Greenhouse, conservatory and houseplants


Move conservatory plants, such as Cymbidium (left), Yucca, Ficus and Citrus outdoors during warm days but bring in if cold nights are expected.

Pot up houseplants showing signs of being root-bound or top dress large containers with fresh compost.

Pruning and training

Train the new stems of passion flowers and other climbers over frames or on horizontal wires.

In the greenhouse

Pot on any Begonia, Gloxinia and Achimenes plants that you started off earlier in smaller pots, but which are now large enough to re-pot in the next size up.

Try growing on plug plants in your greenhouse. They are a relatively cheap source of large numbers of plants, and can be ordered and grown on quickly if you didn’t get round to sowing seed in good time earlier this season.

Don’t forget to give greenhouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.

Check plants at least every few days, to see if they need watering. Seedlings will need daily attention.

Continue to prick out and pot on new seedlings and cuttings.

Harden off half-hardy bedding plants that were started off under cover.

Open doors and vents on greenhouses to increase ventilation on warm, sunny days.

Pest and disease watch

Vine weevil larvae can be a serious pest of containerised plants, and become active this month. Tip out the rootball of suspect plants, and inspect for the creamy, orange-headed maggots, which tend to curl up into a ‘C’ shape (see left). There are various biological controls available.

Regularly inspect plants, and also the structures of the greenhouse and conservatory, for glasshouse red spider mite, whitefly, thrips and other pests. Careful attention to the undersides of the leaves, and to each plant in turn, can spot early infestations that would otherwise be missed. Control with biological controls, and hang yellow sticky traps to help monitor numbers of flying pests.

Brush up fallen compost and debris, and pick off dead leaves from plants. This will help prevent pests and disease spreading.

Stem and root rots can affect young plants grown from seed and cuttings, especially those grown under glass.

Clean tools, pots and greenhouse staging; where necessary, use disinfectants such as Citrox to help control the spread of pests and diseases.

More monthly advice

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Advice from the RHS

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