American Linden (Basswood)

While the tree is still leafless, take out dead, broken and crossing branches and train young trees to a single central leader. Do not cut back the leader itself. Time it to your own site rather than the calendar: wait for the last hard freeze to pass but finish before the buds swell, which is late winter in the South and can be as late as early spring in the far North. Dormant wounds sit open only briefly before growth resumes and closes them, and the bare branch structure lets you see what to cut without leaves obscuring it. Warm-season cuts stay open longer and invite infection.

If last summer brought heavy honeydew, spray horticultural mineral oil as a dormant or delayed-dormant application while the tree is still bare, covering twigs and bud crevices thoroughly. Delayed-dormant means just as buds begin to swell but well before any flowers appear, so read the tree rather than the calendar. Try dislodging aphids with a water spray first — the source lists that as a non-chemical option before any pesticide. The oil smothers overwintering aphids and eggs before the colonies build on the leaf undersides, which is the only cheap moment to knock the population down.

When the drooping clusters of pale yellow flowers are open and heavily fragrant, pick the cluster together with the pale strap-shaped bract above it. Dry them in a single layer in a shaded, well-ventilated spot, then store airtight. The fragrance is the volatile oil that makes the tea, and it is at its peak while the flowers are freshly open. The bract dries with the flower and is part of the traditional tea.

Through hot dry spells, water slowly and deeply rather than often and shallowly, and keep a ring of organic mulch over the root zone without piling it against the trunk. Check the trunk for string trimmer wounds or cankers while you are there. Linden scorches when water cannot reach the leaf margin fast enough to keep up with transpiration, so the edges and tips brown and die back. Anything that restricts flow, including trunk injury, produces the same symptom.

Walk the trunk through the growing season and cut or rub off the shoots coming up from the roots and low on the trunk while they are still soft and green. American linden is prone to producing root sprouts at the base of the tree, and left alone they thicken into a competing shrubby skirt that steals growth from the leader.

Once the flowers are done, check the sunlit top of the canopy for beetles and lace-like skeletonized leaves. Hand-pick what you can reach into soapy water, early, before the feeding damage draws in more beetles. Linden is one of the Japanese beetle's preferred hosts, and the beetles start emerging from the ground in late June or early July. Once they are present in large numbers they are much harder to manage.

If beetles are stripping a tree planted in the last two or three years, chlorantraniliprole gives two to four weeks of protection and is low risk to bees. Wait until flowering is completely finished. Large trees generally need a professional applicator. If you harvest this tree's flowers for tea, do not treat it unless the product label covers that use — see safety notes. Defoliation of a well established, healthy linden is usually not fatal, so the spray is worth it only where the tree is young or already in poor health and cannot afford to lose its canopy.