The danger of frost should be past at last, so it will be safe to plant out bedding, half-hardy annuals and veg plants like tomatoes and aubergines. You still need to harden them off before planting out though.
Pinch out the tips of sweet peas and other bedding plants to encourage them to be bushier.
Growbags can be a good way of growing crops like tomatoes, aubergines and peppers, either in or out of the greenhouse. The advantages are that the bags will retain moisture and keep the compost from drying out, but are porous so they will not get too waterlogged. They are sterile so will not have any disease or fungal spores, and also contain all the nutrients the plants need for the first six weeks.
A few pointers on how to get the most out of a growbag:
1) Site your Growbag in the sunniest spot you can. Tomatoes do prefer a bit of shade at midday in the height of summer, but peppers, aubergines and chillies generally need as much sun as possible. If you do only have a part shaded spot, try cherry tomatoes.
2) Roll the bag backwards and forwards when you get it home to loosen up the compost.
3) Pierce the bag a couple of times at each end to improvedrainage.
4) Cut a hole about 20-25cm per plant in the top. You can cut the bottom out of pots this size and sink them into the bag through each hole, which makes watering easier, or plant direct into the bag.
5) To improve drainage further, mix in a small handful of perlite or grit into each planting hole.
6) Water in each plant thoroughly, but don’t wet the whole bag. Leave for a few days before watering again – young plants need oxygen at the roots to develop a good root system.
Some spring flowering plants will benefit from a good haircut now. Alpines such as Alyssum or Aubrieta can be trimmed back after flowering and might give you another flush later in the year.
Early spring flowering deciduous shrubs, such as Forsythiaand Chaenomeles can be trimmed or pruned after flowering. If you prune later you risk forfeiting flowers next year. If you want or need to prune a Camellia to keep it in shape, now is also the best time to do it.
Now twiggy plants like Fuschia, Caryopteris or lemon verbena are finally showing some signs of life, you can trim back the stems to a healthy pair of leaves and generally tidy them up. If you haven’t already done the same to Penstemon, then it’s a good idea to but them back too to prevent them getting too straggly.
Remove runners from strawberry plants to allow the plants to put all their energy into flowers and fruit this year. You can pot the runners up to make new plants and plant out in the autumn.
… so called because you do this around the time of the Chelsea Flower show. This is a way of prolonging the flowering period of your later flowering herbaceous perennials such as Echinacea, Anthemis tinctoria, Phlox paniculata, or Helenium by staggering when they will flower. In each clump of a perennial, you prune 1/3 back by 1/3, a further 1/3 back by 2/3 and leave the last 1/3 untouched.
It’s a good time to repot houseplants, permanent planters and any congested plants such as Agapanthus. Permanent plants are best potted in a mixture of compost, topsoil and sand/grit. John Innes No.3 is a premixed compost which contains a good mix of these for pots.
If you don’t want to fully repot containers, you can just topdress the top of the pot with some fresh compost, and add/or a handful of slow release fertilizer.
After flowering, leave the foliage on tulips and daffodils to die back naturally to allow the bulb to store energy for next year and water with a liquid feed.
Pests and diseases
Aphids, caterpillars, lily beetles and sawflies are all going to start putting in an appearance now. Keep an eye on susceptible plants, especially at the tips. If you notice ants climbing up and down the stems that is usually a sure sign you have aphids: the ants are moving the aphids into prime position on the new shoots and then harvesting the honeydew the aphids produce.
You can buy various pesticide sprays which are usually non-specific and will kill all bugs, including pollinators. On individual plants its often more effective (and kinder to the environment) to wipe them off with a damp piece of kitchen towel.