Growers sometimes ask me: Is your peat or mix sterile? Why don’t you stertilize it?

These inquiries come up especially when growers see molds, nematodes, bugs or hear of E. coli or Salomnella, etc. Sometimes growers go ahead and sterilize the mix themselves.

Sterilization is generally a big mistake. Peat or mix usually have some microorganisms. Sterilization kills ALL the microbes and now you have a huge vacuum in the mix. Imagine the first organism to enter this sterilized mix is a plant pathogen like Pythium or Phytophthora. The pathogen will have exploding growth in the mix without any competition there. Like many things in life, some competition within the mix is better.

That’s why we don’t sterilize peat or mix nor do I advocate sterilization by growers. And sterilization costs lot of money. So I tell growers to save those dollars.

Here is a technical quip to help you feel smug at those open house cocktail parties.

If you hear of any plant growing problem, say: ‘I bet it is pH.’ Odds favor you, as in university and industry circles, the general consensus is that 3 out of 4 growing problems are pH related.

Maintaining a proper growing medium pH is important in achieving a high quality crop and has received a tremendous amount of attention in the horticultural press. Much of the information suggests maintaining a narrow growing medium pH range. Consequently, we often receive requests from customers requiring or “guaranteeing” growing media with a narrow pH range or specific pH when it arrives at their greenhouse/ production facilities. Acceptance or rejection of a shipment is often contingent on meeting this guaranteed pH or narrow pH range.

The use of limestone is the principle means of adjusting initial medium pH. While initial medium pH is an important aspect for the addition of lime there are also other important aspects for the addition of lime. All these factors are considered in the development of the lime source and rate used. It is very important that we help our customers understand the many purposes of adding limestone to potting media.

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Figure 1: Calibrachoa in high pH mix (photo courtesy of Dr. Paul Fisher, University of New Hampshire)

Current research on pH in search of a ‘bloody’ mix

Growing media pH is a perennial subject of interest in our industry. One reason is that unlike mineral soils where plants grow naturally, peat mixes are not well buffered against pH changes. Another reason is that, again, unlike in natural conditions where plants can grow more roots in favorable pH zones, the limited volume of mix in containers exacerbates pH effects. Drastic pH changes upset plant quality (see an example in figure 1).

Though grower’s water, the fertilizer regime the grower is practicing and even the plant species being grown also affect pH, the growing medium is the first thing questioned when pH problems occur, because pH changes occur right in the medium.

Here, I present the latest research in the area of growing media pH. The information may fulfill your curiosity, your practical needs or just give you talking points about how industry is striving to manage materials to produce a better growing media.

Truck-wide variation
Peat is acidic and lime is added to neutralize some of that acidity and raise its pH. However, even when the same amount of lime is added to the same amount of peat every time, the resulting mix pH is not the same every time. The pH variation can be, as the famous remark goes— wide enough for the truck carrying the mix to go thro— from 5.0 to 7.0. Remember that pH scale is logarithmic: a pH of 5 is 10 times more acidic than pH of 6 and 100 times more acidic than 7. Therefore, the variation is wide. If your blood pH varies by just 0.2, problems occur in your body. Don’t worry, your body is so efficient, its buffer system kicks in and brings blood pH back to the original value in less than a minute. Don’t you wish your mix maintained pH like blood in your body? To build such a buffer system into a mix, first we should know what causes pH variation in mixes. So, we wanted to explore this further in a quantitative manner.

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TRADING SYMBOL: Toronto Stock Exchange – GRO.UN

VANCOUVER, BC, June 3, 2005/ –
Sun Gro Horticulture Income Fund today announced that its wholly owned subsidiaries, Sun Gro Horticulture Distribution Inc. and Sun Gro Horticulture Canada Ltd. (Sun Gro), have signed agreements to become the US and Canadian Greenhouse and Nursery Master Distributor of Haifa Chemicals’ (Haifa) Multicote product line.

Effective May 20, 2005, the pending agreement provides for Sun Gro to begin taking orders on both existing Multicote formulations and those that were developed by Sun Gro in cooperation with Haifa. Haifa will manufacture these formulations per Sun Gro’s specifications at their state-of the art production facility in Haifa Bay, Israel. The formulations include those for the greenhouse industry and for use in outdoor container production. Within the container production formulations, both flowering and nonflowering plant material formulations will be available. The formulations are available in a selection of longevities that will make the product suitable for use in production throughout North America.

“The addition of the Multicote product line is directly in line with our strategic focus on the professional grower market,” said Mitch Weaver, President and CEO of Sun Gro and a Trustee of the Fund. “The addition of this quality brand to our product offerings will strengthen our position in the fertilizer segment of the professional market, expand our sales into the container nursery industry and further solidify our relationship with our key distributors.”

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