Chicago Botanic Garden Fall 2020

Ask the Experts Keep your lawn looking lush Although spring is a popular time for lawn renovation, fall is even better. The cooler temperatures and warm sun and soil help grass seed germinate quickly, so this is a good time to assess your carpet of green. Spot disease: See brown patches or ring spots? Those may be due to diseases that attack grass roots. Necrotic ring spot shows as crescent-shaped or circular patches of dead grass. Correct soil problems and implement proper cultural practices (such as proper watering and mowing methods). Sow grass seed over the dead areas. Control weeds: When the summer heat subsides, weeds start to grow actively again, taking nutrients into their root systems. If the lawn is small, you can pull weeds by hand—it's efficient, safe, and effective. A dandelion weeder is handy for this task. Next spring, you can apply a pre-emergent herbicide to target par- ticularly invasive weeds. Change mower setting: When cutting the lawn, set the mower high. The ideal height for grass in the fall is about 3 inches. A taller lawn creates deeper roots, does a better job at holding moisture, and deters weeds. When you leave grass clippings on the lawn, they’ll return nutrients to the soil. Water wisely: Water deeply and allow soil to dry out before watering again. This encourages lawns to develop a healthy root system before going dormant in late fall. The healthiest lawns get enough water at one time to moisten the top 6 inches or so of soil. Fertilize your lawn: Although mid-May is a popular time to fertilize lawns, fall is prefer- able. Use a slow-release, organic fertilizer— the label may say 4-1-2 or 3-1-2, which is the fertilizer ratio. Remember: Less is more. Don't over-fertilize, and avoid fertilizers with high levels of phosphorus, which can lead to water contamination and algae blooms. Sow seeds: Cultivate those bare patches, and sow seeds with a grass mix suitable for sun or shade conditions. At the Garden, we have found success with a mix of 80 percent bluegrass and 20 percent perennial rye, and within that is a blend of five different blue- grasses and three perennial ryes. Do core aeration: Aerating loosens the soil, increases drainage, encourages good root- ing, and limits thatch. Thatch is an accu- mulation of dead and decaying plant mat- ter that prevents water and food from getting to the roots. Follow up core aera- tion with overseeding. Learn more chicagobotanic.org/plantinfo Q. I have some beautiful potted chrysanthemums I purchased from the nursery. If I plant them directly into the garden, will they return next spring? A. Although many garden mums are con- sidered hardy, ​it is difficult to get mums to survive winter when planted in the fall. However, there are some precautions you can take to encourage their healthy return. Potted mums should be planted directly into the ground in a very sunny location as soon as possible so that they can develop a sturdy root system before winter. Water the plants well to encourage root growth, but do not apply fertilizer. When the foliage browns later this fall, let the stems remain to collect leaves, which will provide addi- tional insulation. ​Mulch the plants with 6 to 8 inches of shredded material to help keep the ground temperature relatively constant,​ but only after at least one hard freeze. Re- move the mulch early next spring as new growth appears; at that time, you can prune back dead stems from last season. Pinch the new shoots regularly until early July to encourage full-bodied plants. Learn more Send your plant questions to plantinfo@ chicagobotanic.org or call (847) 835-0972. Plant Information Service is sponsored by