Dear Master Gardener : I have lots of geraniums on my deck and many of the leaves have turned red. Is this normal or is there something wrong? Answer : When the leaves of an annual geranium (Pelargonium) turn red it is a sign that the plant is stressed. There are typically three reasons for geranium leaves turning red: over or underwatering, nutrient deficiencies or cool temperatures.
We can rule out cool temperatures and with all this rain underwatering can probably be ruled out, too. Most likely a nitrogen deficiency is the problem. With all this rain the nutrients may have leached out of your containers.
Plants in containers need regular fertilization because potting mixes quickly lose nutrients through absorption and watering. Annuals are heavy feeders. You can correct a nitrogen deficiency by fertilizing your plants every 1-2 weeks with a water-soluble fertilizer at half-strength.
Dear Master Gardener : My coneflowers have some weird-looking flowers. Some have petals on only part of the blossom, others have only green petals, and still others have strange, bushy growths and flowers. What’s wrong with them? Answer : Aliens have not invaded your flower beds.
The symptoms you describe sound like aster yellows, a common garden disease. It also frequently affects asters (as the name implies), chrysanthemums, cosmos and marigolds, as well as vegetables such as carrots and potatoes. It is caused by microscopic organisms called phytoplasmas and is transmitted by leafhopper ins.