This week’s radio slot dives into real questions from Irish gardens: what to do when hostas are shredded by slugs, whether an insect can control Japanese knotweed, how to handle mildew on gooseberries and blight on potatoes, why rose flowers drop early, if out-of-date seeds still germinate, lily buds that brown and fall, broom (Cytisus) pruning, whether to seal tree cuts, sticky peony buds, and getting started with a glasshouse. Here’s the quick, practical roundup.
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Highlights & advice
1) Hostas destroyed by slugs
Cut the plants back hard now; damaged leaves won’t recover.
Focus on prevention for new growth: encourage natural predators (hedgehogs, birds), avoid harmful pellets; if using pellets, choose pet-safe options.
2) Japanese knotweed & a “special insect”
In Japan, natural predators (e.g., psyllids/moths) help keep it in check.
UK trials (e.g., Cornwall) showed mixed results due to climate; not a silver bullet here. If someone claims success locally, treat as experimental and proceed cautiously.
3) Wildflower meadows lift biodiversity
A nod to UCC’s wildflower meadow and a reminder: even a small patch of wildflowers at home helps pollinators.
4) Gooseberry mildew & British Queen potatoes with brown leaves
Copper sulphate (bluestone) is a preventative for both mildew and blight, but use sparingly (once per season; at most twice).
British Queens (earlies): if tops are curling/browning, lift and enjoy rather than keep spraying.
Gooseberries: prune out infected growth, one careful copper treatment, and improve air flow.
5) Cat mess in the greenhouse near onions
Remove the affected soil—animal faeces can carry harmful pathogens.
6) Roses drop flowers after 2–3 days (no disease present)
Most likely drought stress, not feeding.
Mulch (composted bark/farmyard manure) to reduce evaporation and improve soil structure; water (grey water if needed) during dry spells. Feeding helps overall performance but won’t fix drought.
7) Out-of-date flower seeds
Plant them. Many seeds remain viable for years; wildflower seed can persist decades in soil. “Best before” is often marketing.
8) Where to buy organic plant food (Nature Safe)
Irish, seaweed-based range; ask your local garden centre/co-op to stock it.
9) Asiatic lilies: buds brown and fall
Likely fungal. Remove the stem, then feed the bulb (tomato feed works well).
Dust bulb with copper sulphate before replanting; it won’t rebloom this year.
10) Potato blight spraying & broom (Cytisus) pruning
Blight: one copper spray now if warnings are active; max twice/season. Earlies showing symptoms: lift.
Broom: prune just after flowering; late pruning can remove next year’s buds, though there may still be time this season.
11) Should I seal tree pruning cuts?
Usually no if the cut is clean and flush; trees callus naturally.
If the wound is ragged/storm-torn, light sealing can help—but beware reducing the tree’s ability to “breathe”. Monitor.
12) Peonies in pots with sticky buds that won’t open
Likely honeydew from nearby aphids. Wash buds with warm, soapy water and rinse gently.
13) Thinking about a glasshouse
Consider aspect (sun), shelter, and quality. For tailored advice, start a thread with me on Facebook: The Irish Gardener, or ask at your local garden centre.
Quick recap
Hostas: cut back + natural slug control • Knotweed insect: trialled, mixed • Gooseberries/Queens: prune + minimal copper; lift earlies • Roses: drought/ mulch • Old seeds: sow them • Lilies: fungal; remove stem, dust bulb • Blight: max 2 sprays • Broom: prune after flowers • Trees: seal only ragged cuts • Peonies: wash honeydew • Glasshouse: plan site & spec.
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