Gardening Q & A: Seed Germination and more
Master gardener Paul James answers the three most common gardening questions: why are some flowers reluctant to bloom, why won't certain seeds germinate and why do plants die suddenly?
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"I can't begin to guess how many gardening questions I've answered over the years, but I do know that I've been able to answer about 95 percent of them," says master gardener Paul James. "And it's not because I'm that smart; it's because I've been answering gardening questions for over 25 years."
Gardeners from all over the country share a number of common problems, from weeds and fungal diseases, to molds. Certain questions are extremely difficult to answer, such as the following three:
Q: Why don't certain flowering plants ever bloom? A:
A:Flowering plants are genetically hard-wired to bloom, so why are so many slow to bloom, or never bloom at all? In the case of spring-flowering bulbs (figure A), the lack of luster can be caused by a failure to do one of two things: Either the bulbs were planted too deeply in the first place, or they've become extremely crowded and need to be divided.
The same is often true of daylilies and irises (figure B). Too much shade can also cause problems, especially because most flowering plants need at least a half-day of sun to develop flower buds. To complicate matters, even if a plant develops plenty of flowering buds, they may be zapped by an early frost, chewed off by pests or destroyed by disease.
Improper pruning can also cause problems, especially if a plant is pruned the wrong way, or more commonly, at the wrong time. Nearly all plants, particularly flowering trees and woody shrubs, form flower buds on either one-year-old wood (the previous season's growth) or new wood (the current season's wood). As a result, if you prune at the wrong time, you may wind up removing all the developing flower buds.
Spring-flowering beauties, such as dogwoods (figure C), azaleas, forsythias, lilacs and certain hydrangeas, produce blooms on the previous year's growth, which is why you should wait to prune them until after they've bloomed. Some types of hydrangeas, fruit trees, roses and other summer bloomers produce flowers on the current season's growth, so it's best to prune them only when they're dormant.
Lastly, failure to bloom can be caused by overusing a nitrogen fertilizer, which can result in the production of tremendous foliage growth at the expense of flower production. But in many cases, a plant simply hasn't matured enough to reach the blooming stage. That's particularly true for many woody shrubs such as wisterias and lilacs that are grown from seeds rather than cuttings.
Q: Why can't I get seeds to germinate? A:
A:Everything a seed needs to germinate is contained within the seed itself. However, several factors can affect a seed's ability to germinate, most importantly how the seed is collected and stored, and whether the seed is considered recalcitrant or orthodox.
Most store-bought flower and vegetable seeds are considered orthodox seeds, which can be stored for one or more years as long as they are exposed to as little as 5 percent moisture, ideally at room temperature, and out of direct sunlight. I keep seeds in a plastic bag filled with a little bit of rice to protect them from moisture (figure E). However, seeds collected from the wild or from your garden may be recalcitrant seeds, including wildflower, tropical and tree seeds. Recalcitrant seeds must be collected while they are ripe and either planted right away or stored under ideal conditions with a moisture level above 30 percent.
Planting seeds too deeply can be another reason germination fails, so cover seeds with only a 1/4 to 1/2 inch of soil. The use of pre-emergent herbicides applied at the wrong time can certainly prevent seeds from germinating. Temperatures that are too hot or too cold and soil that's either too moist or too dry can also prevent seeds from germinating. Many seeds, especially those with really tough coatings, may have to be soaked in water or acid before they'll germinate. In fact, the seed of a particular palm must first pass through the acidic environment found only in the intestinal tract of a certain bird before it will germinate.
Q: Why do plants die suddenly? A:
A:It's sad when a plant suddenly dies, and in many cases, the exact cause is never known. Of course, obvious factors include too much or too little water, or maybe even a chemical spill. But when a plant dies overnight and for no apparent reason, such as a pest or disease, it's next to impossible to determine the cause without sending a tissue sample to a plant pathologist for analysis. Very often however, the sudden death of a plant is caused by a very nasty viral, bacterial or fungal infection. And if that's the case, you can take heart in knowing that you couldn't have done anything to prevent the plant's demise.
In many cases, the plant may have simply reached the end of its life cycle. It's interesting to note that in many regions of the world — in the olive groves of Italy for instance — farmers will often leave a dead tree standing to remind themselves of that very thing: the cycle of life.