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Saturday, July 05, 2008 • 05:54 am

July 7, 2004
Food glorious food
By René Trim

• Plant of the week
• Transplanting in Summer
• Green myths: the “blue” Hydrangea

July is upon us, signaling the time to have a good look at our gardens, make notes of the weak spots (and do something about them in the fall), and feed our plants.

Many a gardener will do everything that is required in spring and then forget about the garden for the rest of the season (with the possible exception of watering and staking). Unfortunately, this is not sufficient. You will need to feed your plants regularly, both the ones in the soil and the ones in pots – especially the ones in pots.

One dose of fertilizer in spring is not sufficient to last them a full season. Even the highest quality potting soil only contains enough food for roughly 6 weeks, so ensure that you add some fertilizer to your watering can roughly every 4 to 6 weeks (or add slow-release pellets to the soil). The right quantity depends on the kind of fertilizer you use, but the instructions on the packaging material should tell you when and how much fertilizer is required.

For plants that are grown in soil, a little more effort is necessary. As mentioned in this column previously, before spending any money on plants it is crucial to find out if those plants will thrive in your garden’s soil. The best way to discover your garden’s soil makeup is to perform a soil test - to determine the pH value and the level of nutrients. In doing so, you will know what kind of fertilizer to add, if any at all (too much of a good thing CAN be harmful). Soil test kits are available for a modest price in garden centers and stores (like “Lee Valley”, for example) and are definitely well worth the investment.

The pH level of your soil (measure of acidity or alkalinity) determines how well the plants are able to use its nutrients. Although garden soil may contain all the appropriate nutrients, an inhospitable pH level can render it impossible for the plants to actually utilize them. Certain plants (i.e. Rhododendrons) prefer an acid soil, whereas others (i.e. Roses) thrive in alkaline soil. An attempt to grow Roses in an acid soil is destined for failure, and even though it is possible to change the pH level of your soil (by adding peat or rusty mails), it is an unending process that not many gardeners maintain in practice.

The nutrients that we test for are Nitrogen (N), Phosphorus (P) and Potassium (K). Each element performs a different function in the growth of plants. The three-number code notated on the wrapping material of fertilizer indicates the levels of these essential nutrients. The proper level of Nitrogen promotes healthy foliage, so green vegetables like lettuce (as well as your lawn) have high Nitrogen requirements. Phosphorus is important for strong root structure and development, while Potassium is responsible for seed production and germination, as well as for sugar formation in fruits and vegetables. "Healthy soil" contains appropriate concentrations of these components. Once we have determined how rich or poor the soil is, we can start digging in organic matter (such as compost) as needed, to improve its structure and determine if fertilizer is necessary. But....what kind of fertilizer do we add?

First, we have to ask ourselves whether to use a chemical fertilizer or an organic one. Both types do the same job, but in an entirely different manner. With “old-fashioned” chemical fertilizers, the dose of each individual element is much higher than the dose found in organic ones, so by adding a chemical compound you are actually force-feeding the plants. The result is a lot of "soft growth" - longer stems and bigger leafs, both of which are incredibly attractive to pests and diseases. Ironic as it may seem, in certain ways a plant is actually weakened by this type of chemical fertilizer.

As well, plants can only ingest a finite amount of nutrient material from the soil, and the rest is washed away by rainwater (to eventually end up in our drinking water). Organic fertilizers may contain smaller doses of the individual elements (N, P and K), but they release them over a much longer period of time, so these nutrients remain in the soil longer, available to the roots when the plants need them. Nowadays, the chemical industry attempts to copy this process by producing slow-release fertilizers. In itself this is a good idea, but in this author’s humble opinion, part of this effort is made redundant because the dose of each individual element is still much higher than strictly necessary.

So why do we use chemical fertilizers? Just as with chemical pesticides and herbicides, we imitate commercial growers who use chemicals in order to grow large crops. When we buy a head of lettuce, we are looking for an abundance of soft green leaves, preferably undamaged by insects. The only way a commercial grower can achieve this (keeping in mind that he grows thousands of heads of lettuce) is by using a "soup" of chemicals that will force fast-growing, lush plants that are protected from insects. (By the way, this is exactly why organically-grown vegetables are always more expensive than their chemically-treated "cousins". Instead of using herbicides, organic growers hand-pick weeds which is – of course – much more labour-intensive)

It is not my place to try to influence anybody’s opinion on this subject. Most gardeners have their own style and preferences and will do either what they were taught or have been doing for years. As always, everybody is entitled to their own opinion and preference, but as far as yours truly is concerned, unless you are participating in a "Who Grows The Largest Pumpkin" competition, there is no real reason to use chemical fertilizers in your garden. More so, the trick to growing healthy plants is to keep your SOIL fertile rather than concentrating solely on the plants.

I realize this has been mentioned in this column several times over the last weeks, but it IS the best gardening tip anyone can give you. Since honesty is the best policy, we should tell you upfront that you will need lots of bulky, organic material in order to achieve this. Manure, compost, bone- and blood-meal, and mushroom compost are some of the "secret ingredients" for healthy soil. By using organic material you are not just adding nutrients, you are also promoting a healthy biological environment (insects, bacteria, worms) which are crucial aids in achieving and maintaining strong and healthy plants.

Green myths: the “blue” Hydrangea
And now for a nice segue: blue Hydrangeas will NOT stay blue UNLESS your soil is ACID. If you buy a blue Hydrangea and plant it in alkaline soil, the flowers will come back pink the next year. If your soil is neutral (which is very rare, but it happens) the flowers will be white (unless you purchase a climbing Hydrangea, in which case the flowers will always be white).

Transplanting in Summer
Don’t you hate it when the plant you so carefully dug in last year ends up being too big for the spot you picked? And isn’t it a shame that the cuttings that were given to you seem to wilt and die regardless of how often you water them? Fear not, there is a solution – albeit it a somewhat radical one – to (trans-) planting on hot summer days.

Firstly, only (trans-)plant in the evening and not during the day. Secondly, make sure to THOROUGHLY water the newly dug hole (if you are transplanting, also make sure to water the plant that is about to move BEFORE you dig it up). Thirdly, water again once you are done planting.

And now for the radical part: cut back at least half the foliage and continue to water twice daily (morning and evening) until the plant is well established and starts to show signs of new growth.

It may seem brutal, but it works. A plant takes up water through its roots and loses it through its leaves. Both transplanted plants and cuttings have damaged (reduced) root balls that are not capable of supplying the plant with enough moisture for all its green parts, especially on days when the sun is blazing. The plant clearly demonstrates this by allowing its leaves to wilt. By significantly reducing the amount of leaf surface (i.e. cutting it back rather viciously), and adding moisture to the root ball on a regular basis, the plant will stand a much better chance of survival.

Plant of the week
This week’s pick is Calamagrostis x acutifloria “Karl Foerster” or feather reed grass.

Completely hardy in the Ottawa area, this reed grass is a vertical masterpiece that provides wonderful contrast among low shrubs and perennials. It is a long-blooming, low maintenance, long-lived perennial grass for full sun to partial shade. This grass grows best in well-drained fertile soils with sufficient moisture, but will tolerate heavier clay soils and drier sites. Five feet tall, it sways gracefully in the lightest breeze, yet withstands the heaviest of storms without problems. This clump forming grass is not invasive, nor does it not self-seed, which – combined with its beauty – was why the US Perennial Plant Association awarded it with the title “2001 Perennial Plant of the Year”.

Happy Gardening!

René Trim

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About René
René Trim was educated and trained in The Netherlands, before moving to Canada in 2000. After studying the differences in climate and season faced by Ontario gardeners he established Trim Garden Design and Rescue in May 2002. A gardener since the 1980’s, he has a wealth of knowledge and experience, a vast library of reference materials from which to draw answers to various garden situations as well as an enthusiastic and professional staff.

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