We have some real signs spring is going to happen, and the calls, emails and visits to the Illinois Extension Master Gardener Help Desks often start with "What's the best time to…?"
Here are a few FAQs for the start of the home gardening and landscape season.
Q) What is the best time to apply crabgrass preventer?
A) Crabgrass seed will not germinate until the soil temperature reaches 55 degrees and stays there for at least 7 days. Last week, soil temperatures were just hitting 48 to 50 degrees. Bare and dark-colored soils warm quicker than sandy and covered soils (lawns and mulched areas). Crabgrass preventers put down too early will break down long before crabgrass seed stops germinating. Put down too late and you will still see crabgrass. Timing is everything.
Q) What is the best time to start apple tree sprays?
A) We are very close right now. To protect foliage and later the developing fruits, sprays start as soon as you see what we call "green tip." As the protective bud scales begin to soften from spring rains, the foliage buds (and quickly to follow, the flower buds) start to push out. The green tip we see represents all the leaves for the season. Keeping the leaves covered from green tip to fully expanded and beyond will prevent Apple Scab and Cedar Apple Rust fungal diseases, which damage the leaves. If you are unclear about "green tip," here is a situation where starting too early is not a bad approach. Starting after the leaves are already infected may help any leaves that show up later, the infection will remain season long. The part to remember is the leaves produce the resources needed to: 1) create this year's apples, and 2) create next year's foliage and flower buds. Of all our tree fruits, apples are the most challenging. Timing is everything.
Q) What is the best time to start the vegetable garden from seed?
A) Vegetables have a range of soil temperatures they prefer. If the garden bed is in good condition already, the earliest leafy vegetables are leaf lettuce, kale, and spinach. Others include onion and peas. Closer to our average frost-free date (AVFD, anywhere from April 25 through May 5) beets, carrots, chard and radishes work. A good way to get more out of the garden is to sow carrots and radishes together in the same row. Radishes come up early, marking the row and are harvested long before carrots need the space. Once we hit the magical AVFD, tender vegetables like snap beans and summer squash are sown. Lastly, we have vegetables that absolutely need warm soils. These are a lot of our other vine crops like, cucumbers, melons, watermelons (if you are up to the challenge), and our winter squashes harvested in late summer or fall. So what about tomatoes and peppers? We normally put these in as transplants. Tomatoes go in with the tender vegetables and peppers with the warm soil group. We lose at least 2 weeks of growing if we plant the tomatoes at the right time for peppers.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.