Zucchini is an absolute must for any summer garden. Quick-growing, abundant and almost fuss-free – almost! - if it wasn’t for the mildew, bugs, and poor pollination that can sometimes hamper our efforts.
If your heart’s desire is for truly perfect zucchini every time, you can do it! But you’ll need to know a few tricks of the trade first. Read on or watch our video to soak in the know-how required to zhuzh up your zukes...
If you haven’t sown your zucchini yet, that’s absolutely fine! You don’t want to sow too early or your plants will be ready to plant way before your last frost date, and then you’ll have an anxious few weeks wondering if your plants will make it! Ideally night-time temperatures should be up to around 50ºF (10ºC), which in my part of the world means sowing later in spring, or even early summer.
Sow one or two seeds per pot or plug. Push the seeds into your potting mix, making sure they’re sitting on their edge. This way water won’t sit on the top of the seed, which could cause it to rot, though if you’re sowing at the correct time and conditions are good this shouldn’t be an issue. Germination is pretty snappy – within a week.
Grow your zucchini seedlings on somewhere warm, sunny and sheltered. If you don’t have a greenhouse or cold frame, try starting them off on a sunny windowsill, or somewhere sheltered outdoors like a suntrap patio, with protection on hand for the cooler nights.
You can also sow direct into the ground if it has warmed up nicely, in which case I’d recommend sow two seeds in each position as insurance against any loss. If both germinate, just remove the weaker of the two seedlings by cutting it off at ground level.
If all goes well, it shouldn’t take any longer than around three weeks to go from sowing to planting, so bear that in mind when coordinating with your last frost date.
Prepare Your Soil
Choose a sunny spot for your zucchini, and boost the soil with a topdressing of a good inch or so (2-3cm) of compost. Feeding your soil with lashing of organic matter is really important because these are big, hungry plants and the main thing they ask from you in return for all those fruits is a soil that provides them with plenty of nutrients and moisture to power all that growth.
If you haven’t prepared your soil in advance, try creating a planting pit. Just dig out a hole at least a foot (30cm) deep and wide, fill with garden compost or well-rotted manure, then return some of the soil on top. Your zukes will love you for it! For an added boost, spread an organic slow-release fertilizer on the soil surface and rake it in. Some gardeners plant on a mound to help with drainage, but I’ve never done this and it just seems like extra work to be fair!
Zucchini are thirsty plants, so it’s worth making sure that plenty of water can get to their roots during dry spells. To help with this, cut off the bottom of a plastic bottle and poke it into the soil near the plant, neck end down. You can then water into the bottle and the water will be delivered directly to the roots where it’s needed.
Make sure your seedlings are looking healthy, green, and quite stocky. If you leave them too long they will start to exhaust the nutrients available to them in the potting mix, which can cause them to struggle. You may need to repot them into larger containers if they outgrow their original pots or plugs before it’s time to plant them outdoors.
Avoid planting before your last frost date. If you’re not sure when that is, you can find out using our Garden Planner. Simply enter and save your location, and both your first and last frost dates will be shown.
Before planting, harden off your zucchini (acclimatize them to the outdoors) by placing them outside for increasingly longer spells over the course of about 10 days.
Don’t be tempted to cram plants in. It’s essential that they have the correct spacing as this will allow for good airflow between the plants, which is important for two reasons: it reduces the risk of diseases like powdery mildew, and it makes for less of a tangle of leaves, so pollinators can more easily locate the flowers. Space plants at least 2ft (60cm) apart, and ideally up to 3ft (90cm) apart.
If the weather is still cool, cover your plants with some row cover fabric to keep the chill off. This will also help plants adjust to their new surroundings, especially if you haven’t had much time to harden them off.
Ensure plants are kept well watered in dry weather. I’ll be spreading a mulch of wood chips around my plants within a few weeks, which will slow evaporation. Mulching is beneficial anywhere, but I reckon it’s essential if you garden in a hot climate.
Persuade Your Zucchini to Fruit
So, you’ve got your plants in the ground and they’re looking just great – really vibrant and with masses of growth. Then the first flowers appear – hurrah, it won’t be long before you’re picking fruits! But let’s not get too carried away just yet.
The first flowers are often male flowers – and you’ll of course need both male and female flowers if you’re to get a harvest. So why do they do this? Well, one reason might be that male flowers take less energy to produce, so they start with these before building up to the more energy-intensive females, which can be identified by the immature fruit immediately behind the bloom. Don’t worry though, the females will soon arrive, and with them the promise of your first fruit.
A common problem is that young fruits start to rot and then drop off. This is almost always because it hasn’t been pollinated, so the plant is simply aborting the unsuccessful fruit. Bees will do a near-perfect job of pollinating, but if you do want to make double sure you can always hand-pollinate by brushing the pollen from the male flowers onto a fine paintbrush or cotton swab and then dabbing that into the center of the female flower. It’s really simple to do and works for all crops in the squash family – so that includes the likes of melons and pumpkins too.
Zucchini Pests & Diseases
North American gardeners can experience major problems with pests. Squash bugs can feed on leaves to the point of making them ragged, while squash vine borers attack the plant where it really hurts – right at the base of the main stem!
Check plants regularly – at least twice weekly – throughout summer for squash bug eggs. You can just scrape them off or, if it’s a small infestation, cut the egg-carrying leaf off and compost it.
Squash vine borers are trickier customers as they get right inside the stem to feed on the spongy material inside. They give themselves away by the beige frass – that’s their poo – that oozes from the base of the stem where they’ve gained entry. Try wrapping the base of the stems in foil to form an impenetrable barrier. If they do get infested you can try carefully cutting the grubs out or bury part of the stem further along the plant so it can send out roots, effectively bypassing the damaged base.
A problem universal to all gardeners is powdery mildew, which covers leaves in a white, powdery coating. Ensure good airflow by avoiding overcrowding, and don’t allow plants to struggle for water.
A diluted milk spray can be used pre-emptively to prevent powdery mildew. If powdery mildew is already present, clip off affected leaves if there’s only one or two. There’s no need to pull up plants until they’re actually dead though, as they will keep producing and the fruits are perfectly safe to eat.
You should always remove badly damaged, dying or yellowed leaves. They aren’t contributing anything to the health of the plant and only serve to reduce that all-important airflow.
But they you can go a step further, by removing any overlapping leaves. These are typically the oldest leaves lower down on the stem. In fact, up to a third of the plant’s leaves can be removed at a time, and by doing this you’re encouraging the plant to produce fresh, clean growth, while also improving air circulation. The lower leaves get less direct sunshine anyway, making them more prone to powdery mildew, so this is a great preventative step to take.
Most zucchini, apart from compact ‘bush’ varieties, send out vines that snake their way along as they continue to grow from the top. This is why zucchini can take up so much space in the garden. But you can use this growing habit to train them up off the ground, making better use of vertical space. Just hammer in a really sturdy stake up to 6ft (2m) tall close to the plant at planting time. Then tie the main stem up onto the stake every few inches or so to help it climb. Growing vertically means you can fit more into your space, and it should help to make the flowers more visible to passing pollinators too.
Harvest Early and Often
And my final tip for perfect zucchini every time is to keep picking! Ideally you want to be harvest the fruits young, when the flowers are usually still attached. At this stage they are at their most delicious and firm. You’ll pay a premium for zucchini like these in the grocery store, so it’s great we can harvest them at this stage as gardeners.
Never let them get too big (and certainly not to marrow size!) as this will signal to the plant that its job is nearly done and it can stop producing flowers. I aim for a maximum length of 6in (15cm).
If you’re going away for any period of time, ask a friend or neighbor to pick your zucchini while you’re gone, even if they don’t want to eat them, because that ensures the supply won’t drop off before you return. Remember: if you keep picking, they will keep coming.
I find four or five plants is about right for our family of three. Not only does having more than one plant improve overall pollination, it means there really is always something to pick. Plants feel better in good company, just like us! Personally, I can’t imagine ever tiring of zucchini, particularly when you’ve planted a couple of different types for interest – as well as traditional green, try yellow, stripy, ribbed, or even spherical varieties!
How do you keep your zucchini game fresh, and what’s your favorite variety? Let me know in the comments below!