Sunday 1 September 2019

A few angles on fertilisers

Remember when considering fertiliser that some gardens do not need any at all
After blogging for seven years I think I have told you all I know about fertilisers. Some of you might have missed old posts and at the end of this post I provide links to those I hope most useful to gardeners. 

Useful balanced analysis
Some of my stories might have been lost in the undergrowth and for example I told the tale how my friend David Willis  invented a fertiliser called Vitax Q4 for the chemical company he then worked for and how after fifty years continuous production they invited and chauffeured him back to a slap up half centenary celebration.

It is a great general purpose amateur fertiliser that provides almost all essential plant nutrients and for the gardener has multiple uses. This tells you something - that you do not need individual fertilisers for each plant you grow.

David bred this euphorbia
(You might ask what constitutes an amateur fertiliser rather than a professional one. Other than that you will only get amateur ones at the garden centre, they are expensive and are generally weaker. Higher levels of nutrients can cause all kinds of problems to gardeners who do not know what they are doing  - and I confess when I have taken liberties making up my own composts things have sometimes gone pear shaped. Let’s face it although we all love  garden centres most customers are not gardeners. The cynic will say that garden centre fertilisers such as bonemeal are a waste of time but they do little obvious harm)

Fertilisers are concentrated sources of nutrients and should not be confused with bulky manure
It is a complete con to persuade gardeners that they need a special fertiliser for every garden use. ‘Special’ plant specific concoctions are NOT needed and most are anyway frequently wrong approximations invented in an adman's office or based on cheap chemical sources.

Provided that a nutrient is actually available in the soil water a plant will absorb what it needs. This might be an active or passive biological process and plants are masters of selection.

I go further than I ought to and rabbit on how the commercial fertiliser ‘Yaramila’ serves all my fertiliser needs. It may be a case of “do what I say rather than do what I do”. Most gardeners will want to use a degree of variation between ‘slow release’, ‘solid’ and ‘liquid feed’. Single nutrient fertilisers are generally inappropriate although I do love iron sulphate for my lawn (actually two nutrients, iron and sulphur).

Iron sulphate is a single chemical, an example of what is sometimes called a 'straight fertiliser'
The main point is that a 25kg bag of such as Yaramila for twenty five quid will last you for a very long time. It will provide all the six major nutrients and umpteen trace elements that your plants might need.
Lots of little bags of fertiliser for such as orchids, turf, vegetables, cabbage, flowers, shrubs and  you name it, cost an absolute fortune.
You might enquire why commercial growers do buy specialist fertilisers. That’s the economy of scale - they are buying exactly what their specialist crop and/or their soil needs - in 25kg bags or bigger! It’s not that their plants grow better - although they often do, it’s that they are not buying unnecessary resources.
(Nutrients added to the soil unused that season - other than nitrogen - will usually remain in the soil for next year).

Soil analysis
Other than pH testing kits, do-it-yourself stuff at the garden centre is an almost complete waste of time. Don’t put too much faith in pH tests either but it is sometimes useful to have a rough check with that colour indicator you have in the cupboard.

I confess that I have never had a laboratory soil test for my soil. Such testing does have an important place for farmers and commercial growers who work on knife edges of accuracy but is generally of little use to gardeners. They are difficult to interpret for the vast range of different things we grow; so many plants have different requirements and are in small and very variable parts of the garden.
For the major nutrient nitrogen, soil samples sent for testing will vary by a huge amount depending on when you collect it. Your best measure of the soil’s store of nitrogen is to estimate its organic content.
It surprises me how many gardeners are ignorant of the physical make up of their soil as to it’s composition of sand, silt and clay. It tells you a great deal about its nutrient retention and  availability.

Here again professional texture analysis is only of limited help and it is more appropriate to apply common sense investigation. What is the general nature of the soil in your area? Is your soil formed on chalk or limestone? There are simple tests that you can do with your fingers or a bottle of water to learn about its sand, silt and clay.
If you are a beginner the best advice is to have a talk with a knowledgeable neighbour and to have a walk round and see what plants locally thrive.
If you are an experienced gardener just looking at your plants will tell you much about their nutrition.

Which general fertiliser?

As to my penchant for using Yaramila. I like it because it comes with a good balanced analysis, suitable strength and in the form of an easily spread and stored prill. This granule is soluble (but not soluble enough to be suitable for liquid feeding) and does not go mushy in store.
It may be that your local semi-professional supplier carries stock of 25kg bags of a different general fertiliser. Should my supplier, East Riding Horticulture offer something different I would consider a change. 

Should you change from that excellent fertiliser Vitax Q4 or growmore you need to half the amount you have previously applied. In the past I have recommended growmore to amateurs  - its a good compromise with it’s 7:7:7 analysis but lacks magnesium, sulphur and trace elements and is half as strong. Your soil does not usually lack trace elements but you cannot be sure.

I used growmore for years
How I get through 25kg general fertiliser in about two years 
I have a very large garden and my soil is sandy and subject to leaching! If your soil unlike mine contains clay and/or you have regularly added compost you might need no fertiliser at all. Particularly so if you liquid feed and buy ready made compost. If you make up your own compost I recommend you use just one slow release coated fertiliser. For liquid feeding I suggest you use a tomato liquid feed for any plant.
In most circumstances slow release fertiliser and liquid feeds are inappropriate and rather expensive for plants growing in the garden - their value is for container grown plants.

I look after several other gardens than my own; Bolton Percy churchyard, the village plot, Lyndi’s field and Cathi’s garden. None of them receive any fertiliser at all. If your vegetable garden is annually heavily manured it might need no fertiliser either

Very rough guide as to how I use my Yaramila
1. Perhaps 30% goes to feed my 800 sq. metres of lawn

2. I find it more convenient to top dress container plants than liquid feed. These vary between small trees and shrubs permanently outside in very large containers, collections such as cacti and alpines, plants in my nursery, ten litre pots of tomatoes and house plants galore. We do indulge in summer and winter bedding in large tubs too.
Plants in containers are subject to leaching and if you do not feed them they will eventually starve.

My tomatoes get top dressed five times and get more fertiliser than anything else I grow

I lightly scatter yaramila on my small pots three or four times a year

The bedding plant soil has yaramila added when prepared and is carefully top dressed not leaving fertiliser lodged on the leaves. The shrubs and small trees are fed three or four times a year

3. I use yaramila when I make up my soil based composts - but not for propagation or delicate plants. When such as planting up tubs of mature bedding plants or starting up large pots of tulips or daffodils I prefer to top dress later and the amount mixed in the soil is zero or very small.
Other than for large display planters I DO NOT advocate using Yaramila  for making up potting compost for inexperienced gardeners. Best to stick to slow release fertiliser.

When I planted my tulips yaramila was lightly added to the compost and more heavily top dressed on the surface to be washed in by the rain
4. My garden soil is almost pure silt/sand and nutrients leach out of the ground in winter. Significantly nitrogen and potash and perhaps magnesium and calcium too. I do find it rewarding to fertilise my blackcurrants, autumn raspberries, rhubarb, my large thornless blackberry and asparagus. Such plants are top dressed once in the year, usually in March. Note top dressing does NOT need working in and the fertiliser is just flung on the surface over the whole of the rooting area. I tend to apply earlier than normally recommended - roots are active sooner than you think.

5. When I used to grow vegetables I would top dress my winter greens in February or March.

6. Although I don’t reckon to feed my ornamental borders a few plants such as delphiniums just do not grow well on my soil. A light dressing in March works wonders.

7. I confess too that when I want to get a young plant from my nursery or a plant bought at the garden centre to establish quickly although I usually do NOT fertilise at planting time I do a few weeks later.

8. This Summer I bought some rather hungry shrubs for planting this Autumn on the village plot (delayed because of watering difficulties) and after dunking them up in my tub, top dressed with Yaramila. They jumped for joy.

These links provide more detail - apologies that they are merely cut and pasted from an earlier post

Why you do not need to buy lots of little bags of specialist fertiliser. 
My thing against bonemeal
All year round use of fertiliser
Why general fertiliser is suitable for your lawn
My penchant for using charcoal
Restoration of a slag heap 
Buying professional fertiliser
Crushed rock myth
Do fertilisers degrade soil? - whoops I have been repeating myself
My homemade soil potting compost
My post about hard and soft growth was a damp squib

Blogger Robert Pavlis takes a rather different view


  1. Hi Roger,
    If I were cynical I would think that virtually everything for sale in your local garden center is over-priced and aimed at the non-gardener.I am ashamed that the horticultural industry is now basically more intent on ripping off people with little knowledge who actually believe that they will be given honest advice.Few and far between are the small nurseries where dedicated horticulturalist,or dare I say gardeners,grew their own stock and would offer genuine advice to the customer. Unfortunately gardening has become like cooking, they all watch the TV shows but don't actually do anything about it instead they hire a "mow and blow" merchant who has no idea about gardening and is just as likely to rip anything that is an actual plant up along with the weeds, I have seen it! I despair, gone are the days when you learnt from you parents or a neighbour all about gardening and developed a natural interest. There are new houses selling in this area now for comparatively obscene amounts of money with virtually no garden,apparently this is what people want.

  2. Good to hear from you again Rick, you old backwoodsman - just like me.
    Actually I do have a post coming up about garden centres that does share some of your reservations. You can sometimes get a good lunch!
    I have missed your formally regular blogs - wonder if you are doing any more.I do hope you are still active in your garden. Perhaps we both need one of those new houses you mention - a firm NO

    1. Hi Roger, please excuse one of my rants, sometimes I can't resist. I have downsized considerably and have a small garden back and front which I am currently working on but nothing like I had before. I am considering doing the occasional blog in the future but I am not sure when I will start again. I have kept up with your blog along with a few others so the interest is still there. Till the next time then.........

  3. Thanks for this excellent post on using fertilizers in the garden...have added it to my list for future reference, as I am determined to use up all the ones I have. Simple is best I think, and will just get the one you mention in due course.

    1. In due course let me know how you get on, Stasher
      (Sounds as if you have been stashing them away)

  4. Very interesting post, and important for gardeners who are susceptible to bogus advertising claims. Most of my garden don't get any fertilizer at all, except for decaying plant matter. For a few plants considered heavy feeders (roses, clematis, etc.) I give them a healthy dose of compost and a slow release general fertilizer. Containers get just the slow release stuff, though I refresh the potting mix with compost before each season.


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