Vegetable Seed Production: Beet

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Common Name: Beet Scientific Name: Beta vulgaris (Crassa group) Family: Chenopodiaceae

In addition to reading the information in this section, please view this narrated video on Beet seed production (The video will open in a new window.)

Botany

Most plants in the Chenopodiaceae family have small single flowers and plants are bisexual or unisexual, sometimes dioecious. In some cases two or more flowers grow together in a dense cluster and form a multiple fruit called a utricle that contains multiple embryos. With beets, the calyx continues to grow after flowering, becomes corky and completely covers the seeds. The utricle is the propagule planted to grow beets and chard.

Soil Nutrition

Beets are only slightly tolerant of acid soils and grow best at pH 6.0-6.8. Beets need high levels of most trace elements in the soil to grow and develop normally. Beets are sensitive to boron deficiencies which leads to cavity spot (black necrotic lesions on the roots). Beets have a moderate requirement for N-P-K. Beet are tolerant of saline soil conditions and are considered to be a halophyte.

Isolation

It is generally accepted that pollen of Beta vulgaris is wind-borne over relatively long distances and sufficient isolation should therefore be ensured. Most authorities stipulate isolation distances of at least 500 m between cultivars of the same type (e.g. red globe) and at least 1000 m between different types of cultivar (e.g. between red globe and cylindrical types).

Beetroot is cross-compatible with the other subspecies of Beta vulgaris (i.e. sugar beet, mangolds, spinach beet and Swiss chard) and adequate isolation of different seed crops has to be ensured. This is usually accomplished by a zoning scheme. In the UK scheme, the stipulated minimum isolation distance between the different types of Beta vulgaris is 1 km, although the recommended distance in some states of the USA is at least three times this.

When seed of high genetical quality is required or pollen contamination is suspected, the discard strip technique can be used. Although this technique was developed for sugar beet seed production, the same principles apply with other wind—pollinated Beta vulgaris types.

Planting

Beets are direct seeded 1/2 inch deep in rows 15 to 20 inches apart with a final in-row spacing of 3 inches. Direct-seeded plots are generally thinned if monogerm cultivars are not used. Beets germinate at soil temperatures above 40 degrees F but optimum germination occurs at 85 degrees F.

Irrigation

Beets have a shallow root system so they must receive a consistent supply of water to keep the roots from becoming woody. On mineral soils, overhead irrigation is used. The requirement of one inch per week applies.

Roguing

The roguing of plants for beetroot seed production is considerably more thorough when the root to seed system is used. The seed to seed system does not allow the mature root characters to be observed.

Seed to seed
The main roguing is done at lifting and re-planting, although plants which bolt prematurely can be removed before lifting.
1. Lifting
Discard plants showing any of the following: incorrect leaf shape and color, premature bolting, incorrect root shape, seed—borne pathogens.
2. Re-planting
Characters as described above.

Root to seed

1. Before cutting tops for lifting
Remove plants showing any of the following: incorrect leaf color and morphology, early bolters and seed-borne pathogens.
2. Lifted roots
Discard roots which are not true to type. Shape, size, crown and surface corkiness should be taken into consideration.
3. Re-planting
If roguing has been done in accordance with stage 2 described above, no further roguing is required, although roots showing storage diseases should be discarded.
4. Bolting plants (before ‘topping’)
Remove plants showing incorrect leaf shape, leaf color, vigor and seed-borne pathogens.

Seed Harvest

The harvesting of beet seed commences when the ‘fruits’ at the bases of inflorescent side shoots mature. By this stage the fruits have turned from green to brown. An additional check is to cut transversely a sample of ripe fruits. Unripe fruits are milky when cut and ripe fruits are mealy. Seeds ripen successively from the bases of the side shoots to the terminal point. Care is needed to determine the optimum time for cutting because the immature seeds shrivel if cut too early, and if cut too late seeds are lost as a result of shattering.

Ripening beetroot stems tend to be prostrate rather than vertical. The method of cutting depends on the scale of operation. Large-scale producers in the USA use a swather, but for small-scale production, basic seed or larger scale production with relatively low hand labor costs, the crop is cut with knives or hooks.

The cut stalks are left in windrows to dry and carefully turned once or twice. In areas where autumn rain is a problem the cut stalks are tied in bundles and dried on ‘four poles’ placed in shocks (stooks) or alternatively open sheds. Large heaps of cut material are placed on tarpaulins, or polythene sheets, to avoid loss of seed from shattering. The cut material can take from three to fourteen days to dry according to the air temperature and rainfall.

Cleaning

After drying, the material is threshed by a stationary thresher or a combine. The dry straw of beetroot seed is extremely brittle, and it is therefore important to use a relatively low cylinder speed and air blast. Concave openings must be wide in order to avoid producing too many small pieces of straw as it is difficult to separate these off afterwards. There is relatively little chaff from beetroot material.
The final separation of beetroot ‘seeds’ from the small pieces of plant debris is done on a gravity separator.

Seed Yield

A satisfactory yield of beetroot seed in most areas of the world is approximately 1000 kg/ha (892 pounds per acre), although up to twice this amount is achieved in the USA.

Seed Identification: