Plant tonics expertly explained and recommended – thank you ‘The Telegraph’ – with some home thoughts too …

Love your plants, flowers and wild life ….

Plant tonics expertly explained and recommended ….

I’m very taken with this article on plant tonics that appeared in The Telegraph today – always the bastion of excellent gardening advice (regular readers to my blog will know this already and be converted as I am).

Taken so much am I that here it is in full, with links and credits of course!

The best plant tonics and supplements for your garden

I am a bit of a sucker for food supplements: cod liver oil and raw cider vinegar are must-haves for me, but what about the plant equivalents? Many are used commercially, which helps to validate their efficacy in my eyes.

Growers do not whack on products that are expensive both in man hours and material costs if there are no tangible benefits. Yet, if you are an amateur, it is not always easy to identify whether or not tonics make a difference.

Alex Stevenson works for Dejex Supplies Ltd of Spalding. Dejex supplies a huge range of herbicides, fertilisers and more to thousands of commercial growers as well as a few ordinary gardeners like me. Alex specialises in the horticulture sector and is a mine of information. He tells me that the advantage of many tonics for amateur gardeners is that they can be used at home, unlike commercial products which can only be applied by holders of PA1 and PA6 certificates (which entitle you to apply pesticides on a commercial basis).

I asked Alex for his best sellers and he emailed me a long list. At the top is SB Invigorator, which I use a fair bit. This is a plant stimulant which works as a broad spectrum pesticide and fungicide. It has a physical mode of action, sticking wings and body parts together, so works against white fly, spider mite, scale and many more. It is also a foliar feed. I use it on my most pest-affected crops, especially tomatoes and cucumbers, any lacklustre roses, brassicas and my quince trees. It is applied as a spray to the upper and lower sides of the foliage at around weekly intervals and there is no spray interval between application and eating, a huge bonus commercially and to us gardeners.

Plant tonics – how they work

Many tonics are applied to foliage. They are absorbed mainly through the stomata (pores), which are predominantly on the underside of the leaf.

The best time to apply foliar feeds is when the foliage stomata are wide open, in the early morning or evening. In hot sun stomata close to prevent too much transpiration (loss of water).

Relatively low concentrations are applied and nutrients are absorbed rapidly (usually within 6-24 hours).

Foliar feeding can act as a catalyst, increasing the plant’s nutrient uptake from the soil. According to Amigo Bob Cantisano, California’s foremost organic farmer, liquid feeds frequently give you produce with higher Brix levels. A high Brix level (measured with a refractometer) equates to high sugar content/sweetness, which equates to healthy plants more able to resist pests and diseases.

Leading plant tonics and supplements

Maxicrop, a leading seaweed feed, was next on Alex’s list. There are four main products: one contains iron (Maxicrop plus Iron) – useful for ericaceous plants; one is a basic seaweed tonic (Maxicrop Original); two have fertiliser added. Seaweed tonics have a big following amongst amateur gardeners. I am partial to deploying them when plants start to look slightly distressed. They are easy, safe and pleasant to use.

Garlic – this is another popular product amongst amateurs. Alex stocks two products – Aston Rabitof, a garlic foliar spray designed to control not only the bunnies but also deer and other mammals. Aston Garshield is another foliar spray designed to help stimulate natural plant defences.

I have used garlic in the past, but I am not convinced. As a I favour Grazers G2 formula (sprayed onto the foliage) which also strengthens and stimulates growth, and I use the original Grazers (sprayed onto the foliage again) for rabbits, deer and bigger fry.

Ground aluminium sulphate (17 per cent) is commonly used by gardeners who hanker after blue hydrangeas but garden on alkaline soil. It is a popular product but must be applied when the plants first go in. Try to acidify the soil, too, by adding bark mulch and sulphur.

Potassium bicarbonate (baking powder) for mildew is not just an old wives’ tale. Dejex sell it commercially, too. It has EU approval by virtue of being “a commodity with approval for use as a professional pesticide”. It acts as a mild fungicide and is very safe to use.

Magnesium sulphate (Epsom salts), another household product, is used to correct magnesium deficiency. Magnesium is a constituent of chlorophyll and if the plant is deficient the leaves may be pale or have yellowing between the veins. Thin soils exacerbate this deficiency; sometimes high applications of potash-rich fertilisers cause magnesium to be unavailable to the plant. Apply it when necessary and you will see almost magical, instant results.

Chelated iron is often applied to acid-loving plants that are growing in too highly alkaline soils, which causes a yellowing of leaves. Librel SP Iron is a form sold as a soil drench and Dejex say it is popular with growers of amenity plants, they especially use it for camellias, rhododendrons and citrus plants.

Latest developments

There are many other supplements that are popular. I am a big fan of  Biochar and by adding it to my thin soil it helps the water holding capacity. I am also a fan of  mycorrhizal fungi for use when replanting roses in soil where roses have been grown before, it saves moving mountains of soil.

I have used  effective microganisms having been impressed by their use in agriculture and horticulture in Japan. This is a cocktail of fungi and bacteria which suppress harmful fungi and bacteria. I think perhaps they are of greatest use in impoverished soil. A client told me it doubled his rice crop (in Japan), but his was quite poor acid soil.

Another great tip I got from Japan was Neem oilThis is a very effective against many pests and fungi and is widely used in commercial crops across the world. Here, as with most of these non mainstream products, they legally cannot make claims for use as a pesticide or fungicide under EU law. But if you have a problem with aphids or other pests Neem oil is extremely effective.

Apply it once a week for three weeks to the foliage and/or use as a drench.

There is a relatively new Dutch product,  Topbuxus which claims to cure box blight. It contains magnesium oxide plus nitrogen. On the website it claims to be 100 per cent effective in stopping fungal disease in box. If you do not want to go down the systemic fungicide route (which is extremely effective) this may be your best option, but I can not vouch for it.

Alex also stocks some biofungicides and insecticides that are only for use professionally – these are growing in popularity as the restrictions on chemicals such as neonicotinoids, are clamping down on their use.

These supplements are being used more and more as many pesticides and fungicides are increasingly withdrawn from the market. I rely on them increasingly and find them mainly pleasant to use. It is confusing though, especially as manufacturers legally can not always say what the products do because of the prohibitive costs necessary to register them. Whatever you use, make sure you keep a keen eye on your plants though and act early on.

The shadow of the gardener is the best tonic, after all.



I seem to be right on the button with my own practice of using these ingredients and products, as well as in the advice I give my customers. Excellent news! How they work adds to my understanding and there are new things in here too – the box blight remedy deserves closer inspection.

Happy Plants and Happy Pollinators …

I know that SB Plant Invigorator is used by David Austin, bathing their plants in a fine mist of it before dispatching their plants off to the nurseries; also it is the only product used in the Princess of Wales’ Conservatory at Kew – and their collection is immaculate. I’ve been using it for two seasons now and it has certainly helped damp down white fly and aphid populations on plants within the glasshouse environment – especially when the mix is given a splash of liquid seaweed. I’ve used it regularly on my roses too and have just bought six bottles for my stockpile.

Stan Bourard’s Invigorator isn’t readily available in garden centres – I’ve seen it at Wisley for example – but large online retailers have it for just shy of £16 for 500ml concentrate. Much recommended.

Importantly it is compatible with the use of biological controls – predatory mites and wasps – so can be used as part of a complimentary regime, an integrated biological approach to pests and diseases. A plant tonic and pesticide, it acts like many soaps, suffocating the poor little aphids who haven’t the puff to pop the bubbles that form over their breathing siphuncles – while also coating their bodies, subsequently crystallising, making moving – and feeding – impossible. Cue Bach’s Toccata and Fugue.

Avoiding neoniconitoids will help towards safeguarding our bee populations

I’ve long been a fan of Maxicrop seaweed extract – and have a source now which has wholly organic credentials – and have used it as a foliar feed on all my roses while in leaf and flower. It benefits the plants enormously, to my mind, and keeps aphids at bay too – salty perhaps?

Garlic I’ve been recommending as a treatment to prevent slug attacks – and it mixes well with mint to make your home-brewed concoctions more fragrant – but it works on bunnies, deer and other mammals too it seems.

Baking powder – bicarbonate of soda – too has been in my arsenal of treatments against mildew and blackspot. Germination of the pesky spores of these fungal diseases requires the leaf surface to be just a bit acidic – and the baking soda makes things just a little alkaline. The spores are still there but unable to germinate and spread, are inactive.

Epsom salts – well there I am again in the good graces of this useful article as the combination of magnesium and sulphur can indeed work miracles – as well as making the most of a good long soak in the bath for us humans. We won’t green up in quite the same way as your poor yellowing evergreens, but we can both feel the benefit.

Painted Heathers - No!
Painted Heathers – No! Not what I mean by greening things up…..

Chelated Iron, or sequestered iron, is a supplement for acid-loving plants that might be grown in less than perfectly ericaceous/lime-free compost, or where watering might be from the tap rather than rainwater. There are liquid versions of it, alternatively sachets of powder can be mixed with water – with great difficulty, it seems to be positively hydrophobic – and then used as a drench. This is different to the hydrangea colourant – where we hope to keep our blooms blue. If in doubt, move to Cornwall where the prevailing soils are much more acidic.

rhodeodendron christopher wren orange neon
Rhododendron Christopher Wren

Biochar in all its variants – well yes, I use this too – the mix of nutrients are locked in with the charcoal to prevent it from being leached out of the soil so quickly, so the benefits for soil structure and mineral, nutrient and water retention are numerous.

Mycorrhizal fungi is a staple now I think in tackling rose replant disease and in establishing new roses and indeed, shrubs in general – and is a relatively inexpensive supplement, especially since you would usually incorporate either a fertiliser like bone meal or the mycorrhizal supplement into the planting hole – one or the other. In young plants, the supplementary association of fungi blooming around the hosts’ roots can increase the plant’s ability to take up water and nutrition by 200- 2000 times. Just the ticket.

waterperry gardens roses raubrittter bonica pink
Roses Bonica and Raubritter

And the roll call continues with Neem Oil which is a useful winter wash – suffocating aphid eggs just as much as it deals with the live critters – suffocation again, but also impacts on breeding, larval maturation, feeding. Not a good thing for the pests we love to hate. Helps against some fungal diseases too.

Pure mineral oil can be similarly effective – and a splash of one or other can be added to the mix for foliar sprays of say, seaweed extract, acting as an emulsifier and helping the nutrients stick to the leaf surface, where it is taken in by the plant – rather than, I mean to say, in runoff.

Helping Your Plants With A Neem Oil Foliar Spray

I should mention, though the article does not, worm cast teas, moo poo teas and compost teas which I’ve covered in detail beforehand. Easy to make, available to buy commercially and with excellent properties and results in plant health and cropping. Go explore! There are posts on organic gardening, composting, macro- and minor nutrients – and what the plants use them for, home-brewing for compost and worm cast teas, manure teas, comfrey teas and in the case of some particular plants, like roses, detailed care instructions.

Complimentary tonics and pesticides that do not harm the wild life we want … like this Astrantia/Bee Hostel


Good to you I am …





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