I have a wisteria vine that is healthy, and over 20 feet tall. This plant is three years old and has never bloomed. What can I do to get it to bloom?

Congratulations! You are well on your way to a blooming wisteria. A little basic biology may help you understand why it has not yet bloomed and what you can watch for to insure it does bloom. Wisteria seems to be a vine that thinks it is a tree; they can be so heavy that they need heavy duty support. That being said, your 3-year-old is just a baby and is not ready to bloom and set fruit (what plants do when they mature). The wisteria is a member of the pea family and the blooms are the precursor to pods (fruit). Be patient and do not start fertilizing; being members of the pea family, they are nitrogen fixers and form nitrogen-containing nodules on their roots. Overfertilization can stimulate foliar growth, but will not encourage blooming. Feeding it once a year with super phosphate to encourage root growth is about all it needs.

What is the cause for maple tree leaf veins to be much darker than the leaf itself?

What you are describing is symptomatic of leaf chlorosis. Chlorosis is the general yellowing of a leaf that can be brought on by a variety of factors. Disease, insects, cold weather, pollutants, a high level of minerals, or nutrient deficiencies can cause it. Your best course of action is to conduct a soil test. Call your county MSU extension office and they will help you obtain a kit complete with easy instructions. The results will help confirm or rule out problems in the soil. The test will also check the pH level in your soil. The correct pH level enables your plants to take up needed minerals and nutrients that are available in the soil. Read your test results carefully and if you need any clarification of the information, the extension office will again be glad to assist you.

Do cosmos reseed themselves? Do I take off the spent blooms or leave them to dry and fall off?

Most cosmos reseed themselves but not always reliably or true to the variety. The common cosmos in Michigan is an annual, so the best way to have nice plants that are the color and height you want is to sow new seeds each spring when the ground has warmed to 70 to 80 degrees. Or you can purchase plants from local garden centers. Plant them in full sun in the back of the garden where a fence or other plants can hold them up. They tend to flop in wind or heavy rain, and it is difficult to stake them because of their thin stems. In her book Annuals for Michigan, Nancy Szerlag suggests placing twigs around the young plants for support that will be covered when the plant is older. The plants germinate easily in the garden with only 1/8 inch of soil covering them. They are very drought tolerant and don’t need much, if any, fertilizer for the whole growing season.

To keep the plants blooming throughout the summer it is best to remove spent blooms. It also makes the plant look neater. If they get too tall and blooms are weak you can trim them back to half their height. They will grow back bushier to bloom again later in the summer. You can selectively cut them back, so there are still some blooming while the others grow back. If you want to encourage reseeding (and that means anywhere in the garden with help from the wind and critters), leave the seed heads on in the fall. The finches and other small birds love the seeds, and what they don’t eat may reseed.