Gardening with Xpress: On blueberries and plastics

Crisp autumn greetings, gardeners. Next month will be the last gardening feature for the year. Please send in any final questions that you have so I can get them answered (gardening@mountainx.com). It’s been a pleasure to share my knowledge and love of gardening with you!

This month we’re exploring best practices for growing blueberries and safe ways to use plastics as part of your gardening toolbox.

My husband and I want to grow blueberries. When should we plant them, and what varieties do best in our region? Is it true you need several to cross-pollinate?

Yay for blueberries! They are such a wonderful crop in general and particularly for our region. As you may know, blueberries are native here. And while wild blueberries are somewhat different from cultivated varieties, both can thrive in our conditions.

Blueberries are perennial, shrubby plants, meaning that they will live for several seasons (up to 20-plus years for certain varieties in good conditions), and they have a woody, bushy growth habit. All blueberries require sun, moisture, organic matter, acidic soil and fertility in order to thrive.

They’re a member of the heath family, along with cranberries, rhododendrons, azaleas and others; all these plants like acidity and can’t tolerate alkaline soil. Lucky for us, we have naturally acidic soil, though it’s a good idea to get a soil test and/or add acidity when planting blueberries. Agricultural sulfur is a great pH reducer (lower pH = higher acidity), and gypsum can also be used.

Even though blueberries can survive in semishade, they will be way more productive in full sun, so choose your planting location accordingly. Along with adjusting acidity, you’ll want to add in a source of organic matter at planting time and continue adding organic matter in the form of mulch once the plants are established. Soil conditioner, sometimes called “pine fines,” is made of finely ground pine bark and is a great, locally available and fairly inexpensive source of organic matter. Other options for organic matter are compost, rotted manure or peat moss. If you’re using compost or manure, make sure that the pH is low (acidic), so you don’t inadvertently harm your blueberries with alkalinity. Mix in organic matter into a 3-foot diameter hole before planting — that should give your plants what they need to get going. In terms of mulch, wood chips or pine straw are great choices, with wheat straw being another option if that’s what’s available to you.

To feed your blueberries, an acid-loving plant food like Holly-tone is a good choice, along with mineral sources such as Azomite and ground kelp at the time of planting. Blueberries particularly like nitrogen in the form of urea, so peeing at the bases of plants can actually be a great way to fertilize. (To learn more about fertilizing with urine, visit avl.mx/c0f.)

Watering and irrigation are crucial for blueberries, as they have fairly shallow root systems. In order to thrive, blueberries need consistent moisture and cannot dry out. At the same time, their roots can easily rot, so they don’t want to sit in waterlogged or soggy soil. Regular watering, along with good drainage are keys to blueberry success. Water every other day for the first week after planting, then once or twice a week, for a total of one inch per week once plants are established.

While you can transplant blueberries any time of the year, late fall or early winter is ideal. This is because the plants will be dormant at that time, which makes them less susceptible to transplant shock. Additionally, the cool temperatures during that part of the year mean that newly planted bushes will be less likely to dry out as their root systems get established in new ground. Don’t be surprised if the bushes don’t grow much during the first year, due to shock, if they’re transplanted while fully leafed out, flowering and/or fruiting.

There are two main groups of blueberry bushes: northern highbush and rabbiteye. Here in Southern Appalachia, we can grow both kinds, though the high-bush types tend to thrive and are what most commercial growers use. This group grows to be about 4-6 feet tall and are hardy in colder temperatures, though not as tolerant of sustained high temperatures. Rabbiteye blueberries can grow to be 10-plus feet tall and are less cold tolerant and better adapted to warmer conditions and sandier, more alkaline soils (though they still thrive with some acidity). Also, rabbiteye varieties are not self-fertile, meaning they need to be planted close to other rabbiteyes that flower at the same time in order to receive pollen and make berries.

Some great varieties of northern high-bush blueberries for our area are: Hannah’s choice, Elizabeth, Chandler and aurora. These are all self-fertile, so you don’t need to plant multiple varieties to get fruit, though planting a few different varieties close to one another can improve yield. Bear Necessities Farm sells plants of these varieties and more at the downtown tailgate market on Saturday mornings and at the West Asheville Tailgate Market on Tuesday afternoons. Farmer Lewis Blake is knowledgeable about blueberries and is happy to chat about what varieties would be best for your conditions. He’s also the instructor for growing blueberries, bramble berries (blackberries, raspberries, etc.) and strawberries with the Wild Abundance Online Gardening School that I co-direct. (To learn more, visit avl.mx/bbd.)

Do keep in mind that blueberries take a few years to produce fruit. You won’t be getting baskets full of goodness right away. But once they mature, they’ll provide fruit year after year for quite some time.

I’ve seen a lot of people using black plastic in their gardens recently. Can you explain how this works and if it’s safe for a food garden?

Yes, mulching with black plastic has become a common practice over the past several years. It serves multiple purposes: to kill weeds by smothering; to prevent weeds around crops by covering and preventing light from reaching the soil surface; and even to warm up soil as part of season extension practices.

There are various different materials that folks use for these purposes, with different levels of ultraviolet stability, and therefore different levels of risk. All plastics eventually break down into microplastics and, in some cases, chemical derivatives that can be harmful, especially to our hormonal systems.

For these reasons, I use agricultural plastics judiciously. Because they’re so effective, especially at killing weeds, I definitely rely on black plastic in my garden, but I also use organic mulches when those are at hand and appropriate for the job. For me, this means using plastic to prepare beds and mulch for large areas, such as the spaces between squash or sweet potato plantings that will be impossible to weed once the vining plants take off. For my regular vegetable beds, I use thick layers of hay, straw or hardwood leaves as mulch, instead of plastic.

If you’re curious about using plastic mulch, be sure to purchase a material that has been UV stabilized and is made for agricultural use. If you simply buy plastic sheeting from a home improvement store, it will break down into a million pieces after prolonged sun exposure, creating a big mess for you to clean up.

Two good options for plastic mulch material are high-quality silage tarps made of UV-treated low-density polyethylene and woven landscape fabric/ground cloth made of UV-treated polypropylene. Tarps can be purchased through Farmer’s Friend (avl.mx/c0h) and woven material is widely available; I recommend Dewitt Sunbelt fabric.

With plastics, I’ve found that if I put them out as needed, then stow them out of the elements between uses, they stay in good shape year after year.

One important step when using plastic mulch is securing the material so it won’t blow away in the wind. Sandbags, logs, rocks or clumps of soil can be helpful here, along with landscape staples in the case of the woven material.