Gadenin日本語Get the appPlant two, not one
Most olives are only partly self-fertile. A single tree standing alone will flower, may set a scatter of fruit, and will disappoint you every year. Plant a second, genetically different olive within about fifty feet (15 m) and the crop on both trees typically increases several times over.
Olive pollen is carried on the wind, not by bees, so the second tree does not need to be beside the first. What it does need is a clear air path and an overlapping flowering period, which in practice means another olive of a different type rather than a cutting taken from the same plant. Two trees grown from cuttings of one parent are the same plant twice and pollinate each other no better than one tree alone.
For a container grower with room for only one large pot, the workable answer is a second smaller pot standing nearby during the flowering weeks. It can be moved somewhere less prominent for the rest of the year.
If you already have a lone tree that flowers heavily and sets nothing, this is almost always the reason. Adding a second tree usually produces a crop the following season.
Drainage decides everything else
An olive will take poor, thin, stony soil without complaint. What it will not take is ground that holds water in winter. Before planting in the open ground, dig a hole about a foot (30 cm) deep, fill it with water and let it drain, then fill it again. If the second filling has not gone within a few hours, the site is too wet for an olive as it stands.
The fix is height rather than drainage material in the bottom of the hole, which does not work. Plant on a raised mound or a low raised bed eight to twelve inches (20 to 30 cm) above the surrounding level, and mix coarse grit through the soil you backfill with. A tree planted high on a mound survives a wet winter that kills one planted at grade a few feet away.
- Dig wide, not deep Make the hole two to three times the width of the rootball but no deeper than it. A hole dug deep and backfilled settles, and the tree sinks into a sump.
- Keep the root flare visible The point where the trunk widens into the roots must sit at or slightly above the finished soil level. Burying the flare rots the bark at the base.
- Backfill with the soil you dug out Add grit for drainage, but do not fill the hole with rich imported compost. A pocket of soft compost in heavy ground becomes a bucket that holds water.
- Water in once, thoroughly Soak the rootball at planting to settle the soil against the roots. After that, water only during dry spells in the first two summers.
- Mulch, but keep it off the trunk A gravel or bark mulch two inches (5 cm) deep suppresses weeds and keeps the surface roots cool. Leave a clear ring of four inches (10 cm) around the trunk.
Spacing and position
A garden olive left to grow will reach fifteen to twenty-five feet (5 to 8 m) across in time, though most gardeners keep them pruned to a fraction of that. Plant trees intended as a pair at least fifteen feet (5 m) apart so each keeps a full sunny canopy, and keep them well clear of walls that will shade the lower branches.
Choose the sunniest, most open spot you have. A south or west aspect against a wall gives the best fruiting in cool climates, provided the wall is not a heated house wall that will rob the tree of its winter chill. Wind is not a problem for an established olive and helps pollination, so do not tuck the tree into a sheltered corner.
| Situation | Minimum spacing | Notes |
|---|---|---|
| Two trees for pollination | 15 ft (5 m) apart, under 50 ft (15 m) | Different types, clear air between them |
| Single specimen from a wall | 8 ft (2.5 m) | Avoid heated house walls |
| Container tree | Pot 16 in (40 cm) across minimum | Move up one pot size every two or three years |
| Informal screen | 8 to 10 ft (2.5 to 3 m) | Accepts hard pruning to keep the line |
Planting into a pot
A container olive needs a mix that drains far faster than standard potting mix. Aim for roughly two parts of a loam-based compost to one part of coarse grit, and choose a heavy pot, since a mature olive in a light plastic pot blows over in the first gale.
Plant at the same depth the tree was in its previous pot and leave an inch (2.5 cm) of space below the rim for watering. Stand the pot on feet so the drainage holes stay clear of the ground, and site it where you can move it: the same pot needs full summer sun and an unheated, bright winter position, and those are rarely the same place.
What to record on planting day
Write down the planting date, where each tree stands, and which two trees are meant to pollinate one another. Olives take several years to come into bearing and by the time a fruiting problem shows up you will have forgotten which is which.
Note the drainage test result too. If the tree later struggles, knowing that the hole took four hours to empty is far more useful than guessing about feed or pests.