By Dr. Larry Stein
Have you ever wandered down the produce section of your favorite supermarket and thought about all the work that went into the production of those awesome fruit on display? I know the answer is no, because in this day and age one rarely has a spare moment, especially in a grocery store when you are trying to keep your kids in line!
Still, today I want to take you through the commercial production cycle of one such fruit, the strawberry, so you have a better idea of the challenges a farmer faces to make strawberries available to you for year-round fresh consumption. Prior to this discussion, some background information about the plant is helpful in understanding this process.
The strawberry, a small, evergreen plant of the rose family, has three main parts, namely the roots, crown and leaves. Approximately 90 percent of the root system is in the top 6 inches of the soil. Hence, water management is critical for best production. The crown is located at the soil line and is made up of woody stem tissue. It is the site of leaf and fruit bud initiation, plant support and storage of food reserves. A strong, thick crown is necessary for good leaf and fruit production as well as plant survival during stressful periods. The leaves of course are the food-making sites. Without the leaves, no fruit, no sugar, nothing! Ideally the leaves will produce two or three times their own weight in berries.
The fruit grows close to the ground on stems in groups of three. Strawberries are not really berries or fruit, but rather the enlarged ends of the plant’s stamens. The strawberry has seeds on the outside skin rather than having an outer skin around the seed. Typically they do not reproduce by seeds, but rather from runners. The green to white fruit turn to a rich red color at maturity. When the strawberry ripens, the petals of the flower fall off and all that remains is the green stem or calyx.
Although the strawberry is not very exacting in its soil requirements, it will NOT tolerate poorly drained, water-logged soils. It does prefer slightly acid soils but good crops have been produced on soils with pH units as high as 7.5 to 7.8. Plants growing on soils with a pH above this will require some type of iron supplement, hence these soils are usually avoided.
These, along with root diseases and nematodes are the main challenges for the commercial growera plant with a shallow, fibrous root system which cannot tolerate wet feet. To combat these problems, the commercial grower must fumigate the soil. To date the product of choice has been methyl bromide. However, as everyone knows this product is being phased out and scientists are searching for an able replacement. To date few products have been as good, but the search continues. One might think that growers could simply leave fumigation out of the management program, but production on fumigated soils is twice that of non-fumigated soils. One potential alternative for the home gardener is solarization which we will discuss in more detail later.
Once the soil is fumigated, raised beds are built and covered with a black polyethylene mulch. The mulch assists with water conservation and weed control and also warms the soil. Of course this last characteristic can be a challenge at planting but it is most beneficial in early winter. The mulch also serves to keep the berries off the ground, which reduces fruit rots and makes the berries cleaner at harvest. In addition a drip tape is placed in each bed to ensure adequate control of moisture and prevent undue stress.
Typically such fields are also equipped with overhead sprinkler irrigation to guard against early spring freezes. It should come as no surprise then that commercial strawberry culture is quite an investment.
Of course not only are the investments high per acre, but the labor costs are off the chart as every berry which ends up in your pint-size container has to be individually picked.
To make matters worse, strawberries are actually perennial plants and can be categorized into two types: spring bearing, and everbearing or day neutral. The spring-bearing types include most of the top quality and productive varieties for Texas. They usually ripen over a one-month span in early springlate February in the south to mid June in the north. The performance of the everbearing and day-neutral berries is about the same even though they are technically different. They both begin to ripen in the spring and continue to ripen into the cooler parts of summer and fall. Unfortunately, ever-bearers and day neutrals were developed for cooler climates and both perform poorly in our horrible heat. As a result, commercial growers stick with an annual (where new plants are set out each year) production system as opposed to a perennial system, where the plants are left in place and multiply, year after year. The annual system is the most ideal for the home gardener as well.
Advantages of the annual system over a perennial matted-row system include: earlier fruit maturity, longer picking season, and cleaner, more disease-free berries as a result of the plastic, which cannot be used in a perennial system. In addition, the need for weed control and irrigation during the growing season is eliminated, since the plants are not carried over.
The annual system will not only work in the south, but with a little effort will pay off in the north as well. Dormant plants (those dug from October to December of the previous year and stored at 28 degrees until planting) are set by late September in Central and East Texas and late November in extreme South Texas. Planting depth is critical as plants set too deep or shallow are both prone to dying off. The plants are then grown through the winter, set fruit in the spring, and then tilled under. Typically a double row of plants is planted on 40-inch beds. The two rows on top of the bed are 12 inches apart and the plants are 12 inches apart in the row. The plants will require daily watering for two weeks after planting to ensure their survival in the fall heat.
The greatest challenge for the home gardener for fall planting is the availability of good varieties. As everyone knows, there are hundreds of varieties out there, but only a few perform admirably for the home gardenernamely Chandler, Sequoia and Douglas.
Chandler, the leading strawberry variety sold in supermarkets, is the best variety to plant in South and Central Texas. Unfortunately, Chandler is not always readily available in local nurseries. Sequoia, an older variety with good quality berries for gardening, is the most commonly sold variety in local nurseries and Sequoia will suffice if you cannot get Chandler. Douglas is another good variety for fall planting. Actually, many other spring-bearing strawberry varieties will also work satisfactorily for the garden, following the fall-planting system.
The main thing to avoid is everbearing or day-neutral varieties. It is not that everbearers cannot be planted in the fall, but they are at best mediocre bearers under our spring and summer heat and as such are not recommended for planting any time.
In summary, all the steps that a commercial grower takes would be ideal for the home gardener. However since this is not always possible, one would attempt as many steps as feasible for one’s garden situation. The most critical points are:
1. Strawberries do best on a raised bed of sandy or sandy loam soil that is neutral to slightly acid. If your soil is heavy clay or caliche, build a bed above this with good topsoil or grow the strawberries in containers filled with potting soil. Most gardeners would be better off to plant in containers or build a raised bed so they do not have to deal with the headaches of poor soil. Also the planting will be smaller and thus easier to provide care.
2. Mix fertilizer in the soil prior to planting. About 2 cups of a 3-1-2 ratio fertilizer (such as 15-5-10) per every 25 feet of row will get the plants off to a good start. Then apply a low rate of nitrogen fertilizer every three weeks after the plants are actively growing. Use ¾ cup of 21-0-0 per 25 feet of row.
3. A black plastic cover over the bed prior to planting offers several advantages including warmer soil for more winter growth, weed control, moisture conservation and protection of the berries from soil contact. The bed can be covered in early summer. The buildup of summer heat in the soil will effectively kill many disease organisms and weeds prior to planting. This technique is known as soil solarization.
4. Water daily for the first two weeks after planting if the weather is hot and dry. Water infrequently as needed during the winter.
5. Provide winter protection from severe winter freezes. This may be accomplished with organic mulches such as hay or commercial grow covers. Grow fabricsthin woven materials that are available from garden centersmake good plant coverings. Grow fabric can be laid over the plants to provide freeze protection for the plants and then be removed when the temperature warms again. Protection must be provided when the temperatures drop into the teens.
Fall planting of strawberries works well throughout Texas. Colder winters will reduce plant growth and subsequent berry production, but with good care, a good spring crop can be harvested in most years.