A Plant Spacing Case Study: artichokes & zinnia

We all do it. Shoving plants or seeds into a space that feels so empty and vast, only to be met with the inevitable struggles. Some plants are slower growing which, in turn, creates the need to stretch and elongate, making them leggy and weak. Other plants have massive leaves and their leaf area, the density and space that their leaves collectively occupy and thus shade out below, quickly becomes the dominant planting for the season. Still more seem to dwell happily in the understory, perhaps not producing at maximum vigor but also, remarkably, producing in spite of that shade cast by their vivacious neighbors.

Short of coming to each of your gardens and working side by side with you to help with plant spacing, I want to share some ideas for how to ruminate on this during the off-season so when it’s time for that trowel, you have a solid plan that will yield a perfectly-planted garden come late summer.

More plants don’t mean more food or more flowers. One of the biggest shocks to me was when some of you couldn’t believe that my Thumbelina zinnia were spaced 12” apart and were looking so massive and lush in my artichoke bed. This planting was intentional and caused much oohing and ahhing from hundreds of visitors this past summer.

One of you admitted yours were planted much, much closer and they looked much, much smaller. I don’t know if sunlight was a factor, but plant spacing unequivocally was.

That is a huge lesson learned. It even greatly helped me understand what might be troubling more than one of you, the fact that you might be planting everything too close together. The reason we have minimum plant spacing guidelines is because plants need space in the soil, that mysterious unseen buffet of nutrition, to thrive above ground.

And if it’s the only lesson you carry with you between now and when your spring garden is planted, it will serve you really well for years to come.

The most effective way to achieve this is to envision the empty space full, if that makes sense. And if you’re not a visual thinker, use circles on a computer to scale or draw it on a piece of paper. What you want to understand is what the planting will look like at maturity.

So let’s take my artichoke and zinnia bed as a case study.

What I had intended the maturity to become, fully grown and overlapping slightly, but with more space for the artichokes than zinnia.

How it actually grew out … while the intended dominant plant, the artichokes, still clung to the center of the bed and did in fact grow taller, the zinnias were actually the dominant planting here by square footage. And while it could have gone terribly wrong, it worked out, luckily.

Read your seed packets carefully, and really take in the size at which plants will mature. If a flower packet says plants will grow 12-18” wide and tall and you want them to look full and lush and eventually grow together into one massing, plant them 12” apart. If you want a more stand-alone look for that flower, like a fully grown shrub with space around it, plant it at 24” apart. If you want them to just fill out the space, I’d go for 18” plant spacing and hope that when late August comes they are just starting to touch tips.

The other big factor with spacing things is what else is going on in that bed. Take my new love, Thumbelina zinnia. I interplanted them at 12” apart with my Imperial Star artichoke. They looked possibly not close enough for part of July. Then they filled in more and in August they were perfect: the artichokes were producing and the zinnia were lush and full and covered in pollinators. Come late August, I could barely see the artichokes, and, ironically, the zinnia had nearly choked them out.

In early June I was momentarily wondering if I didn’t plant it all close enough. Soon I’d be asking myself why I don’t trust my instincts more.

And I chose this plant spacing carefully. I read the seed packet which stated plants would grow 10"–16" tall and 8"–10" wide. Boy were these numbers wrong! This plant easily grew 24” wide and tall. This has happened to me with many varieties, seed packets not reflecting reality. Most notably Tiger’s Eye half runner beans which Seed Savers Exchange calls a bush bean has always grown 5’ tall for me.

I share this as a tale of caution.

This bed could have been called a zinnia bed with a touch of artichokes. Actually, it really was a flower bed, as I let many artichokes fully flower just for the experience.

Sometimes our garden dreams require a season or two of learning alongside plants to dial in plant spacing needs of varieties. Don’t despair. Instead, revel in the wonder of our annual plants and listen as they teach us how to be in relationship with them.

Now I knew that the artichokes needed 3-5’ plant spacing. I gave them 3’ between plants. And by that I mean just the artichokes. I then went on to plant zinnia at 12” plant spacing on both sides of the artichokes, lining the bed with flowers. The artichoke-zinnia plant spacing was more like 18” apart, a far cry from the 3-5’ spacing the artichokes requested. And this is how the zinnia choked the ‘chokes.

All that being said, I knew what I was doing. I was going for an overplanted massing. I wanted the plants to end up mingling. But I also thought that the zinnia would have stayed a little shorter and the artichokes would have grown a bit taller, thus not competing in the same space they ended up lingering in after all.

The artichokes did grow taller than the zinnia, but not a 24” difference I was expecting between the flowers and the artichokes.

So with an empty space, try and envision plants in their full maturity if you know what they will look like. And work back from there. And understand that seed companies don’t always have the best or most accurate information about their seeds, even though they should.

And take some time to understand what kind of an aesthetic you’re going for. Formal, tidy gardens have a lot of elements that have space around them, fully mature specimens with some literal breathing room. That means planting things a good 6-12” wider than the recommended plant spacing.

The only right way to plant is to create what you’re dreaming. And because we can only have these experiences once a year, enjoy the process of experiential knowledge. For me, it is the most exciting part of gardening. Each year I am more expert in some areas and a complete novice in others. I find comfort in the gained knowledge, and sheer joy at not knowing what I’m doing in other areas.

This is why I grew artichokes, to nurture that wide-eye little girl ever curious, ever hopeful. And she sure was happy I took care of her.