Do your plants need a tonic? Do you need a tonic?

Sometimes everything starts to feel much too much and you begin to have that dragging feeling. Does that sound familiar? Perhaps you prescribe yourself a (gin and) tonic, begin to take some multivitamins or eat superfoods or other kinds of a pick-me-up, and then you start to feel you can take on the world again.


green smoothie as a tonic

'Smoothie in "Vegafe" in Vilnius' by Sigurdas is licensed under CC BY-SA 3.0

Ericaceous plants (acid-loving and lime-hating) growing in an alkaline (limey) soil can feel the same, especially in the spring. (More about your soil’s acidity.) Alkaline soil conditions can make leaves turn yellow (chlorosis) and cause weakened growth. Raspberries, rhododendron, camellia, pieris and skimmia, for example, may all be suffering. So may plants which are long-term container residents, watered with tap water. All these plants need a tonic, something that changes the pH of the alkaline soil to allow them to take up the nutrients they need. Give them a one-off treatment of Sequestrene, which contains sequestered iron and various trace elements, and they’ll start to feel a lot better. (Other soft fruit will benefit from a balanced fertiliser at this time of year, such as Growmore or ‘blood, fish and bone’.)

Those of us who garden on acid soils are not protected, though, from tired and emotional plants. A seaweed-based tonic may be what’s required to help yours become healthier and tougher individuals. This liquid concentrate of kelp reduces plant stress by stimulating microbes, improving soil health and nutrient take-up, and encouraging early root development.

Seaweed is an excellent fertiliser, used widely around the coasts of Britain, Ireland and beyond. It’s part of what makes Jersey Royal potatoes taste so special.

Seaweed as a tonic for plants

Seaweed harvest at Meigle Bay, North Ayrshire

Have you got horticultural grit?

It’s tough and it gets results.

Use grit on the top of pots of cuttings and get four excellent results.

Result 1: moisture is kept in the pot but drains from the top of the cuttings so they don’t rot or dry out.

Result 2: rot and fungi or algal growth are prevented.

Result 3: weed seeds flying around will not germinate in the grit, or your pot.

Result 4: the weight of the grit compresses the compost very slightly, so the cuttings are anchored into the compost.

And adding grit into compost makes it better drained – which suits plants like alpines.

And what about horticultural vermiculite?

You can tell from the name that vermiculite is a much more glamorous member of the ‘compost’ family. It’s those silvery-grey flecks you often see in potting compost and in the soil in pots of plants you buy.

Vermiculite is a natural mineral. It’s flaky until it’s heated and then it expands and becomes light, fluffy and fire-resistant. Horticultural vermiculite is perfectly safe.

Vermiculite can hold its drink: its value in your garden is an amazing quality to absorb large quantities of air, water and nutrients and release them as and when the plant needs them.

Adding it to potting compost or soil improves airflow, and water drainage, absorption and retention! Amazing stuff.

Vermiculite is also good for seeds: sprinkle on top of seed compost to cover newly sown seeds in trays or pots. Young seedlings have no trouble pushing their way to the surface. Outside, it’s good for covering small seeds like carrots, preventing any weeds from competing for the space.

Be gentle with vermiculite. If it’s handled too roughly it sticks together and loses the qualities you want for your plants.