Gadenin日本語Get the appLeaf miner: pale blotches with a wandering line inside
The commonest complaint on lovage is celery leaf miner, whose larvae tunnel between the upper and lower surfaces of the leaf. You see irregular pale blotches, often with a thin darker line wandering into them, and holding a leaf to the light shows the grub itself as a small dark shape inside the mine. It is disfiguring and it makes the affected leaves inedible, but it does not kill a plant.
It arrives on the spring growth, which is exactly the growth you are going to cut down in early summer anyway. Bringing the whole-plant cut forward by a fortnight in a bad year removes almost the entire population with the leaves, and the second flush comes up clean. Bag or bin the cut material rather than composting it in an open heap.
For a light attack earlier in the season, pick and destroy individual mined leaves as they appear, squashing the grub inside the leaf before you bin it. Sprays are close to useless because the larva sits inside the leaf tissue. A row cover cover over a young plant in spring keeps the adult fly off, though it is rarely worth the trouble on a plant you are about to cut back.
| Problem | What you see | What to do |
|---|---|---|
| Celery leaf miner | Pale blotches with a wandering line, grub visible against the light | Cut the plant to the ground early; bin the leaves, do not compost |
| Aphids | Colonies on stem tips and under flower umbels; sticky leaves | Wash off with water, or cut the affected stems out entirely |
| Slugs and snails | Ragged holes in new shoots after cutting back | Clear cut debris off the crown; protect regrowth for two weeks |
| Leaf spot | Small brown spots with pale centers, worst in a wet season | Remove affected leaves, thin the clump, avoid overhead watering |
| Crown rot | Shoots collapse; base is brown, soft and smells sour | Improve drainage now; lift and divide, salvaging firm outer sections |
| Powdery mildew | Gray-white bloom on late-season leaves, usually after drought | Water deeply, cut affected growth, expect it to clear on new leaf |
Aphids, and why the flower umbels are where they gather
Aphids concentrate on soft growth, so on lovage that means the tips of the flowering stems and the undersides of the developing umbels. A heavy colony leaves the leaves below sticky with honeydew, which then goes black with sooty mold. On a plant grown for leaf rather than seed the answer is simple: cut the flowering stem out, which removes the colony and the reason for the colony at the same time.
Where you are letting a plant flower for seed, a strong jet of water knocks the colony down and repeated washing over a week usually breaks it. Umbels are flat and open, so predators find them easily. Hoverfly larvae and ladybirds clear a lovage aphid outbreak within a fortnight if you have not sprayed something that killed them first.
Soft, overfed growth is aphid bait. If the same plant is badly infested every year, cut the nitrogen. A spring mulch of compost and one balanced feed after the summer cut is enough; repeated liquid feeding through the season produces exactly the sappy growth aphids want.
Because you eat the leaf raw as well as cooked, avoid reaching for sprays here. Cutting, washing and waiting for predators deal with everything lovage actually gets.
Crown rot is the only failure that ends the plant
Lovage tolerates cold far better than it tolerates a wet crown. Where the plant sits in ground that stays saturated through winter, the crown softens, and in spring either nothing comes up or a few weak shoots appear and then collapse at the base. Scrape the soil away and the crown is brown, soft and sour-smelling rather than firm and white.
There is no treatment once the center has gone, but the plant is often salvageable. Lift the whole crown, cut away everything soft, and look for firm outer sections that still carry a bud and a length of healthy root. Replant those in a better-drained spot, on a slight mound if the site is heavy, with grit worked into the planting hole.
Prevent it at planting. Deep, moisture-retentive ground is what lovage wants; waterlogged ground is not the same thing. On heavy clay, plant on a low ridge, work grit into the base of the hole, and keep the winter mulch pulled back an inch or two from the crown itself so the collar can dry between spells of rain.
- Check the crown in early spring If nothing has appeared two weeks after your recorded emergence date, scrape the soil back and press the crown with a thumb. Firm means wait; soft and brown means act now.
- Lift and cut back to clean tissue Fork the crown out whole, wash the soil off and cut away every soft or discolored part with a clean knife until only firm white tissue remains.
- Replant the good sections high Set salvaged sections on a low mound of improved soil with the bud just at surface level. Water once to settle, then leave the plant alone until growth restarts.
- Record what the winter was like Note whether the site stood wet, how long, and what you changed. A crown that rots twice in the same position is telling you the position is wrong, not that the plant is difficult.
Keeping notes that shorten next year's diagnosis
Write down the date you first see leaf miner blotches each year. It repeats within a week or so from season to season, and once you know it you can time the whole-plant cut to land just after the first generation is in the leaves and just before the second one arrives.
Note where on the plant a problem started as well as what it was. Aphids that always begin on the tallest stem, leaf spot that always begins on the shaded side against a fence, slugs that only ever hit the regrowth after a cut: each of those points at a fix that is about position and airflow rather than treatment.
Keep a note of anything you applied and what happened over the following two weeks. Most lovage problems resolve on their own or with a cut, and a record stops you crediting a spray with a recovery that was going to happen anyway.