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Gardening Q & A

Today’s Common Gardening Questions…Answered!

How do I keep my tomatoes from turning black underneath?

Blossom-End Rot (BER) is a common problem for tomatoes in our climate. It happens when conditions prevent the plant from taking up calcium at the time of fruit set (when the flower becomes an immature fruit). If your tomatoes are in the ground, it’s unlikely that you have a calcium deficiency in your soil. The main things that cause BER are uneven watering and low temperatures at fruit set. Let’s look at each of these:

Watering: If you plant in the ground, give your plants a deep soak no more than twice a week. This encourages a deep root system that’s resistant to drought and sudden rains. Using a thick mulch of straw under your plants will also help keep the moisture even. If you plant in containers, make sure your containers are large enough for the plants, and water them every day.

Temperature: The first fruits of the season are usually the ones with BER. This can be from unseasonably cool temperatures, but also from transplanting to the garden too early in the season. We recommend planting Tomatoes outside no earlier than Memorial Day (in Dane County), when the night temperatures are above 50F.

Because BER often corrects itself as the season progresses, look at the bottoms of the fruits on your plants, and remove any that have a brown spot on the bottom. This way your plant can put its energy into growing new, rot-free tomatoes.


Some of the leaves on my plant are puckered and deformed, and the tips of the stems are curled. What happened, and how can I fix it?

Unfortunately the answer is usually herbicide damage. If herbicides are sprayed on a windy day, or someone isn’t careful while spraying, small amounts of herbicide can end up on the leaves of your plants. This disrupts the plant’s ability to grow normally, and the new growth comes out deformed. I’ve seen this recently on Columbines, Tomatoes, Peppers, Grape Vine, Redbud trees, and Dogwood shrubs.

In mild cases, the plant will survive and eventually resume normal growth as the chemical leaves its system. In severe cases, the plant will die. Regular watering and trimming off affected growth are the only treatments.

When applying herbicides, be sure not to spray on windy days. If applying near desirable plants, a large piece of cardboard can be used to protect then while absorbing excess chemical.


How do I get rid of moss in my lawn?

Moss will grow in lawns with any of these conditions: low light, wet soil, and compacted soil. We do carry a granular product called MossMax which will kill the moss you currently have. However, if the conditions that caused the problem aren’t fixed, the moss will grow back. Also know that the moss is not competing with the grass—it has no root system, and it’s too short to shade the grass. The moss is growing because the grass isn’t.

If your grass is growing thin because of shade, you can either get your trees thinned out by a certified Arborist, or you can plant shade-loving perennial ground covers instead. If the soil is compacted or heavy, getting your lawn aerated or spreading an inch layer of compost over the area. If the soil is too wet, you may need to consult a landscape architect to get your yard re-graded to take care of moisture issues. Any which way, after fixing the underlying problem you can re-seed the area so it fills in with healthy grass.


I bought a blue Hydrangea a few years ago, but last year the flowers were pink! How can I make them turn blue again?

Some species of Hydrangeas will be either pink or blue depending on the pH of the soil. In our area, Hydrangea macrophylla (Bigleaf Hydrangea), and Hydrangea serrata (Mountain Hydrangea) are the species that will do this. These will include the Endless Summer®, Twist-and-Shout, Bloomstruck, Paris, and Mars varieties.

Because most of us have alkaline soils, the Hydrangea flowers will turn pink. To make them turn blue again, add a Soil Acidifier containing sulfur to the soil around the plants in the spring, well ahead of blooming. Lowering the pH allows the plants to take up Aluminum into the flowers, which turns them blue. Continue to apply every two months until August.

Panicle, Annabelle-types, Oakleaf, and Climbing Hydrangea are not affected by pH, so don’t expect them to ever turn blue!


I planted some evergreens and shrubs this spring. Can I stop watering now?

Newly planted trees, shrubs, and perennials continue to need water until the ground freezes. Around Madison, the ground usually freezes in early December! My advice is to continue to water weekly until the leaves fall from the trees. After that, water every 10-14 days through Thanksgiving weekend. This is especially important for evergreen plants, because they lose water through their leaves over the winter, but cannot draw any up from the frozen soil. If we receive an inch of rain in a week, it isn’t necessary to water that week.


When do I dig my dahlias and gladiolas?

For most spring-planted bulbs, best practice is to wait for the tops to either yellow back and wilt or freeze off before digging. Caladiums are the exception—they should be dug before the first frost to avoid cold damage and rot. After you dig the bulbs, clean them with the hose or a soft brush. Let them dry on cardboard or newspaper out of the sun for a few days for smaller bulbs, up to a few weeks for large bulbs like elephant ears. Store them in a cool, dry place in peat/vermiculite/shredded paper for the winter.


When can I plant my Tulips & Daffodils?

Most bulbs do best if you wait to plant until we’ve had a frost… that’s usually a good indicator that the soil has cooled enough to prevent top growth. If we do not get a frost by mid-October, I’d say go ahead and get them planted. They can easily be planted as late as Thanksgiving if need be.

There are exceptions to this rule. Iris, Colchicum, and fall blooming crocus should be planted as soon as they’re available (mid-August to mid-September).  Winter Aconite, Chionodoxa, Snowdrops, Lilies, Surprise Lilies, and Fritillaria should all be planted as soon as possible to prevent the bulbs from drying out.


Why isn’t my Zucchini/Squash/Pumpkin producing fruit when it has so many flowers?

One of two things is happening here. Squash plants have separate male and female flowers. When the vines/bushes are young, they tend to just produce male flowers. They’ll typically produce both female and male flowers after the plant gets larger. You can tell female flowers because they have a mini squash/zucchini/pumpkin on the stem end. Excess male flowers can be harvested and eaten raw or fried. They’re excellent stuffed with goat cheese!

The other cause is a lack of pollinators in your garden. If you’re using a floating row cover, it needs to come off the plants when they start flowering so the bees and other pollinator insects can do their job. Try not to use insecticides in your garden, and if you must, use ones that break down quickly and spray in the evening to avoid killing the “good bugs”. Plant bee-feeding plants in your garden such as ‘Bee’s Friend’ and Borage to attract more pollinators.

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