Planting time in Iran is not uniform: in cold regions after leaf fall or in March; in hot, dry regions from late autumn to January. Leave summer out, and treat evergreens separately.
Planting saplings in Iran has no fixed calendar. A gardener in Shahrekord who picks the same week as a colleague in Yazd usually sacrifices one of the two saplings to the climate. In orchards and landscapes in Isfahan and the neighbouring provinces, Farin Kesht Taban has repeatedly seen a healthy sapling die in its first summer, or stay so weak that it takes three years to make one season's growth, simply because the planting date shifted by a month. Roots do not work in cold, frozen soil; and in the hot, dry soil of summer they get no chance to establish. The right decision is taken from the behaviour of soil temperature and the tree's dormancy, not from local habit or the date of a nursery fair.
Cold regions: Azerbaijan, Shahrekord and their equivalents
In the cold zones — Tabriz, Ardabil, Urmia, Shahrekord, Hamadan and the high slopes of the Zagros — there are two sensible planting windows. First, late autumn after complete leaf fall, when the deciduous tree is dormant but the soil has not yet frozen and can still be dug; usually November into December, depending on altitude. In that case the roots take some direction in the new soil before the hard frost and wake in spring without transplant shock. Second, March into early April, before bud swell, when the risk of deep soil freezing has passed. Planting in February onto frozen soil, or into spring mud, almost always ends in compaction around the roots and suffocation. If winter in your area freezes early and opens late, the March window is safer than December; if you have a long autumn and well-drained soil, planting after leaf fall is better.
In cold regions, move bare-root stock only in full dormancy. Containerised stock is more flexible, but still should not be planted on a frosty day or in a dry wind. After planting, one deep irrigation is needed to settle the soil; repeated shallow waterings only make surface ice. A light mulch over the root shade reduces the swing between freezing and thawing. Avoid nitrogen fertiliser on planting day; stimulating vegetative growth before the roots have established hands soft shoots to the cold in the first spring.
Hot and dry: Yazd, Kerman, Khuzestan and the similar belt
In Yazd, Kerman, Zahedan, the hot parts of Fars and Khuzestan, the main issue is heat and evaporation, not a long frost. The best window is from late autumn to January: the soil is still warm enough for root growth, crown transpiration has dropped, and the sapling has several months to root before the heatwaves of spring and summer. Planting in March is sometimes too late in these areas; the sapling has not yet settled into the soil before hot wind and the salinity of irrigation start to press on it. Leave out summer planting even if you have containerised stock and shade. The shock of transpiration, sunscald on the trunk and salt accumulated in the surface layer sharply reduce the take rate, and compensatory irrigation often only leaves the collar wet and diseased.
Count evergreens separately from deciduous trees
A deciduous tree transpires very little in winter dormancy, and moving it bare-root is natural. An evergreen — cypress, pine, olive, citrus in the warm belt — has leaves and loses water on the very day it is planted. In severely cold regions, put evergreen planting off to late winter or a mild early spring, so the roots are not imprisoned in frozen soil and the dry winter wind does not scorch the leaves. In hot, dry regions, plant evergreens in the same late autumn to January window, but take temporary shade and regular irrigation seriously for the first two or three months. Olive and citrus are sensitive to late spring frost; on the cold margin of a warm zone, shift the window towards early spring rather than towards December.
- Bare-root deciduous: only in full dormancy; in cold regions after leaf fall or in March; in hot dry regions from late autumn to January.
- Containerised deciduous: a wider window, but still keep away from the heat of July and August and from severe frost.
- Evergreens in cold regions: preferably late winter to a mild April; avoid December planting on frozen plains.
- Evergreens in hot dry regions: late autumn to January, with shade and establishment irrigation; summer is not recommended even in a container.
- Grafted saplings: keep the graft union above soil level and do not plant on frosty days or in a hot wind.
Read the calendar from soil temperature and bud dormancy, not from the date of the nursery fair. One week of suitable soil beats a month of haste.
Planting day: the pit, the collar and the first watering
The right time is not enough without the right execution. Dig the pit larger than the volume of the roots, but do not leave the base compacted, and break the glazed walls of clay soil so the roots can leave. In the calcareous soil of Isfahan and many central plains, mixing fresh manure or concentrated chemical fertiliser into the base of the pit burns the roots more than it helps. The collar must stay slightly above the finished soil level; subsequent settling brings it level. If the collar goes under the soil, collar rot in the first spring is common. Put the stake on the prevailing wind side and tie the sapling so the trunk can move a little; a rigid stake raises a weak trunk.
- Inspect the roots before planting: correct broken or circling container roots so they do not strangle the tree later.
- Prepare the pit the same day, or at most the night before, so the walls do not dry out and glaze.
- Give the first irrigation deep and slow so the air pockets fill; level the surface again the next day.
- In hot dry regions, keep the irrigation interval shorter than for a mature tree for the first two or three months, but do not create permanent flooding.
- In cold regions, keep the mulch away from the trunk so ice and rodents do not threaten the collar.
If you want only one rule: leave summer out of planting. In cold regions, choose between after leaf fall and March on the basis of soil freezing; in hot dry regions, do not miss late autumn to January. Do not move evergreens as if they were bare-root deciduous trees. In landscape and orchard projects, before ordering the saplings, Farkesht puts the planting window for that particular district on paper — because a good cultivar in the wrong month is the same cultivar, weak, the following year. If your soil is saline or strongly calcareous, look at planting time together with the establishment irrigation plan and the choice of rootstock; none of them alone guarantees the take.
