Gardening with Xpress: Fungi, fall carrots and elderberry harvests

Hello to you as autumn whispers in the crisp morning and evening air. While your summer gardens wane and your fall crops grow, remember to send me questions at gardening@mountainx.com, and I’ll be happy to answer them.

Uninvited mushrooms

I grow in raised beds, and I filled the bottom of them with twigs and wood chips, then covered those with soil and compost. Lots of mushrooms are popping up along with my veggies. Is this OK?

Woody material like the twigs and chips you laid in the bottom of your raised beds are prime food for fungi. It’s a totally normal and natural part of the process of those things decomposing to see mushrooms sprout up on the surface of the soil above them. What’s happening is the underground part of the mushroom, the mycelium, is digesting the fibers in the wood, thus releasing nutrients and breaking them down into soil. Mushrooms are simply the visible fruiting bodies of the unseen mycelial networks down below. Given the right conditions — usually a combination of moisture, temperature and enough food — mycelia send up mushrooms that will make spores (the fungal equivalent of seeds) to spread that particular kind of fungus out into the world.

Up to 90% of plants have mutualistic (win-win) relationships with fungi in the soil. In fact, there’s a special name for fungi that hang out in the rhizosphere (root zone) of plants: mycorrhizae. This group of fungi helps plants access nutrients and moisture, while gleaning sugars and other compounds that the plants make through their alchemical magic.

Without more information about the specific mushrooms that are popping up in your raised beds, I can’t know for sure if they’re helpful to the vegetables you’re growing there. However, it’s extremely unlikely that they’re harmful. At worst, they’re working on breaking down the woody stuff and having a neutral impact on your crops. 

As I’ve mentioned here before, gardens in our region are especially prone to fungal pathogens that can cause problems. So, how can I be so sure that the mushrooms aren’t a threat? Well, fungal pathogens are usually in the form of molds and rots, not mushrooms. These organisms all fall under the broader name fungi but are distinct groups within that vast kingdom. Fungal pathogens that infect plants can also infect mushrooms that you might be cultivating, like shiitakes or oysters.

In the case of your mystery visitors, feel free to pick and then compost them if they’re in the way or just let them do their thing. 

Spotty tomato leaves

My tomato plants have spots on the leaves that turn brown-yellow and seem to be spreading from the lower leaves upward. What can I do?

What you’re describing sounds to me like septoria leaf spot, or septoria blight, which is caused by one of the nasty fungal pathogens I was talking about above. This one is called Septoria lycopersici and is pretty common on tomatoes in warm, humid conditions. It’s distinct from the most common tomato issue around here during this time of year, late blight, which is caused by the fungus Phytophthora infestans. The main difference in appearance of these two issues is that late blight shows up as big, water-soaked splotches that spread and kill leaves, leaving them looking as if they’ve been burned or frosted. Septoria, on the other hand, is more distinctly spotty, like morbid polka dots, though if it’s left to spread it can also kill entire leaves and cause a similar amount of damage as late blight. 

If you’re interested in being sure about which pathogen you’re dealing with, bring a sample of your infected plant to your county cooperative extension office. The people there may be able to tell you exactly what it is, or they may advise you to send it off to the N.C. State Extension department of plant pathology. 

Either way, take care to remove all infected leaves and either compost them well away from the garden or trash or burn them. After you do this, wash your hands and any tools you used to avoid spreading the fungus around to other plants. Septoria leaf spot, which I’m guessing is what you’ve got, strongly prefers tomatoes as a host but can also infect other plants in the Solanaceae or nightshade family, such as eggplants, potatoes and peppers. 

Once the tomato harvest is finished, or the disease takes down your plants, whichever comes first, be sure to remove the plants from your garden and dispose of them in the same manner as I suggested with the leaves. Septoria leaf spot can overwinter in plant debris and in the soil, so definitely don’t plant tomatoes again in that same spot, or any other related plants, if you can help it. This practice of crop rotation is the best move not just to avoid diseases but also to vary the impact of different plants on the soil and to disrupt pest life cycles. 

Elderberry bounty

My elderberry bushes are full of ripe clusters of fruit. Can I just eat them, or do I need to make elderberry syrup?

Heavy clusters of elderberries are one of the gifts of autumn bounty. Whether you’ve planted them or are tending wild plants, their berries are full of medicine for the changing season, plus they’re tasty. Some varieties of elderberry are toxic if eaten raw, so it’s best to cook them. You don’t have to make elderberry syrup, though it is one great way to preserve and ingest their goodness throughout the fall and winter. Other ways to prepare elderberries are to make jams or jellies, or to dry them and turn them into tea or syrup later on. You can also freeze the berries now and process them later, during the cozier time of year when indoor tasks are more appealing. For a simple elderberry syrup recipe and more information about this wonderful plant, check out this blog post from Wild Abundance at avl.mx/e2b.

Carrot season

I planted carrots in the spring and didn’t have good luck with them. I’ve heard you can plant them in the fall too. Is this the time to do that? Are they easier in the fall?

Yes, it’s time, and yes, they’re easier in the fall! Not only are carrot seeds quicker to germinate in warm summer soil, but the developing roots will get sweeter as temperatures drop. Growing carrots in the spring can be tricky because this is flipped around: The soil is still very cold, which means it takes a long time for the seeds to germinate, and then it gets hot by the time the roots are forming. Warm weather leads to more bitterness and toughness in carrots. 

In either season, it’s important to choose a suitable variety of carrot. If you’re planting now, pick a carrot that will mature in about 70 days or fewer. Carrots, along with other veggies, slow their growth as the day length shrinks. Once the hours of sunlight go below 10 per day, growth will halt. You want to make sure your carrots are ready to harvest before this happens, which is in mid-November around here. 

My favorite variety of fall carrot is an old French heirloom called Red Cored Chantenay. It takes around 70 days to mature. Other things to look for in a carrot variety are the shape and size; our rocky soil tends to welcome short, squat carrots more easily than long, slender ones.