Growing early Lettuce
It’s easier at this time of year to buy imported lettuce than grow it in your greenhouse or to grow rocket, endives and oriental greens instead, but lettuce is preferred in many households and home-grown is much fresher. Choose varieties that are tolerant of short days and low temperatures, and resistant to mildew. ‘Little Gem’ and ‘Winter Gem’ are cos-type varieties, ‘May Queen’ and ‘All the Year Round’ are butterhead types, and ‘Salad Bowl’ is a looseleaf type for cut-and-come-again harvesting. If in doubt check the information on the back of the seed packet.
You can sow the seeds thinly and 1cm deep in the greenhouse soil. Keep the drills about 30cm apart and thin the plants to the same spacing when they are big enough. This wide spacing leaves plenty of air between plants to discourage mould and slugs. Sow a little every two to three weeks for a succession of crops.
It’s easier to sow the earliest batches in cell trays with small cells. Sow just a few seeds in each. Keep them indoors to avoid slugs and mould, and don’t let them get warmer than 25°C (77°F) or they won’t germinate. Thin the plants to one per cell with a fine-pointed scissors as soon as they are big enough to work with, and plant them out as soon as their roots have bound the compost in each cell together. Keep the plants well watered, and ventilate the greenhouse whenever the weather allows. Water in the morning to allow the plants and soil surface dry out before night. Protect the plants from slugs and remove all weeds, dead leaves and rubbish. Harvest hearted lettuce by pulling whole plants, and looseleaf types with a scissors, leaving the plants to grow more leaves.
End of the line – by our blogging Horticulturalist Peter Whyte
October is the month when production of greenhouse tomatoes, aubergines and peppers usually comes to an end. With falling temperatures and longer nights, growth is slowing down and your plants will be less able to ripen fruit. Remove all flowers as they are unlikely to set usable fruit in time for them to ripen this late. Thin out some of the fruits already set, especially the smaller ones. Stop shoots from growing any more by cutting off their tips. The above actions divert all the plants’ resources into filling the remaining fruit, so you get bigger, riper, tastier fruit instead of many small unripe ones. Do this earlier or later depending on your location and how mild the autumn is.
With the rising humidity, disease control becomes more important by the day. So make sure to remove any dead leaves, spent plants, weeds, rubbish and dropped fruits from the greenhouse. Open the vents or doors on sunny mornings, but close them up earlier in the evening before it gets too cold. Feeding should have ended in September, and watering should be reduced to match the plants’ lower needs. As a rule of thumb, don’t water until the soil surface is dry. Avoid wetting the leaves.
By about mid-October it can be too cold to ripen tomatoes well. If so pick all the fruit and ripen them indoors in a dark, airy cupboard. Don’t leave them on a sunny windowsill: if they once get heated above 35°C (95°F) the red pigment is destroyed and they stay pale and blotchy. Some people put a ripe apple or banana with them to speed up ripening with the ethylene gas it gives off. Remove plants when their fruits are all picked, and clean up the greenhouse for the winter.
Pelargonium Cuttings
Pelargoniums (geraniums) are easy to grow from cuttings whenever the plants are growing, but easiest in late summer. Fill a pot with seed compost and moisten it by standing it in water for a while. Then let the surplus water drain away. Choose your healthiest, most vigorous pelargonium plants for cuttings. Non-flowering stems are best because flowers give off hormones that inhibit root growth, but if you have to use flowering stems remove any flowers and flower-buds. Stout stems grown in good light are better than spindly stems grown in poor light; a few weeks on greenhouse staging can produce good stems.
Cut the chosen stems below the third node (joint) from the top. Cut off all but the top leaves, insert them into the pot leaving one node and the top leaves showing and firm them in gently to ensure good contact between the cutting and the compost. Place the pot in a warm bright spot out of direct sun. Don’t cover it as dampness can rot the cuttings. For the same reason, water it only from below by standing the pot in water for a while and letting it drain as before. Remove any cuttings that start to rot. Plant out the rooted cuttings when new leaves appear on them: let them recover where they were until growth starts again before placing them in full sun.
Potatoes for May
If you like your early potatoes early and you have enough room, why not plant some in your greenhouse in January? They could be ready for harvesting as soon as May. Yields can be modest, but the flavour of fresh early potatoes is unbeatable. Choose seed potatoes of an early variety, and stand them on a warm bright windowsill indoors to start sprouting. Keep the eyes facing upwards so the emerging shoots will be straight and tall.
When the sprouts are about five centimetres tall plant the seed potatoes in the greenhouse, either in the ground or in large pots. Some compost or well-rotted manure could be added to the soil, but not too much if slugs are a problem. When planting take care to trickle soil gently down between the sprouts to avoid damaging them. Some growers who use pots plant the seed potatoes in half-filled pots and add more soil as the sprouts grow up, always leaving their tips exposed to the light to speed up growth.
Keep the soil moist but not wet, ventilate the greenhouse (or bring pots outside) on warm days, and protect the plants from frost and slugs. Add soil around the bottoms of the stems to stop light from greening potatoes near the surface. You can start eating the potatoes when flowering is over, but the potatoes will continue growing bigger until the foliage dies down. They taste best when freshly dug, so unless you need the space or have a slug problem dig them only as you need them. Bon appétit!
Dahlias – our resident horticulturalist Peter Whyte gives some tips
Every year somebody predicts a hard, cold winter. If they are right this year, the roots of plants such as Dahlias will be killed when the soil freezes. To keep them safe you should lift the root tubers and store them indoors until spring. As soon as their stems are blackened by frost, dig up the plants carefully, avoiding root damage. Gently shake off the loose soil, and cut the stems back to about 15 centimetres. If you have different varieties label them with their names and colours right away – you may well forget which one was which before spring. Stand them on wire mesh or similar in the greenhouse for a few days to dry off fully. Then place them upright on a layer of dry peat or soil in containers, filling more in around them to cover the tubers. Keep them dry and cool but frost-free under staging until spring, and then divide and plant them out a fortnight or so before the last likely frost date for your area. If you want to take cuttings, start them growing in the greenhouse in February and use the new shoots as cuttings when about 75mm high.
Paperwhite narcissi
Paperwhite narcissus is a type of white scented daffodil which can be forced to flower for Christmas. A greenhouse makes it easier to grow better blooms. You need to buy specially prepared bulbs, and compost them afterwards because they rarely flower normally again. Store the bulbs in a cool, dry, dark, airy place until 4-6 weeks before you want them to bloom. Place them on a 5-centimetre (2”) layer of damp (not wet) bulb fibre or potting compost or even pebbles in a container such as a shallow bulb-pan. For small containers an odd-numbered group of (for example) three or five bulbs looks better than an even-numbered group. They should be close together but not touching each other or the sides of the container, with their pointy ends upwards and leaning in towards the middle of the container. Add a little more compost or pebbles to firm in between the bulbs but leave their tips exposed.
Place the container in a cool spot away from direct sunlight. Check them every couple of days to make sure they don’t dry out completely, but never add enough water to reach the bottoms of the bulbs or they will rot. As soon as the green shoots appear, move the containers to your greenhouse and give them as much light as possible. The more light and the less heat they get the less leggy and floppy the stems will be. Keep the greenhouse cool by ventilation but frost-free at nights, and make sure the plants don’t dry out. Turn them often to keep growth regular and upright. Bring them into the house when the buds are well formed, and the flowers will open in a few days.
Peter Whyte
Polytunnel growing course
A customer of ours – Mr Tanguy de Toulgoet, is hosting a training session to help people make the most use out of their Polytunnels. It is on the 3rd of October and he is in Durrow, County Laois.
He will cover plant production, herb drying, companion planting, winter storage and much more.
The cost is 50 euro per person, it is a half day course and starts at 10am and finishes at 1pm.
Here is a link to a leaflet about it: Course Leaflet
Red Spider Mite in Greenhouses – by our blogging horticulturalist Peter Whyte
A few years ago our cucumber plant wasn’t looking good. The leaves were mottled yellow and the plant had completely stopped growing. I watered and fed it, thinking it might be hungry. It got worse. That was my first encounter with red spider mites.
These tiny pests are only red in autumn. In summer adults are yellow or pale green, with two dark spots on their backs. They stay on the undersides of leaves, and you may need a hand lens to see them. Females lay their tiny spherical eggs in clusters and the larvae that emerge suck sap, sometimes leaving clusters of tiny yellow spots on the upper surface of the leaf. Leaves later become mottled and dry, and may fall early. Really severe infestations create a fine web under and between leaves, and may kill plants. The adults overwinter from about October to March on weeds, under soil clods and in crevices in the greenhouse or its equipment. Almost any plant can be attacked.
These mites thrive in warm, dry conditions. Mist or syringe the plants with water, and wet the ground to dampen and cool the air. Destroy (don’t compost) any unwanted infected plants. Clear all weeds and unused equipment and materials from the greenhouse to remove hiding-places. Wash down empty greenhouses with disinfectant. Give plants plenty of light, water and space. Chemicals are not very reliable because most don’t kill all stages of the mites and they quickly build up resistance. Frequent spraying with plant oils, plant extracts or fatty acids may be more effective. The predatory mite Phytoseiulus persimilis gives good control.
Spring Is Coming
“Now crocuses come smiling through
Grey February’s fog and mist
gold like the sun, deep lilac too
Defying winter’s icy kiss.”
By David Squire
This month there are signs of the approaching spring. Although the weather still fluctuates temperature wise, spring is coming. Bulbs are appearing and birds and wildlife waking up as light levels and temperatures increase. Before heading out to enjoy the oncoming spring remember there’s plenty to do indoors this month, all in preparation for the season ahead.
- Place a heating mat under your seed trays and begin planting your seeds indoors. Keeping the soil warm will assist with faster germination and plants will develop a stronger root system
- Start feeding your houseplants again once they begin to show signs of new growth
- Prune conservatory climbers
This are just a few tips to get you started. Remember also this is a great time of year to check your Polytunnel/Glasshouse for repair’s that need to be carried out before the spring season. For replacement glass or polythene or advice on the right thing to do, feel free to contact us via www.polydome.ie
