Gadenin日本語Get the appCats will destroy a young vine
Kiwi stems and roots contain a compound closely related to the one in catnip, and cats respond to it the same way. They chew the bark, rub against the stem, roll on the roots and scratch at the base. On a mature vine with thick bark this is a nuisance; on a newly planted vine with a stem the thickness of a pencil it is fatal, often overnight, and gardeners frequently blame rabbits or deer for damage that was done by the neighborhood cat.
The damage is distinctive: bark stripped in vertical shreds from the lowest one or two feet (30 to 60 cm), the stem bent or snapped at the base, and the soil around the crown scuffed and compacted. There is no repair for a stem girdled all the way round. The only answer is prevention, and it has to be in place from planting day.
Protect the whole lower stem with a cylinder of wire mesh, at least a foot (30 cm) across so cats cannot rub the stem through it, staked so it cannot be knocked over, and running up to about three feet (90 cm). Keep it on for the first three or four years until the bark is thick and corky. Once the vine is up on its structure and the trunk is woody, you can usually take the cage off.
Cats also dig at freshly planted, freshly mulched kiwi roots. A layer of coarse gravel or a pinned-down mesh mat over the root zone in the first season stops the digging without stopping the water.
Frost catches it twice
The vine itself is reasonably hardy once dormant and woody, but its two vulnerable moments are the new spring growth and the young trunk in a hard winter. New shoots in spring are killed outright at about 30F (minus 1C), and a late frost after bud break can take every flower bud on the vine, which means no fruit at all that year even though the vine recovers and regrows fully by midsummer.
There is not much you can do about a frost on a mature vine on a pergola beyond siting it away from frost pockets in the first place, keeping the soil bare and firm underneath during frost season so it radiates stored heat, and covering the head of a small vine with row cover on a forecast night. Do not encourage early growth with a spring nitrogen feed in a climate that gets late frosts.
Young trunks split in hard winters, particularly where a cold night follows a sunny afternoon that warmed the bark. Wrapping the trunk of a young vine for its first few winters with row cover, cardboard or a purpose-made spiral guard prevents that, and doubles as a cat guard.
| Stage | Damaging temperature | What you can do |
|---|---|---|
| Fully dormant, mature wood | Below about 5F (minus 15C) | Trunk wrap on young plants, avoid frost pockets |
| Swelling buds | Around 28F (minus 2C) | Row cover over a small vine on forecast nights |
| New shoots and flower buds | Around 30F (minus 1C) | Nothing once it has happened, regrowth comes but no crop |
| Fruit on the vine | A hard freeze | Pick the whole crop ahead of it |
Wet feet and sudden collapse
Kiwi roots are fleshy, shallow and intolerant of standing water. A vine sitting in ground that stays saturated for days at a time will decline over a season or two and then, typically in the first real heat of summer, wilt suddenly and completely as if it had been cut off at the base. The wilt is the visible event but the roots died months earlier; the vine simply could not move enough water once demand rose.
Look for the early signs instead: leaves that scorch brown at the margins in midsummer while the soil is plainly wet, growth that is short and pale, and small fruit. Dig down a foot (30 cm) at the edge of the root zone and look at the roots. Healthy kiwi roots are firm and white or cream inside; rotted ones are brown, soft, and the outer skin slips off between finger and thumb.
Once collapse has happened there is no cure. Prevention is drainage: plant on a raised mound in heavy ground, do not overwater an established vine in wet weather because someone told you kiwi is thirsty, and never let a hose or downpipe discharge near the crown. Mulch kept off the trunk keeps the collar dry, which is where collar rot starts.
Canker, bleeding and pruning wounds
Bacterial canker is the disease that has done the most damage to kiwi worldwide, and it enters through wounds: pruning cuts, frost cracks, hail damage and leaf scars. The signs are a rust-red or white ooze from the trunk or arms in late winter and spring, reddish leaf spots with a yellow halo, wilting of individual canes while the rest of the vine looks fine, and dark sunken patches of dead bark.
Sanitation is most of the defense. Prune in dry weather in the middle of dormancy so cuts seal quickly, disinfect your pruners between plants, avoid leaving long stubs that die back, and take prunings away rather than leaving them under the vine. If a cane shows ooze or a sunken lesion, cut it out well below the affected wood, back into clean tissue, and disinfect the blade before the next cut.
A clear, watery sap running from late winter cuts is a different thing and is not disease: it is normal bleeding from pruning too close to bud break. It rarely kills the vine but the wounds heal badly, so shift your pruning earlier next year.
Insects and the smaller troubles
Kiwi has relatively few insect pests, and most of what appears is manageable or can be tolerated. Scale insects on the trunk and older wood are the most common, showing as small brown or gray bumps that scrape off with a fingernail, with sticky honeydew and black sooty mold on the leaves below. Scrub them off with a stiff brush in winter and improve air movement by pruning; a heavy infestation on the fruit downgrades it cosmetically but does not spoil eating.
Leafroller caterpillars web leaves together and sometimes graze the skin of developing fruit, which scars it. Squash them by hand where you can reach. Root-knot nematodes in warm sandy soils cause stunting and swellings on the roots, and the practical response is heavy organic matter and mulch rather than treatment. Wasps and birds go after any fruit left hanging until it softens, which is one more reason to pick the crop hard.
| Symptom | Likely cause | Action |
|---|---|---|
| Bark shredded on the lowest foot of stem | Cats | Cage the stem now, keep it caged for years |
| All new shoots black and limp in spring | Late frost | Wait, it will regrow, expect no crop this year |
| Sudden whole-vine wilt in early summer | Root rot from waterlogging | Check roots, improve drainage, replant on a mound |
| Rust-red ooze on trunk in late winter | Bacterial canker | Cut back into clean wood, disinfect tools, remove prunings |
| Clear watery sap from a fresh cut | Pruned too near bud break | Harmless, prune earlier in dormancy next year |
| Brown scorch on leaf margins, soil wet | Roots failing, not drought | Stop watering, check drainage |
| Sticky leaves, black mold, brown bumps on wood | Scale insects | Brush off in winter, open up the canopy |
| Flowers open then drop with no fruit | No pollination | Check the sex of your plants and the bloom overlap |
Keep a note of what showed up and when
Write down the first date you see each problem, on which vine, and how bad it was. First frost damage, first ooze on a trunk, the day the cats got at a stem, the week the scale appeared. Add what you did and whether it helped.
Kiwi problems are seasonal and repeat, so a two or three year record turns them into something you can anticipate. Knowing that your late frost damage almost always falls in a particular week of spring tells you when the row cover needs to be within reach, and knowing which vine gets canker first tells you where to start looking each winter.