Ground Elder – otherwise known as Goutweed, English Masterwort, Bishop’s Weed or Snow-in-the-Mountain – is a plant that you really don’t want to have in your garden. True, its tender but pungent-tasting leaves are edible and were used during the Middle Ages as a spring vegetable, especially in soup. It has also been used to treat gout and arthritis, acts as a mild sedative and has a laxative effect. But ground elder, which can grow to a height of about a metre, is also a thug and a pest. For it grows from underground stems or rhizomes which spread through the soil, sucking the nutrients out of it. It spreads rapidly, crowding out other plants. And it is almost impossible to eradicate: you can try to dig it out but a new plant will grow from even the tiniest fragment of rhizome that’s left in the ground. In other words, it is a persistent and invasive species.

I’d like you to hold that information in your mind as we turn to Mark’s Gospel and, specifically, to Jesus’ little story about a mustard seed. On the face of it, this parable is very simple, one of several which talk about growth. For it speaks of something with which we’re all familiar (but which is still miraculous): of a single tiny seed which, when sown, germinates and eventually grows into a large tree. As an American writer has put it, “This is a feel-good kind of image that resonates with other familiar aphorisms like ‘good things come in small packages’ or the sentiment expressed by Mother Teresa when she said, ‘be faithful in small things because it is in them that your strength lies’”. Indeed we might go back to our own Dewi Sant who is famous for having said, “Do the little things in life”. Jesus seems to be saying something which can give us a great deal of hope: that our world, full of imperfections and pain as it is, will slowly but surely be improved, balanced and corrected by God; that his kingdom will increase until one day it has infused and healed the entire creation.

Well, that’s one way of looking at the parable. But it’s not the only one. For another interpretation shifts its focus to the Church. This, of course, didn’t yet exist when Jesus was speaking but, by the time people were reading Mark’s Gospel, there were several communities of Christian believers, mostly Jewish, scattered around the Mediterranean region. That sounds great but most of them must have been pretty small and insignificant, hardly a major force in first-century religious life. However, says this reading of the parable, that will change. For although the Gospel seed planted by Jesus hadn’t developed beyond the seedling stage at the time Mark was writing, its growth would be unstoppable. In time it would become such a large tree that it would be able to offer shelter and shade to anyone, Jew or Gentile, who might seek it. Again this is a picture of hope, which must have given huge encouragement to the missionary movement. For, using imagery that’s actually drawn from the Old Testament, it seems to say that the Church starts with the tiny seed of Gospel preaching which, when people believe, grows within them. They then pass on the message and, little by little, more and more people come to faith. Eventually they become a vast multitude that fills the entire world. Here is a Church which has grown from small beginnings to become Revelation’s crowd drawn from every nation and tongue.

Those are both time-honoured ways of understanding this parable. But are they right ways? To answer that, we must do a bit of thinking and ask: how would Jesus’ original hearers have understood his words? To do that, we need to go even further and think about some background information which Mark doesn’t provide because he knew it was familiar to both Jesus and his listeners – information which we need to know if we’re going to come to a correct understanding. Let me explain what I mean with a silly story (nothing to do with this parable!) about a strict preacher back in the 1950s who was “having a go” at Christian young women who, he felt, were using too much “worldly” make-up. He railed at them for “painting their lips the colour of pillar-boxes”. As everyone knows that those are bright red he didn’t spell it out, he could take it as common knowledge. What he’d unfortunately forgotten is that he was actually in the Republic of Ireland – where the post-boxes are green!

So what is this information that Mark doesn’t tell us because it was something that “everyone already knew”? Well, it’s this: that the mustard plant is an annoying and invasive pest that spreads everywhere and is almost impossible to get rid of, just like the ground elder I mentioned earlier. The Roman author Pliny the Elder wrote this about it: “Once the [mustard] seed has been sown it is scarcely possible to get the place free of it, as the seed when it falls germinates at once”. The Mishnah, an early collection of Jewish teaching which echoes what was being taught in Jesus’ day, lays down the law: mustard seed “should not be planted in the garden but only in a larger field where it can be carefully segregated by itself”. And it’s also been suggested that any gardeners and farmers in Jesus’ audience wouldn’t have been happy about the birds which the prolific mustard plant would attract if it got into their carefully cultivated fields of corn; in fact they would have been horrified.

So what’s going on here? Why does Jesus shock or at least puzzle his listeners by saying that God’s Kingdom is like a pernicious and even unwanted weed? Well, when we learn that the mustard seed, though small, is not in fact the tiniest of all seeds, and that the plant itself never becomes a mighty tree able to bear the weight of birds on its branches because it’s just a large shrub, then we begin to realise that Jesus – as so often – has taken us into the world of satire and burlesque, that he’s using humour to make some serious points: “What, God’s Kingdom is like that pesky weed? You must be kidding!”

For it’s not the smallness of the mustard seed that’s in focus here, but the characteristics of the plant itself. Yes, its culinary and medicinal properties make it useful; but it also has this tendency to spread out of control. This suggests that God’s Kingdom, while beneficial and wholesome, is something which respectable society finds extremely irritating. For it challenges the complacent norms that we take for granted, it undermines imperial and domineering powers, it exalts the weak and pulls down the strong (where have we heard that before?), it may even invade sacred spaces such as cathedrals to advance its cause. God’s subversive Kingdom isn’t, of course, destructive (except to tyranny, exploitation, injustice and sin); it is in fact highly constructive as it levels up the economy, supports the poor, brings words of comfort and forgiveness, gives value to people on the margins, tells everyone that there is more to life than the daily grind and offers a grand hope and vision for the future. But it certainly is disruptive: as Jesus says, its growth cannot be stopped. It sneaks in under the radar and, if someone succeeds in cutting down one shoot, another soon springs up from the same root.

Sarah Brown is the Canon Missioner at Peterborough Cathedral. At the start of the pandemic she wrote of her belief that signs of the Kingdom of God were bursting out everywhere, and noted that many people – not necessarily Christians – in our so-called “woke” generation are yearning for a better world of kindness, fairness and peace. She continued: “For the Christian, the Kingdom of God is the ultimate endgame. It is a future time when we so co-operate with God and one another that there will be no need for politics or religion or competition – when the values of our human power structures will be turned on their heads and all will thrive, when we genuinely honour and reward our truckers, hospital porters, shelf-fillers and carers as much as we have honoured our celebs and athletes (and go on doing so beyond this crisis); when the air stays clear over our cities, the ozone layer repairs, the fish still swim in previously fouled waters, and we give back to society and the planet more than we take, then the Kingdom of God will truly be in sight”.

I agree wholeheartedly with that sentiment, though I would want to add to it something about belief in the Gospel message and the growth of the Church. The Kingdom of God is precisely what it says – it’s “of God” – so it’s more than just progress towards a better society or a planet which is looked after with care. One might also question if the Kingdom’s growth is quite as inevitable as Jesus made out; I’d like to believe that it is but, sadly, advances in some places have been balanced by increased injustice and oppression elsewhere. Still, one can still hope and pray that, despite setbacks, nothing will ultimately hinder the advance of Christ’s reign on earth. For that is what this parable about: the messy and insidious spread of God’s Kingdom. Let’s look for signs of it in the obvious places and in the unexpected ones. And, in contrast to what we’d do with ground elder or wild mustard, let’s not seek to eradicate it but do everything we can to help its growth.