CROP OF THE WEEK: Vegetable transplants

• Vegetable transplanting in the Yuma area is in full swing, with cauliflower, fennel and select broccoli varieties being planted. Yuma-area vegetable growers get a jump-start on the fall vegetable season with the use of transplants. Celery, peppers, onions and watermelons are other crops that may be started in greenhouses for transplanting into fields.

• Transplants (mainly cole and watermelon crops in Yuma) are used in vegetable production for two main reasons. Earlier production from a plant that is initially grown in a greenhouse and later transplanted to the field can give the crop a head start for an early winter marketing window and, perhaps, higher prices.

• Also, transplants may be more uniform and stronger since direct-seeded cole crops in our late summer Yuma climate are subject to severe temperature extremes and periodic heavy insect pressures. Moreover, with some kinds of vegetables, it is almost impossible to establish good stands from seed sown directly in the field or garden.

• Over the years, an industry has risen to meet the increasing demand for transplants. Among the companies is Greenheart Farms, which has a production area in Yuma County. Others farmers may grow their own transplants.

• Last year, Yuma-area greenhouses produced more than 2.3 million seedlings for use by local producers and for export to production areas in the western United States.

• The most common form of producing transplants is growing the plants in plugs, which are very small cells filled with peat and/or vermiculite media. Plug trays come in sizes holding 200, 400 or 600 cells and can be automatically seeded. Less labor is required for mixing and sterilizing soil, filling flats and pulling plants. Plug transplants establish better in the field because roots are not damaged in pulling.

• Growing transplants requires skill and care. Factors such as light, temperature, humidity, watering and the physical condition and fertility level of the plant-growing media must be considered.

• Gradually, vegetable plants are “hardened” for a week or so before being transplanted into the field. Hardening prepares plants to withstand conditions such as high temperatures, drying winds and water shortages. Withholding water and nitrogen fertilizer and increasing sunlight or temperature are the best ways to harden transplants.

• Older transplanters open a furrow and plants are placed in the furrow by hand. Newer models transfer plants to the furrow by “arms” on the machine that grip the plant and drop into the furrow from a cone over the transplanting furrow. Models of “punch” planters are also available that puncture plastic mulches and set the plant into the holes.

• Commercial vegetable producers are experts in producing transplants for a growing area and time of planting. They evaluate crop type, time of year, farm ground quality and geographic region, method of transplanting, and economics of rooting size.

• Trying to do a good job in raising different crops within the same greenhouse environment can be a challenging process. Cabbage transplants require relatively cool temperatures and low fertility levels, while pepper transplants require higher temperatures and more fertility.

Source: Kurt Nolte is an agriculture agent and Yuma County Cooperative Extension director. He can be reached at knolte@cals.arizona.edu or 726-3904.