Hartley Magazine

All the latest news, hints, tips and advice from our experts

Flowers and vegetables – the productive greenhouse in winter.

The hippeastrum season is about to begin.

It’s still not too late to sow batches of winter salads every week or two in an unheated greenhouse. Growing them in trays, pots, old growing bags or borders as ‘cut and come again’ crops to harvest through autumn and into winter. Try hardy salads like land cress, radish, carrots for leaves, any of the oriental vegetables like pak choi, mizuna and mibuna greens plus lettuce, lamb’s lettuce, chicory and radish or what’s left of packets of brassicas like kale and cabbage. Alternatively, sow them in modules and transplant into the greenhouse border. The above can also be sown in trays of compost and harvested when a few centimetres tall as ‘microgreens’ when the first two leaves appear. Even though they look delicate like mustard and cress, they are full of vitamins and energy and can be used as garnish. Trays of peas can be harvested for their shoots, starting them off in a propagator in gentle heat if needed. Growth stops if it gets too cold so have a layer of horticultural fleece on hand to provide extra protection during cold snaps.

Bring pelargoniums into the greenhouse before the first frosts. Cut back the main stems to within a few inches of the base and keep them slightly moist over winter (more are killed by overwatering than under watering) maintain a temperature of around 10°C (50°F). Tender Fuchsias and marguerites can also be overwintered the same way. Lift dahlia tubers after the first frosts and store in under the glasshouse bench where it is cool and frost free.

Buy ‘Lily of the Valley’ from bulb suppliers and plant the bulbs (or ‘pips’) close together, the tips just covered in John Innes no 2 or Multipurpose with added John Innes. The compost level should be just below the rim of the pot. Use deep ‘Long Tom’ pots to accommodate the roots then force them in the greenhouse. It takes 25-40 days (4-6 weeks) at a maximum of 15 from planting to flowering. Keep them cool and dormant and they will flower earlier in the new year; raise temperatures giving them a little more heat and they will flower earlier. The art is to make sure they have enough heat to grow steadily but not so the stems and leaves ‘leggy’. It is a matter of balancing light and heat. Remove the flower stems after flowering then replant in the garden in a moist shady spot. It will take them two years to recover and bloom once more.  It is also time to bring your citrus plants into a frost free greenhouse over winter.

Now is also the time to plant Hippeastrum’s in John Innes No.2 or multipurpose compost with 2/3 of the bulb above the surface, put in the propagator in a bright position at 21C, water sparingly until the new leaves appear then increase watering with tepid water, to prevent the compost from drying out. Turn the pot regularly every few days, to prevent the flower stalk growing towards the light. Large flowered cultivars may need staking.

When watering plants, from now on and through the winter, avoid wetting the leaves, which encourages fungal problems.

Happy Gardening. Matt