How to grow Ranunculus

When to plant

Our ranunc plants are ready to be planted straight away, if you're not quite ready for them we recommend possibly potting them up to a bigger pot to buy yourself more time and not risk slowing them down at all - just make sure they don't fully dry out and if you can water less often but more thoroughly to encourage deeper roots and reduce algae growth which can be a problem during winter.

If you are sprouting from saved tubers/corms, you can wake them up anytime from about March through to July, give or take a little depending on your climate.

Where to plant

Plant in a mostly sunny spot, a little afternoon shade can help them flower for longer, as ranuncs hate the heat. Good airflow is important so make sure other plants aren't too close. Some shelter from rain is advised in wet regions or during wet spells for best flower quality, a little rain isn't a problem but when flowers can't dry out quickly it can affect flower quality. They do tend to handle the rain better when it is cooler, with the warmer spring rains causing the most damage.

Ranunculus are hungry plants, so give them your very best most fertile beds and they will reward you in kind. We do recommend topping their bed with a general organic fertiliser. Unlike most other flowering plants, especially for seedlings ranuncs, a good boost of nitrogen is very beneficial as they need to pump out sufficient foliage from the get go in order to sustain producing their very best flowers later on.

Spacing

I plant my seedling ranuncs 10cm apart in the row and about 20cm apart between rows (except when I've got more plants than space, then I squeeze the row spacing down to about 15cm so I can fit an extra row per bed :)

If you are growing from saved corms, they will need more space. Earlier (March – April, early May) sprouted corms need more like 25cm apart in the row and 20–30cm apart between rows. And later sprouted corms (late May–July) are a little smaller so need about 20cm apart in the row and about 20cm between rows.

Planting 

Plant plants in a well drained soil, extra compost and bulb type fertiliser or general organic humate based type fertiliser (with extra calcium if you can) mixed in. I usually just use my compost as a top layer mulch.

A pre-planting soaking in liquid seaweed + Superzyme, with a dusting of mycorrhizal fungi helps inoculate them with all the best beneficial bacteria & fungi, helping them be their very best selves.

Care

Ranuncs like a lot of babying - so I aim to foliar spray every week with a mixture of fish emulsion. I generally also dose my mix with a very unscientific concoction of 'good stuff' depending on what we have on hand at the time. I don't know if it really makes any difference, but I don't think it hurts, so I concoct away with ingredients like liquid humates, aminos, calcium, fermented nettle, and comfrey, anything that will help boost their health, nitrogen, calcium, and general micro-biology is worth spoiling your ranuncs with when you can. When mixing different ingredients it is important not to mix them all to full strength so do reduce their individual strengths so that together they work out about right (reduce by about half or a third is a good idea).

The oiliness from the fish emulsion seems to be very beneficial and preventing powdery mildew (once you have a blank slate, it definitely won't clear any existing powdery mildew). For this reason weekly foliar sprays are ideal (or once every 10 or so days).

Keep plants well watered, but do allow the soil to breathe and dry on the surface to prevent algae growth. Drip irrigation is best but overhead is fine so long as it's done earlier in the day with plenty chance of drying off the foliage quickly.

A straw type mulch can be beneficial once the plants start budding up, in preparation for warmer spring temps - the mulch will help insulate the soil from the worst heat & maintain moisture. In hot spells make sure to keep plants well watered.

Disease

The most common disease with ranunculus is Powdery Mildew, in NZ's warm humid climate it is a when not if it'll be a problem, so make sure you have a plan ready to go as soon as you see the first signs. I haven't found a reliable organic solution to our powdery mildew, but we have found that at least two strategic sprays with Yates Super Shield does go a long way to avoiding needing to spray more regularly. We aim to spray our first after we've planted, so we can have a blank slate of no disease. I then find that our weekly fish emulsion sprays are also a key part, so ideally with weekly fish emulsion sprays we can get through to the plants budding powdery mildew free.

We then do one last Super Shield spray just before any buds start showing colour. We usually stop straying any good or bad sprays after this point as we don't want to damage our flowers, so this last sprays gives us about 3 good weeks for them to get through most of their peak flush before the powdery mildew starts popping up. Once they're flowering we do not spray or try to get rid of powdery mildew, at this stage it doesn't cause much damage to the plants, it doesn't affect the vase-life of the flowers, so we just let it be from then on. The key thing with powdery mildew is that you don't let it get out of control when the plants are young, as that will definitely have an effect on the plants health.

Ranuncs can also get brown leaf spots which are more of water/wet foliage problem so make sure they have good air flow and keep babying them with all the good stuff.

Powdery Mildew on Ranunculus.

Pests

Aphids are very fond of ranuncs! So need to be dealt to early before their population quickly explodes. So as soon as they’re leafed up and especially once buds are spotted, inspect them regularly for aphids and deal to them promptly—my favourite control is using predator insects from Bioforce before I even see the first aphid (Aphidius & Lacewings are my favourites).

Slugs & snails are also worth keeping an eye out for at this time of the year as well.

Rabbits are also quite the ranunc lovers, and quails can nibble at foliage and buds,  too it will be beneficial to fence them out if they're a problem for you.

 

Harvesting flowers

The rule of thumb is to harvest flowers after they've opened & closed for three days. That however can be rather hard to keep track of!

We aim to harvest anywhere from loose 'marshmallow' stage (when the bud is soft and loose, not tight and hard), through to when the flowers are open but their back petals still curve/cup upwards, and there's still plenty of layers left to open in their centres.

Ranunculus have incredible vase-life, so they do not need to be harvested super tight, leaving them to be a little more open when harvested does help them open to their biggest, most glorious selves.

I am not a fan of chilling ranunculus flowers for any more than a couple of days, and only if the flowers are fully definitely dry, as I find they are much more susceptible to botrytis developing in our chiller rather than out.

Salmone in their perfect loose cupped harvest stage.

 

Saving Corms

I used to be hesitant at saving ranunculus corms (or tubers which they technically are, but they are more commonly know as 'corms'), however we have discovered that while ranuncs may be fussy to grow, they have an incredible will to live when it comes to their ability to produce and revive from corms.

If saving corms, make sure to leave plants till the foliage, yellows and starts browning. Once lifted store them somewhere warm and dry for the summer. There isn't any need to wash them off.

In their first year from seedlings, they typically just produce one corm, however in their second year those corms can then produce up to 4-6 new corms per plant!

You can attempt to leave your corms in the ground over summer, and they may come back to some degree, but we personally find that to be a lower percentage as we don't really get as dry of a summer as they'd need not to rot. So it is definitely worth lifting and storing over summer.

 

Waking Corms

Your stored lifted saved corms will shrivel up and dehydrate over summer, and look very dead, this is normal. Ranunculus are naturally woken by their first big autumn rain, so simulating this is the trick to getting the highest germination rates. We either just water them in (into their bed, pot, or tray) with one very big very soaking first watering, then leave them without watering for about two weeks. Ideally you want them to dry out slightly after that initial watering then to hover at the perfect moist (not wet, not dry) stage until they start sprouting, so making sure you don't keep them somewhere too warm or too cold and shady is the key.

When sprouting big batches, we'll pre-soak the ranuncs (with air stones/pump to keep them from drowning) for a couple hours then layer them in almost dry slightly damp potting mix in buckets or tubs. They will usually be ready to plant in about two weeks maybe three if it is cooler.

Learn more about why we essentially have to grow ranuncs from seeds/plants vs corms in NZ