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Growing Perennials Part 1

Verbena Hastata White Spires & Pink Spires Seedlings

Perennials are such an understated work horse, often forgotten about or overlooked in favour of flashy easy to grow annuals. But don’t!

Whatever your purpose is, be it a purposeful cut flower patch or just a beautiful low maintenance garden (FYI low maintenance doesn’t have to mean ugly, boring and just full of rhododendrons) or even if you are aiming for a harmonious balance of the two, then it’s time to talk perennials.

Before you delve into reading bear these 2 things in mind:

  • I’m in rural South Island New Zealand. Very seasonal weather with long warm dry summers and cool winters - with frosts, dipping below 0 at night etc in winter. I don’t understand ‘zones’ but if I did classify, I think I’d be considered 8 or 9.

  • When I say ‘the year’ this for me begins in spring and ends in autumn often at the first frosts. My garden becomes dormant over winter, and all my perennials die back and do not regrow until the spring.

Firstly we need to understand the difference between annuals and perennials to grasp why my much loved perennials are often a pain in the a*** to germinate.

Annuals - These are in such a hurry, they germinate, grow, flower, set seed, and die within the year. The majority are very easy to germinate and grow, requiring little effort and special treatment (You do still need to pay attention to sowing requirements however - When to sow, depth, light etc). The downside of annuals is you have to resow them every year. They are a few different types of annuals, hardy/half hardy/cool etc, and some annuals can be a little more particular- but this is worthy of its own space and won’t talk about those differences now. You can reasonably expect a strike rate of 85% + for annuals.

Perennials - Now perennials are a different beast altogether compared to annuals. These are not in a hurry. Perennials can be notoriously tricky to germinate often requiring several rounds of cold stratification to break the dormancy in the seed. Or just leaving Mother Nature to do her thing, sowing in the autumn and letting them naturally germinate in their own time (this is only if you live somewhere with cool winters). Germination is slow and erratic and you can only expect a strike rate of around 50-60%. Don't be put off however, as once germinated, perennials are here to stay (so long as you kill them).

Now I hear you saying….I can’t be bothered with faffing, so just pass me the cosmos seeds! But perennials are absolutely worth the effort and in any garden should be a priority.

Here’s why:

  • Once they have germinated they are here to stay, the plants grow for years, and often by the 3rd year it’s recommended you divide them. A double bonus of more plants for you and allows the newly divided plants to flourish and thrive again. However if you are growing for a cut flower crop it’s important to remember you are unlikely to have a decent harvestable crop until the 2nd or 3rd year (if growing conditions are optimal you may get a few flowers in the first year). As perennials spend a lot of time focusing their energy in establishing a strong root system in the first year.

  • You don’t need to repeat the process every year once you have established plants.

  • Perennials are really low maintenance once established. They are happy to grow, flower and do their thing with just the occasional splash of seaweed emulsion to give them a happy boost. If you are not picking for cut flowers then the occasional deadheading a few times over the year may be needed if you want to encourage more blooms.

  • Perennials are also frost hardy and regrow in the spring. Flower dependent some completely die back above ground others just hold onto their foliage.

  • Perennials are often the first to flower in spring really plugging that gap between spring blooms and summer annuals, and most go on to flower all summer being fantastic true cut and come again plants. You will probably surprise yourself how much you to come to rely on your perennials.

Why are perennials so finicky compared to annuals?

Germinating slowly and erratically is actually an inbuilt survival mechanism. If all these seeds actually germinated at the same time, then something came along such as unfavourable weather/animals had a nibble/disease which would lead to the demise of the seedling, which is turn would reduce plant population. This is why perennials in particular are fussy.

How to grow Perennials

Now we’ve got this far I’ll talk about how to grow perennials.

The key thing for germinating perennials is to think logically about their country of origin - and you need to often mimic those growing condition. Perennials set seed in autumn at the end of the growing year and need the winter to break the dormancy in the seeds. Most of perennials worth growing originate in climates which experience cool, moist winters and hence the need for cold stratification (they are a few exceptions).

  • Sow your seeds according to the packet, in either seed raising mix, or in your soil blocks - I prefer soil blocks as you can grow substantially more seeds in a small space - invaluable when it comes to cold stratifying. Allow up to 4-6 weeks (sometimes longer if required on the packet) for germination to occur.

  • If germination hasn’t occurred in this time frame, it’s time to cold stratify. Cold stratify for a minimum of 4 weeks.

  • Return the seeds to the warmth and watch for germination. If after 4weeks germination has not occurred repeat cold stratification. Even if germination has occurred, prick out the seedlings that have germinated and place the rest of the sowed seeds back into the fridge.

  • It’s absolutely CRUCIAL you do not let your seeds or seed raising mix dry out at any point, if you do chances are the seeds will have perished and won’t grow.

  • Have patience! It's easy to through a tantrum and biff the seed trays out, convinced its a dud packet of seeds - but wait! follow the process, cold stratify and be patient (Yer I struggle with this). Some perennials take MONTHS to germinate, and some no matter how much you try and trick them, they will only germinate once they experienced a natural winter. As long as you've not let the seeds dry out, do not chuck sowed seeds away in a sulk.

What is cold stratification?

It’s quiet simple really - place the sowed seed trays into a plastic bag (cringe) and into the fridge for 4 weeks. This is why I prefer soil blocking (again) as I use takeaway tubs as mini greenhouses - so just put the top on. Glass tubs works the same. Covering the seeds is essential, it keeps the moisture in. It’s important to check your seedlings every week, and if necessary, give a spritz of water.

In my next post I’m going to talk about my favourite perennials for cut flowers and my tips and tricks for getting them to grow. You may also be relieved to hear I do have some which are surprisingly easy to grow!

This will include: Verbena, Echinops, Sea Holly, Loosestrife, Geum and Linaria.

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