Potting On Plug Plants, Aftercare and Planting Out

Plug plants are young plants that need a little extra care before they’re ready for your garden or planters. “Potting on” simply means transferring them into a larger pot so they have space to grow strong roots before being planted outside.

Follow these steps for the best results:

What You’ll Need

• Clean pots or trays (with drainage holes)
• Good quality multi-purpose compost
• A dibber, pencil, or your finger for making holes
• Watering can with a fine rose
• A sheltered, frost-free growing space (greenhouse, cold frame, or bright windowsill)

1. Unpack and Water Immediately

• Unpack plug plants as soon as they arrive.
• Stand them in water for about 1 hour so they can rehydrate.
• They may look slightly dry or yellow after their journey — this is normal and they’ll quickly perk up.
• Place them somewhere bright, airy, and frost-free to help them acclimatise.
• For mixed plug collections, check the label on the outside of the packaging — it will match the letters embossed on each plug cell for easy identification.

2. Potting On

• Always handle plug plants by their leaves, not the stem, to avoid damage.
• Gently push plugs out from the bottom of the cell using a dibber, pencil, or similar tool.
• Use clean 9cm pots, shuttle trays, or windowsill planters filled with a good quality multipurpose compost.
• Make a hole large enough for the plug, insert the plant, and press in lightly — don’t compact the compost too much, as this can cause water to pool on the surface.

3. Light & Temperature

• Place in a bright, frost-free location.
• Avoid placing them in direct hot midday sun when they’re young, as it can scorch leaves.

Aftercare

Once your plug plants are potted on, they’ll need consistent care to grow strong and healthy before planting out in the garden.

1. Preventing Damping Off

• Damping off is a fungal disease that causes seedlings to collapse at the base.
• It spreads through water, air, or contaminated pots and compost.
• To prevent it:
  • Ensure good air circulation.
  • Avoid overwatering and overly humid conditions.
  • Always use clean pots — wash reused ones with a disinfectant like Jeyes Fluid.
• If a plant becomes infected, remove it immediately and move healthy plants to a fresh, well-ventilated space.

2. Correct Watering

• Water in the morning so leaves dry before nightfall, reducing disease risk.
• Use tap water rather than water from a butt (which may contain fungal spores).
• Water only when the compost surface feels dry, it should be moist but not soggy — overwatering can cause root rot.  Alternatively, you can water from below to keep foliage dry by placing pots in a shallow tray of water to encourage deeper root growth

3. Feeding

• After 2–3 weeks of growth, start using a dilute liquid plant feed every 1–2 weeks.
• Choose a balanced feed for leafy growth, switching to a high-potash feed (like tomato feed) once flowers begin to form.

4. Frost Protection

• Do not plant outside until all risk of frost has passed in your area.
• If frost is forecast, bring plants indoors or cover them with fleece overnight.
  

5. Hardening Off

• About a week before planting out, place plants outside during the day and bring them in at night.
• This gradual exposure toughens them up for outdoor life.

Tip: Healthy plug plants should have sturdy stems, vibrant green leaves, and strong root systems before you plant them in their final location.

Planting Out

• Wait until plug plants are strong, well-rooted, and all risk of frost has passed (usually late April/early May).
• Prepare the soil by removing weeds and enriching with compost or well-rotted manure.
• For beds and borders, space plants about 20cm (8") apart.
• For hanging baskets and containers, use a quality compost and add Swell Gel & Feed for longer-lasting results.
• Feed regularly with a high-potash fertiliser (e.g., Blooming Fast Superior Soluble Food) to encourage blooms.
• Deadhead regularly to keep flowers coming.

Tip: Always check your plants regularly — early care makes for stronger, healthier displays later in the season.

A full video planting guide is below:

Related products to help with growing and looking after your plug plants

1. Pack of 3 Windowsill Propagator Kits
2. Professional Shuttle Trays
3. Easy Fill Hanging Baskets 38cm (15in) Pair
4. Blooming Fast Swell Gel & Feed 250g