Question 1

What are mycorrhizal fungi, and do root boosters work?

Accepted Answer

**Mycorrhizal fungi** form a genuine partnership with plant roots, and the biology is well established. Whether the products sold in garden centres do anything useful is a much narrower question, and the honest answer is: sometimes, in specific circumstances.

**The biology.** Mycorrhizal fungi colonise plant roots and extend a network of **hyphae** far out into the soil — vastly finer than roots and reaching a much greater volume of soil. They absorb **phosphorus, nitrogen, water and trace elements** and pass them to the plant, receiving **sugars** from photosynthesis in return. The great majority of land plants form these associations, and it is thought to have been essential to plants colonising land at all.

**Two main types:** **arbuscular** mycorrhizae, which penetrate root cells and associate with most herbaceous plants and many trees, and **ectomycorrhizae**, which sheathe the root exterior and associate with many conifers, oaks, birches and beeches. **A product must contain the right type** for the plant, which is a point rarely made on packaging.

**Where inoculation genuinely helps:**

**Disturbed, sterile or degraded soil** — new-build gardens where topsoil was stripped, reclaimed land, or heavily cultivated ground where the existing network was destroyed.

**Bare-root trees, roses and hedging at planting**, where the product is placed in **direct contact with the roots**. This is the application with the best supporting evidence, and it is what RHS guidance is most positive about.

**Where it makes little difference:**

**Established garden soil**, which usually already contains appropriate fungi.

**Brassicas and beetroot family plants**, which do not form mycorrhizal associations at all.

**Scattered on the surface or watered in** — the fungi must touch roots.

**High-phosphorus soil**, where plants suppress the association because they do not need it — which also means heavy phosphate feeding works against you.

**What reliably supports the existing network:** minimal soil disturbance, keeping soil covered, adding organic matter, and avoiding excessive fertiliser.

Question 2

What is a bare root plant, and when should you plant one?

Accepted Answer

A plant lifted from the ground during dormancy and sold without any soil around its roots — cheaper, frequently establishing better than a potted equivalent, and available only for a few months a

Question 3

How do you take a cutting, and what are the different types?

Accepted Answer

By removing a piece of stem and inducing it to produce roots — and the type of cutting is determined by how mature the wood is, which in turn determines when you take it and how you treat it. Why it

Question 4

How do legumes fix nitrogen?

Accepted Answer

They do not — bacteria do it, inside nodules on the plant's roots, in one of the most consequential symbioses in agriculture. The plant supplies energy and a protected environment; the bacteria

Question 5

What is a green manure and should I use one?

Accepted Answer

A green manure (or cover crop) is a plant grown not to harvest but to be cut down and returned to the soil, or left as a living cover over winter. What it does: Prevents nutrient leaching. Bare soil

Question 6

What do earthworms actually do for soil?

Accepted Answer

Rather more than aerate it. Worms are physical engineers, chemical processors and distributors of organic matter, and the effects compound over years. The three groups, which do different jobs. This

Question 7

How do plants actually drink, and why does a plant wilt?

Accepted Answer

Water is not pumped — it is pulled up the plant by evaporation from the leaves, and wilting is what happens when that pull outruns the supply. The mechanism, working from the top down: Transpiration.

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