Compost tea is water in which compost has been steeped, and which therefore contains some of the same nutrients, micro-organisms and heaven knows what else. I’ve never been quite sure what compost tea is supposed to do that the original compost wouldn’t do just as well, if not better. When Which? Gardening tested compost tea, they found it did precisely nothing. Save your time and money.
Hold back on the mycorrhiza
Mycorrhiza, a symbiotic association between plant roots and beneficial fungi, is very important for the uptake of nutrients, especially phosphorus. But it does raise the question: just because you know something is good for your plants, does that mean it must be a good idea to buy more? The answer is: probably not.
The problem is that most garden soils already contain a diverse collection of mycorrhizas, either as active fungus or as dormant spores, so most plants will quickly recruit the mycorrhizas they need. On top of that, there are at least 300 different species of mycorrhizas, yet the typical commercial product contains very few, so maybe it’s not surprising that they usually don’t add much to what’s in the soil already.
Finally, whenever anyone bothers to check, plants arriving from the nursery often turn out to be mycorrhizal before you even plant them. Here’s tree expert Peter Thomas on the subject: “It is far better to take a small amount of soil from beneath a nearby successful tree to act as an inoculant.” This is more likely to have the right local fungi and is, of course, free.