First Published 12/30/2004
Precious Germplasm

When you’re relaxing over the holidays, poring over the latest gardening magazines or seed catalogues to admire the hot new plant varieties, take a moment to thank some real heroes: the germplasm collectors. You’ve almost certainly never met a member of this rare breed, but they have, nonetheless, played an important role in the composition of your garden.

The Goods on Germplasm

What the heck is germplasm and why would anyone collect it, you ask? Well, germplasm is just a fancy name for certain kinds of plant material: specifically, seeds, cuttings or any other plant parts that are capable of growing and producing more of the same plant. For example, the starchy interior of a Russet Burbank potato alone wouldn’t qualify as germplasm because it can’t produce another potato plant; but add the eyes and you have all the genetic material necessary for reproduction.

Highly trained horticulturists (and amateurs through the centuries) have dedicated a lot of time and energy to collecting germplasm so that it can be stored and used for breeding purposes, which in turn leads to a wider selection of plants for everyone. It’s easy to forget that our favourite tomato varieties, for example, originated with an assortment of ancient tomato species growing in South America. It was the germplasm of those original tomato species that was cross-bred over and over to produce the sweet, plump and juicy varieties we enjoy today. It’s the same story for many of the other outstanding fruit, vegetable and ornamental plants in our backyards.

Building a Better Begonia

Around the world, there are numerous germplasm storage facilities. The Ornamental Plant Germplasm Center in Columbus, Ohio has a huge collection of germplasm, and it’s all available to professional plant breeders for the development of new varieties. Take begonias, for example. Most of us are familiar with the popular begonias such as Rex begonias, Non-stop begonias and fibrous begonias. At the germplasm centre in Ohio, there are over 600 species of begonias stored away! With crossbreeding, millions of new varieties are possible. (Of course, the reality is that just a precious few of these new creations will be good enough for home gardens.)

Each species brings its own array of genes to the table, genes that determine leaf and flower colour and shape, the plant’s height and growth habit, its resistance (or vulnerability) to specific pests and diseases, its scent or lack thereof, and even less obvious traits like its efficiency in utilizing sunlight and nutrients. Breeders cross plants that exhibit the best of these traits in the hopes that they will create new varieties that have as many positive aspects as possible, and as few negative – not a simple task. In the case of begonias, I’ll be ecstatic if they can one day develop a variety that doesn’t get powdery mildew!

Germplasm facilities are not merely a luxury, a convenient source of stock for plant breeders. These facilities are, in fact, protective storehouses for irreplaceable genetic material. Germplasm is frequently rescued, for example, from areas where development overruns natural habitats – and it’s not always the safest job in the world. Just this past summer, while waiting for a flight at the St. Paul airport, I ran into horticultural researcher and germplasm collector Dr. John Erwin, a man whose lectures I’ve often attended. We chatted for a while and I discovered that Dr. Erwin had spent several months in South Africa searching for the germplasm of a number of plant species. He said that the most challenging part of the job was not finding the plants, but avoiding the poisonous snakes hidden among them!

Germplasm collectors are willing to take these kinds of risks because they know that saving this material has huge potential implications not only for gardening, but for medicine, industry and the arts; the sheer value of plant species to humanity has been incredibly underestimated.

A Solemn Responsibility

As the human population and our demands upon the environment grow, we need to keep finding ways to preserve and protect the natural world. Germplasm centres don’t get much publicity, but they’re absolutely vital – not just to preserve precious genetic material for breeders, but because the species are worth saving for their own sake.

First Published 12/23/2004
Holiday Scents

I don’t mind the look of artfully decorated artificial Christmas trees; from a distance, they look quite festive, and there are no annoying needles to vacuum up. But I do miss the smell of a real, live Christmas tree. The fragrance of a fresh cut pine or spruce awakens some pretty powerful memories of childhood Christmases past that an artificial tree just can’t match.

It’s All in the Oils

The incomparable scent of real Christmas trees is caused by a category of plant oils: specifically, essential oils. Essential oils are so named not because they’re “essential” to plant growth, but because they produce an essence. In fact, essential oils are the source of most odours found in the flowers, fruit and wood of many plants. They are very common in the Pinaceae family, of which both pine and spruce are members.

It’s been estimated that the vegetation of the world releases some 400 million tons of these materials into the atmosphere every year. In fact, the release of volatile hydrocarbons from vegetation is an important source of air pollution. Yes, I know that “air pollution” seems an odd choice of phrase to describe compounds naturally emitted from trees, but they are hydrocarbons, and under the right conditions they can leave the air a little hazy. In fact, the Blue Ridge mountains of Virginia are so named because of the blue haze that hangs over the range on calm, warm days, courtesy of released essential oils. The haze is occasionally mistaken for smoke from forest fires.

Not only do essential oils smell wonderful, they’re useful in other ways: turpentine, for example, is the most economically important essential oil harvested from trees.

So why do pine and spruce trees produce essential oils in the first place? Well, it’s not to make us feel all warm and fuzzy at Christmas. From a tree’s perspective, essential oils are costly to construct; they take a lot of energy to produce, compared to other compounds.

But the cost is worth it. Essential oils are powerful attractants for some pollinating insects, while also serving as deterrents for some insect pests (though, like people, pine and spruce beetles find the scent very enticing).

A Heady Christmas Scent

To get the maximum amount of pine or spruce fragrance in the home, you need fresh trees, and they must be kept well watered. The oils are released from the needles, primarily through the needle pores (stomata) that close tight when water is in short supply. Keeping the water level consistent will keep the tree healthy and the scents wafting through your home.

First Published 12/16/2004
A Heavy Load

The Prairies are notorious for late spring and early autumn snowfalls, and occasional gale-force winds. It seems that at least once every few years, our yards and city streets are littered with tangled masses of fallen, snow-covered branches, necessitating a laborious and heartbreaking cleanup job. But why worry now, in the dead of winter?

Because now is the perfect time to take a good look at your deciduous trees. With their branches bared, trees provide some very critical information – information that will have a huge impact on their continued health.

The Tempests

Some trees fare better than others when wind and snow wreak havoc. One tree may lose several thick, healthy branches, while its neighbour, of similar size and age, escapes the storm unscathed. Why the discrepancy? Tree species, age, and other factors come into play, but the main determiner of a tree’s ability to withstand the rigours of fierce winds and heavy snow loads is its architecture. A large, fully leafed tree hit by sticky, wet snow must have the structural strength to shoulder the enormous deadweight, otherwise its branches, or even the entire tree, are certain to fail. Basically, a structurally sound tree has fewer, larger, stronger branches, rather than a profusion of thin, weak branches.

A Heavy Burden

Of course, not all trees are going to perfectly match this configuration. For example, many urban trees are “overbranched,” that is, they often have plenty of sun, water and rich soils, and as a result of this easy life, they tend to produce plenty of branches – branches they’d never develop in the competitive environment of a dense forest. As a result, these super-branched trees have very large surface areas, and the leaves and branches can trap a tremendous amount of snow and wind, putting enormous mechanical stress on the tree’s structure.

Fortunately, you can take corrective measures, and winter is the perfect time to evaluate your trees, since the branches of deciduous trees are bare, and can be thoroughly and easily inspected. Here’s one troublesome feature to watch for: the “split” tree, with two large but narrow V-shaped branches. (When this happens, arborists say that the tree has developed co-dominant stems.) During a severe storm, one of the prime sites for branch failure is the tree’s fork – the spot where the co-dominant stems diverge. This V-shaped crotch is structurally weak, and in a very bad storm, both branches in the V may fail. I’ve seen a lot of trees around the city that have these weak, co-dominant stems; it’s a shame, because simply pruning off one of the stems back when the tree was young would have prevented the problem.

If your inspection reveals that one or more of your trees has co-dominant stems or is largely composed of many thin, weak branches, you need to take action. On such overgrown trees, the best solution is to employ a pruning technique called “crown reduction,” which, in essence, means selectively removing branches from the crown of the tree in order to reduce the tree’s surface area, and therefore lower the potential snow load. Crown reduction doesn’t harm a tree’s appearance, nor its health, provided the pruning cuts are made properly and in moderate amounts.

Crown reduction and removal of weak, V-shaped branches sounds simple, but this isn’t a job for the untrained. If you have a large, mature tree, don’t try to prune it yourself. Call in a certified arborist; he or she will have the training and equipment to safely solve the problem. Professional crown reduction isn’t a perfect defence against snow and wind damage, but it does enormously reduce the risk of injury. Your trees are well worth the investment. (One important reminder: because of the risk of Dutch elm disease, American elms must only be pruned from October to March.)

Easing the Load Early

If you have a small, young tree, get into the habit of doing a little corrective pruning every year. When trees are small, it’s not such a daunting task, and you’ll save yourself a lot of money and headaches in the future. More importantly, you’ll preserve the majesty of a beautiful deciduous tree for many generations to come.

First Published 12/9/2004
Perlite vs. Vermiculite

If you have even one plant growing in your home or office, I can virtually guarantee that its soil contains perlite, vermiculite, or both. But I would also speculate that most people have confused the two materials at one time or another. Is the perlite the white stuff of the brown stuff? These two soil amendments have similar backgrounds, but they perform entirely opposite functions in potting soils, so it’s important to understand the difference to get the best performance from your plants.

Perlite

Perlite is simply a white, round pearl-like volcanic rock. It’s mined, then crushed and rapidly heated to about 1,000 degrees C, whereupon it starts popping like popcorn. Perlite is popped to reduce its bulk density – in other words, to make the pebbles much larger and subsequently a lot less dense.

Adding lots of puffy, lightweight perlite particles into potting soils ensures that those soils are well drained. In essence, perlite is a lightweight substitute for sand. If you filled two equally-sized pots, one with sand, one with perlite, the pot with sand will be much, much heavier than the one filled with perlite.

Perlite is a relatively expensive material, which is why poor quality potting soils contain very little of it. In fact, there is so little perlite in some poor quality potting soils that it’s nonfunctional; what perlite exists is nothing more than window dressing. A high quality, well-drained potting soil should have at least 25% perlite to ensure that water drains easily and that the roots have plenty of oxygen.

Vermiculite

Vermiculite, like perlite, is a mineral, heated and blended into potting soils. But while perlite increases drainage, vermiculite does just the opposite. Its role is to temporarily trap water and nutrients, thereby giving plant roots enough time to draw upon these precious resources before they drain away. Vermiculite performs this role very well because of its structure, which roughly resembles a stack of plates. In between these plates, water and nutrients are trapped rather tightly, but plant roots have the knack for extracting what they need.

The problem that I’ve found with vermiculite is that it performs this role just a little too well. For many years, we grew our greenhouse plants in a blend of perlite, vermiculite, and peat moss, but we’ve eliminated vermiculite from the mix simply because it reduces air infiltration into the mixture and also because it often traps far too much water, leaving the potting soil excessively soupy. Peat moss mirrors vermiculite’s role, holding water and nutrients very effectively, and with the right percentage of perlite, it makes vermiculite unnecessary. We still use vermiculite in seedling mixtures, because seedlings need the consistent moisture levels that vermiculite is adept at providing.

The Right Mix

Each supplement has its own strengths. I always tell people that one of the most important components of potting soil is air, and having sufficient perlite in your pots lets roots breathe a little easier. On the other hand, if you’re raising moisture-loving seedlings, a little vermiculite in the seedling trays will help them thrive.

First Published 12/2/2004
Jim’s Basil

I love fresh basil. I toss it into my soup, mix it into tomato sauce for pasta dishes, and sprinkle it atop a variety of other dishes.

By far the best way to enjoy basil’s rich, pungent flavour is to grow your own. Unfortunately, while home-grown basil is thick, robust and flavourful during the summer, when winter rolls around it tends to get thin, pale and the flavours fade. Luckily, prospects for growing high-quality basil in the wintertime are bright – and bright is the theme to keep in mind to be successful with this plant.

The Trouble with Basil

During our short, low sunlight intensity days of winter, basil still grows, but only as a ghost of its summer self. The flavour of winter-grown basil tastes a little washed out – to my palate, anyway. Fortunately, it’s a problem that’s easily corrected.

The exquisite flavours of basil and other herbs are determined by the quantity and ratio of essential oils they contain. These oils (named for the “essence,” they impart, not because they’re “essential”) require plenty of light energy to develop properly. The more light you can shed on your basil, the greater the essential oil development, and therefore the greater the flavour.

When I grow basil indoors in the winter, I cheat. I borrow an HID (High Intensity Discharge) light from the greenhouse; it’s a terrific source of light energy for my basil, more than enough for the essential oils to reach their peak. I grow my little patch of basil in my basement’s furnace room. The HID light is timed to switch on at 11 p.m. and off at 5 a.m. As a result, my basil grows in a kind of topsy-turvy world, experiencing bright nights and dark days.

Of course HID lights aren’t for everyone; they’re rather expensive. But even grow lights sold in hardware stores and garden centres can provide just enough extra light to keep your basil in good shape. You should also use as much sunlight as possible; it’s free, after all. Just use the grow lights as a supplement.

During the day, place your basil (or other herbs) as close to a south or southwest facing window as you can; during the night, turn on the grow lights for three or four hours – preferably during off-peak electricity hours. Position the basil as close as possible to the fluorescent tubes; the tubes don’t radiate enough heat to damage the plants. Placing the basil as little as a metre away from the light source will substantially reduce the amount of energy the plants receive. If you double the distance from a light source, you reduce the light received not by two times, but by four times. (It’s the inverse-square law in action!)

Fine Dining

I love the fact that it takes all of about 30 seconds to harvest my basil and deliver it to my plate of spaghetti and pasta sauce. I sow ‘Genovese’ basil seeds thickly in a pot, harvesting some of the seedlings shortly after they emerge, which frees up space for the remaining seedlings. Then I leave those remaining seedlings alone until they’re large enough for me to harvest the fully-developed leaves. All told, with very little effort (a few minutes to sow the seed and a few more minutes once a week to water the pot), I enjoy basil every week.

Producing high-quality culinary basil is easy: use high quality potting soil and seeds, and in the winter, provide the plants with as much light as you possibly can. Light up your basil, and your basil will light up your meals with a hefty dose of incredible flavour.