Gadenin日本語Get the appUnderstand the size of the thing you are planting
A mature pecan reaches 70 to 100 feet (21 to 30 m) tall with a crown 60 to 75 feet (18 to 23 m) across, and it lives well past a century. Nothing about a two-year-old whip in a pot suggests this. Gardeners plant them 20 feet (6 m) from a house, and thirty years later the tree is dropping heavy limbs over the roof and the crop is unreachable.
Give a single tree at least 40 feet (12 m) of clearance from buildings, drives, septic fields and overhead lines. The root system spreads well beyond the branch tips, and the surface roots lift paving. Because pollination needs a second tree of the opposite timing group, plan for a pair from the start rather than squeezing one in and regretting it.
The other consequence of that size is time. A grafted tree begins bearing a handful of nuts in its sixth to tenth year and does not reach a real crop until fifteen to twenty. A seedling grown from a nut takes longer still and gives you an unknown result. Plant on the assumption that you are planting for the second half of your life, not for next autumn.
The season pecans actually need
Pecans need heat, and a great deal of it. Filling a nut takes roughly 180 to 220 frost-free days with hot nights, not just warm days. In a marginal climate the tree grows perfectly well, flowers, sets nuts, and then hands you shells full of shriveled or half-empty kernels every year, because the season ended before the kernel finished filling. That failure looks like a pest problem and is not one.
The tree itself is hardy well below the range where it will ripen a crop. Wood survives to around -10F (-23C) once established, but that tells you nothing about whether nuts will fill. If your growing season is under about 170 days, or your summer nights sit below 65F (18C), expect foliage rather than food, and choose the site as you would for a large shade tree.
Water matters as much as heat. Pecans evolved on river bottoms and are shallow-rooted for their size, so deep fertile soil with a water table within reach suits them. Avoid thin soil over rock, and avoid ground that stands wet in winter.
| Site factor | What pecans need | Sign you got it wrong |
|---|---|---|
| Frost-free days | 180 or more | Kernels shriveled or hollow at harvest |
| Summer nights | Above 65F (18C) | Slow fill, late shuck split |
| Soil depth | 4 feet (1.2 m) or more | Stunted growth, drought scorch in midsummer |
| Drainage | Never standing water in winter | Yellow leaves, dieback in the crown |
| Sun | Full sun all day | Thin crown, no nuts on shaded side |
| Space from structures | 40 feet (12 m) minimum | Limbs over the roof, lifted paving |
Planting a bare-root tree
Pecans are almost always sold bare-root and dormant, and they carry a long taproot that is easily ruined. Plant while the tree is fully dormant and the ground is workable. Get it in the ground the day it arrives; if you cannot, heel the roots into damp soil or sawdust and keep them out of the wind.
- Dig deep, not wide Dig a hole deep enough that the taproot hangs straight down without curling, usually 24 to 36 inches (60 to 90 cm). A coiled taproot cripples the tree permanently. Width matters less than depth; two shovel widths is enough.
- Trim only damaged roots Cut back torn or broken root ends to clean tissue. Do not shorten the taproot to fit the hole. If the taproot is too long, dig deeper or use a post-hole auger to extend the bottom of the hole.
- Set the graft union above ground Place the tree so the soil line on the trunk matches the old nursery line and the graft union sits 2 to 4 inches (5 to 10 cm) clear of the finished soil. Burying the union invites the rootstock to take over.
- Backfill with the soil you dug out Use the native soil, no compost or fertilizer in the hole. Firm it in layers and water heavily as you go to collapse air pockets around the taproot. Amended backfill encourages roots to circle inside the hole instead of leaving it.
- Cut the top back hard Head the whip back by a third to a half at planting. The root system lost a large share of its feeder roots on lifting and cannot support the whole top. Trees left uncut leaf out, then die back anyway.
- Mulch and stake Mulch 4 inches (10 cm) deep in a circle 4 feet (1.2 m) across, kept off the trunk. Stake only if the site is windy, and remove the stake within two years so the trunk builds its own strength.
Record the planting date, the exact position of each tree, and which timing group each one belongs to. Ten years on, when one tree crops and the other does not, that note is the only way to work out why without guessing.
The first three years
Establishment is slow and looks like failure. A newly planted pecan often puts on almost no top growth in its first season while it rebuilds the root system. Judge the tree by whether the leaves stay green and firm through late summer, not by height.
Water is the one thing that decides survival. Give a young tree 10 to 15 gallons (40 to 55 liters) a week through the growing season in the absence of rain, applied slowly in one soaking rather than daily sprinkles. Keep a weed-free, grass-free circle out to the mulch edge; grass competes hard for water and will halve the growth rate on its own.
Hold back on nitrogen the first year. From the second spring, a light application as growth starts is enough. Pecans are also prone to zinc deficiency on alkaline soils, which shows as small, narrow, crinkled leaves with short spacing between them on new shoots; foliar zinc sprays on the expanding leaves in spring correct it, and soil applications on alkaline ground do not.