St Johnswort Agronomic Data
Answered by: Conrad Richter
Question from: Robert Waters
Posted on: May 22, 1998

I have been trying to get definitive answers on growing SJW in Montana on the 2500 acre farm for quite a while--little success. Can you help with the following?

A. What is the approx. DRY WEIGHT yield per acre on dry land (13" per year annual rain-approx.)?

St Johnswort will produce as much as 2500 kilograms of dry herb per hectare of land. That is about a ton per acre, dry weight. You must be careful not to put too much stock in such data though, because results could vary enormously depending on local conditions. The one ton per acre figure is based on European experience. It is too early to tell what North American farmers are getting.

B. Can I use a double disk seeder or grass seeder to plant the SJW?

If you sow directly, yes, you could use such a seeder. However, direct sowing is not necessarily the best way to go. Much depends on what weed control strategy you adopt and whether you intend to grow organically or not. Organic growers are using weed barriers or drip irrigation of target plants to suppress weeds (in dry areas). These require plug transplanting regularly spaced out. Broadcasting or even row seeding is not viable for organic growers.

C. When is the best time to plant--Is the fall OK? Amd let it winter under the snow?

You can sow anytime from early spring to late summer, provided that there is adequate rainfall or irrigation. If you choose to sow in plugs, you can start earlier in a greenhouse.

D. Seeding rate appears to be about a pound per acre? Correct?

Direct sow at 400 to 800 grams per hectare, which is roughly a half pound to a pound to an acre. For plug transplants you need less seed for the same area, about 100 to 200 grams per hectare.

E. Is organically grown the only market or is a reduced market around for non-organically grown SJW? How much per pound either way?

The market right now is vigorous for either form. Recent experience suggests that buyers are desparate for anything, as long as the hypericin content is high.

Market prices are difficult to comment on because much depends on the quantity involved and the quality. For example, brokers are paying (spring 1998) US$8/kg to US$10/kg for good quality herb with hypericin in the 0.5% (by weight) range for container-sized lots. But if the hypericin content is below 0.1%, buyers are paying only US$3/kg to US$4/kg.

F. What is the estimate of price coming down in the next two years?

There is no doubt that the price will drop but by how much is anybody’s guess. I would think that a 30-50% drop is possible over the long term. This drop does not necessarily mean profits will disappear because growers will become more efficient. Already, some growers are experimenting with special techniques to reduce weed pressure and speed growth.

G. How long before the estimated 1-2 tons per acre yields will be established?

You should get good yields in the second or third year.

H. What diseases attack SJW?

According to Westcott’s "Plant Disease Handbook" (second edition, Van Nostrand, 1960), Hypericum species are susceptible to:

Black knot (Gibberidea helopsides), leaf spot (Cercospora hyperici, Cladosporium gloeosporioides), root knot nematode (Meloidogyne spp.), powdery mildew (Erysiphe ichoracearum), rust (Melampsora hypericorum, Uromyces triquetrus). So far none of these appear to present significant problems.

Growers in Ontario have noted that St. Johnswort is susceptible to a unidentified crown rot that develops when grown in plastic mulching for weed control. The problem was serious enough to force abandonment of some crops. There is no information yet on how to control this problem other than by changing cultural methods.

I. When times of year can I plant SJW? Spring, fall, summer? All of the above?

See answer to question A.

J. Our soil pH is 7.8 and clay loam.

St Johnswort will grow in a wide variety of soils and moisture regimes, but well-drained, dry soils appear to be optimum.

K. The farm is located 60 miles south of Montana Glacier National Park on the east side of the Rockies.

L. Growing season is from about April 17th to September 15th.

M. Current crops are wheat, barley, oats, and rye. Some years alfalfa and clover are grown in the area.

N. Can we harvest the SJW by swather and dry indoors on racks?

Yes, although you may need low heat and ventilation depending on the relative humidity in the drying shed.

I have been reluctant to seed SJW until these questions are answered. A ten acre test plot is probable with another 20 acres soon--IF--it looks profitable at all!

If the cost associated with a ten acre test plot is not too onerous, then, fine, go ahead. If you are depending on selling the first crop then you may be exposing yourself to unacceptible risks. Consider that the hypericin content has a profound effect on the price and you don’t know what hypericin levels you will get. Stated hypericin levels in some strains of St Johnswort are not guaranteed; they are only an indication that higher levels are possible with the right conditions. In your case, you may get a very different result even if you are using the same seeds as another farmer in Europe or elsewhere.

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