When mushrooms pop up after a rain, many gardeners assume something’s gone wrong. In truth, they’re a sign that something is going very right. Mushrooms are the fruiting bodies of fungi — nature’s recyclers and connectors, quietly breaking down organic matter, feeding plant roots, and enriching the soil beneath your garden.

Fungi are the unseen foundation of every healthy ecosystem. They recycle nutrients, form partnerships with plants, and even protect roots from disease. Understanding them — and inviting them into your garden — is one of the best ways to nurture soil health naturally.

Fall in Napa Valley brings that familiar mix of cool air and golden light — and for many of us, the instinct to start “cleaning up.” Out come the rakes, clippers, and green bins. It feels good to set things right. But before you clear every leaf and prune every branch, take a moment to look around.

The garden is already doing its own cleanup. Leaves drop, microbes go to work, and the soil begins quietly rebuilding itself for spring. Microbes do the tidying. Our job is to notice what they’re doing — and avoid working against it.

Let’s talk about Citrus. It’s a wonderful genus — a prolific producer of fruits we know and love. Oranges. Limes. Grapefruits. Mandarins. But also: Citrons. Kumquats. Finger limes. Pomelos. Etrogs. Yuzu. Calamondins.

But of course: lemons.

You’ve heard the phrase, “When life gives you lemons, make lemonade.” As if lemons are just a default bad thing life throws at you. But honestly? Lemons are all kinds of amazing.

Citrus trees, with their glossy green leaves and fragrant blossoms, can be a rewarding addition to any garden in Napa. But while our Mediterranean climate suits many fruit trees, citrus comes with one important caveat: it doesn’t love the cold.

Unlike stone fruits or apples, citrus trees are tropical at heart. When winter temperatures dip below 30°F, tender varieties like Bearss lime or Mexican lime may suffer or even die. Even nighttime temperatures below 50°F can slow growth and fruiting, especially for the more sensitive types.

Working as a garden consultant, this time of year I am called in to advise on the pruning of fruit trees and roses more than almost anything else. When I’m asked to look at roses that are struggling, the symptoms are often familiar before I even reach the plant. Lower leaves yellowing and dropping. White residue coating tender new growth. Orange-colored pustules popping up on the undersides of leaves. These are the signs of fungal diseases for black spot, powdery mildew, rust, and, less commonly, downy mildew. These funguses account for the vast majority of rose problems I see in Napa Valley gardens.

What often surprises the gardeners I speak with is that these diseases appear in gardens where roses are otherwise well cared for.