Is it OK to plant during the summer? I heard it’s best to plant in the spring and fall. I will primarily be buying shrubs and perennials grown in containers so it will be easier for me to plant them.
— Jessica Anderson, Crystal Lake
I continue to install plants all summer long and have done so with success for many years. Gardeners just need to pay close attention to the proper watering of plants installed in the summer, with extra attention given to plants grown in containers. Numerous types of containers and growing media have been developed for container growing of nursery stock. Media mixes without topsoil were developed for producing plants in containers because the poor soil aeration and drainage caused by using garden soil in a container will result in subpar plant growth and performance. The container mix used for the plants growing in containers that you purchase will be coarser and better drained than the soil in your garden.
Plants grown in containers will need more frequent, light watering to get established, as the container growing medium will dry out more quickly than the surrounding garden soil. Water will not readily move from the finer soil particles in the existing garden soil to the coarser container mix. Weather will also have a major impact on the frequency and amount of water that the plants will need. In the initial four to six weeks after planting, check the root ball growing medium to see if the plant is dry, as the garden soil can be moist while the roots of the new plant are in a dry container medium and under drought stress. This can happen fast on a hot, sunny day. Once the plant roots grow out into the garden soil, you can water less frequently and more deeply as you would normally do.
Plants that have been grown a bit too long in the container can be root-bound and will need more frequent watering, as the plants can dry out even more quickly. Be sure to break up any roots circling the root ball when you are planting to encourage the plants to root out into the soil. I recently installed some Bobo hydrangeas in full flower growing in 3-gallon containers that immediately began wilting. I anticipate watering them three times a week for the first month to get them established since they are in full flower with a lot of foliage to support a small root system. I learned this approach the hard way after losing some of the same plants last summer due to inadequate watering.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.