Everyday Gardener // Tackling tough gardening challenges

Now that it’s warming up, the gardening questions are coming in so I’m going to devote this column to the ones I’ve heard most in the last few weeks. If you’ve got a question I don’t answer here, you can email me (my address is below) and I’ll try to help.

Q: I’ve been using peat moss in my garden for years but now I’ve heard that it’s bad for the environment. Is that true?

A: That depends who you talk to. Conservationists and peat producers have been debating this issue for years and years. Peat moss is the partially decomposed remains of sphagnum moss that comes from peat bogs, which can literally take hundreds to thousands of years to develop. When peat moss is harvested or “mined,” as some describe the process, parts of the bogs are destroyed by all the digging and stripping away of layers. This, conservationists and scientists assert, is not only destroying habitat for everything from bog rosemary to wildlife and insects found only in these bogs. It is destroying wetlands that help purify our water and our air (moss absorbs carbon dioxide just like rain forests do). Manufacturers of peat moss products claim these bogs are renewable resources that quickly reestablish. To help protect peat bogs, boycotts have been started in many countries and parts of Ireland (where bogs are plentiful) have banned the harvesting of peat moss completely. As gardeners, it’s up to us to decide what to do. I have decided to stop buying it and I’m currently looking for good alternatives to try.

Q: Is it true that it’s best to plant trees in the fall?

A: That is true for most trees. The soil is already warm by that time and once the tree loses its leaves the new root system will not have to work so hard to provide nutrients for them as it gets used to its new home. There are a few trees, though, that should be planted in the spring because they just seem to struggle more when they’re planted in the fall and the reasons for this don’t seem to be fully understood. Those trees are: hawthorn, magnolia, birch and many oaks.

Q: My hydrangeas have stopped blooming and I’m wondering if it’s because they’re in too much shade. Could this be the problem?

A: Definitely. Hydrangeas will bloom in dappled shade but dense shade could definitely keep them from flowering. This could also be due to a nitrogen problem. Too much nitrogen will get you lots of lush, green growth but few flowers.

Q: Why do my blue hydrangeas turn pink after they’ve been in the ground awhile?

A: It’s all about aluminum, really. When they’re planted in acidic soil, blue hydrangeas will stay blue because the acid converts aluminum compounds in the soil so it can be absorbed by the shrub, making the flowers blue. In alkaline soil, which is the norm around here, aluminum is not taken up by the plant, so the flowers remain pink. White hydrangea blooms can’t be changed to a different color, but you can change blue blooms to pink and pink to blue by raising or lowering the pH (acidity) of the soil. Blue hydrangeas prefer a pH of about 5.2 to 5.5 and you can test your soil using an inexpensive kit. To lower soil pH and make it more acidic for blue flowers you could use garden sulfur or aluminum sulfate or naturally acidic materials like sawdust and oak leaves. Raise the pH for pink flowers using powdered limestone. Be sure to follow package directions and be aware that this will be an ongoing process because soil will just revert back to what it naturally is if left to its own devices.

Q: Is it true that ants play a role in helping peonies bloom? It doesn’t seem true to me, but people always talk about how they’re needed to make the buds open. What do you think?

A: You’re right; it isn’t true. Ants don’t just go around kindly doing good deeds like helping flowers open. In this case, what’s in it for them is tasty nectar in the structure that covers the buds though they do help the buds, too, by keeping pests that might harm the blooms away.

Q: What can I do to protect my trees from emerald ash borer? Is it a good idea to treat them or not?

A: As you may know, ash trees are usually at risk when EAB infestations have come within 10 to 15 miles of where they are planted. So Minneapolis and St. Paul trees are currently susceptible. Insecticides seem to work in protecting trees from EAB. The question is, do you want to use them? To help people decide, the University of Minnesota Extension Service is advising ash owners to think about several things. How healthy is your ash tree? If it’s in good shape and hasn’t yet been affected by the borers, treatment is more likely to be successful. How much do you value your tree? Is it important for shade, aesthetics or sentimental reasons? If so, maybe it would be worth it to treat it. Just know that once you start using insecticides you’ll have to keep using them if you want to protect the tree. So, really, people need to weigh the one-time cost and work to remove an ash tree and plant something else against the cost and effort it will take to provide long-term treatment.

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.