Herbs
If you left a rosemary plant outside and winter protected it, remove the protection about the same time you do strawberries. It is interesting to see what herbs tolerate or even seem to prefer our clay soils. Surprisingly tarragon seems to grow well in it. Be sure to get the "true" French tarragon if you buy any. Russian tarragon is awful substitute - inferior for seasoning, grows too large and may be invasive. Lavender is difficult to grow in Missouri; it liked the sandy soils I had when in Michigan and thrived anywhere with sun. Many of the Mediterranean herbs like sage and thyme prefer drier soil, so locate where the soil is raised, the spot sunny and perhaps in a rain shelter from an overhang.
Chives come on strong before onions begin growing much in the vegetable garden. I substitute them for green onions in cooking during the spring.
Trees
Rainy Aprils aggravate a number of foliar diseases; one of the most noteworthy is anthracnose, which affects many shade trees. A frequently observed symptom is the sudden wilting and death of a young leaf, which is often confused with frost damage. Because these fungi primarily infect in mild weather when there is a film of water on the leaf surface, spring and fall are the seasons when infection occurs. Ten common trees are affected, such as maple, ash, sycamore and white oak. Spots develop on more expanded leaves, and the type of spots vary with tree.
Lawns
Get ready to start mowing, and remember, the first one often takes longer as you'll likely have to clean up sticks and leaves. Do you need a new lawn mower? Consider an electric mower. I got one a few years ago, figuring it was less maintenance and it would be safer for my teenagers to use. The quietness is pleasant; my son described like pushing an air conditioner across the lawn. It has two batteries, and you can get about 45 minutes out of it between the two.
Crab grass preventer is commonly applied to cool season lawns and should be put down before April 15. But a little-realized detail is bare soil warms up quicker than sod. Since crabgrass germinates based on soil temperature, it will do so earlier where the soil is bare/open places. If you have that situation, consider applying at the earlier date, which is April 1. Many crab grass preventers include fertilizer. This is OK, especially if you only fertilized once in the fall. But if you fertilize now, it would be best to NOT fertilize later this spring with another weed control and fertilizer product. Two applications of fertilizer in the spring will aggravate some diseases of cool season grass like brown patch on tall turf type fescue.
Flowers and ornamentals
Choosing annual and perennial flowers to benefit pollinators has gained interest. Many common perennials are good, although there is variability between which pollinators they might benefit, e.g. bees, butterflies or others. A good source of information is www.pollinator.org. Good lists with the differing plant attributes can be found.
More difficult to find are annual flowers that are beneficial. Missouri Botanical Garden's ever useful "Plant Finder" can assist. It allows filtering for butterflies and hummingbirds, but not bees. A fairly short list of "showy" annuals comes up, which include Cleome, Cuphea (blue waxweed), jewelweed (Impatiens capensis), lemon mint (Monarda citriodora ) African and French marigolds, phlox, Mexican sunflowers (Tithonia) and zinnias. Sunflowers appear on many other lists with the branching types preferable for a longer bloom period. Double flowering types (of any flower, roses included) often produce less nectar and pollen (or are less accessible to the pollinators) so favoring single types is considered better.