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Last updated on October 24th, 2019
May is the perfect time to continue all of those operations you started in April and to get a jump start on a few more plants. This is really a time to hunker down into the repetition of the main growing season and ensure your plants and garden are well prepared for the summer months. Towards the end of May of perfect for most areas of the Uk for planting out summer bedding such as lobelia, bizzie lizzies, marigolds, salvia and begonias.
Jobs for May in the garden
- Mow lawns on a weekly basis and feed lawns with a summer high in nitrogen feed to give them the best start and apply a lawn weedkiller if needed.
- Towards the end of May plant out summer bedding plants into borders, containers and baskets.
- Earth up potatoes and plant any you have leftover before its too late.
- Continue to control weeds by hoeing borders and pulling up weeds.
- Trim evergreen hedges whilst on the lookout for bird nests.
- Open greenhouse vents on warmer days to allow fresh air to circulate and avoid them getting too hot.
- Lift and divide any spring-flowering bulbs that have finished if they are overcrowded.
- Protect plants from late frost by covering with fleece when low temperatures are forecasted.
- Continue to watch out for Lilli beetles on Lillies.
- Collect recycled water where possible and water early in the morning and evening to get the most out of the water.
- Harden off tender plants by putting them outside during the day and putting them inside at night, do this for around 10-14 days before planting out.
- Divide hostas as they shoot from the ground – see our guide on dividing hostas
- Divide herbaceous perennials where needed.
- Prune back woody penstemons to ground level.
- Take cuttings from tender perennials and softwood cutting from shrubs.
- Tie in sweet peas to a framework.
- Treat ant roses with signs of blackspot with Roseclear spray or suitable fungicide and remove affected leaves.
- Thin out vegetables you sow direct to give the remaining veg more room to grow.
- Harvest rhubarb but make sure you leave around one-third of stems.
- Check gooseberries for sawfly caterpillars daily.
At this point, the warmer weather will encourage your grass to grow significantly stronger than it did earlier in the year. You should be cutting your lawn at least once a week, but if your grass is growing particularly fast, you can do so more frequently.
You can also think about feeding your lawn to make it extra plush.
Planting your summer garden beds, containers and hanging baskets
It is finally time to invite summer by planting summer bedding that was not previously possible because of cold weather by planting bedding plants such as marigolds, lobelia, salvia, bizzie lizzies and petunias. These can go outside in the middle of May, so long as any danger of frost is over.
When you head to your local nursery to peruse the plants available, be on the lookout for those that have lots of flower buds, not open blooms. If you buy the latter, they may concentrate on flowering rather than growing and getting their roots out.
Before you plant your new plants, remove any weeds from the area and mix in some compost to help the plants during their transition. Water the garden bed thoroughly in the morning or evening if the soil is particularly dry.
How to plant them
Simply dig the hole, put them in not planting any deeper than they are in the trays or pots. How far apart to plant more than each one plant is based on variety. Make sure they are not too close together, or too low inside a container, as this will be difficult to rectify later and hinder their growth in the interim.
Keep an eye on the weather; if there are signs of an unexpected, late frost, cover your new flowers with fleece to give them a little extra protection.
Control the weeds
You have already been at weed control by now, but it is the month to step up your game. This is the month where you should remove them as soon as you see them. Hoe the garden if you can to keep them away. Weeds grow strongly during this month so check the garden at least once per week and don’t let any weeds go to seed.
In the garden, hoeing is effective at removing the weeds from the root level, so that they don’t just come back again in full form the following week but this only really works with seedlings, larger weeds will have to be dug up using a trowl or weed puller. Alternatively, you can apply a weedkiller but on lawns make sure you use one that is sold as safe on lawns.
You can spray weedkiller on patios, driveways, and walkways to help reduce the outbreak as well. Such measures will keep the weeds from returning for months. Alternatively you can use a glyphosate weedkiller if you are spraying around shrubs being careful not to get any sprayer on the green parts, remember not to do this around plants you eat.
May is an odd month when it comes to your vegetables. The winter crops have likely been removed, but most of the other crops are not yet ready. So, for now, you can sow some fast-growing varieties in between the things that take longer so that you can have something to enjoy every month. For example, plant lettuce in between your cucumber plants so that the lettuce can be nibbled on here and there while the cucumbers grow.
So, what can you sow and plant in May? Things like French beans, cucumbers, celery, salad, Spring onion, sweetcorn, tomato, squash, cauliflower, carrots, and artichoke.
Start trimming evergreen hedges
If you have evergreen hedges, May is the first month of the year to trim them. Make them as well-manicured as you like with some large hedging shears or hedge trimmer. Make sure you watch out for birds nests though inside of your hedges, as it is against the law to disturb these. (That’s partly why nest boxes set up earlier in the year are so important).