Everyday gardener // Gardening Q & A

Newfangled burlap, mint gone wild and the woes of powdery mildew

I usually wait until July or so to do a Q & A column, but I’ve received a lot of questions on the same topics so far this year, so I’m going to go ahead and try to answer some of them now. If I get a bunch more, I’ll just do another one of these round-up columns later this summer. I’ll start with a good question that comes up all the time.
Q: What do the three numbers on fertilizer packages mean?
A: Those numbers refer to nitrogen (N), potassium (K) and phosphorous (P), respectively. Like us, plants need nutrients to be healthy and strong. Nitrogen helps plants build chlorophyll, which helps them use sunlight to turn water and carbon dioxide into sugars that feed the plant. You can tell if a plant isn’t getting enough nitrogen if its leaves look yellow or pale green. Symptoms usually appear on the lower leaves first.
Potassium helps stems and roots develop and gives flowers their rich coloring. Plants that are low on potassium will often have yellow leaves, too, but the yellow starts at the leaf’s edges and works its way in. Phosphorous is important for rapid root growth, so it isn’t always easy to see a deficiency in this nutrient until a plant is clearly stunted.

Q: Every year my phlox and bee balm get powdery mildew. Is there anything I can do to prevent that?
A: Powdery mildew really is an ugly thing. If you’re not familiar with the term, powdery mildew is a fungal disease that makes a plant’s leaves look as if they’re coated with dusty, white powder. Some plants, like phlox, bee balm, zinnias and roses are more susceptible to it that other plants, so one thing you can do to avoid it is look for varieties that have been bred to be more resistant to the disease. Keep powdery mildew at bay, at least for the most part, by providing susceptible plants with full sun and good air circulation. Try to avoid getting the leaves of these plants wet whenever possible. There are fungicides you can buy to control the disease, but use these with caution because they may do more harm in your garden than good. As a last resort, you may just want to rip the mildewy plants out and get something else.

Q: I bought a balled-and-burlapped tree. Do I need to remove the burlap before planting?
A: Yes, and here’s why. Burlap used to rot over time, so it was no problem to bury it along with your tree’s roots. Nowadays, though, burlap is made from synthetic fibers that don’t decay well. If your tree is unimaginably heavy and already down in its freshly dug hole, you may not be able to get all of the burlap off before planting. In this case, do your best to cut away as much of the material as possible. It’s most important to remove burlap from the sides of the root ball because tree roots grow laterally. (Always remove the wire cage around the root ball, too.)

Q: What is the best time to prune raspberries?
A: That depends on the type of raspberries you have. Summer-bearing raspberries offer just one crop per year, so you can cut all of the canes that produced fruit to the ground once they’re done for the season. Leave all of the other canes because they’ll be the ones with the raspberries next year. Ever-bearing raspberries bear fruit in the summer and fall, so you’ll want to cut all of the canes down to the ground in the early spring.

Q: Last year, mint went completely insane in my garden and spread everywhere. I’m planning to rip some of it out. How can I grow this herb without having it take over everything?
A: It’s true. A little bit of mint goes a long way. If you don’t want to have to do the back-breaking chore of yanking a bunch out each year, plant it inside a deep container in your garden bed, leaving the pot’s rim just above the soil line. Use this trick with other invasive plants, too, such as milkweed, which butterflies love.

Q: What’s the difference between “determinate” and “indeterminate” tomatoes?
A: Good question. When you buy tomatoes, you’ll notice that most labels offer one of these terms. Determinate varieties or “bush” tomatoes grow to about four feet with fruit setting on the top bud and ripening about the same time. For this reason, you don’t need to go to great lengths to cage these guys, and you don’t want to do a lot of pruning or you’ll wind up losing a lot of your crop. Indeterminate tomatoes are considered vining tomatoes because they can grow more than six feet in a season and will produce fruit right up until the cold kills them off. For these, you need to provide ample cages and/or stakes.

Meleah Maynard is a Master Gardener and freelance writer. If you’ve got a gardening question you’d like her to address in her column, you can email it to meleah@everydaygardener.com.