September is a busy month in the garden as we prepare for autumn and ensure that our plants, flowers, and crops remain healthy and productive. Here’s what you should focus on this month to keep your garden looking its best.

Flowers

• Divide Herbaceous Perennials: Now is the time to divide your herbaceous perennials to keep them vigorous. Make sure to enrich the soil with compost before replanting.
• Plant Spring-Flowering Bulbs: Start planting spring-flowering bulbs like Narcissus and snowdrops early in the autumn, as they prefer an early start.
• Continue Deadheading: Keep deadheading roses, Penstemons, and Dahlias to extend the flowering season. This will encourage new blooms and keep your garden vibrant for longer.
• Feed and Maintain Displays: Keep feeding and picking over hanging baskets, planters, and bedding displays so they look good until the first frosts arrive.
• Prune Rambling Roses: Prune back flowered wood on Rambling Roses once they have finished flowering, and tie in new growth to prepare for next year.
• Watering: Continue watering Camellias and Rhododendrons to ensure that next year’s flower buds swell properly.
• Weed Borders: Regularly weed your borders to keep them under control and prevent weeds from taking over.

Vegetables

• Watering: September can be dry, so make sure to keep watering, especially crops like celeriac and swede, which need water to swell.
• Sow and Plant: This is the time to sow and plant spinach, spinach beet, winter turnip, winter radish, spring cabbage, land cress, winter lettuce, cauliflower, and autumn planting onions and garlic.
• Care for Squashes: Cut off mildewed leaves of courgettes and squashes, and give them a feed to keep them growing. Lift large squashes and pumpkins off the ground with slabs or wood to prevent rotting. Remove leaves around the fruits to allow them to ripen fully.
• Harvest: It’s time to harvest herbs, potatoes, carrots, tomatoes, beetroot, peas, beans, Swiss chard, spinach, onions, peppers, salad leaves, turnips, courgettes, and sweetcorn. Freeze, pickle, or dry any surplus.
• Potatoes: Cut off the tops of any potato plants still growing to prevent blight from reaching the crop. When digging them up for storage, leave them on the surface for a few hours to allow the skins to dry and harden. Store in paper or hessian sacks in a cool, frost-free, dark place, and check regularly for any signs of rotting.
• Onions: Dry harvested onions until the skins are papery, then tie them in strings to hang and store in a cool, dry place.
• Tidy Up: Start tidying away finished crops to the compost heap. Dig over the ground as crops are harvested, and leave pea and bean roots in the soil to gradually release the nitrogen they have fixed.
• Green Manures: Sow green manures such as mustard or ryegrass on uncultivated areas to improve soil structure and prevent winter weeds.
• Herbs: Pot up herbs like mint, parsley, and chives for winter pickings on the windowsill.
• Brassicas: Protect Brassicas from pigeons with netting, and stake top-heavy Brussels sprouts before winter storms. Keep picking off caterpillars as you spot them.

Fruit

• Harvest: Harvest figs, apples, plums, pears, autumn raspberries, blackberries, and grapes as they ripen. Freeze or make jam with any excess or bruised fruit.
• Pick Apples: Pick apples as they ripen by gently lifting the fruit upwards—if they are ready, they will come away easily. Promptly pick up any windfalls to discourage wasps and use them immediately.
• Strawberries: Tidy away straw and dead leaves from strawberry plants and remove any unwanted runners.

General Tips

• Greenhouse Care: Keep greenhouse windows and doors open during the day, but close them at night to manage fluctuating temperatures. Remove diseased leaves as soon as you spot them to prevent rot. Watering early in the day will also help to prevent diseases. Clean the glass to allow maximum light in.
• Lawns: September is the best time to sow lawn seed or lay turf, as the soil is still warm and grass is growing well. Raise the mower blades towards the end of the month as growth slows down. Feed your lawn with an autumn lawn fertilizer.
• Ponds: Net ponds to prevent falling leaves from clogging them.
• Prepare for Bare-Rooted Plants: Prepare the ground for planting bare-rooted hedging and trees when the leaves drop later in autumn.

With these tasks in mind, your garden will continue to thrive as we move into the cooler months. Happy gardening!