Dear Master Gardener: Which azaleas and rhododendrons do you recommend? Do they grow well here?

Answer: Rhododendron is the genus that includes azaleas and there are some gorgeous ones that grow well in the Brainerd lakes area. Ninety percent of your success growing rhododendrons and azaleas will depend on soil preparation. Like blueberries, they are acid-loving plants that need a soil pH in the 4.0 to 5.5 range. If your soil is more alkaline than 5.5, the plants will probably not grow very well. You can lower the pH of your soil by adding peat, sulfur, or iron sulfate. Once established, you will want to apply an acid forming fertilizer in the spring before they bud to maintain soil acidity and supply nutrients. When you plant them, dig a shallow hole, loosen up the root ball, then plant it deep enough at or above where it was in the pot. Backfill around the plant with peat or a mixture of peat and the existing soil. Rhododendrons have shallow root systems and can dry out quickly, so they need a consistent moisture supply.

PJM Rhododendron is hardy to zone 3b (35 degrees below zero). It grows 5 feet tall and 4 feet wide and has lavender-pink flowers. The University of Minnesota developed the Northern Lights series of azaleas. Those that are hardy to zone 3b include: Lilac Lights, Northern Lights, Orchid Lights, White Lights, Rosy Lights, and Spicy Lights. Roseshell azalea, native to southern Quebec and the eastern U.S., is a parent of the Northern Lights hybrid azaleas. It has very fragrant white to rose-pink flowers and is hardy to 40 degrees below zero. Pinkshell azalea is a very hardy, lovely addition to a woodland garden because of its loose form.

Dear Master Gardener: I’ve seen Annabelle hydrangea flowers used as a wedding cake topper and you mentioned in a previous column that pansies are edible. What flowers are edible?

Answer: Edible flowers are often used as a garnish. However, not all flowers are edible. Hydrangeas are sometimes used as a cake topper, which might make people believe they are edible, but they are not! Hydrangea flowers contain low levels of cyanide. It is important to choose only flowers that are safe to eat and have not been treated with pesticides. One part of a plant may be safe to eat, but don’t assume that all parts are safe -- usually it’s the petals of the flower that are edible. Flowers from herbs usually taste similar to the leaves. Here is a U of M list of some edible flowers:

• Alpine strawberry (flowers have a strawberry flavor, leaves used for tea)

• Anise hyssop (flowers and leaves have a licorice flavor, used in tea)

• Apple or plum (flowers are mild with sweet floral flavor, use candied or as a garnish)

• Bachelor buttons (flowers have a delicate spicy-sweet flavor, eat fresh or dried for tea)

• Calendula (petals are a slightly bitter saffron substitute, more for color than flavor)

• Daylily (flower bud flavor compares to green beans and eggplant, but open flower flavor is milder, flavor varies by cultivar)

• Hibiscus (tropical) (flowers have a mild cranberry-citrus flavor, used in teas)

• Nasturtium (flowers and leaves have a peppery taste, use fresh in salads for spicy flavor)

• Pansy (flowers have a grassy, green flavor)

• Pinks (Dianthus) (flowers have a sweet clove flavor, remove the base of the petal – usually white in color – it’s usually bitter; use in sorbets, cold drinks, salads with fruit)

• Rose (use petals but remove white base of petal; use rose hips for tea and vinaigrette)

• Scented geranium (flower flavors vary by variety; flowers and leaves used to flavor jellies, sugar, butter, cakes, tea, honey)

• Tuberous begonia (flower petals have a tangy citrus flavor)

• Tulip (flower petals have a pea or bean flavor, remove from stem and use in salads)

Dear Master Gardener: Is it too late to plant a tree this spring?

Answer: You know what the Chinese proverb says: The best time to plant a tree was 20 years ago; the second-best time is now. The ideal time to plant a tree in Minnesota is in the fall. Roots continue to grow until the ground freezes solid and the cooler temperatures and fall rains get the tree settled in to take off the following spring. Plus, you can frequently find trees on sale late in the season.

However, if you are willing to give your new tree some extra TLC, you can successfully plant now. Hot weather and less rain mean your tree will have to be watered frequently, without fail. Deep soaking a couple times a week is better than a quick drink every day. Properly mulching several inches deep, but always 3-4 inches away from the trunk (think donut, not volcano) will conserve moisture for the roots and keep weeds or turf from competing.

When shopping for a tree, don’t be shy about checking the root ball. Gently slide it out of the container to make sure there aren’t circling roots that will eventually choke the tree. Reject any specimen that is totally root bound or has soft, rotting roots.

When you are ready to plant, give the root ball a “box cut.” Using a sharp knife, slice the root ball down all four sides to make a square. Slicing an X across the bottom will finish the process. Feel free to rinse the clay potting soil off and then plant in a hole only as deep as you need to keep the root flare at or slightly above grade. Don’t add any amendments to the hole - just put back whatever you dug out! Water thoroughly as you add the soil back, raising the tree if the flare gets below grade. You may put some compost on top and let nature work it in, but no fertilizer for at least a year. Don’t prune the crown, except for dead or crossing branches. Then stake loosely, or not at all. Let the tree sway in the breeze -- it’s the only way it knows it needs to grow roots.

June Gardening Tips

• Check pine trees for pine sawfly larvae that look like caterpillars. Knock them off with a blast of water from your garden hose.

• Move houseplants outdoors to a deck or patio the first week in June. Acclimate them to the change by placing them in a shady site, then gradually moving them to stronger light. Potting soil dries out faster outdoors, so plants will need more water during hot and windy weather.

• Mulch flower gardens to conserve moisture, insulate plant roots, and suppress annual weeds. Mulch might be a problem around hostas because slugs hide in it during the day, then come out to feed at night.

• Prune spring flowering shrubs such as lilacs, forsythia, and spring-blooming spireas right after they finish blooming to avoid removing next year’s flower buds. Older stems can be removed to the ground and plants can be lightly shaped by cutting the longest branches part way back with a pruning shears. This results in plants with a more natural look that will stay dense in the middle and bloom well again next year.

• Water young trees and shrubs once or twice a week all summer, depending on rainfall amounts, heat, and wind conditions. Water at the base of the plants, preferably in the morning, to conserve moisture. Add more mulch over the root area if it is less than three inches deep, keeping the mulch at least three inches away from the trunk and stems.

• Assess the performance of your spring-flowering bulbs. Dig up and discard any that failed to bloom well -- they won’t improve next year. Fertilize the others and allow their foliage to mature naturally.

• Water your lawn deeply and infrequently when grass shows signs of drought stress: dull color, blades curl inward, or footprints are obvious in the grass.

You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A Master Gardener will return your call. Or, emailing me at umnmastergardener@gmail.com and I will answer you in the column if space allows.

University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.