Mulberry

Skip the fertilizer on an established mulberry

Do not feed an established mulberry as a matter of routine. Hold off unless a soil test or genuinely poor growth says the tree needs something, and water only through the first year or two while it roots in, or during an extended drought. Mulberries thrive in sandy, infertile soil and rarely need irrigation once established. Pushing a tree that is already among the fastest-growing fruit trees with nitrogen mostly buys you more wood to cut out next winter and lifts the fruit further out of reach.

Prune only while the tree is leafless and fully dormant

Prune in late fall or winter, once the leaves are off and the tree is fully dormant. On a young tree, make light cuts to build a strong framework of well-spaced scaffolds and to hold the head low enough to pick from the ground, because a mulberry left alone will outgrow hand harvest fast. On an established tree, take out only dead, damaged, or crossing limbs rather than opening it up with big cuts. Every part of a mulberry runs with milky latex, and cuts made once the sap is moving bleed heavily; the wounds left by removing a major branch are also slow to callous over, so a large cut stays open to decay organisms for years.

⚠ The milky sap causes skin rashes in some people (UF/IFAS) - wear gloves and long sleeves, and keep the latex off your face. The leaves and young shoots contain a white latex that is mildly toxic if eaten.

Popcorn disease: pull and destroy every deformed berry

As the fruit colors, walk the tree and look for berries whose individual segments have swollen into pale, puffy lobes that stick out past the healthy fruit like popped corn. Pick every deformed berry off the tree and rake up the ones that have dropped, then bury or bag them. Do not compost them and do not leave them lying under the canopy. The fungus survives nowhere but in those infected berries. Each one left on the tree or on the ground dries into a mummy that produces the spore-bearing cups which reinfect next spring's flowers, so removing them is the control - and white mulberries and their hybrids are the most susceptible.

Spotted wing drosophila: your mulberry is the neighborhood's first nursery

Start watching about two weeks before the berries begin to color. Hang a trap baited with apple cider vinegar or a commercial lure in the shaded side of the canopy, three to five feet up. Whether or not you trap, pick up overripe and fallen fruit promptly - seal culls in a plastic bag and leave it in the sun, or bin them. Never compost infested fruit, and do not bury it shallower than about two feet. Mulberry is one of spotted wing drosophila's favorite wild hosts and ripens ahead of most cultivated berries, so an unpicked mulberry quietly breeds the flies that go on to hit your raspberries, blueberries, and cherries weeks later. The fly lays into sound, ripening fruit rather than waiting for damage, so the fallen crop underneath is a reservoir, not litter.

⚠ This rule is deliberately sanitation-only. Insecticides for spotted wing drosophila are labeled for commercial berry and cherry crops and carry crop-specific pre-harvest intervals; mulberry is not on those labels, so do not carry a berry spray over to it.

Popcorn disease: protective Bordeaux as the tree leafs out

Only worth doing if popcorn disease deformed your crop last year. As the buds break and the first leaves push, apply Bordeaux mixture (copper sulfate plus hydrated lime) to the whole canopy, before the flowers and young fruit are exposed. Fungicides are not routinely recommended on mulberry and full coverage of a big tree is genuinely hard, so treat this as a supplement to sanitation, never a replacement for it. Ciboria carunculoides overwinters in mummified berries and releases its spores at the developing flowers and young fruit in late spring; a protectant copper film on that tissue during the infection window is the only chemical measure reported to help.

⚠ Bordeaux mixture is a copper fungicide - follow the label rate and confirm the label covers mulberry or fruit trees generally before you spray. Copper can burn foliage applied in hot or slow-drying weather.

Net the tree as the flowers finish, not when the fruit turns

Put netting up near the end of flowering, while the fruit is still small. Drape it over a frame rather than the branches themselves, run it to the ground on every side, and pin it down every two to three feet with sod staples so there are no gaps. Harvest by lifting a section of staples and picking from underneath instead of pulling the whole net off. Netting is the only reliable defense - birds learn within days that pie pans and rubber snakes are bluffing. Waiting until the berries color makes the net far harder to install, and any gap left at the bottom lets birds walk in and then trap them inside.

⚠ Gaps in the netting trap birds rather than exclude them - check the perimeter after installing, and keep the net off the foliage so berries and wildlife do not tangle in it.

Pick at full color, and expect a short, repeated window

Take the berries once they have gone fully dark - deep purple-black on red and hybrid types, or fully blushed on the white-fruited ones - and pull free with no resistance. Go over the tree every day or two. On an everbearing hybrid the ripening rolls on for weeks, but on a red mulberry the whole crop is often done in a few weeks in early summer. A fully ripe berry drops on its own within a day or two, so anything you leave feeds the birds, stains what is underneath, and breeds fruit flies. Unripe fruit is not worth taking either: greenish-white berries are simply not ripe, and the tree's latex is mildly toxic if eaten.

⚠ Pick only fully colored fruit - do not eat greenish-white unripe mulberries, and note that the leaves and young shoots contain a white latex that is mildly toxic if eaten. Ripe fruit stains badly, so keep the harvest and the drop off driveways, patios, and walkways.