Gardening FAQs

Here is a list of the questions we receive most frequently about gardening or planning a garden. If you have more specific questions you would like to have answered please contact us.

  • What are the average spring and fall frost dates in Central Iowa?

    At the Botanical Garden the rule of thumb is late April to early May and late September to early October. On average we have about six months of frost-free weather, six when below-freezing temperatures are likely.

  • What is average precipitation by month in Central Iowa?

    April is driest at slightly over 3 inches, June the wettest at nearly 7 inches. The other months vary between 4 and 5 inches, for a year’s total of around 60 inches.

  • What are the lowest winter temperatures?

    According to the U.S.D.A. Zones of Plant Hardiness, Central Iowa hovers between Zone 4 (winter lows to minus 30°F) and Zone 5 (winter lows to minus 20°F). The nursery industry strives to include on each plant tag its cold tolerance.

  • Should I have my soil tested?

    Probably not necessary if your plants in general are performing well. However, if you are disappointed in the results you are getting or if you are concerned there could be contaminants in the soil, testing is recommended. If science appeals, you can have fun and get useful results from a soil test kit, available at local garden centers and by mail from seed catalogs. For a nominal fee you can have your soil tested professionally by the Soil Test Lab at Iowa State University: (type ST11 in the search box and download the instructions).

  • How can I get help with plant disease and insect questions?

    At most local garden centers and nurseries you will find at least one employee who will know the answers, or ask a friend who gardens, especially if he or she is a Master Gardener. The professional horticulturists at the Botanical Garden are always glad to help and the Learn on Saturdays classes held January - March cover all aspects of cultivating a healthy garden.

  • What is the difference between an annual and a perennial?

    Annuals complete their life cycle in a single growing season and then die. Perennials persist from year to year and tend to spread, until about the third year when they need to be divided. There are also sub categories. Tender annuals such as periwinkle and impatiens cannot withstand freezing and are therefore not set out until after Mother’s Day. The seeds of hardy annuals such as larkspur and Shirley poppy can be broadcast over snow cover any time in winter; melting snow carries the seeds into contact with the soil, they sprout in early spring and bloom in early summer, then die. Tender perennials such as bedding geraniums and coleus can be treated as annuals or they can be wintered as houseplants.

  • Short of building a tall fence, how can I keep deer from decimating my garden?

    Stop planting what the deer favor, hostas for example, and plant what they don’t like, pulmonaria, brunnera, tricyrtis and Japanese painted fern are examples. Deer love the taller growing tulips but ignore the ground-hugging species, otherwise most spring-flowering bulbs - daffodils, alliums, hyacinths - are not bothered by deer or rabbits. For a broader range of deer-resistant plants, type the appropriate category into your search engine, for example “deer-resistant shrubs for Iowa,” and you will find numerous choices.

  • I am planning a new garden. How can I get help with plant selection?

    Visit the Botanical Garden frequently in all seasons. Make lists of what you like and the time of bloom, or other interest such as colorful berries or bark. Whether your site is sunny or shady, moist or dry, you will find many appropriate plants among those that make up the different gardens at the Botanical Garden.