Sow These Seeds in April!

25 March 2023, written by Benedict Vanheems

Spring is my favorite time of year because there’s so much to do in the garden. Plants are growing fast and there’s lots (and I do mean lots!) to be sowing. So, let me show you my top seeds to sow right now...

Zucchini and Summer Squash

Zucchini and other summer squashes are some of the most productive vegetables of all. Once they get going, they’ll keep pumping out the fruits – your main job is to keep picking them! I also see the fruits as a sort of garden-grown currency – you can share the abundance with friends and neighbors in exchange for, say, watering the garden while you’re away on a well-earned break. Who doesn’t love fresh flavorsome food grown with love and care!

Sow the big, easy-to-handle seeds into plug trays with large cells. If they outgrow their plugs too soon, pot them on into a larger pot so they can grow on unhindered until it’s time to transplant into the garden after your last frost. All-purpose potting mix (ideally peat-free) is fine for these chunky seeds.

There’s some debate about whether the seeds should be sown on their side or not. The argument for sowing the seeds on their side is that water can’t collect on top of the seed, so it’s less likely to rot. But sow them at the right time, so germination is speedy, and this really shouldn’t be an issue.

Dib a hole into the compost with your finger then pop the seed in and cover to a depth of about half an inch (1cm) deep or so.

Winter Squash and Pumpkins

Winter squash and pumpkins are sown the same way as zucchini. While zucchini can be started later in spring – even early summer – winter squash need as long a growing period as you can offer them in cooler regions.

Germinate both summer and winter squashes on a warm, sunny windowsill if you’re in a cool climate, and keep them safe from cold temperatures.

Beans

I like to grow both runner beans and snap beans (also known as green beans) because snap beans are often more susceptible to the cold, while runners can struggle in the heat, so if one of them suffers due to unseasonal heat – or chill – you’ve still got the other to fall back on.

Beans can be sown later in spring directly where they are to grow, but you can start them earlier under cover. Sow into plug trays or small pots of all-purpose potting mix. Pop the seeds in at a depth of around an inch (2cm). A simple rule of thumb for any seeds is simply to cover them with a depth of potting mix equal to the size of the seed.

Transplant outdoors after your last frost date, and once they’ve been properly hardened off (acclimatized to outdoor conditions over a period of about a week so that they get used to being outside). If you can’t guarantee a frost-free environment, I’d suggest waiting til late spring to sow your beans. Beans sown later in warmer conditions should soon catch up with plants started off earlier.

Corn

There’s nothing like a freshly picked cob of sweet corn to get you salivating – absolute bliss! Corn should also be planted after the risk of frost has passed. Once warmer weather sets in it’s genuinely astonishing how quickly they’ll grow!

Last summer was unusually dry and blisteringly hot in my garden, but a more typical summer in my part of the world is a lot cooler. My advice if you’re growing anywhere with shorter summers is to seek out varieties specifically bred for cooler conditions – they’ll fare much better.

You can sow them direct in late spring but for an earlier start, sow into small pots or plug trays with large cells. Dib a hole and drop one seed in per plug or pot, then cover them back over. Germinate them under cover in a greenhouse or cold frame, but if frost is forecast move them indoors.

Watch out for mice – I’ve had sweet corn seeds pinched by the pesky rodents with alarming speed! One trick to mouse-proof your sowings is to pop them into a lidded container till they pop through. Or you could just use a propagator lid if you have one, which will also help to retain moisture and warmth.

Carrots

Starting seeds in plug trays or pots is great for getting a head start earlier in the growing season, but some veggies are best sown directly where they are to grow – especially some, like carrots, which produce a long edible taproot that could get damaged if plants are transplanted.

Mark out a shallow drill a little less than half an inch (1cm) deep. The seeds are tiny, so it’s worth taking a little care and time to space them out. The aim is for a couple of seeds every half inch (1cm) of row. Cover them back over. I like to add a couple of sticks at the end of my rows so I know where the seedlings will pop up. When they pop up, thin out the seedlings to leave a couple every inch or so, or one per centimeter.

Parsnips

Parsnips can be slow to germinate in cold soil, so there’s little point rushing things. If it’s still on the cool side, wait another week or two. How do you know if the soil’s too cold? Well, the traditional advice is to sit on it on your bare bottom, and if it’s comfortable to do so, you’re good to go. Or if neighbors can see into your garden, just check with the back of your hand!

Again, let’s mark out a few drills about a foot (30cm) apart. Parsnip seeds are easy to handle one a time. Sow a couple of seeds per inch (one per centimeter). Parsnips can take up to four weeks to appear – and they do keep me on tenterhooks waiting for them most years! A little tip is to sow some radishes in the same row. These will come up within a matter of days, helping to mark out the position of the row so you can safely weed around them.

Once the radishes are harvested the parsnip seedlings will have more room to really pull away and then these in turn can be thinned to about 6in (15cm) apart. Yes, parsnips are slow to germinate but, honestly, aside from that, they are a really resilient, low-fuss root crop.

“Harvesting — Harvest broccoli heads then leave the plants to produce a few smaller heads for a bonus harvest

Summer Broccoli

I like to sow seeds of broccoli into small pots, just covering them with potting mix. They germinate pretty quickly, and you can then carefully transfer one seedling into individual plugs or pots to grow on till it’s their turn to transplant outdoors. It’s usually best to grow them under insect mesh or fine netting to keep egg-laying cabbage white butterflies off in summer.

When you harvest broccoli heads, don’t pull the plants up straight away – you’ll usually get a secondary cut of smaller heads shortly afterwards. This means a cropping period of up to a month, but you can stagger your sowings to extend it even further.

Celery

Like onions and carrots, celery is one of those versatile crops that finds its way into so many recipes. It used to be a right nuisance to grow – to put it mildly – mainly because you had to plant it in trenches then bank up the soil around the stems to get those crisp, pale stems. Thankfully modern ‘self-blanching’ varieties do away with all that. Plant them in blocks about 10in (25cm) apart, and be sure to keep plants really well watered because, believe it or not, celery was originally a marshland plant. Because the soil wilk be kept damper than for some crops, you’ll need to watch out for slugs.

Celery seeds are almost impossibly tiny! Sieve some all-purpose potting mix so that it’s very fine-textured, then sow a pinch of seeds into a pot. They don’t need to be covered over. To help keep the potting mix moist until the seeds germinate, cover the pot with some clear plastic. Once they have germinated, celery seedlings can go into individual plugs or small pots.

Leeks

As the last of the leeks are lifted, the first of this year’s leeks are sown. I like to sow mine outdoors in an out-of-the-way spot, or you could sow all of your leek seeds into pots of potting mix. Sow the seeds nice and thinly dropping a couple of seeds every half inch (1cm), then cover back over. Water and keep the seedlings moist.

Aim to transplant them around midsummer when they’ll be getting on for pencil thickness and about 8in (20cm) tall. Separate them out then plant into dibbed holes.