Gadenin日本語Get the appA crop that gets off lightly, with two exceptions
Garland chrysanthemum is one of the easier leafy crops to keep clean. The strong resinous scent that makes the leaves distinctive also makes them unattractive to several pests that ruin brassicas: flea beetles largely ignore it, and cabbage caterpillars rarely bother with it at all. If you have struggled with shot-holed rocket and lace-curtain kale, this crop will feel like a holiday.
The exceptions are aphids and leaf miner. Aphids are not deterred by the aroma in the slightest and go straight for the soft growing tips, which are exactly the part you eat. Leaf miner larvae tunnel between the leaf surfaces and are usually noticed only once the trails are obvious. Neither is difficult to manage, but both need looking for rather than waiting for.
What to look for, and what it means
Turn a few leaves over and look into the shoot tips every time you pick. Ten seconds a plant catches nearly everything at the stage where the response is simple.
| Symptom | Cause | First response |
|---|---|---|
| Curled shoot tips, sticky leaves, dense colonies at the growing point | Aphids | Jet with water or squash by hand; cut off the worst tips and stop feeding |
| Pale winding tunnels between the leaf surfaces | Leaf miner | Pick off and bin the affected leaves; cover new sowings with fine mesh |
| Large ragged holes with slime trails, worst near the base | Slugs and snails | Clear mulch away from the crowns; hand-pick after dark |
| Seedlings toppling at soil level with a pinched brown stem | Damping off | Sow thinner, water less, improve airflow; the affected seedlings will not recover |
| Round brown or gray spots with a darker margin on older leaves | Leaf spot | Remove the marked leaves, widen spacing, water the soil rather than the foliage |
| Fine pale stippling with webbing in dry warm weather | Spider mite | Raise humidity, water thoroughly, cut back hard if it has spread |
| Whole plant wilts and does not recover overnight | Root rot in wet soil | Pull and remove it; fix the drainage before resowing |
Aphids live where you least want them
Aphid colonies here sit in the tightest part of the shoot tip, wedged between the folded young leaves. That position means they are sheltered from sprays and from rain, that they are invisible from above until the tip visibly curls, and that they contaminate the tenderest part of the crop. A plant can look immaculate from a standing position and be carrying hundreds at the tips.
Soft overfed growth is what draws them. A plant pushed with high-nitrogen feed produces exactly the thin-walled, sappy tissue aphids feed on best, which is one more reason to feed at half strength. Crowded rows make it worse, because still air between plants suits the colony and hides it from predators.
The practical response is mechanical and repeated. A firm jet of water into each shoot tip removes most of a colony, and doing it every three days for a fortnight will usually end the problem, since the survivors are picked off by ladybirds and hoverfly larvae that arrive within a week or two. Where a tip is badly infested, cut it off and remove it rather than trying to clean it; you were going to harvest that tip anyway.
Anything you cut off with aphids or leaf miner in it should leave the garden rather than go on an open potting mix heap. Leaf miner larvae in particular will complete their development in discarded leaves lying beside the row and re-emerge as adults a few feet from where you started.
Seedling losses are almost always your watering
The heaviest single loss most growers take on this crop happens in the first fortnight, and it is not a pest. Damping off flattens a dense sowing in cool damp conditions, particularly under cover or in a container, and it is driven by sowing too thickly and keeping the surface permanently wet.
Because germination is slow and uneven, there is a strong temptation to sow heavily and water constantly to keep the surface damp for a fortnight. That combination is exactly what the fungi involved need. Sow at twice your target density and no more, water the row rather than misting it repeatedly, and give a covered sowing real airflow rather than a sealed lid.
- Pull immediately Any seedling that has toppled at the base, any plant that has wilted and not recovered overnight, and any plant where more than half the leaves are marked with spot. Take them out of the garden entirely.
- Treat and look again in a week Aphid colonies on a few tips, scattered leaf miner trails, slug damage on lower leaves. Deal with the cause, then reassess after seven days. If it has spread across the row, cut the row hard and resow.
- Ignore it A few tunnels on old lower leaves you were going to strip off anyway, and light slug grazing at the base of an otherwise strong plant. Neither costs you a usable harvest.
The record that saves you next season
Write down the date you first see aphids at the shoot tips, and the date you first see a leaf miner trail, along with the bed. Both arrive within a fairly narrow window in any given garden, and after two seasons of first-sighting dates you know precisely when fine mesh needs to go over a new sowing and when to start checking tips every time you pass. Record seedling losses as a rough percentage too; a row that lost a third at the seedling stage almost always tells you something about how thickly you sowed it rather than anything about the seed.