Feb 18, 2014

Different forms of seed

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Native Seeds sells a range different grass types, but there are different ways that the seed is prepared for sale.

Seed is sold as:

• clean seed
• floretted seed
• pelletised seed
• seeds and awns (kangaroo grass)
• seed in thatch form
• summary.

The method used is usually the result of the different characteristics of the seed.

Australian native grass seeds have notbeen modified by years of selective breeding and usually come wrapped in fluffy appendages or with long awns or with awns that make them form asmall ball like steel wool.

So what are the advantages and limitations of these various seed forms?

Clean-SeedCleaned seeds

These are seeds that have been cleaned of their appendages to expose the caryopsis, or kernel of the seed. These seeds are easy to sow through conventional equipment as they flow easily and can be sown to the desired depth.

The disadvantage of using cleaned seed is that it is not able to bury itself, relies on human activity for dispersal and needs to be sown into the soil under controlled conditions. Sometimes these seeds will germinate faster than floretted seed, but this only occurs when conditions are ideal – the soil is well cultivated, the temperature is correct and there is a regular and constant moisture level.

Native Seeds sometimes prepares seed in the cleaned form for use by specific clients such as turf farms where conditions are guaranteed to be ideal, otherwise we usually recommend sowing seed in the floretted form or the pelletised form.

Floret-seedFloretted seed

This means seed that is still enclosed in its various appendages such as fluffy lemmas or glumes or even twisted awns. For some seeds such as wallaby grass, this means that it is very hairy and wide; for others such as spear grass it means long awns that twist and interlock; while for others like weeping grass this means interlocking awns. All of these appendages make these seeds impossible to sow through conventional equipment.

They do offer advantages for establishment in some conditions. Often the appendages help to disperse the seed, often they help to help bury the seed in the ground and in many cases the appendages help to hold moisture around the seeds which aids germination.

  Pelletised-seedPelletised Seed

Recent technological advances have seen the development of pelletising processes that wrap the entire floretted seed in a coating. This has dramatically improved the ability of the seed to be sown by conventional equipment as the seed, once pelletised, is able to flow freely. It also offers other potential advantages through the capacity to include other ingredients into the pelletising material. It is possible to add in some plant protection factors such as a fungicide for protection against seedling diseases, an insecticide for control of sucking pests in the early plant stages and even beneficial fungi to help to promote plant growth on difficult or sterile soils. It may even be possible to add small amounts of specific plant nutrients on soils that are known to be limited by the availability of the ingredient.

Seed pelletizing does add weight to each seed and hence there are fewer seeds per kilogram. But there are many compensating advantages through higher rates of seedling establishment. However, the sowing rate usually needs to be doubled for pelletised seed.

Native Seeds is continuing to investigate the use of seed pelletising for our native grasses and will incorporate new technologies once they have been proven to be advantageous to seedling establishment.

Kangaroo-seeds-lawnsSeeds and Awns

This form applies mainly to Kangaroo grass as it is a particularly difficult grass to clean down to cleanseed. We have been spending considerable time on our efforts to develop a successful cleaning method, developing new machinery in the process. At this stage, all our top end Kangaroo grass product is sold in this form. It consist of seed and awns with a small amount of mulched straw. It is easy to sow, as the seed will flow through commercial seeding equipment.

Kangaroo-floret Thatch form

 Kangaroo grass has been sold in the thatch form for some years and occasionally Native Seeds keeps a smallpart of its crop for cutting and sale in the thatch form. To produce thatched seed, the entire stem of the kangaroo grass plant is cut about 150mm (6 inches) off the ground and gathered together. Sometimes these stems are simply laid flat on the areas to be sown; while at other times they are stacked and stored prior to dispersal.

Kangaroo-clean The advantages of this process are that seed is not lost through the harvesting process and that there is an amount of mulch material available for protection of the prepared ground. There is also a potential gain from ongoing maturation of some partially ripe seeds while in the thatch, though this is somewhat unreliable.

The disadvantages are that the amount of seed included cannot be precisely known, the viability of the seed cannot be tested, the rate of spread of the seed cannot be controlledand the evenness of sowing is very poor.

Summary

Clients should contact Native Seeds to see what seed form is the most appropriate for the application.

Provenance

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When revegetation projects are undertaken, there is occasionally a demand for seed of local provenance, that is seed which has been gathered from the local area where revegetation is to occur. This is because the local trees and shrubs have adapted well to that environment and local material of these plants usually does perform better. Many people assume that the same rule will apply to grasses.

While local provenance is relevant for trees and shrubs, it is not relevant for revegetation using native grasses because of the way grasses reproduce. It is often assumed that cross pollination is the normal fertilisation for all plants, but this is not so for native grasses. While there is considerable variety in the way Australian native grasses flower and produce seed, all the grasses studied to date produce the majority of their seed by some form of self-pollination and not by cross pollination. Many grasses including Wallaby grass and Weeping grass are self fertilising and spikelets are fertilised before they emerge from the leaf sheath. Some grasses are able to produce fertile seed asexually. The grasses don’t display inbreeding characteristics because they have more than two basic sets of chromosomes. Kangaroo grass, for example, has from two to six sets of chromosomes and Weeping grass has four sets of chromosomes. Other grasses such as Redgrass and Bluegrass species have some flower spikelets with two sets of chromosomes, while others on the same plant may have many sets of chromosomes.

Thus there is genetic diversity within each plant rather than within different individuals within a population. So there can be distinct genetic variations within one species in the same paddock. It then becomes impossible to determine what is local.

Furthermore, distance is not a factor in determining genetic diversity for native grasses. Studies have shown that different types of Wallaby grass, Rytidosperma caespitosum, can be found with different characteristics within one to two kilometres. We know that in other areas variation is far less and the same type can extend to several hundred kilometres. Both wild species and bred cultivars of native grasses will grow well outside their normal range thus displaying broad scale adaptation.

Often too, there is a fear that by introducing new genotypes of species into an area that the local population of plants will be contaminated. As the native grasses are self fertilising, out-crossing is likely to be very infrequent with a minimal risk of contamination of other plants.

Long term studies over many years of native grasslands, have shown there are quite rapid changes in the dominant species in the grassland community. Thus the grasslands themselves are constantly changing in response to climate and other environmental factors. The introduction of native grass seeds from commercially available sources should improve genetic diversity and there should be no concerns about unwanted contamination of species through outcrossing as the grasses are self fertilising.

See Presentation by Dr. Wal Whalley

New Review article on Seed Supply for Restoration :Florabank article:

Sowing Notes: Summer lawn mix

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Sowing Notes: Summer lawn mix

– a blend of Wallaby Grass, Griffin Weeping Grass and Redgrass

A lawn made of a mixture of Weeping grass, Wallaby grass and Redgrass is fine textured, yet more hardy and drought tolerant than Griffin or Wallaby grass on its own.

Wallaby and Griffin Weeping grass are cool season perennial grasses while Redgrass is a summer growing perennial. All the grasses will grow on clay loam to light sandy soils. This grass blend has above average tolerance to high temperatures and will grow very successfully in shading situations. Griffin Weeping grass may brown off during summer, but greens up when moisture is available. Wallaby grass will usually stay green and the Redgrass will actively grow during the summer months.

During the cooler months, the Griffin and Wallaby grass will actively grow and the Redgrass will go dormant, taking on a slight reddish tinge in colour.

Sowing:

Native grasses do not like competition from weeds as they have relatively slow growth rates, so ensure the soil is well prepared and weed free prior to sowing.

Sow the seeds in spring or early autumn when the soil is moist for best results. The Redgrass will only germinate once air temperatures are above 25˚C. Sow the seed by distributing it evenly over the soil surface then lightly rake over to ensure that all seed is in good contact with the soil.

Keep the seed moist until the seedlings are established, but do not flood or waterlog the soil.

Germination should take place within 10 – 14 days for the Griffin Weeping grass, within 14 – 21 days for the Wallaby grass and approx. 7 – 10 days for the Redgrass.

Please be patient.

Wallaby grass seedlings are very small and fine when they emerge.

Weeping grass seedlings are wider and flatter than Wallaby grass.

At the early stages of establishment, keep broad leaved weeds under control by hand weeding.

Maintenance:

Allow the seedlings to thicken up before mowing.

Keep the mowing height above 40mm.

The lawn should only need infrequent mowing, possibly only 6 times per year.

A general lawn fertilizer can be applied at 3 months and then only occasionally, if at all.