April gardening guide: what to do in your garden in April
In April, the weather remains unpredictable, and we can have anything from a heatwave to ground frosts and sleet in a matter of days, so do be prepared. The best protection for tender vegetable and bedding plants, if frost strikes, is cloches or horticultural fleece.
Cover the tender plants until the frost or cold weather has passed. Conversely, on warmer days, you’ll need to protect the new growth from slugs and snails that will view the young shoots of Delphiniums, Hostas and lettuce as the equivalent of caviar.
April gardening guide: Planting
Buy and care for bedding plants
If you have a greenhouse or frost-free area, you can save money by buying small bedding plants in April (which are cheaper) and growing them on in the sheltered conditions of a greenhouse.
Pelargoniums, Cosmos, Ammi and highly scented Sweet peas and Nicotiana are all essentials, while Geraniums, Gazanias and Marigolds will thrive in sun-drenched spots. Use Begonias, Petunias and Violas to add colour to lightly shaded areas.
Sowing bedding plants from seed can be time-consuming and tricky. Also, there’s a more extensive choice of plug plants for bedding and vegetables online and in garden centres. These smaller plants need a frost-free environment with as much all-around light as possible - think greenhouse, conservatory, window sill or porch.
Take care with watering. Too much at the early stages, and the small plants can rot. It is best to increase watering slowly as the plant grows. When the plug plants arrive, they’re often in small thumb-sized pots. These small plug plants need potting on immediately, but take care to pot them up just one stage up in pot size and increase the pot size gradually. If you put a small plug plant into a large pot, it will not thrive.
If you’re going to plant the plugs in containers or hanging baskets, as opposed to borders, once the plants are more established, it’s a good idea to plant them in the container and grow them on in the greenhouse until they’re ready to plant out. This will help the plants establish a good root system in the container before being placed outside.
When growing bedding plants, nip out the growing points to produce a bushier plant. Otherwise, some plants, particularly petunia, fuchsia, and verbena, will grow leggy later in the season.
The rule of thumb is not to plant out bedding plants until the risk of frost has passed. Depending on where you are in the county, this is likely to be towards the end of May. You can plant out earlier, but monitor the weather, and if frost is forecast, you’ll need to protect with a cloche or fleece. Most bedding plants are not hardy, which means they will not withstand a frost which could severely set back the plant or even kill it.
With their vibrant flowers and fragrant foliage, pelargoniums are long-standing favourites for both indoors and out. Give them sun and free-draining soil, in containers or borders, to add Mediterranean cheer all summer. They’ll survive drought with ease, but not frost, so bring plants indoors before temperatures drop or take cuttings for overwintering.
Wait until frosts have passed if you are growing your pelargonium in a bedding scheme or standing pots outdoors for the summer. This is not usually before the end of May in most parts of Oxfordshire. Also, it’s vital to take a couple of weeks to harden off your plants, i.e. acclimatising them to outdoor living.
In borders or beds, plant in fertile, neutral to alkaline soil. Most will flower best in full sun. However, Regal cultivars prefer partial shade, and Zonal cultivars will tolerate some shade. When growing pelargoniums in containers, either indoors or out, use peat-free multipurpose compost or soil-based compost.
Pelargoniums are not thirsty plants, so water them moderately from spring to summer, taking care that the compost doesn’t become too wet. Open windows or vents in a conservatory or greenhouse in summer to be sure of good airflow. Water only sparingly in winter so that the compost has time to dry between waterings.
You can simply grow your pelargoniums as annuals, pulling them out and adding them to the compost heap at the end of the year. But since pelargoniums are perennial plants, you might like to save them for another year. This is especially so if you have grown a type or colour that you are particularly fond of.
Growing sweet peas
March and April are suitable times to sow and plant out Sweet peas. It is time-consuming to grow but very rewarding and near impossible to beat for colour, height and scent in a garden.
Sweet peas like moisture and are best planted in an area not too dry as that will encourage mildew. If possible, line the trench with newspaper to aid moisture retention. Sweet Peas are hungry plants, and adding lots of organic matter will improve the soil and help with moisture retention. Also, add a mulch to help retain moisture as dry ground is not ideal for Sweet Peas.
Sweet Peas grown under glass in sheltered conditions need to be hardened off before planting outside. This means getting the plants accustomed to outside conditions. Put plants outside on warmer days, increasing the time spent outdoors until they’re used to the weather and ready to plant out. Do this over some time so that the young plants are fully ready for the rigours of the weather. (This applies to all young plants grown in sheltered conditions.)
It is advisable not to plant out during a chilly spell as this can knock back sweet peas and other young vegetable or bedding plants. And if conditions are poor, they could take weeks to pick up. If it’s cool, it’s better to let the Sweet Peas hang around in pots for longer. Once Sweet Pears are hardened off, do not worry too much about the weather. They’re half-hardy annuals and will tolerate a fair degree of chill.
If you’re growing from seed or buy Sweet Peas as small plants, a good tip is to pinch out the growth point. This will make the plant send out additional shoots, prevent it from getting leggy and make a bushier plant with multiple flowering stems instead of just one. You should do this at least once with spring-sown Sweet Peas.
Seed and grow summer annuals
The advantage of sowing annuals is that you can buy a wide range of seeds and grow plants you rarely see in garden centres. The specialist seed catalogues have a fantastic range, and it’s great fun to grow something unusual.
A great summer annual is Cobaea scandens, also known as the Cup and Saucer plant. Cobaea Scandens is native to South America, it is tender (non-hardy) and a lovely climbing plant to have as part of a summer display. Amaranthus caudatus, common name Love lies bleeding, is another exotic looking annual which is easy to grow from seed.
Both need warmth to germinate and to grow on in a frost-free environment. It is best to delay planting out until they’re good-sized study plants. Other easy annuals to grow from seed, which provide an equally bold splash of colour, are Nasturtiums, Sunflowers, Calendula and Cornflowers. All are easy to germinate and not as tender as Cobaea and Amaranthus.
Sow a wildflower patch
A wildflower patch creates a splash of colour, and you don’t need lots of room and time. If the idea of having growing wildflowers appeals to you, but it seems too much like hard work, there is a simple, quick, easy and foolproof way to create a wildflower patch, which is by using a pre-seeded roll or matting. But whether using seeds or a pre-seeded roll, the area needs to be free from weeds and the soil warm enough for germination.
Start planting out potatoes
April is the traditional month for planting-out salad and first early potatoes. Late April is fine for second early potatoes and for planting maincrop, which means potatoes can be chitted throughout the month ready for planting out.
Maincrop potatoes are generally the largest you can grow, needing 15-20 weeks to reach full size. By the end, you’ll be rewarded with large potatoes that store well and are ideal for mashing, roasting and baking.
Whilst it is good to get the potatoes planted, no gardening rules are hard and fast, and as always, advice is tempered by the weather. If there is a cold spell, delay planting until later in the month.
Potatoes take up a lot of space in the vegetable plot, and if that is at a premium, potatoes can be comfortably grown in large pots. Remember that the top growth on potatoes, the haulm, is vulnerable to frost and will need protection if frost strikes. Cover with a fleece or cloche.
It is crucial when growing potatoes not to let the tubs or containers dry out - given that April and May can be among the driest months. If you’re only growing a few potatoes, you can plant them all out together later in April.
Plant hardier vegetables outside
The weather can still be cold in April, so it is vital to distinguish between the hardier vegetables and the more tender. In sheltered areas in April, you can plant outside hardier vegetables such as Broad beans, Beetroot, Carrots, Swiss chard, summer cauliflower, Kohl rabi, Lettuce, Leeks, Radish, Turnip, Spring peas and Perpetual spinach. The more tender vegetables will need to be protected, so germinate and grow them under glass in a greenhouse or conservatory.
If you’re growing the more tender vegetables such as Courgettes, Squash, Peppers, Tomatoes, Cucumbers, Aubergines, Celery, Celeriac, French beans, Sweetcorn and Globe artichokes, they need to be grown in frost-free conditions until ready to be planted out in the vegetable plot from mid-May onwards, when the risk of frost should have passed, depending on where in the country you’re gardening.
One problem when growing vegetables from seed is that the seedlings can get leggy. If germinating on a windowsill, physically turn the seedling container around each day because when the light comes from one source on one side on a windowsill, the seedlings will grow to the light and can become leggy. Regularly turning the pot around helps to reduce this.
April is also a suitable time to sow vegetables in the greenhouse for planting out later, peas and beans - French Green and Runners. To avoid gluts later in the season, do this at regular intervals so that they flower and fruit at regular intervals.
The planting order for the bean family is that Broad Beans can be planted out in March/April - they’re the hardiest of the bean family, followed by Runner beans and French beans if it is sheltered or in May with frost protection. All peas and beans need a long root run and are best in root trainers, which can be expensive, or toilet roll holders, which are cheap.
If the conditions are right and the soil has warmed up, you can also sow directly into the vegetable plot the hardier vegetables such as carrots, broad beans, onions, garlic and purple sprouting broccoli. Aim to sow or plant vegetables successively every fortnight works well.
If you notice that the carrot seed has failed to germinate, it may be because the soil is too cold. Sow again later. Carrots can be slow and sometimes tricky to get going but trouble-free once germinated. If you’re companion planting, April is a good time to sow, say, poached eggplants. But only once the vegetables are in situ, as poached eggplants are great for pollination but they will not transplant.
April is a suitable time to plant out Strawberries, either in the vegetable plot or containers, but remember to protect them from the birds later when the fruits show. For an earlier crop of strawberries, cover the plants with a cloche, but do not forget to water under the cloche. Strawberries are fully hardy and can be left in the vegetable plot all year round.
April is time to plant Onions and Garlic, both of which are easy crops to grow. Simply plant to the correct depth in a sunny spot, and they grow themselves. A good advantage of growing your own garlic is that the choice of varieties available on sale to grow now is extensive. Both onions and garlic store really well, so they will overwinter, ensuring you have a plentiful supply of both for months, well into the following winter.
Start growing herbs
Herbs bought in the supermarket are expensive and don’t seem to last very long. And growing your own herbs enables you to grow different and interesting varieties that can be hard to find in the supermarkets, such as Thai basil, which is just as easy to grow as regular basil and gives a great flavour to stir-fries.
April is the time to sow, under glass, tender herbs such as basil, Coriander, Dill, Thai basil, and Tarragon, which you can plant out later in the year or carry on growing in pots in a sunny spot. If you’re sowing Parsley and struggle to get it started, keep sowing, it can be tricky to get going but trouble-free once it germinates.
Hardy herbs can be planted out in pots or in the vegetable plot, such as Chives, thyme and Oregano. A word of warning about growing oregano, also known as Marjoram, botanical name Origanum. It is lovely, aromatic, great in Greek salads, easy to grow, and tolerates most conditions, except extreme wet. It is also a wildlife-friendly plant that is very attractive to bees and insects.
The drawback is that it is vigorous and would self-seed around the garden, so you’ll need to be vigilant to pull out any new plants if you don’t want an oregano garden. Most herbs need a sunny spot in the plot, but some are shade tolerant.
April gardening guide: Care and maintenance
Pruning in April
Early April is a suitable time to prune Hydrangea Macrophylla - the common Hydrangea with pink or blue, but also white flowers. If it is an established Hydrangea, prune down to a bud or a pair of buds and cut out about a quarter to a third of the older, more woody growth each year to make for new growth. If the Hydrangea is newly planted, just prune down to a bud until the plant is more established. Hydrangea is a lovely summer flowering shrub.
It’s not too late to prune Buddleja davidii, also called summer lilac, which helps to keep them in shape and flowering. April is also the time to prune, or perhaps trim, Lavender, including both French lavender (Lavender stoechas) and Cotton Lavender (Santonia species). Prune Rosemary and Sage too, and, as with lavender, avoid cutting into the woody parts of the plant.
April is the last chance to prune Cornus. By pruning hard in March or April, Cornus will have a vibrant red colour next winter. This is a hard prune. Cut down to within a few buds to the base. Early flowering Erica (Heather) can be trimmed back once flowering has finished.
It’s a good idea not to prune anything during severe weather; delay pruning if the outlook in spring is poor. It’s also tempting to prune shrubs in April - to tidy everything up for the spring. But it is crucial to know which shrubs to prune in April and which to leave alone until later in the year.
April is the right time to give garden shrubs a feed - just as the growing season begins. Sprinkle a general fertiliser around the base of all the shrubs and plants as the soil warms up and everything starts growing.
Suitable ones would be fish blood & bone, Growmore, Bone meal and organic chicken manure pellets. Handle with gloves, and don’t do it on a windy day unless you want to sprinkle yourself with fertiliser. Dig in gently just under the surface, and if rain is not imminent, water in as well.
Some shrubs such as Camellias, Rhododendron and Magnolia need a specialist ericaceous feed. And organic rose feed is best for roses. In some parts of the county, roses may be putting on a good bit of foliage and growth. April is often a good time to give roses a preventive spray against the many diseases they can suffer from.
Tie in new plant growth
New growth on plants and climbers will benefit from being tied in. There’re many types of plant ties - from simple strings to bendy ones, green metal ties and, of course, simple raffia ties
Raffia is quite strong and won’t look too intrusive on the plant. It is also cheap and readily available. And it doesn’t look offensive if it blows around or ends up in the compost heap. Raffia is also soft and forgiving as a tie.
Care for Hellebores
Hellebores are fading, and depending on how they look, time to cut down the stems. The new growth can be seen at the plant’s base, and care is needed to ensure this is not snipped instead.
The taller Helleborus argutifolius (also known as Corsican hellebores) is prone to flop all over the place by this stage and is hard to stake. It is best chopped - taking off the flower and stalks down to the ground. Other types of Hellebores can be left alone.
Many perennials will need support, and early April is the time to stake perennials, especially the early flowering ones, such as Peonies. It can be tricky to place the stakes over or around the plant without damaging the emerging plants if staking is left too late.
April gardening guide: Wildlife and pests
Carrot flies will severely damage the crop, and although it is a nuisance to erect mesh around the crop, it is the best protection. Specialist varieties of carrots such as ‘Flyaway’ are less vulnerable to carrot flies, but that’s not guaranteed.
April gardening guide: Other garden tasks for April
If you have had baskets of indoor bulbs, these can be planted out after flowering for display in the garden next year, except for tulips which are best treated as annuals.
Feed the lawn
April is an appropriate time to feed the lawn with a high-nitrogen fertiliser after scarifying. By April, many will have had their first cut. It is vital to have the blades high to start with and lower as the spring and summer months roll on.
Pot up vegetable seedlings
Seedlings of vegetables sown earlier, such as Tomatoes and Cucumbers, may be ready for potting on. To do this, select another plant pot, which is just a little bigger by a few centimetres and fill it with compost.
Press gently on the compost to remove air pockets that present little vacuums for the tiny roots. Lift the seedling out gently by its leaves, not the stem, and sink it into the pot.
If the seedling has gone leggy (long spindly stem), sink it in deeper, fill in and water gently. It’s tempting to put them into a larger pot, but smaller seedlings will not thrive in big containers. When growing tomatoes, for example, it may be necessary to pot on 2, 3 or even 4 times until the eventual container or grow bag.
Make a compost bin for garden waste
As the debate around the climate crisis heightens, gardeners are becoming more aware of the need to garden in an eco-friendly way. Avoiding peat in compost is one way.
Another is to make your own compost, perhaps using some odd bits of wood to make a slatted container for compostable waste. It is best sited in a not-too-conspicuous spot, as compost bins are not that pretty, but it’ll need the sun to get hot.
Harden off plants
Plants grown in protected conditions, newly purchased from the garden centre or grown in a frost and wind free greenhouse do not do well if they’re planted outside in the garden or vegetable plot without a period to “harden off”, which means getting the plant accustomed to the weather.
On mild days in April, place the trays of bedding plants and tender vegetables outside and bring them back in at night under shelter or glass. Over some time, gradually extend the time the plants spend outdoors until eventually, they’re only inside (or outside, but covered) in the event of frost.