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WCCO Radio "Smart Gardens" Q&A - August 2, 2014

Thanks for listening! P1250793.JPG

We aren't always able to answer everyone's texted questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources.

Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

From Dave in South St Paul:
My tomatoes are flat and rotting on the bottom. What causes this? I water at the base and they are in containers.

Answer: This is a condition called "blossom end-rot". It is the result of calcium deficiency in the developing tomato fruit. This does not necessarily mean there is not enough calcium in the soil though - just that plant is unable to acquire it. This is due to environmental conditions such as fluctuations in soil moisture, heavy applications of nitrogen fertilizer, and injury roots.
Read more ...
Question: Why do my squash and cucumbers always cross-pollinate? They are planted 15 feet apart.

Answer: It's typical for Cucurbits varieties to cross-pollinate. They are in the same genus, they bloom at the same time and they are both pollinated by (usually) bees. Successful pollination produces a seed(s) and the tissue that surrounds it. It's important to note that this year's pollination will produce the seeds for next year's plants provided you save seed. Therefore, if you are planting seeds from a seed packet you purchased or transplants you purchased from a greenhouse, you should get the kind of squash / cucumber on the labeled. It's next year you  may get a variation on the original seed due to cross-pollination.

Question: I have had some success wintering begonias. Do you have suggestions for more success?

Answer: When you bring plants indoors for the winter, take this opportunity check them thoroughly for insects and insect eggs especially under the leaves. Wipe / rinse leaves, remove any signs of insects like webbing, and remove/dispose of dead leaves and flowers both on the plant and on the soil surface. Transplant into a clean pot with new potting soil. If the plants are large, consider cutting the plants back about 1/3 to just above a leaf node (a node is the point where a leave grows from a stem). Water and place in a sunny window. Begonias do not do well when over-watered, so check the soil about 2" down with your fingers before watering (recommended for all houseplants). and water if dry. You may find plants that are brought in from the out of doors will drop leaves initially. Remove the dropped leaves and continue watering as usual. Wait to fertilize when new growth appears with a complete fertilizer - 10-10-10 (N-P-K) or similar - at half the recommended strength.

Question: We want to seed about an acre. What type of seed do we use that takes, grows fast, and makes a great grass?

Answer: Choose a grass variety based on your conditions (the amount of light, soil type, moisture level) and based on the kind of activities for which you plan on using the area (sports, low-traffic, play area). Here is a good resource: Turfgrass Selection for Sustainable Lawns

You'll see from the Upper Midwest Home Lawn Care for Cool Season Grasses calendar that mid-August to mid-September is the optimal time for seeding your lawn. Seeding in this time period provides cooler temperatures, encourages germination, and enables the grass seed to form healthy roots before gradually going dormant for winter.

Question: Plum tree loaded with fruit. When is the best time to prune so the branches are not on the ground?

Answer: A good problem to have! Support the plum branches with sawhorses, PVC pipe, or other sturdy braces. Harvest the fruit as soon as it is ripe to reduce attracting pests like yellow jackets or birds damaging fruit. Then prune the tree when it is dormant - March or early April in Minnesota. See Stone Fruits for Minnesota Gardens for specifics on pruning including diagrams. Extension also has a great publication on pest management for stone fruits here.

Question: My Hydrangea doesn't have any flowers on it yet. Do they bloom every year?

Answer: Hydrangeas that are hardy in Minnesota typically bloom every year. Factors that can influence blooming include:

  • whether the plant is hardy in your zone (example: the Hydrangeas from a florist are not typically hardy for our landscapes);

  • weather issues such as late frosts that affect flower buds;

  • the amount of light the plant receives;

  • fertilization;

  • pruning techniques - some people prune off flower buds unknowingly;

  • whether the plant blooms on old or new wood;

  • animal damage such as deer browsing.

Some Hydrangeas are just starting to bloom now too. Without knowing the kind of hydrangea and the care you have given it, it's hard to say why your particular plant isn't blooming. However, we have had numerous people ask why their Endless Summer Hydrangea looks healthy, but doesn't bloom or bloom well.

From Paul Cherba: I am getting powdery mildew on my lilacs. Or something white. What can I do about that?

Answer: Common lilacs often get powdery mildew at this time of year due to higher humidity levels. It's typically more cosmetic than detrimental to plant health, and the spores are common and windblown, so there isn't a way to avoid it now or any action to take. Fungicides are available to spray. They are most effective if used at the onset of the mildew (see publication reference below).

Choosing plants that are resistant to pests like powdery mildew is the best option for minimizing its affect. Spacing plants according the their mature size and pruning to increase light and air circulation through the canopy / shrub also is helpful. Prune lilacs within two weeks of flowering before they set flowers buds for next year. Watering at the base of the plant will help keep plant leaves free of water droplets that can hold bacterial and fungal spores. More on powdery mildew on lilacs.

Question: My impatiens were beautiful and now they have been snipped of their leaves and flowers with only stalks left.

Answer: If the leaves have been eaten (they are not lying on the ground), then I would say it was rabbit damage or deer damage. If the leaves have dried up and fallen off the plant, you may have a disease such as impatiens downy mildew. This is a relatively new pest for Minnesota gardeners that affects shade-loving impatiens Impatiens walleriana (not New Guinea impatiens). White fluffy growth forms on the underside of the impatiens leaves. There is no cure and the plants should be removed. Avoid replanting Impatiens walleriana in the same bed. Read more here.

Question: I plan on planting an Autumn Blaze maple where my hackberry once was. When is the best time to plant this?

Answer: Planting a diversity of trees is really important. Trees provide shade, habitat for birds, animals and beneficial insects, and create canopies that cool our landscapes and homes - not mention being beautiful and valuable additions to our landscapes. Late summer / early fall is a good time for planting trees, so right now! Cooler temperatures mean less heat stress on the new trees. Here's a helpful Extension publication on planting trees. Good luck!
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