As the nation’s most comprehensive resource center for gardening information, the Missouri Botanical Garden’s Kemper Center for Home Gardening gets thousands of questions from home gardeners across the country each year. You can ask your questions in person at the Center for Home Gardening, open 9 a.m. to 3 p.m. Monday through Friday, by calling our Horticulture answer service at 314-577-5143 between 9 a.m. and noon Monday through Friday, or by sending an email any time to plantinformation@mobot.org.
Gardening help staff shared a few of the most common questions this spring below.
What to do about lasting winter injury
Last December, the St. Louis region experienced a dramatic cold snap that negatively affected many ornamental plants including broadleaf evergreens and other shrubs. Temperatures fell from a high of 36°F at 8 AM to a low of -6°F at 10 PM. This sharp drop in temperatures along with steady winds from the north during the cold snap and drier than average soil conditions from the preceding fall combined to create perfect conditions for widespread winter injury. Leaf browning, leaf drop, and twig and stem dieback have been the most common symptoms on laurels, euonymus, crape myrtles, hollies, rhododendrons/azaleas, and roses. Stems or branches that are not showing signs of new growth at this point in the season should be cut back. Future winter injury may be prevented by siting plants in a location protected from northerly winds, and making sure all shrubs and trees (especially evergreens) are well-watered going into winter.
How to stop critters digging in containers
Squirrels and chipmunks are drawn to the loose soil of newly planted containers. Not only can they create an unsightly mess, but the repeated digging can disrupt root establishment and lead to slower, potentially stunted growth and reduced plant vigor. Commercially available or homemade repellants can be effective, but typically need to be reapplied after rain. Animals tend to get used to the scents and will eventually resume their behavior. Exclusion tools are the most effective option to keep critters from digging in pots. Plastic netting, chicken wire, and other fencing materials can be used to keep animals out of pots. Rocks or spike strips can also discourage digging behavior.
How to get rid of aphids
Reports of these sap-sucking insects seemed to be higher than average this spring. Aphids are a large and diverse group of insects that can be found feeding on almost any plant in the home garden. The good news is that their damage is almost never fatal and is often only cosmetic. They can be easily controlled using a strong stream of water from a garden hose. Insecticidal soap and oil sprays are also effective. Aphids are a favorite food source for many predatory insects such as lady beetles, green lacewings, mantids, and hoverfly larvae. Before reaching for the hose or bottle of insecticide, consider these “good bugs,” which will be negatively impacted by the removal of their food source and the use of insecticides.
Why are sycamores losing their leaves?
Many St. Louis residents wanted to know why the sycamore trees in their neighborhoods were losing all their leaves this spring. Sycamores are susceptible to a fungal disease called sycamore anthracnose. The fungus overwinters in twig cankers and fallen leaves. It grows rapidly during cool spring weather and releases spores that are spread by wind and rain. The spores infect newly expanding shoots and leaves, causing dieback and leaf drop. Severely infected sycamores can appear almost bare in spring. Luckily, sycamore anthracnose rarely kills mature and otherwise healthy trees. Once temperatures start to rise, the disease will no longer spread and healthy leaves will replace what was lost.
How to add native plants
More and more gardeners are looking to add native plants to the home landscapes. Including Missouri native plants to St. Louis area gardens offers many benefits including lower water, fertilizer, and pesticide requirements and providing food and shelter for wildlife. Although native plants typically take a few years to get fully established, they are worth the wait. Shaw Nature Reserve has excellent online resources for home gardeners, and offers classes as part of their Native Plant School series.
Justine Kandra
Horticulturist, Kemper Center for Home Gardening