Does vitamin B1 help transplants take root?

Sunset, May, 1992 by Lauren Bonar Swezey

Not really. But the right fertilizer can make a big difference

FOR MORE THAN 50 years, vitamin B1 (thiamine hydrochloride) has been touted as a cure-all for transplant shock. Labels typically claim that B1 aids rooting and growth of a wide range of plants.

But University of California research on vegetables failed to prove that B1 reduces transplant shock or stimulates root development. Researchers found "no discernible differences in color or vigor among treatments" when B1 and B1 plus iron, manganese, and zinc were used on peppers, pole beans, squash, sweet corn, tomatoes, and watermelons. Elsewhere, studies on chrysanthemums, citrus, and

roses have reached similar conclusions.

At Sunset, we decided to run our own tests on the effects of various B1 formulations on plant growth when compared with fertilizers.

We tested four formulations containing B1: B1 alone; B1 plus iron, zinc, and manganese; B1 plus iron and phosphorus (0-2-0); and B1 plus 3-10-3 fertilizer. For comparison, we included a 10-10-5 fertilizer and a control plant given no treatment.

We used marigolds, because they're fast growers and differences in growth show up quickly. We ran tests in spring and summer.

We began by transplanting marigolds from sixpacks into 5-gallon pots filled with potting soil, using five plants per pot. For each test, we used 48 pots--8 pots per treatment. We applied the products according to label directions and monitored growth until plants filled in.

Some labels suggested just one application; others recommended a dose with every watering until plants became established. For liquid fertilizer, we followed recommended application of every three weeks (to avoid fertilizer burn, the liquid 10-10-5 was first applied three weeks after transplanting).

FERTILIZER IS KEY

Two weeks after planting, all the marigolds were established and had new leaves (except plants given B1 alone, which lagged behind the rest, particularly in our first test).

Four weeks after planting, marigolds receiving 10-10-5 or B1 plus 3-10-3 began to flower. Flower buds on the remaining plants opened a week to two weeks later.

At the end of the test, six weeks after planting, marigolds treated with 10-10-5 or 3-10-3 were much bushier and darker green, and had more open flowers (see photograph) than the others.

When we repeated the test in summer, results were similar. In both cases, marigolds treated with products containing nitrogen were fuller and healthier, and bloomed earlier than plants that didn't receive nitrogen. The control did as well as or better than the B1 treatments without nitrogen.

Our tests underline the benefits of fertilizer, whether or not it's in a product containing B1. For best growth and development, apply a dry or controlled-release fertilizer at planting time or use a liquid fertilizer shortly after transplanting, following label directions for new plantings.