Japanese Apricot Care: Protecting Winter Blossom, Watering and Feeding

The season turns on the flowering weeks

Japanese apricot flowers earlier than almost anything else you can grow, opening on bare dark wood before a single leaf appears, in the coldest part of the year. That is why people plant it, and it is also the single biggest risk to the crop. Open blossom is killed at around 28F (minus 2C), and a fully open tree caught by one hard night will drop every flower and give you nothing, however good the rest of the season is.

Nothing you do later recovers a crop lost that way. Feeding, watering and thinning are all worth doing, but they are second-order next to getting the flowers through the cold nights and getting pollen moved while they are open. If your time is limited, spend it there.

This also shapes how you think about the tree's value. Many gardeners grow it primarily for the winter flowers, which are scented and last two to three weeks in cool weather, and take whatever fruit follows. If that is your position, you still want the tree sheltered, because wind and frost shorten the display as surely as they kill the crop.

Getting the blossom through the cold nights

You cannot delay flowering by much, so the work is protection on the nights that matter. Watch the forecast from the moment the buds show color, and treat any night forecast to fall below 30F (minus 1C) as a night to cover a tree that is in flower.

1. Cover before dusk, not at bedtime Put row cover on in the late afternoon while the ground still holds the day's warmth. Covering a tree that has already gone cold traps cold air and does very little. Two light layers hold more heat than one heavy one.
2. Keep the row cover off the flowers Drape the cover over canes or a frame so the fabric does not touch open blossom. Where row cover rests directly on flowers, those flowers freeze anyway and the petals brown where the fabric touched.
3. Uncover in the morning Take the cover off once the air is above freezing so the flowers can be worked by any insect that is flying, and so the tree does not sit warm and damp all day. Damp still air under a permanent cover invites blossom rot.
4. Water the ground before a frost night Moist soil holds and releases far more heat overnight than dry soil. A soaked root area on the afternoon before a still, clear night is worth two or three degrees under the canopy.
5. Move a container tree A potted tree can go into an unheated porch or against a house wall for the flowering weeks. Do not bring it into a warm room; heat pushes the flowers over in days and the pollen dries out.

A still, clear night after a bright day is the dangerous kind. A cloudy or windy night at the same forecast temperature rarely does the same damage, because the tree is not radiating heat to an open sky. If you can only cover on some nights, cover on the clear ones.

Move pollen yourself while the flowers are open

At this time of year there is almost nothing flying. Most bees and hoverflies work only above about 55F (13C), and on a bright cold day at flowering you may look at a tree in full bloom and see no insect on it at all. Combine that with the fact that many kinds need pollen from a different tree, and a full blossom converting to nothing is entirely ordinary.

Hand pollination pays for this crop more than for almost any other garden fruit. Take a soft artist's brush about a quarter inch (6 mm) wide, work in the middle of a dry day when the pollen is loose, and go flower to flower along each branch. If you have two different kinds, load the brush on one tree and carry it to the other, then reverse. Repeat daily for as long as new flowers keep opening, which is usually a week to ten days.

If the tree spends the flowering period under row cover or in a porch, hand pollination is not optional. You have shut out the few insects that were available, so you are now the only delivery mechanism the tree has.

Watering and feeding through the growing season

An established tree in open ground is fairly drought-tolerant and needs watering only in its first two summers and in a genuine drought. The exception is the stretch from fruit set until picking, when swings between bone dry and soaking split stones and crack skins. Give one long soak a week that wets the soil to 12 inches (30 cm) rather than a daily sprinkle, and water at the base rather than over the fruit.

A tree in a large container is a different animal. Its compost can dry out within a single hot day, and once the rootball shrinks away from the pot wall, water runs down the gap and straight out of the bottom without wetting anything. Check pots daily through summer, and stand a dried-out pot in a tray of water for an hour to rewet it properly.

Nitrogen after midsummer is the feeding mistake that damages this tree. It pushes soft sappy shoots that will not harden before the cold, and unripened wood is exactly what canker and winter dieback take first.

Thinning, mulching and the record that helps next year

The tree drops a proportion of its set fruit by itself a few weeks after flowering. Once that drop has finished, thin what is left to about 2 to 3 inches (5 to 8 cm) apart so the fruit that remains can size up and air can move between them. A tree left to carry everything gives small fruit, more rot, and a much lighter crop the following year.

Mulch 2 to 3 inches (5 to 8 cm) deep over the root area each spring, kept clear of the trunk. It steadies the soil moisture through the swelling period, which is the thing that most affects fruit size.

Keep a short record of the flowering weeks in particular, because that is the part of the year you will want to reason about later. Write down the date the first flower opened, the date the tree was fully out, every night you covered it and the temperature that night, whether you hand pollinated, and roughly what fraction of the flowers set. Three seasons of those notes tell you whether your site is workable for fruit or whether you should treat the tree as a blossom tree and stop fighting the weather.