Spring Gardening Q&A
Master gardener Paul James weighs in on a variety of topics, including ants on peonies, river rock as mulch and pruning yews.
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Q: I've got ants on my peonies. Will they hurt my prized flowers?
A: Ants on your peonies are little more than a nuisance. They do no harm, and contrary to what you may have heard or read, ants don't eat flowers. They're simply feeding on the syrupy nectar in the flowers.
For those of you who have never grown peonies (figure A), you don't know what you're missing. They're incredibly rugged, long-lived plants that are easy to grow in well-drained soil and a sunny location. One important tip when planting: don't plant them too deeply. That's the number-one cause of bloom failure, and given the beauty of the blooms, you certainly don't want that to happen.
Q: The utility company wants to prune a gorgeous oak growing near the power lines. Can I stop them?
A: Chances are you can't do anything to prevent the utility company or its contractors from clearing away branches close to power lines (figure B), since the lines themselves aren't technically on your property, but rather on an easement owned by the city. However, in some cities you may be allowed to sign a waiver that makes you responsible for repairs to the lines that result from damage to them during storms.
A word of warning, however: those repairs can be very expensive. And if the damage knocks out power to the neighborhood, you may not be invited to the next block party.
If your concern is the manner in which the tree will be pruned, you might consider having a professional tree service do the necessary pruning for you. They can do it in a way that satisfies the utility company but preserves the look of the tree.
Q: Is there a downside to using river rock as mulch?
A: In permanent settings such as a path or an informal patio, river rock makes an excellent mulch and creates a look unlike any other material. But it's not without a few drawbacks.
For example, if deciduous trees grow nearby, their leaf litter in the fall can be a bit difficult to remove. Weeds can grow through the rocks (figure C), so you should first put down a layer of landscape fabric to prevent weed growth. And finally, in a full-sun setting, the rocks can get really hot on bare feet.
Q: What's the secret to growing a dwarf Alberta spruce in the South?
A: Unfortunately, USDA Zone 7 is the southern limit for this small, conical tree. And even there it may wind up with tip-burned leaves and problems with spider mites. However, there are some steps you can take to encourage success with your spruce. Give it about two hours of morning sun followed up with partial to full shade for the rest of the day. Don't let it dry out--provide adequate and even moisture.
Interestingly, the dwarf Alberta spruce (figure D) was discovered in 1904, growing near a lake in Alberta, Canada, by two tree experts who decided to take a short walk while waiting for a train. That's why its botanical name is Picea glauca var. albertiana.
Q: I saw a redbud with beautiful reddish-purple leaves. What variety is it?
A: You saw a 'Forest Pansy' redbud (figure E), and its leaves are indeed beautiful throughout the growing season. Where you plant a 'Forest Pansy' can have an effect on leaf color. Redbuds are understory trees, and as such they actually prefer filtered rather than direct light. However, this particular variety holds its color best in sun. So put it in a spot that gets a good half-day of sun followed by filtered light the rest of the day, and you'll get the most of what this tree has to offer.
Q: How and when do you prune a yew?
A: Yews are somewhat unique among evergreens in that they can be pruned back to old wood and still generate new growth. So don't be afraid to cut them back. In fact, yews are often sheared once or twice a year to create formal hedges. As for when to prune, spring is arguably the best time because the plant will generate new growth. It will then have a chance to mature before winter arrives.
Q: We bought a house that has sheared hedges. How can we return them to their natural form?
A: The only solution is to stop the shearing process and give your shrubs or trees time to return to their natural form. The process may take two or three years, perhaps even longer. Keep in mind though, you may not be pleased with the outcome.
Q: My bougainvillea looks healthy, but it doesn't bloom. Can you offer any recommendations on making it flower?
A: Assuming it's grown in full sun and watered regularly, I can't say for certain why your bougainvillea (figure F) isn't blooming. However, here's a tip: stop watering. Withholding water, not quite to the point where the leaves begin to wilt, will stress the plant and very often will cause it to begin the flowering process.
Q: I like the look of bishop's weed, but I heard it can be invasive. Is that true?
A: Yes, Aegopodium, also known as bishop's weed or goutweed (figure G), can be extremely invasive, and very often it's not labeled as such at nurseries. Once it gets out of hand, it's difficult to control. However, when planted in dry soil, it's a bit more tame, and there's no getting around the fact that it's an attractive groundcover.
Q: Why aren't all roses fragrant?
A: For the most part, the answer has to do with hybridization. In their quest to develop a more beautiful bloom or roses that are more disease resistant, rose growers ignore one of the most important attributes of a rose--its wonderful scent. So if fragrance and disease resistance is what you're after, consider old-fashioned roses (figure H).