and who are looking for ideas on where to start.

Richgro Organics^® Fruit and Citrus Plant Food

Note: this picture at left is of an old bag I have here, and both the name and packaging have since changed. Go here to view the latest, and to read their Safety Data Sheet (’SDS’).

Richgro make other food and citrus fertilisers; this one happens to be a ‘certified organic’ one. This is the more ‘natural’ of the three I’m writing about in this post, in that it is made from ingredients you could readily source — or even make yourself should you be that way inclined! This fertiliser contains natural potash (a source of potassium), blood and bone (a source of nitrogen and phosphorus), feather meal (dried, ground poultry feathers) (a source of nitrogen), and composted chicken manure (a source of nitrogen and phosphorus).

You may be able to make out these individual components in this photo at right:

This product is promoted as a booster and does not claim to be a complete fertiliser. The bag lists five macronutrients as weight per total weight, expressed as a percentage (% w/w). These are:

nitrogen (N) 6.5% w/w
phosphorus (P) 1.0% w/w
potassium (K) 1.6% w/w
sulfur (S) 4.5% w/w
calcium (Ca) 1.3% w/w

The sixth macronutrient, magnesium, is not listed. However, the information on the bag and here suggest supplementing with epsom salts (magnesium sulfate, and a natural source of magnesium) closer to fruit ripening. No micronutrients are listed.

The ‘6-1-2-4′ you may see written on the bottom of the bag refers to the ratios of the four most prominent components, rounded. Here they refer to nitrogen:phosphorus:potassium:sulfur, or N:P:K:S. You may recognise the first three by themselves as the N:P:K ratio commonly listed on many other fertilisers.

The manufacturer’s recommendation is to apply when buds first form — they say late August/early September, which is the case for jujubes, and again when fruit starts to ripen. They suggest December/January, though this is a little early for most jujubes which don’t ripen until late February and even into April. In this case keep a close eye on how your particular cultivars grow in your location, and apply accordingly.

The suggested application rate for stone fruits (of which jujubes are) is 50 g/m². The new packs may come with information as to how much 50g is, but I had to work this out with the pack I have, with some scales and an old laundry powder scoop that looked the right size. For those interested enough, a loosely packed, level scoop from the Aldi Trimat Advanced enzyme laundry powder box did the job!

Note that these recommended applications are not spaced evenly through the year, but are timed for key development stages in a fruit tree’s cycle.

While this product can’t be regarded as a complete fertiliser, one advantage it does has over the two manufactured formulations mentioned below is the presence of composted chicken manure. This is a rich source of organic matter that will help improve soil structure if in soil, and enhance other properties if in potting mix. I’ll be writing more about manure in future posts. (Update: here and here.)

Scotts Osmocote^® Plus Trace Elements: Fruit, Citrus, Trees & Shrubs

Scotts are well-known and regarded for their Osmocote^® controlled-release fertilisers. They have formulations for pretty much any garden plant group you can think of — and maybe some you didn’t! (Aquatic plants and water gardens is one such one for me!)

You can read more about this particular ‘Fruit, Citrus, Trees and Shrubs’ formulation, including the Safety Data Sheet (’SDS’), here.

Unlike the Richgro product above, these formulations are heavily manufactured, as a peek inside any of those colour-coded containers will reveal (picture at right).

This isn’t a criticism. Making these little balls, called prills, is a very specialised and technical field with one purpose in mind — to ensure the nutrients contained within are released at a careful, controlled rate you don’t have to think about.

These prills break down in response to temperature. Nutrients are released more slowly in cold to cool temperatures, when trees need them less. And are released faster as the weather heats up, when trees are growing and developing most rapidly.

These formulations are intended to be applied evenly through the year — two applications six months apart, one in early spring and one in early autumn. It is also recommended by the manufacturer to add to soils at time of planting — but for bare-rooted jujube trees planted/potted on delivery this will be close enough to spring to count as the same application.

Two types of application rates are listed on the container. One is of a table of numbers of tablespoons depending on the age of the tree. The other is a suggested 50-80 g/m² if broadcast over a garden bed. A tablespoon of Osmocote^® is stated as weighing 15 g.

The following nutrients are listed as percentages (presumably % w/w):
nitrogen (N) 18.7%
phosphorus (P) 2%
potassium (K) 6.5%
sulfur (S) 9.1%
calcium (Ca) 0.3%
magnesium (Mg) 2.5%
iron (Fe) 0.2%

and the trace elements below are listed expressed as concentrations in mg/kg:
boron (B) 48 mg/kg
copper (Cu) 120 mg/kg
manganese (Mn) 144 mg/kg
molybdenum (Mo) 48 mg/kg
zinc (Zn) 36 mg/kg

The N:P:K ratio here is 18.7:2:6.5 (9.4:1:3.3), but the Scotts website states a ratio of 16.6:2:6.6 (8.3:1:3.3) — again, my container is a few years old and this suggests the composition has changed.

PowerFeed^® Organically Enriched Plant Food Flowers, Fruit & Citrus

PowerFeed^® is made by Seasol, famous for their highly-regarded liquid seaweed concentrate. PowerFeed^® is a granular product like the Osmocote^® above, but differs in two ways. One is that its formulation contains both slow- and quick-release nutrients. The other is that their balls are larger and are made from Troforte, a unique fertiliser comprised of natural rock minerals and beneficial soil microbes (picture at right).

You can read more about PowerFeed^®, as well as access a Safety Data Sheet (’SDS’), here.

I have a soil microbiology background and was fascinated to discover that a fertiliser could come with beneficial soil microbes! I have a deep appreciation as to how important microbes are to soil and plant health and will be writing about these organisms in future posts.

The recommended application times are evenly spaced as with the Osmocote^®, but at more frequent intervals of six to eight weeks. The first application should be when first potting or planting your bare-rooted jujube tree. PowerFeed^® comes with a scoop and a table of recommended rates based on that scoop.

The following nutrients are listed as weight per total weight, expressed as a percentage (% w/w):
nitrogen (N) 10% w/w
phosphorus (P) 1.8% w/w
potassium (K) 8% w/w
sulfur (S) 8% w/w
calcium (Ca) 6% w/w
silicon (Si) 6.8% w/w
iron (Fe) 2% w/w
magnesium (Mg) 1% w/w
zinc (Zn) 0.1% w/w

and the trace elements below are listed expressed as concentrations in parts per million (ppm) — a 1 ppm concentration equates to 1 mg/kg, or 1μg/g:
manganese (Mn) 4300 ppm
copper (Cu) 400 ppm
nickel (Ni) 32 ppm
boron (B) 30 ppm
molybdenum (Mo) 2 ppm

The N:P:K ratio here is 10:1.8:8, or 5.6:1:4.4.

This is by no means an exhaustive list of fertilisers, and nor are they the sole product of their respective manufacturers. But each of these three were different enough to make interesting comparisons, and perhaps give you an idea as to which to buy. Do you lean towards the completely ‘natural’ fertiliser/booster formulations in conjunction with supplements of the nutrients these lack? Or do you like the idea of a scientifically-advanced, low-maintenance, slow-release one that delivers everything required? Maybe one somewhat in between, made of minerals and microbes, is more your thing.

By all means peruse all the different fertilisers and boosters that are available at your garden centre — it’s not so daunting when you know more about how they work — and see which one(s) strike a chord with you!