Coir seed starting mix

I just received a catalogue from Gardens Alive. They sell a Natural Beginnings Seed-Starting Mix which they state is coir based. See: Best-Selling Insect Control, Weed Control, Grass Seed|Gardens Alive!

Title: Optimization of transpiration and potential growth rates of ‘Kardinal’ rose with respect to root-zone physical properties

Authors: Raviv, Michael; Lieth, J. Heinrich; Burger, David W.; Wallach, Rony

Authors affiliation: Newe Ya’ar Research Center, Department of Ornamental Horticulture, Ministry of Agriculture, Agricultural Research Organization, Ramat Yishay, 30095, Israel.

Published in: Journal of the American Society for Horticultural Science, volumn 126, pages 638-643, (2001).

Abstract: “Physical characteristics of two media were studied concerning water availability to roots, as reflected in specific transpiration rate, stomatal conductance, and specific growth rate of very young leaflets of ‘Kardinal’ rose (RosaXhybrida L.), grafted on Rosa canina L. ‘Natal Brier’. Plants were grown in UC mix (42% composted fir bark, 33% peat, and 25% sand (by volume)) or in coconut coir. Water release curves of the media were developed and hydraulic conductivities were calculated. Irrigation pulses were actuated according to predetermined media moisture tensions. Transpiration rate of plants was measured gravimetrically using load cells. Specific transpiration rate (STR) was calculated from these data and leaf area. STR and stomatal conductance were also determined using a steady-state porometer. Specific growth rate (RSG) of young leaflets was calculated from the difference between metabolic heat rate and respiration rate, which served as an indicator for growth potential. Low STR values found at tensions between 0 and 1.5 kPa in UC mix suggest this medium has insufficient free air space for proper root activity within this range. Above 2.3 kPa, unsaturated hydraulic conductivity of UC mix was lower than that of coir, possibly lowering STR values of UC mix-grown plants. As a result of these two factors, STR of plants grown in coir was 20% to 30% higher than that of plants grown in UC mix. STR of coir-grown plants started to decline only at tensions around 4.5 kPa. Yield (number of flowers produced) by coir-grown plants was 19% higher than UC mix-grown plants. This study demonstrated the crucial role of reaching sufficient air-filled porosity in the medium shortly after irrigation. It also suggests that hydraulic conductivity is a more representative measure of water availability than tension.”


Title: Suppression of Phytophthora and Pythium damping-off of tomato by coconut coir dust

Authors: Candole, B. L.; Evans, M. R.

Authors affiliation: Dept. of Horticulture, University of Arkansas, Fayetteville, AR, 72701, USA.

Published in: Phytopathology, volumn 93 (6 Supplement), pages s13-s14, (2003).

Abstract: “Coconut coir dust, a waste product from coconut fiber processing, has been shown to be a good alternative to peat in growing media. Greenhouse experiments were conducted to determine if coconut coir dust can also suppress soilborne plant pathogens by using tomato damping-off caused by Phytophthora capsici, Phytophthora nicotianae, Pythium aphanidermatum, and Pythium ultimum as model pathosystems. Tomato seeds cv. ‘Bonnie Best’ were planted into noninfested and infested growing media contained in 5X5, 2.5-ml plastic plug trays. Growing media were infested with two-week-old cultures of the pathogens in V8 juice-peat medium at the rate of 1% (w/w). Stand counts were made when noninfested controls reached complete emergence. Populations of Phytophthora capsici, Phytophthora nicotianae, and Pythium aphanidermatum; and damping-off incidence were significantly reduced by 68-76% and 94-100% respectively in coconut coir dust compared to controls in peat. Results from Pythium ultimum were not conclusive. Autoclaving coconut coir dust had no effect on suppressiveness indicating that the nature of the suppressiveness is not biological.”


Title: Growth and nutrient use of ericaceous plants grown in media amended with sphagnum moss peat or coir dust.

Author: Scagel, Carolyn F.

Author affiliation: Horticultural Crops Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 3420 NW Orchard Avenue, Corvallis, OR, 97330, USA.

Published in: Hortscience, volumn 38, pages 46-54, (2003).

Abstract: “Using several different ericaceous ornamental species, we compared the growth, mineral nutrition, and composition of plants in response to growing media amended with varying proportions of sphagnum moss peat (peat) or coir dust (coir). Plants were grown for 16 weeks in media consisting of 80% composted Douglas fir bark with 20% peat, 20% coir, or 10% peat and 10% coir. Sixteen weeks after planting, decreases in extractable P were larger in peat-amended medium than the coir-amended medium, while decreases in extractable NH4-N and NO3-N were larger in the coir-amended medium. In general, leaf and stem dry weight, the number of leaves and stems, and total stem length increased with increasing proportion of coir in the medium while root dry weight either increased (Kalmia latifolia), decreased (Rhododendron, Gaultheria), or was not influenced by increasing the proportion of coir in the medium. The composition of the growing medium also influenced aspects of plant marketability and quality including: leaf greenness (SPAD), plant form (e.g., number of leaves per length of stem), and partitioning of biomass (e.g., root to shoot ratio). Nutrient uptake and fertilizer use was significantly different between the media types. Depending on the cultivar, we found that the coir-amended medium resulted in higher uptake or availability of several nutrients than peat-amended medium. Uptake or availability of N, P, K, Ca, and S was enhanced for several cultivars, while uptake or availability of Mg, Fe, and B was similar between media types. Most cultivars/species growing in the coir-amended medium had higher production or accumulation of proteins and amino acids in stems than plants growing in peat-amended medium, while the production of proteins and amino acids in roots was lower in plants growing in coir-amended than in peat-amended medium. For the cultivars/species we tested, coir is a suitable media amendment for growing ericaceous plants and may have beneficial effects on plant quality.”


I picked up a few bricks of coir last weekend for experimentation. I am especially intrigued by it’s resistance to decay. We have a tremendous amount of bacterial and fungal breakdown in most organic soil amendments here in the Palm Springs area resulting in dramatic soil subsidence using most commercial potting soils.

So far I’m quite pleased but will only be using it in pots till I find a less expensive source.

Coir is also a renewable resource unlike peat which takes so long to form and can be purchased in several different grades so as to be adaptable to different uses. Thanks, Robert

Thanks for the heads up Henry. There’s a large greenhouse grower that organizes a barge of it into the Twin Cities each year and other greenhouses get some of it too. You inspired me to see if I can buy some from one of these growers.


We have been using coconut fiber for some time. It works great! We like the moisture retention factor - can hold 9 times its weight in water plus it has a pH of about 6.3. We buy 3 cu ft compressed bags at a large nursery/greenhouse supplier for about $15 a bag. We favor it over peat as it doesn’t form a crust on the surface which makes for difficult watering.

I bought some Lignocell bricks from The price was reasonable, and the delivery was prompt.

In the U of FL report linked below, the ratio of water to brick is suggested as 2 gallons per brick. My experience is that one gallon of water is just right for 2 bricks, leaving the coir at just about the right moistness. Apparently whoever typed the report misread the experimenter’s notes, exactly reversing the ratios. Or else the water in Florida doesn’t work as well as our water in West Virginia.

Since I don’t have a shredder, breaking apart the moistened brick and fluffing up the coir does take a bit of hand work, but for small quantities that is not a problem for me. Good exercise, no?


I’ve been using it as a medium for stratifying seeds. I find it very easy to remoisten & the little rootlets are easy to see when checking the bags. I’m still getting germinations from seeds from 2001.

I bought a bag for $3.99 of “Aqua-Coir” at my K-mart store and it is indeed the right stuff and not in a brick form so it was easy to just put in the flats and water. It seems to hold moisture extremely well and I have seen no signs of fungus. The texture and consistency make it very easy to work with with tender babies.