May and June are really the best months for many perennials, before the real heat of the summer cuts them short. Work in the garden takes on the familiar rhythm of seasons past, with some staking, potting up seedlings, preparing beds for annuals, planting out, etc etc. A busy time, but filled with promise and good things ahead…
1. Pot on young plants and rooted cuttings regularly to ensure that they don’t get potbound and slowed down in their growth. At least every 10 days to two weeks, they should be checked by gently removing them from their pot (turn it over and tap out the rootball). If you can start to see roots around the edges, it is time to put it into the next size pot. If you have left it too late and the young roots are circling around the bottom and sides of the pot, don’t despair! Just rough up the root ball a little to loosen the tight roots and place gently in the next size pot. In drastic situations, remove a bit of the overgrown roots by cutting them away.
2. Continue sowing seeds of annuals directly into the ground until the end of this month. They will grow and bloom this season. Try easy and reliable favourites such as cosmos, lavatera, nigella, california poppies and marigolds.
3. Plant some marigolds (tagetes) around the vegetable plants such as tomatoes and carrots. The strong smell of the flowers can help in keeping insects such as whitefly and carrotfly away from the crops. Besides, their cheery and bright colours add interest to this area of the garden until the fruit ripes. Nasturtiums are great for this job also, and are very attractive to aphids, and may keep them off other plants. A few annuals also help in attracting pollinating insects to improve the crop yield in a vegetable area.
4. Feed your roses now as they are just starting to grow vigorously. If you are using a dry fertiliser, scatter around the base of the plant and scratch it in gently. Water if the soil is dry to start it working.
5. Also feed your flowering bulbs as the flowers fade. If you can deadhead them, that’s great, but leave all the foliage intact (don’t bend them over, tie them up, or cut them off). The leaves are the only source of food for the bulb underground, and if they are removed before they have done their job and replenished the bulb’s nutrients, there won’t be any flowers next year. If they are unsightly where they are, it is fine to remove them intact gently with as much soil around them as possible and move them into a nursery bed or quiet corner of the garden where they can finish the season’s growth unnoticed.
6. Don’t be in a hurry to plant out summer bedding or tender annuals – bad frosts can still occur at night until the end of May. Keep them in the greenhouse or coldframe until the end of this month, or be prepared to act quickly if necessary to cover them up with fleece or other material if a cold night is forecast.
7. Now is the time to put stakes in place for all perennials that may need them! Don’t wait until they’ve already toppled over since at that time, they will look terrible propped or tied back up. Plant supports come in many shapes and sizes, from fancy willow cages and small trellises, to shiny metal canes. A simple and effective way that also blends in unobtrusively is to use pea sticks – small branches cut from any shrub or plant stuck into the ground around the plant to be supported. The new branches will grow up around and through the pea sticks and be supported gently without having to be individually tied in.
8. Lawn care – you may need a slight trim at this time, but make it a gentle one with the mower settings as high as possible. They can be lowered later as growth gets more vigourous. Lawns benefit from a raking to remove winter debris such as old leaves and moss. If they are compacted, try aerating them by spiking or even pulling out cores (make sure these are raked up and composted as they look terrible otherwise, and probably plug up the holes they were meant to open!)
9. Prune back stems of hellebores and primulas that have finished flowering. If you want the plants to set seed, leave one or two stems to finish maturing. This will tidy the area, save the plant some energy and prevent too many unwanted seedlings spreading around.
10. Harvest rhubarb now by gripping stems firmly at the base and pulling away from the crown sharply. Try to remove any flowering stems completely.