By Susanne von Rosenberg, UC Master Gardener of Napa County
Some gardening advice seems so sensible or obvious, or has been repeated so often, that we “know” it to be true. As gardeners, we need to be careful about falling prey to myths. In this column, we'll explore some widespread gardening myths, although perhaps I should call them confusions.
We are usually told that wilting leaves indicate that a plant needs water. This is often the case, and you can check to see if your soil is dry. But there are other reasons that a plant's leaves could be wilting.
If the soil is waterlogged, the oxygen that roots need to grow is replaced with water. This happens often to plants in containers without drainage. Plants may also become waterlogged in compacted soil that doesn't drain well. When roots lack oxygen, they can't supply water to the rest of the plant. The leaves continue to photosynthesize and to use water. By forcing roots to shut down, waterlogged soil leads to wilted leaves.
Fungal or bacterial disease can also cause leaf wilt. Fusarium and verticillium are common in local soil. These fungi block the plant's water transport structures, causing leaves to wilt even when there is plenty of soil moisture. Often the entire plant dies.
Keeping your soil too moist can promote fungal disease. Another culprit for wilting leaves is animal damage to the roots. Gophers, nematodes and other insects feed directly on roots, and other animals may create tunnels that drastically reduce root contact with surrounding soils.
Another possible cause of wilting is overfertilizing or excess salt in the soil. Always follow the directions on any packaged fertilizer, and be aware that steer manure is relatively high in salt.
You may have heard that bark chips are a better mulch for your perennial woody plants than tree chips. Some say that tree chips could contain disease-causing organisms or compounds that inhibit the growth of other trees.
Neither of these concerns has been documented as a significant issue. Conversely, bark chips, while a more attractive mulch than tree chips, have poor water retention. Tree bark is designed to prevent water loss. It contains a waxy compound, suberin, that repels water.
Tree chips, on the other hand, consist mostly of inner wood, which has the capacity to absorb and hold moisture. Depending on where the logs were stored before the bark was collected and chipped, bark chips can also contain weed seeds. Tree chips are more environmentally friendly, too, because they are local. By using them, you are reducing the amount of material that needs to be processed in a composting facility.
While we're talking about mulch, let's explode the myth that there is any permanent solution for weed control other than paving over your yard. Landscape fabric, which differs from black plastic mulch in having small holes for air and water exchange, is often touted as a permanent solution. It is used in commercial vegetable and ornamental plant production, where it is successful at keeping weeds out. It can also be easily removed and replaced each year.
However, landscape fabric is not good for permanent weed control around perennials. If left exposed, the fabric can degrade in a year. If you cover it with mulch or allow plant debris to accumulate on top of it, weeds will colonize the plant material or mulch and grow through the fabric, making it difficult to remove.
You can cover the fabric with gravel, but you'll still need to keep removing the weeds that manage to colonize gravel-covered fabric. Your plants may also grow into the fabric, so when you remove the fabric, you damage their roots.
As the fabric degrades, you'll have a clean-up and aesthetic headache, with lots of shredded bits. (I know this from personal experience.) Gophers can exert so much pressure building mounds under the fabric that the fabric rips. If it doesn't rip, you end up with exposed landscape-fabric-covered mounds.
Unfortunately, there is no magic bullet for weed control. You can reduce them, but you still need to remain vigilant no matter what method you use. Organic mulches are best as they improve soil texture and health and can be replenished as needed. Couple them with targeted watering.
If you want to learn more about garden myths, Dr. Linda Chalker-Scott, an extension horticulturist and associate professor at Washington State University, has a wonderful website that discusses all sorts of common Horticultural Myths.
Food Growing Forum: Napa CountyMaster Gardeners will present a discussion of “Perennial Vegetables, Garlic and Alliums” on Sunday, October 10, from 3 p.m. to 4 p.m., via Zoom. Register here to receive the Zoom link.
Free Guided Tree Walk: Join Master Gardeners of Napa County for a tree walk in Fuller Park in Napa on Tuesday, October 12, from 10 a.m. to noon. Limited to 12 people per walk. COVID safety protocols will be followed. You will be asked health questions and asked to sign in. Face masks and social distancing are required. Register here.
Got Garden Questions? Contact our Help Desk. The team is working remotely so please submit your questions through our diagnosis form, sending any photos to mastergardeners@countyofnapa.org or leave a detailed message at 707- 253-4143. A Master Gardener will get back to you by phone or email. For more information visit http://napamg.ucanr.edu or find us on Facebook or Instagram, UC Master Gardeners of Napa County.
With the first warm days of spring I find myself pining for those summer evenings when my husband and I sit on the patio and savor the bounty from our vegetable garden. I think back to the many tomatoes I grew last summer and ponder which ones I will grow this year.
Probably I will repeat many of our favorites, but I will also try a few new ones. Which types to choose? There are so many factors to consider.
Do I want to try a new variety for cooking and preserving, or for eating fresh from the garden? I have plenty of room for another tomato plant, but those with more limited space should consider whether a variety is suited to small spaces or containers.
Tomatoes are classified as either determinate or indeterminate based on their growth habits. Determinate tomatoes tend to be bushy in appearance. They grow to a certain height, generally three to five feet, and bear most of their fruit within a four- to six-week period. Determinate tomatoes are often chosen for canning since they yield so much at once.
Indeterminate tomatoes grow and bear fruit all summer, until the arrival of frost. These types need the support of trellises, stakes or cages to keep them from sprawling on the ground, where the fruit tends to rot.
Another characteristic to consider is disease resistance. Many hybrid varieties have been bred to resist diseases that plague tomatoes. When shopping for tomatoes, you may notice that the plant label includes the letters V, F, N, T or A. This is a code that indicates whether the variety is resistant to verticillium wilt, fusarium wilt, nematodes, tobacco mosaic virus or alternaria stem canker. Keep in mind that resistance does not mean immunity. Home gardeners should still practice crop rotation and avoid planting tomatoes or other members of the nightshade family (Solanaceae) in the same location for more than two consecutive years. That family includes eggplants, potatoes, peppers and petunias.
The popular heirloom tomatoes offer a wide range of flavors, colors, textures and shapes. While heirlooms may not be as productive as hybrids and tend to be more susceptible to disease, many home gardeners appreciate their variety. What’s more, heirloom seeds can be saved and replanted, and they will yield the same variety the following year. In contrast, plants from hybrid seeds don’t retain all the traits of the parent plants.
I generally grow a mix of heirlooms and hybrids so I have the best of both worlds. One of my favorite cherry tomatoes is ‘Sungold,’ an indeterminate hybrid that produces small golden-orange fruits with a tangy, sweet flavor. It is extremely productive. For a color contrast, I grow ‘Green Grape,’ an heirloom that is green on the inside and chartreuse outside when ripe. It is about the size of a large grape and has few seeds. It has a spicy sweet flavor and looks beautiful halved in salads.
‘Mamma Mia’ is my favorite variety for sauces, bruschetta and dried tomatoes. It’s the only variety that I grow in multiples because it is so versatile. It is meaty, ripens earlier than most plum tomatoes and lasts in my garden until the first frost.
For sheer beauty, I grow ‘Marvel Stripe’ every year. This indeterminate heirloom produces large multi-colored fruit with streaks of red, yellow and orange. It is a star in any caprese salad.
My best-tasting tomatoes are ‘Japanese Black Trifele’ and ‘Cherokee Purple.’ Both are indeterminate heirlooms with dark fruit and rich, complex flavor. ‘Cherokee Purple’ produces large tomatoes while the ‘Japanese Black Trifele’ is a medium-sized pear-shaped tomato.
Napa County Master Gardeners have compiled a list of 44 favorite tomatoes that grow well in the county. For more information about these varieties, visit http://ucanr.edu/sites/ucmgnapa/files/163307.pdf. No matter which tomatoes you choose to grow this summer, you will be in heaven with the first bite.
Tomato Plant Sale: Napa County Master Gardeners are hosting a tomato plant sale on Saturday, April 20, from 9 a.m. to 2 p.m. Choose from 44 varieties that grow well in Napa County. Come early for best selection. Tomato experts will be on hand to answer questions. Location: Oxbow Public Market, south parking lot, 644 First Street, Napa. Plan your purchases with this Quick Guide to Tomato Varieties.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners (http://cenapa.ucdavis.edu) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions?